/****************************************************************************
**
** Copyright (C) 2013 Digia Plc and/or its subsidiary(-ies).
** Contact: http://www.qt-project.org/legal
**
** This file is part of the QtOpenGL module of the Qt Toolkit.
**
** $QT_BEGIN_LICENSE:LGPL$
** Commercial License Usage
** Licensees holding valid commercial Qt licenses may use this file in
** accordance with the commercial license agreement provided with the
** Software or, alternatively, in accordance with the terms contained in
** a written agreement between you and Digia.  For licensing terms and
** conditions see http://qt.digia.com/licensing.  For further information
** use the contact form at http://qt.digia.com/contact-us.
**
** GNU Lesser General Public License Usage
** Alternatively, this file may be used under the terms of the GNU Lesser
** General Public License version 2.1 as published by the Free Software
** Foundation and appearing in the file LICENSE.LGPL included in the
** packaging of this file.  Please review the following information to
** ensure the GNU Lesser General Public License version 2.1 requirements
** will be met: http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html.
**
** In addition, as a special exception, Digia gives you certain additional
** rights.  These rights are described in the Digia Qt LGPL Exception
** version 1.1, included in the file LGPL_EXCEPTION.txt in this package.
**
** GNU General Public License Usage
** Alternatively, this file may be used under the terms of the GNU
** General Public License version 3.0 as published by the Free Software
** Foundation and appearing in the file LICENSE.GPL included in the
** packaging of this file.  Please review the following information to
** ensure the GNU General Public License version 3.0 requirements will be
** met: http://www.gnu.org/copyleft/gpl.html.
**
**
** $QT_END_LICENSE$
**
****************************************************************************/

#include "qapplication.h"
#include "qplatformdefs.h"
#include "qgl.h"
#include <qdebug.h>
#include <qglfunctions.h>

#include <qdatetime.h>

#include <stdlib.h> // malloc

#include "qpixmap.h"
#include "qimage.h"
#include "qgl_p.h"

#include "gl2paintengineex/qpaintengineex_opengl2_p.h"

#include <qpa/qplatformopenglcontext.h>

#include <qglpixelbuffer.h>
#include <qglframebufferobject.h>
#include <private/qopenglextensions_p.h>

#include <private/qimage_p.h>
#include <qpa/qplatformpixmap.h>
#include <private/qglpixelbuffer_p.h>
#include <private/qimagepixmapcleanuphooks_p.h>
#include "qcolormap.h"
#include "qfile.h"
#include "qlibrary.h"
#include <qmutex.h>

// #define QT_GL_CONTEXT_RESOURCE_DEBUG

QT_BEGIN_NAMESPACE

class QGLDefaultExtensions
{
public:
    QGLDefaultExtensions() : extensions(0) {
        QGLTemporaryContext tempContext;
        Q_ASSERT(QOpenGLContext::currentContext());
        QOpenGLExtensions *ext = qgl_extensions();
        Q_ASSERT(ext);
        extensions = ext->openGLExtensions();
        features = ext->openGLFeatures();
    }

    QOpenGLFunctions::OpenGLFeatures features;
    QOpenGLExtensions::OpenGLExtensions extensions;
};

Q_GLOBAL_STATIC(QGLDefaultExtensions, qtDefaultExtensions)

bool qgl_hasFeature(QOpenGLFunctions::OpenGLFeature feature)
{
    if (QOpenGLContext::currentContext())
        return QOpenGLContext::currentContext()->functions()->hasOpenGLFeature(feature);
    return qtDefaultExtensions()->features & feature;
}

bool qgl_hasExtension(QOpenGLExtensions::OpenGLExtension extension)
{
    if (QOpenGLContext::currentContext())
        return qgl_extensions()->hasOpenGLExtension(extension);
    return qtDefaultExtensions()->extensions & extension;
}

QOpenGLExtensions::OpenGLExtensions extensions;
/*
    Returns the GL extensions for the current QOpenGLContext. If there is no
    current QOpenGLContext, a default context will be created and the extensions
    for that context will be returned instead.
*/
QOpenGLExtensions* qgl_extensions()
{
    if (QOpenGLContext *context = QOpenGLContext::currentContext())
        return static_cast<QOpenGLExtensions *>(context->functions());

    Q_ASSERT(false);
    return 0;
}

struct QGLThreadContext {
    ~QGLThreadContext() {
        if (context)
            context->doneCurrent();
    }
    QGLContext *context;
};

Q_GLOBAL_STATIC(QGLFormat, qgl_default_format)

class QGLDefaultOverlayFormat: public QGLFormat
{
public:
    inline QGLDefaultOverlayFormat()
    {
        setOption(QGL::FormatOption(0xffff << 16)); // turn off all options
        setOption(QGL::DirectRendering);
        setPlane(1);
    }
};
Q_GLOBAL_STATIC(QGLDefaultOverlayFormat, defaultOverlayFormatInstance)

Q_GLOBAL_STATIC(QGLSignalProxy, theSignalProxy)
QGLSignalProxy *QGLSignalProxy::instance()
{
    QGLSignalProxy *proxy = theSignalProxy();
    if (proxy && proxy->thread() != qApp->thread()) {
        if (proxy->thread() == QThread::currentThread())
            proxy->moveToThread(qApp->thread());
    }
    return proxy;
}


/*!
    \namespace QGL
    \inmodule QtOpenGL

    \brief The QGL namespace specifies miscellaneous identifiers used
    in the Qt OpenGL module.
*/

/*!
    \enum QGL::FormatOption

    This enum specifies the format options that can be used to configure an OpenGL
    context. These are set using QGLFormat::setOption().

    \value DoubleBuffer      Specifies the use of double buffering.
    \value DepthBuffer       Enables the use of a depth buffer.
    \value Rgba              Specifies that the context should use RGBA as its pixel format.
    \value AlphaChannel      Enables the use of an alpha channel.
    \value AccumBuffer       Enables the use of an accumulation buffer.
    \value StencilBuffer     Enables the use of a stencil buffer.
    \value StereoBuffers     Enables the use of a stereo buffers for use with visualization hardware.
    \value DirectRendering   Specifies that the context is used for direct rendering to a display.
    \value HasOverlay        Enables the use of an overlay.
    \value SampleBuffers     Enables the use of sample buffers.
    \value DeprecatedFunctions      Enables the use of deprecated functionality for OpenGL 3.x
                                    contexts. A context with deprecated functionality enabled is
                                    called a full context in the OpenGL specification.
    \value SingleBuffer      Specifies the use of a single buffer, as opposed to double buffers.
    \value NoDepthBuffer     Disables the use of a depth buffer.
    \value ColorIndex        Specifies that the context should use a color index as its pixel format.
    \value NoAlphaChannel    Disables the use of an alpha channel.
    \value NoAccumBuffer     Disables the use of an accumulation buffer.
    \value NoStencilBuffer   Disables the use of a stencil buffer.
    \value NoStereoBuffers   Disables the use of stereo buffers.
    \value IndirectRendering Specifies that the context is used for indirect rendering to a buffer.
    \value NoOverlay         Disables the use of an overlay.
    \value NoSampleBuffers   Disables the use of sample buffers.
    \value NoDeprecatedFunctions    Disables the use of deprecated functionality for OpenGL 3.x
                                    contexts. A context with deprecated functionality disabled is
                                    called a forward compatible context in the OpenGL specification.

    \sa {Sample Buffers Example}
*/

/*****************************************************************************
  QGLFormat implementation
 *****************************************************************************/


/*!
    \class QGLFormat
    \inmodule QtOpenGL

    \brief The QGLFormat class specifies the display format of an OpenGL
    rendering context.

    A display format has several characteristics:
    \list
    \li \l{setDoubleBuffer()}{Double or single buffering.}
    \li \l{setDepth()}{Depth buffer.}
    \li \l{setRgba()}{RGBA or color index mode.}
    \li \l{setAlpha()}{Alpha channel.}
    \li \l{setAccum()}{Accumulation buffer.}
    \li \l{setStencil()}{Stencil buffer.}
    \li \l{setStereo()}{Stereo buffers.}
    \li \l{setDirectRendering()}{Direct rendering.}
    \li \l{setOverlay()}{Presence of an overlay.}
    \li \l{setPlane()}{Plane of an overlay.}
    \li \l{setSampleBuffers()}{Multisample buffers.}
    \endlist

    You can also specify preferred bit depths for the color buffer,
    depth buffer, alpha buffer, accumulation buffer and the stencil
    buffer with the functions: setRedBufferSize(), setGreenBufferSize(),
    setBlueBufferSize(), setDepthBufferSize(), setAlphaBufferSize(),
    setAccumBufferSize() and setStencilBufferSize().

    Note that even if you specify that you prefer a 32 bit depth
    buffer (e.g. with setDepthBufferSize(32)), the format that is
    chosen may not have a 32 bit depth buffer, even if there is a
    format available with a 32 bit depth buffer. The main reason for
    this is how the system dependant picking algorithms work on the
    different platforms, and some format options may have higher
    precedence than others.

    You create and tell a QGLFormat object what rendering options you
    want from an OpenGL rendering context.

    OpenGL drivers or accelerated hardware may or may not support
    advanced features such as alpha channel or stereographic viewing.
    If you request some features that the driver/hardware does not
    provide when you create a QGLWidget, you will get a rendering
    context with the nearest subset of features.

    There are different ways to define the display characteristics of
    a rendering context. One is to create a QGLFormat and make it the
    default for the entire application:
    \snippet code/src_opengl_qgl.cpp 0

    Or you can specify the desired format when creating an object of
    your QGLWidget subclass:
    \snippet code/src_opengl_qgl.cpp 1

    After the widget has been created, you can find out which of the
    requested features the system was able to provide:
    \snippet code/src_opengl_qgl.cpp 2

    \legalese
        OpenGL is a trademark of Silicon Graphics, Inc. in the
        United States and other countries.
    \endlegalese

    \sa QGLContext, QGLWidget
*/

#ifndef QT_OPENGL_ES

static inline void transform_point(GLdouble out[4], const GLdouble m[16], const GLdouble in[4])
{
#define M(row,col)  m[col*4+row]
    out[0] =
        M(0, 0) * in[0] + M(0, 1) * in[1] + M(0, 2) * in[2] + M(0, 3) * in[3];
    out[1] =
        M(1, 0) * in[0] + M(1, 1) * in[1] + M(1, 2) * in[2] + M(1, 3) * in[3];
    out[2] =
        M(2, 0) * in[0] + M(2, 1) * in[1] + M(2, 2) * in[2] + M(2, 3) * in[3];
    out[3] =
        M(3, 0) * in[0] + M(3, 1) * in[1] + M(3, 2) * in[2] + M(3, 3) * in[3];
#undef M
}

static inline GLint qgluProject(GLdouble objx, GLdouble objy, GLdouble objz,
           const GLdouble model[16], const GLdouble proj[16],
           const GLint viewport[4],
           GLdouble * winx, GLdouble * winy, GLdouble * winz)
{
   GLdouble in[4], out[4];

   in[0] = objx;
   in[1] = objy;
   in[2] = objz;
   in[3] = 1.0;
   transform_point(out, model, in);
   transform_point(in, proj, out);

   if (in[3] == 0.0)
      return GL_FALSE;

   in[0] /= in[3];
   in[1] /= in[3];
   in[2] /= in[3];

   *winx = viewport[0] + (1 + in[0]) * viewport[2] / 2;
   *winy = viewport[1] + (1 + in[1]) * viewport[3] / 2;

   *winz = (1 + in[2]) / 2;
   return GL_TRUE;
}

#endif // !QT_OPENGL_ES

/*!
    Constructs a QGLFormat object with the following default settings:
    \list
    \li \l{setDoubleBuffer()}{Double buffer:} Enabled.
    \li \l{setDepth()}{Depth buffer:} Enabled.
    \li \l{setRgba()}{RGBA:} Enabled (i.e., color index disabled).
    \li \l{setAlpha()}{Alpha channel:} Disabled.
    \li \l{setAccum()}{Accumulator buffer:} Disabled.
    \li \l{setStencil()}{Stencil buffer:} Enabled.
    \li \l{setStereo()}{Stereo:} Disabled.
    \li \l{setDirectRendering()}{Direct rendering:} Enabled.
    \li \l{setOverlay()}{Overlay:} Disabled.
    \li \l{setPlane()}{Plane:} 0 (i.e., normal plane).
    \li \l{setSampleBuffers()}{Multisample buffers:} Disabled.
    \endlist
*/

QGLFormat::QGLFormat()
{
    d = new QGLFormatPrivate;
}


/*!
    Creates a QGLFormat object that is a copy of the current
    defaultFormat().

    If \a options is not 0, the default format is modified by the
    specified format options. The \a options parameter should be
    QGL::FormatOption values OR'ed together.

    This constructor makes it easy to specify a certain desired format
    in classes derived from QGLWidget, for example:
    \snippet code/src_opengl_qgl.cpp 3

    Note that there are QGL::FormatOption values to turn format settings
    both on and off, e.g. QGL::DepthBuffer and QGL::NoDepthBuffer,
    QGL::DirectRendering and QGL::IndirectRendering, etc.

    The \a plane parameter defaults to 0 and is the plane which this
    format should be associated with. Not all OpenGL implementations
    supports overlay/underlay rendering planes.

    \sa defaultFormat(), setOption(), setPlane()
*/

QGLFormat::QGLFormat(QGL::FormatOptions options, int plane)
{
    d = new QGLFormatPrivate;
    QGL::FormatOptions newOpts = options;
    d->opts = defaultFormat().d->opts;
    d->opts |= (newOpts & 0xffff);
    d->opts &= ~(newOpts >> 16);
    d->pln = plane;
}

/*!
    \internal
*/
void QGLFormat::detach()
{
    if (d->ref.load() != 1) {
        QGLFormatPrivate *newd = new QGLFormatPrivate(d);
        if (!d->ref.deref())
            delete d;
        d = newd;
    }
}

/*!
    Constructs a copy of \a other.
*/

QGLFormat::QGLFormat(const QGLFormat &other)
{
    d = other.d;
    d->ref.ref();
}

/*!
    Assigns \a other to this object.
*/

QGLFormat &QGLFormat::operator=(const QGLFormat &other)
{
    if (d != other.d) {
        other.d->ref.ref();
        if (!d->ref.deref())
            delete d;
        d = other.d;
    }
    return *this;
}

/*!
    Destroys the QGLFormat.
*/
QGLFormat::~QGLFormat()
{
    if (!d->ref.deref())
        delete d;
}

/*!
    \fn bool QGLFormat::doubleBuffer() const

    Returns \c true if double buffering is enabled; otherwise returns
    false. Double buffering is enabled by default.

    \sa setDoubleBuffer()
*/

/*!
    If \a enable is true sets double buffering; otherwise sets single
    buffering.

    Double buffering is enabled by default.

    Double buffering is a technique where graphics are rendered on an
    off-screen buffer and not directly to the screen. When the drawing
    has been completed, the program calls a swapBuffers() function to
    exchange the screen contents with the buffer. The result is
    flicker-free drawing and often better performance.

    Note that single buffered contexts are currently not supported
    with EGL.

    \sa doubleBuffer(), QGLContext::swapBuffers(),
    QGLWidget::swapBuffers()
*/

void QGLFormat::setDoubleBuffer(bool enable)
{
    setOption(enable ? QGL::DoubleBuffer : QGL::SingleBuffer);
}


/*!
    \fn bool QGLFormat::depth() const

    Returns \c true if the depth buffer is enabled; otherwise returns
    false. The depth buffer is enabled by default.

    \sa setDepth(), setDepthBufferSize()
*/

/*!
    If \a enable is true enables the depth buffer; otherwise disables
    the depth buffer.

    The depth buffer is enabled by default.

    The purpose of a depth buffer (or Z-buffering) is to remove hidden
    surfaces. Pixels are assigned Z values based on the distance to
    the viewer. A pixel with a high Z value is closer to the viewer
    than a pixel with a low Z value. This information is used to
    decide whether to draw a pixel or not.

    \sa depth(), setDepthBufferSize()
*/

void QGLFormat::setDepth(bool enable)
{
    setOption(enable ? QGL::DepthBuffer : QGL::NoDepthBuffer);
}


/*!
    \fn bool QGLFormat::rgba() const

    Returns \c true if RGBA color mode is set. Returns \c false if color
    index mode is set. The default color mode is RGBA.

    \sa setRgba()
*/

/*!
    If \a enable is true sets RGBA mode. If \a enable is false sets
    color index mode.

    The default color mode is RGBA.

    RGBA is the preferred mode for most OpenGL applications. In RGBA
    color mode you specify colors as red + green + blue + alpha
    quadruplets.

    In color index mode you specify an index into a color lookup
    table.

    \sa rgba()
*/

void QGLFormat::setRgba(bool enable)
{
    setOption(enable ? QGL::Rgba : QGL::ColorIndex);
}


/*!
    \fn bool QGLFormat::alpha() const

    Returns \c true if the alpha buffer in the framebuffer is enabled;
    otherwise returns \c false. The alpha buffer is disabled by default.

    \sa setAlpha(), setAlphaBufferSize()
*/

/*!
    If \a enable is true enables the alpha buffer; otherwise disables
    the alpha buffer.

    The alpha buffer is disabled by default.

    The alpha buffer is typically used for implementing transparency
    or translucency. The A in RGBA specifies the transparency of a
    pixel.

    \sa alpha(), setAlphaBufferSize()
*/

void QGLFormat::setAlpha(bool enable)
{
    setOption(enable ? QGL::AlphaChannel : QGL::NoAlphaChannel);
}


/*!
    \fn bool QGLFormat::accum() const

    Returns \c true if the accumulation buffer is enabled; otherwise
    returns \c false. The accumulation buffer is disabled by default.

    \sa setAccum(), setAccumBufferSize()
*/

/*!
    If \a enable is true enables the accumulation buffer; otherwise
    disables the accumulation buffer.

    The accumulation buffer is disabled by default.

    The accumulation buffer is used to create blur effects and
    multiple exposures.

    \sa accum(), setAccumBufferSize()
*/

void QGLFormat::setAccum(bool enable)
{
    setOption(enable ? QGL::AccumBuffer : QGL::NoAccumBuffer);
}


/*!
    \fn bool QGLFormat::stencil() const

    Returns \c true if the stencil buffer is enabled; otherwise returns
    false. The stencil buffer is enabled by default.

    \sa setStencil(), setStencilBufferSize()
*/

/*!
    If \a enable is true enables the stencil buffer; otherwise
    disables the stencil buffer.

    The stencil buffer is enabled by default.

    The stencil buffer masks certain parts of the drawing area so that
    masked parts are not drawn on.

    \sa stencil(), setStencilBufferSize()
*/

void QGLFormat::setStencil(bool enable)
{
    setOption(enable ? QGL::StencilBuffer: QGL::NoStencilBuffer);
}


/*!
    \fn bool QGLFormat::stereo() const

    Returns \c true if stereo buffering is enabled; otherwise returns
    false. Stereo buffering is disabled by default.

    \sa setStereo()
*/

/*!
    If \a enable is true enables stereo buffering; otherwise disables
    stereo buffering.

    Stereo buffering is disabled by default.

    Stereo buffering provides extra color buffers to generate left-eye
    and right-eye images.

    \sa stereo()
*/

void QGLFormat::setStereo(bool enable)
{
    setOption(enable ? QGL::StereoBuffers : QGL::NoStereoBuffers);
}


/*!
    \fn bool QGLFormat::directRendering() const

    Returns \c true if direct rendering is enabled; otherwise returns
    false.

    Direct rendering is enabled by default.

    \sa setDirectRendering()
*/

/*!
    If \a enable is true enables direct rendering; otherwise disables
    direct rendering.

    Direct rendering is enabled by default.

    Enabling this option will make OpenGL bypass the underlying window
    system and render directly from hardware to the screen, if this is
    supported by the system.

    \sa directRendering()
*/

void QGLFormat::setDirectRendering(bool enable)
{
    setOption(enable ? QGL::DirectRendering : QGL::IndirectRendering);
}

/*!
    \fn bool QGLFormat::sampleBuffers() const

    Returns \c true if multisample buffer support is enabled; otherwise
    returns \c false.

    The multisample buffer is disabled by default.

    \sa setSampleBuffers()
*/

/*!
    If \a enable is true, a GL context with multisample buffer support
    is picked; otherwise ignored.

    \sa sampleBuffers(), setSamples(), samples()
*/
void QGLFormat::setSampleBuffers(bool enable)
{
    setOption(enable ? QGL::SampleBuffers : QGL::NoSampleBuffers);
}

/*!
    Returns the number of samples per pixel when multisampling is
    enabled. By default, the highest number of samples that is
    available is used.

    \sa setSampleBuffers(), sampleBuffers(), setSamples()
*/
int QGLFormat::samples() const
{
   return d->numSamples;
}

/*!
    Set the preferred number of samples per pixel when multisampling
    is enabled to \a numSamples. By default, the highest number of
    samples available is used.

    \sa setSampleBuffers(), sampleBuffers(), samples()
*/
void QGLFormat::setSamples(int numSamples)
{
    detach();
    if (numSamples < 0) {
        qWarning("QGLFormat::setSamples: Cannot have negative number of samples per pixel %d", numSamples);
        return;
    }
    d->numSamples = numSamples;
    setSampleBuffers(numSamples > 0);
}

/*!
    \since 4.2

    Set the preferred swap interval. This can be used to sync the GL
    drawing into a system window to the vertical refresh of the screen.
    Setting an \a interval value of 0 will turn the vertical refresh syncing
    off, any value higher than 0 will turn the vertical syncing on.

    Under Windows and under X11, where the \c{WGL_EXT_swap_control}
    and \c{GLX_SGI_video_sync} extensions are used, the \a interval
    parameter can be used to set the minimum number of video frames
    that are displayed before a buffer swap will occur. In effect,
    setting the \a interval to 10, means there will be 10 vertical
    retraces between every buffer swap.

    Under Windows the \c{WGL_EXT_swap_control} extension has to be present,
    and under X11 the \c{GLX_SGI_video_sync} extension has to be present.
*/
void QGLFormat::setSwapInterval(int interval)
{
    detach();
    d->swapInterval = interval;
}

/*!
    \since 4.2

    Returns the currently set swap interval. -1 is returned if setting
    the swap interval isn't supported in the system GL implementation.
*/
int QGLFormat::swapInterval() const
{
    return d->swapInterval;
}

/*!
    \fn bool QGLFormat::hasOverlay() const

    Returns \c true if overlay plane is enabled; otherwise returns \c false.

    Overlay is disabled by default.

    \sa setOverlay()
*/

/*!
    If \a enable is true enables an overlay plane; otherwise disables
    the overlay plane.

    Enabling the overlay plane will cause QGLWidget to create an
    additional context in an overlay plane. See the QGLWidget
    documentation for further information.

    \sa hasOverlay()
*/

void QGLFormat::setOverlay(bool enable)
{
    setOption(enable ? QGL::HasOverlay : QGL::NoOverlay);
}

/*!
    Returns the plane of this format. The default for normal formats
    is 0, which means the normal plane. The default for overlay
    formats is 1, which is the first overlay plane.

    \sa setPlane(), defaultOverlayFormat()
*/
int QGLFormat::plane() const
{
    return d->pln;
}

/*!
    Sets the requested plane to \a plane. 0 is the normal plane, 1 is
    the first overlay plane, 2 is the second overlay plane, etc.; -1,
    -2, etc. are underlay planes.

    Note that in contrast to other format specifications, the plane
    specifications will be matched exactly. This means that if you
    specify a plane that the underlying OpenGL system cannot provide,
    an \l{QGLWidget::isValid()}{invalid} QGLWidget will be
    created.

    \sa plane()
*/
void QGLFormat::setPlane(int plane)
{
    detach();
    d->pln = plane;
}

/*!
    Sets the format option to \a opt.

    \sa testOption()
*/

void QGLFormat::setOption(QGL::FormatOptions opt)
{
    detach();
    if (opt & 0xffff)
        d->opts |= opt;
    else
       d->opts &= ~(opt >> 16);
}



/*!
    Returns \c true if format option \a opt is set; otherwise returns \c false.

    \sa setOption()
*/

bool QGLFormat::testOption(QGL::FormatOptions opt) const
{
    if (opt & 0xffff)
       return (d->opts & opt) != 0;
    else
       return (d->opts & (opt >> 16)) == 0;
}

/*!
    Set the minimum depth buffer size to \a size.

    \sa depthBufferSize(), setDepth(), depth()
*/
void QGLFormat::setDepthBufferSize(int size)
{
    detach();
    if (size < 0) {
        qWarning("QGLFormat::setDepthBufferSize: Cannot set negative depth buffer size %d", size);
        return;
    }
    d->depthSize = size;
    setDepth(size > 0);
}

/*!
    Returns the depth buffer size.

    \sa depth(), setDepth(), setDepthBufferSize()
*/
int QGLFormat::depthBufferSize() const
{
   return d->depthSize;
}

/*!
    \since 4.2

    Set the preferred red buffer size to \a size.

    \sa setGreenBufferSize(), setBlueBufferSize(), setAlphaBufferSize()
*/
void QGLFormat::setRedBufferSize(int size)
{
    detach();
    if (size < 0) {
        qWarning("QGLFormat::setRedBufferSize: Cannot set negative red buffer size %d", size);
        return;
    }
    d->redSize = size;
}

/*!
    \since 4.2

    Returns the red buffer size.

    \sa setRedBufferSize()
*/
int QGLFormat::redBufferSize() const
{
   return d->redSize;
}

/*!
    \since 4.2

    Set the preferred green buffer size to \a size.

    \sa setRedBufferSize(), setBlueBufferSize(), setAlphaBufferSize()
*/
void QGLFormat::setGreenBufferSize(int size)
{
    detach();
    if (size < 0) {
        qWarning("QGLFormat::setGreenBufferSize: Cannot set negative green buffer size %d", size);
        return;
    }
    d->greenSize = size;
}

/*!
    \since 4.2

    Returns the green buffer size.

    \sa setGreenBufferSize()
*/
int QGLFormat::greenBufferSize() const
{
   return d->greenSize;
}

/*!
    \since 4.2

    Set the preferred blue buffer size to \a size.

    \sa setRedBufferSize(), setGreenBufferSize(), setAlphaBufferSize()
*/
void QGLFormat::setBlueBufferSize(int size)
{
    detach();
    if (size < 0) {
        qWarning("QGLFormat::setBlueBufferSize: Cannot set negative blue buffer size %d", size);
        return;
    }
    d->blueSize = size;
}

/*!
    \since 4.2

    Returns the blue buffer size.

    \sa setBlueBufferSize()
*/
int QGLFormat::blueBufferSize() const
{
   return d->blueSize;
}

/*!
    Set the preferred alpha buffer size to \a size.
    This function implicitly enables the alpha channel.

    \sa setRedBufferSize(), setGreenBufferSize(), alphaBufferSize()
*/
void QGLFormat::setAlphaBufferSize(int size)
{
    detach();
    if (size < 0) {
        qWarning("QGLFormat::setAlphaBufferSize: Cannot set negative alpha buffer size %d", size);
        return;
    }
    d->alphaSize = size;
    setAlpha(size > 0);
}

/*!
    Returns the alpha buffer size.

    \sa alpha(), setAlpha(), setAlphaBufferSize()
*/
int QGLFormat::alphaBufferSize() const
{
   return d->alphaSize;
}

/*!
    Set the preferred accumulation buffer size, where \a size is the
    bit depth for each RGBA component.

    \sa accum(), setAccum(), accumBufferSize()
*/
void QGLFormat::setAccumBufferSize(int size)
{
    detach();
    if (size < 0) {
        qWarning("QGLFormat::setAccumBufferSize: Cannot set negative accumulate buffer size %d", size);
        return;
    }
    d->accumSize = size;
    setAccum(size > 0);
}

/*!
    Returns the accumulation buffer size.

    \sa setAccumBufferSize(), accum(), setAccum()
*/
int QGLFormat::accumBufferSize() const
{
   return d->accumSize;
}

/*!
    Set the preferred stencil buffer size to \a size.

    \sa stencilBufferSize(), setStencil(), stencil()
*/
void QGLFormat::setStencilBufferSize(int size)
{
    detach();
    if (size < 0) {
        qWarning("QGLFormat::setStencilBufferSize: Cannot set negative stencil buffer size %d", size);
        return;
    }
    d->stencilSize = size;
    setStencil(size > 0);
}

/*!
    Returns the stencil buffer size.

    \sa stencil(), setStencil(), setStencilBufferSize()
*/
int QGLFormat::stencilBufferSize() const
{
   return d->stencilSize;
}

/*!
    \since 4.7

    Set the OpenGL version to the \a major and \a minor numbers. If a
    context compatible with the requested OpenGL version cannot be
    created, a context compatible with version 1.x is created instead.

    \sa majorVersion(), minorVersion()
*/
void QGLFormat::setVersion(int major, int minor)
{
    if (major < 1 || minor < 0) {
        qWarning("QGLFormat::setVersion: Cannot set zero or negative version number %d.%d", major, minor);
        return;
    }
    detach();
    d->majorVersion = major;
    d->minorVersion = minor;
}

/*!
    \since 4.7

    Returns the OpenGL major version.

    \sa setVersion(), minorVersion()
*/
int QGLFormat::majorVersion() const
{
    return d->majorVersion;
}

/*!
    \since 4.7

    Returns the OpenGL minor version.

    \sa setVersion(), majorVersion()
*/
int QGLFormat::minorVersion() const
{
    return d->minorVersion;
}

/*!
    \enum QGLFormat::OpenGLContextProfile
    \since 4.7

    This enum describes the OpenGL context profiles that can be
    specified for contexts implementing OpenGL version 3.2 or
    higher. These profiles are different from OpenGL ES profiles.

    \value NoProfile            OpenGL version is lower than 3.2.
    \value CoreProfile          Functionality deprecated in OpenGL version 3.0 is not available.
    \value CompatibilityProfile Functionality from earlier OpenGL versions is available.
*/

/*!
    \since 4.7

    Set the OpenGL context profile to \a profile. The \a profile is
    ignored if the requested OpenGL version is less than 3.2.

    \sa profile()
*/
void QGLFormat::setProfile(OpenGLContextProfile profile)
{
    detach();
    d->profile = profile;
}

/*!
    \since 4.7

    Returns the OpenGL context profile.

    \sa setProfile()
*/
QGLFormat::OpenGLContextProfile QGLFormat::profile() const
{
    return d->profile;
}


/*!
    \fn bool QGLFormat::hasOpenGL()

    Returns \c true if the window system has any OpenGL support;
    otherwise returns \c false.

    \warning This function must not be called until the QApplication
    object has been created.
*/



/*!
    \fn bool QGLFormat::hasOpenGLOverlays()

    Returns \c true if the window system supports OpenGL overlays;
    otherwise returns \c false.

    \warning This function must not be called until the QApplication
    object has been created.
*/

QGLFormat::OpenGLVersionFlags Q_AUTOTEST_EXPORT qOpenGLVersionFlagsFromString(const QString &versionString)
{
    QGLFormat::OpenGLVersionFlags versionFlags = QGLFormat::OpenGL_Version_None;

    if (versionString.startsWith(QLatin1String("OpenGL ES"))) {
        QStringList parts = versionString.split(QLatin1Char(' '));
        if (parts.size() >= 3) {
            if (parts[2].startsWith(QLatin1String("1."))) {
                if (parts[1].endsWith(QLatin1String("-CM"))) {
                    versionFlags |= QGLFormat::OpenGL_ES_Common_Version_1_0 |
                                    QGLFormat::OpenGL_ES_CommonLite_Version_1_0;
                    if (parts[2].startsWith(QLatin1String("1.1")))
                        versionFlags |= QGLFormat::OpenGL_ES_Common_Version_1_1 |
                                        QGLFormat::OpenGL_ES_CommonLite_Version_1_1;
                } else {
                    // Not -CM, must be CL, CommonLite
                    versionFlags |= QGLFormat::OpenGL_ES_CommonLite_Version_1_0;
                    if (parts[2].startsWith(QLatin1String("1.1")))
                        versionFlags |= QGLFormat::OpenGL_ES_CommonLite_Version_1_1;
                }
            } else {
                // OpenGL ES version 2.0 or higher
                versionFlags |= QGLFormat::OpenGL_ES_Version_2_0;
            }
        } else {
            // if < 3 parts to the name, it is an unrecognised OpenGL ES
            qWarning("Unrecognised OpenGL ES version");
        }
    } else {
        // not ES, regular OpenGL, the version numbers are first in the string
        if (versionString.startsWith(QLatin1String("1."))) {
            switch (versionString[2].toLatin1()) {
            case '5':
                versionFlags |= QGLFormat::OpenGL_Version_1_5;
            case '4':
                versionFlags |= QGLFormat::OpenGL_Version_1_4;
            case '3':
                versionFlags |= QGLFormat::OpenGL_Version_1_3;
            case '2':
                versionFlags |= QGLFormat::OpenGL_Version_1_2;
            case '1':
                versionFlags |= QGLFormat::OpenGL_Version_1_1;
            default:
                break;
            }
        } else if (versionString.startsWith(QLatin1String("2."))) {
            versionFlags |= QGLFormat::OpenGL_Version_1_1 |
                            QGLFormat::OpenGL_Version_1_2 |
                            QGLFormat::OpenGL_Version_1_3 |
                            QGLFormat::OpenGL_Version_1_4 |
                            QGLFormat::OpenGL_Version_1_5 |
                            QGLFormat::OpenGL_Version_2_0;
            if (versionString[2].toLatin1() == '1')
                versionFlags |= QGLFormat::OpenGL_Version_2_1;
        } else if (versionString.startsWith(QLatin1String("3."))) {
            versionFlags |= QGLFormat::OpenGL_Version_1_1 |
                            QGLFormat::OpenGL_Version_1_2 |
                            QGLFormat::OpenGL_Version_1_3 |
                            QGLFormat::OpenGL_Version_1_4 |
                            QGLFormat::OpenGL_Version_1_5 |
                            QGLFormat::OpenGL_Version_2_0 |
                            QGLFormat::OpenGL_Version_2_1 |
                            QGLFormat::OpenGL_Version_3_0;
            switch (versionString[2].toLatin1()) {
            case '3':
                versionFlags |= QGLFormat::OpenGL_Version_3_3;
            case '2':
                versionFlags |= QGLFormat::OpenGL_Version_3_2;
            case '1':
                versionFlags |= QGLFormat::OpenGL_Version_3_1;
            case '0':
                break;
            default:
                versionFlags |= QGLFormat::OpenGL_Version_3_1 |
                                QGLFormat::OpenGL_Version_3_2 |
                                QGLFormat::OpenGL_Version_3_3;
                break;
            }
        } else if (versionString.startsWith(QLatin1String("4."))) {
            versionFlags |= QGLFormat::OpenGL_Version_1_1 |
                            QGLFormat::OpenGL_Version_1_2 |
                            QGLFormat::OpenGL_Version_1_3 |
                            QGLFormat::OpenGL_Version_1_4 |
                            QGLFormat::OpenGL_Version_1_5 |
                            QGLFormat::OpenGL_Version_2_0 |
                            QGLFormat::OpenGL_Version_2_1 |
                            QGLFormat::OpenGL_Version_3_0 |
                            QGLFormat::OpenGL_Version_3_1 |
                            QGLFormat::OpenGL_Version_3_2 |
                            QGLFormat::OpenGL_Version_3_3 |
                            QGLFormat::OpenGL_Version_4_0;
            switch (versionString[2].toLatin1()) {
            case '3':
                versionFlags |= QGLFormat::OpenGL_Version_4_3;
            case '2':
                versionFlags |= QGLFormat::OpenGL_Version_4_2;
            case '1':
                versionFlags |= QGLFormat::OpenGL_Version_4_1;
            case '0':
                break;
            default:
                versionFlags |= QGLFormat::OpenGL_Version_4_1 |
                                QGLFormat::OpenGL_Version_4_2 |
                                QGLFormat::OpenGL_Version_4_3;
                break;
            }
        } else {
            versionFlags |= QGLFormat::OpenGL_Version_1_1 |
                            QGLFormat::OpenGL_Version_1_2 |
                            QGLFormat::OpenGL_Version_1_3 |
                            QGLFormat::OpenGL_Version_1_4 |
                            QGLFormat::OpenGL_Version_1_5 |
                            QGLFormat::OpenGL_Version_2_0 |
                            QGLFormat::OpenGL_Version_2_1 |
                            QGLFormat::OpenGL_Version_3_0 |
                            QGLFormat::OpenGL_Version_3_1 |
                            QGLFormat::OpenGL_Version_3_2 |
                            QGLFormat::OpenGL_Version_3_3 |
                            QGLFormat::OpenGL_Version_4_0 |
                            QGLFormat::OpenGL_Version_4_1 |
                            QGLFormat::OpenGL_Version_4_2 |
                            QGLFormat::OpenGL_Version_4_3;
        }
    }
    return versionFlags;
}

/*!
    \enum QGLFormat::OpenGLVersionFlag
    \since 4.2

    This enum describes the various OpenGL versions that are
    recognized by Qt. Use the QGLFormat::openGLVersionFlags() function
    to identify which versions that are supported at runtime.

    \value OpenGL_Version_None  If no OpenGL is present or if no OpenGL context is current.

    \value OpenGL_Version_1_1  OpenGL version 1.1 or higher is present.

    \value OpenGL_Version_1_2  OpenGL version 1.2 or higher is present.

    \value OpenGL_Version_1_3  OpenGL version 1.3 or higher is present.

    \value OpenGL_Version_1_4  OpenGL version 1.4 or higher is present.

    \value OpenGL_Version_1_5  OpenGL version 1.5 or higher is present.

    \value OpenGL_Version_2_0  OpenGL version 2.0 or higher is present.
    Note that version 2.0 supports all the functionality of version 1.5.

    \value OpenGL_Version_2_1  OpenGL version 2.1 or higher is present.

    \value OpenGL_Version_3_0  OpenGL version 3.0 or higher is present.

    \value OpenGL_Version_3_1  OpenGL version 3.1 or higher is present.
    Note that OpenGL version 3.1 or higher does not necessarily support all the features of
    version 3.0 and lower.

    \value OpenGL_Version_3_2  OpenGL version 3.2 or higher is present.

    \value OpenGL_Version_3_3  OpenGL version 3.3 or higher is present.

    \value OpenGL_Version_4_0  OpenGL version 4.0 or higher is present.

    \value OpenGL_Version_4_1  OpenGL version 4.1 or higher is present.

    \value OpenGL_Version_4_2  OpenGL version 4.2 or higher is present.

    \value OpenGL_Version_4_3  OpenGL version 4.3 or higher is present.

    \value OpenGL_ES_CommonLite_Version_1_0  OpenGL ES version 1.0 Common Lite or higher is present.

    \value OpenGL_ES_Common_Version_1_0  OpenGL ES version 1.0 Common or higher is present.
    The Common profile supports all the features of Common Lite.

    \value OpenGL_ES_CommonLite_Version_1_1  OpenGL ES version 1.1 Common Lite or higher is present.

    \value OpenGL_ES_Common_Version_1_1  OpenGL ES version 1.1 Common or higher is present.
    The Common profile supports all the features of Common Lite.

    \value OpenGL_ES_Version_2_0  OpenGL ES version 2.0 or higher is present.
    Note that OpenGL ES version 2.0 does not support all the features of OpenGL ES 1.x.
    So if OpenGL_ES_Version_2_0 is returned, none of the ES 1.x flags are returned.

    See also \l{http://www.opengl.org} for more information about the different
    revisions of OpenGL.

    \sa openGLVersionFlags()
*/

/*!
    \since 4.2

    Identifies, at runtime, which OpenGL versions that are supported
    by the current platform.

    Note that if OpenGL version 1.5 is supported, its predecessors
    (i.e., version 1.4 and lower) are also supported. To identify the
    support of a particular feature, like multi texturing, test for
    the version in which the feature was first introduced (i.e.,
    version 1.3 in the case of multi texturing) to adapt to the largest
    possible group of runtime platforms.

    This function needs a valid current OpenGL context to work;
    otherwise it will return OpenGL_Version_None.

    \sa hasOpenGL(), hasOpenGLOverlays()
*/
QGLFormat::OpenGLVersionFlags QGLFormat::openGLVersionFlags()
{
    static bool cachedDefault = false;
    static OpenGLVersionFlags defaultVersionFlags = OpenGL_Version_None;
    QGLContext *currentCtx = const_cast<QGLContext *>(QGLContext::currentContext());
    QGLTemporaryContext *tmpContext = 0;

    if (currentCtx && currentCtx->d_func()->version_flags_cached)
        return currentCtx->d_func()->version_flags;

    if (!currentCtx) {
        if (cachedDefault) {
            return defaultVersionFlags;
        } else {
            if (!hasOpenGL())
                return defaultVersionFlags;
            tmpContext = new QGLTemporaryContext;
            cachedDefault = true;
        }
    }

    QString versionString(QLatin1String(reinterpret_cast<const char*>(glGetString(GL_VERSION))));
    OpenGLVersionFlags versionFlags = qOpenGLVersionFlagsFromString(versionString);
    if (currentCtx) {
        currentCtx->d_func()->version_flags_cached = true;
        currentCtx->d_func()->version_flags = versionFlags;
    }
    if (tmpContext) {
        defaultVersionFlags = versionFlags;
        delete tmpContext;
    }

    return versionFlags;
}


/*!
    Returns the default QGLFormat for the application. All QGLWidget
    objects that are created use this format unless another format is
    specified, e.g. when they are constructed.

    If no special default format has been set using
    setDefaultFormat(), the default format is the same as that created
    with QGLFormat().

    \sa setDefaultFormat()
*/

QGLFormat QGLFormat::defaultFormat()
{
    return *qgl_default_format();
}

/*!
    Sets a new default QGLFormat for the application to \a f. For
    example, to set single buffering as the default instead of double
    buffering, your main() might contain code like this:
    \snippet code/src_opengl_qgl.cpp 4

    \sa defaultFormat()
*/

void QGLFormat::setDefaultFormat(const QGLFormat &f)
{
    *qgl_default_format() = f;
}


/*!
    Returns the default QGLFormat for overlay contexts.

    The default overlay format is:
    \list
    \li \l{setDoubleBuffer()}{Double buffer:} Disabled.
    \li \l{setDepth()}{Depth buffer:} Disabled.
    \li \l{setRgba()}{RGBA:} Disabled (i.e., color index enabled).
    \li \l{setAlpha()}{Alpha channel:} Disabled.
    \li \l{setAccum()}{Accumulator buffer:} Disabled.
    \li \l{setStencil()}{Stencil buffer:} Disabled.
    \li \l{setStereo()}{Stereo:} Disabled.
    \li \l{setDirectRendering()}{Direct rendering:} Enabled.
    \li \l{setOverlay()}{Overlay:} Disabled.
    \li \l{setSampleBuffers()}{Multisample buffers:} Disabled.
    \li \l{setPlane()}{Plane:} 1 (i.e., first overlay plane).
    \endlist

    \sa setDefaultFormat()
*/

QGLFormat QGLFormat::defaultOverlayFormat()
{
    return *defaultOverlayFormatInstance();
}

/*!
    Sets a new default QGLFormat for overlay contexts to \a f. This
    format is used whenever a QGLWidget is created with a format that
    hasOverlay() enabled.

    For example, to get a double buffered overlay context (if
    available), use code like this:

    \snippet code/src_opengl_qgl.cpp 5

    As usual, you can find out after widget creation whether the
    underlying OpenGL system was able to provide the requested
    specification:

    \snippet code/src_opengl_qgl.cpp 6

    \sa defaultOverlayFormat()
*/

void QGLFormat::setDefaultOverlayFormat(const QGLFormat &f)
{
    QGLFormat *defaultFormat = defaultOverlayFormatInstance();
    *defaultFormat = f;
    // Make sure the user doesn't request that the overlays themselves
    // have overlays, since it is unlikely that the system supports
    // infinitely many planes...
    defaultFormat->setOverlay(false);
}


/*!
    Returns \c true if all the options of the two QGLFormat objects
    \a a and \a b are equal; otherwise returns \c false.

    \relates QGLFormat
*/

bool operator==(const QGLFormat& a, const QGLFormat& b)
{
    return (a.d == b.d) || ((int) a.d->opts == (int) b.d->opts
        && a.d->pln == b.d->pln
        && a.d->alphaSize == b.d->alphaSize
        && a.d->accumSize == b.d->accumSize
        && a.d->stencilSize == b.d->stencilSize
        && a.d->depthSize == b.d->depthSize
        && a.d->redSize == b.d->redSize
        && a.d->greenSize == b.d->greenSize
        && a.d->blueSize == b.d->blueSize
        && a.d->numSamples == b.d->numSamples
        && a.d->swapInterval == b.d->swapInterval
        && a.d->majorVersion == b.d->majorVersion
        && a.d->minorVersion == b.d->minorVersion
        && a.d->profile == b.d->profile);
}

#ifndef QT_NO_DEBUG_STREAM
QDebug operator<<(QDebug dbg, const QGLFormat &f)
{
    const QGLFormatPrivate * const d = f.d;

    dbg.nospace() << "QGLFormat("
                  << "options " << d->opts
                  << ", plane " << d->pln
                  << ", depthBufferSize " << d->depthSize
                  << ", accumBufferSize " << d->accumSize
                  << ", stencilBufferSize " << d->stencilSize
                  << ", redBufferSize " << d->redSize
                  << ", greenBufferSize " << d->greenSize
                  << ", blueBufferSize " << d->blueSize
                  << ", alphaBufferSize " << d->alphaSize
                  << ", samples " << d->numSamples
                  << ", swapInterval " << d->swapInterval
                  << ", majorVersion " << d->majorVersion
                  << ", minorVersion " << d->minorVersion
                  << ", profile " << d->profile
                  << ')';

    return dbg.space();
}
#endif


/*!
    Returns \c false if all the options of the two QGLFormat objects
    \a a and \a b are equal; otherwise returns \c true.

    \relates QGLFormat
*/

bool operator!=(const QGLFormat& a, const QGLFormat& b)
{
    return !(a == b);
}

struct QGLContextGroupList {
    QGLContextGroupList()
        : m_mutex(QMutex::Recursive)
    {
    }

    void append(QGLContextGroup *group) {
        QMutexLocker locker(&m_mutex);
        m_list.append(group);
    }

    void remove(QGLContextGroup *group) {
        QMutexLocker locker(&m_mutex);
        m_list.removeOne(group);
    }

    QList<QGLContextGroup *> m_list;
    QMutex m_mutex;
};

Q_GLOBAL_STATIC(QGLContextGroupList, qt_context_groups)

/*****************************************************************************
  QGLContext implementation
 *****************************************************************************/

QGLContextGroup::QGLContextGroup(const QGLContext *context)
    : m_context(context), m_refs(1)
{
    qt_context_groups()->append(this);
}

QGLContextGroup::~QGLContextGroup()
{
    qt_context_groups()->remove(this);
}

const QGLContext *qt_gl_transfer_context(const QGLContext *ctx)
{
    if (!ctx)
        return 0;
    QList<const QGLContext *> shares
        (QGLContextPrivate::contextGroup(ctx)->shares());
    if (shares.size() >= 2)
        return (ctx == shares.at(0)) ? shares.at(1) : shares.at(0);
    else
        return 0;
}

QGLContextPrivate::QGLContextPrivate(QGLContext *context)
    : internal_context(false)
    , q_ptr(context)
    , texture_destroyer(0)
    , functions(0)
{
    group = new QGLContextGroup(context);

    texture_destroyer = new QGLTextureDestroyer;
}

QGLContextPrivate::~QGLContextPrivate()
{
    delete functions;

    if (!group->m_refs.deref()) {
        Q_ASSERT(group->context() == q_ptr);
        delete group;
    }

    delete texture_destroyer;
}

void QGLContextPrivate::init(QPaintDevice *dev, const QGLFormat &format)
{
    Q_Q(QGLContext);
    glFormat = reqFormat = format;
    valid = false;
    q->setDevice(dev);

    guiGlContext = 0;
    ownContext = false;
    fbo = 0;
    crWin = false;
    initDone = false;
    sharing = false;
    max_texture_size = -1;
    version_flags_cached = false;
    version_flags = QGLFormat::OpenGL_Version_None;
    current_fbo = 0;
    default_fbo = 0;
    active_engine = 0;
    workaround_needsFullClearOnEveryFrame = false;
    workaround_brokenFBOReadBack = false;
    workaround_brokenTexSubImage = false;
    workaroundsCached = false;

    workaround_brokenTextureFromPixmap = false;
    workaround_brokenTextureFromPixmap_init = false;

    workaround_brokenAlphaTexSubImage = false;
    workaround_brokenAlphaTexSubImage_init = false;

    for (int i = 0; i < QT_GL_VERTEX_ARRAY_TRACKED_COUNT; ++i)
        vertexAttributeArraysEnabledState[i] = false;
}

QGLContext* QGLContext::currentCtx = 0;

/*
   Read back the contents of the currently bound framebuffer, used in
   QGLWidget::grabFrameBuffer(), QGLPixelbuffer::toImage() and
   QGLFramebufferObject::toImage()
*/

static void convertFromGLImage(QImage &img, int w, int h, bool alpha_format, bool include_alpha)
{
    Q_ASSERT(!img.isNull());
    if (QSysInfo::ByteOrder == QSysInfo::BigEndian) {
        // OpenGL gives RGBA; Qt wants ARGB
        uint *p = (uint*)img.bits();
        uint *end = p + w*h;
        if (alpha_format && include_alpha) {
            while (p < end) {
                uint a = *p << 24;
                *p = (*p >> 8) | a;
                p++;
            }
        } else {
            // This is an old legacy fix for PowerPC based Macs, which
            // we shouldn't remove
            while (p < end) {
                *p = 0xff000000 | (*p>>8);
                ++p;
            }
        }
    } else {
        // OpenGL gives ABGR (i.e. RGBA backwards); Qt wants ARGB
        for (int y = 0; y < h; y++) {
            uint *q = (uint*)img.scanLine(y);
            for (int x=0; x < w; ++x) {
                const uint pixel = *q;
                if (alpha_format && include_alpha) {
                    *q = ((pixel << 16) & 0xff0000) | ((pixel >> 16) & 0xff)
                         | (pixel & 0xff00ff00);
                } else {
                    *q = 0xff000000 | ((pixel << 16) & 0xff0000)
                         | ((pixel >> 16) & 0xff) | (pixel & 0x00ff00);
                }

                q++;
            }
        }

    }
    img = img.mirrored();
}

QImage qt_gl_read_frame_buffer(const QSize &size, bool alpha_format, bool include_alpha)
{
    QImage img(size, (alpha_format && include_alpha) ? QImage::Format_ARGB32_Premultiplied
                                                     : QImage::Format_RGB32);
    if (img.isNull())
        return QImage();
    int w = size.width();
    int h = size.height();
    glReadPixels(0, 0, w, h, GL_RGBA, GL_UNSIGNED_BYTE, img.bits());
    convertFromGLImage(img, w, h, alpha_format, include_alpha);
    return img;
}

QImage qt_gl_read_texture(const QSize &size, bool alpha_format, bool include_alpha)
{
    QImage img(size, alpha_format ? QImage::Format_ARGB32_Premultiplied : QImage::Format_RGB32);
    if (img.isNull())
        return QImage();
    int w = size.width();
    int h = size.height();
#ifndef QT_OPENGL_ES
    if (!QOpenGLContext::currentContext()->isOpenGLES()) {
        //### glGetTexImage not in GL ES 2.0, need to do something else here!
        glGetTexImage(GL_TEXTURE_2D, 0, GL_RGBA, GL_UNSIGNED_BYTE, img.bits());
    }
#endif // QT_OPENGL_ES
    convertFromGLImage(img, w, h, alpha_format, include_alpha);
    return img;
}

// returns the highest number closest to v, which is a power of 2
// NB! assumes 32 bit ints
int qt_next_power_of_two(int v)
{
    v--;
    v |= v >> 1;
    v |= v >> 2;
    v |= v >> 4;
    v |= v >> 8;
    v |= v >> 16;
    ++v;
    return v;
}

Q_GLOBAL_STATIC(QGLTextureCache, qt_gl_texture_cache)

QGLTextureCache::QGLTextureCache()
    : m_cache(64*1024) // cache ~64 MB worth of textures - this is not accurate though
{
    QImagePixmapCleanupHooks::instance()->addPlatformPixmapModificationHook(cleanupTexturesForPixampData);
    QImagePixmapCleanupHooks::instance()->addPlatformPixmapDestructionHook(cleanupBeforePixmapDestruction);
    QImagePixmapCleanupHooks::instance()->addImageHook(cleanupTexturesForCacheKey);
}

QGLTextureCache::~QGLTextureCache()
{
    QImagePixmapCleanupHooks::instance()->removePlatformPixmapModificationHook(cleanupTexturesForPixampData);
    QImagePixmapCleanupHooks::instance()->removePlatformPixmapDestructionHook(cleanupBeforePixmapDestruction);
    QImagePixmapCleanupHooks::instance()->removeImageHook(cleanupTexturesForCacheKey);
}

void QGLTextureCache::insert(QGLContext* ctx, qint64 key, QGLTexture* texture, int cost)
{
    QWriteLocker locker(&m_lock);
    const QGLTextureCacheKey cacheKey = {key, QGLContextPrivate::contextGroup(ctx)};
    m_cache.insert(cacheKey, texture, cost);
}

void QGLTextureCache::remove(qint64 key)
{
    QWriteLocker locker(&m_lock);
    QMutexLocker groupLocker(&qt_context_groups()->m_mutex);
    QList<QGLContextGroup *>::const_iterator it = qt_context_groups()->m_list.constBegin();
    while (it != qt_context_groups()->m_list.constEnd()) {
        const QGLTextureCacheKey cacheKey = {key, *it};
        m_cache.remove(cacheKey);
        ++it;
    }
}

bool QGLTextureCache::remove(QGLContext* ctx, GLuint textureId)
{
    QWriteLocker locker(&m_lock);
    QList<QGLTextureCacheKey> keys = m_cache.keys();
    for (int i = 0; i < keys.size(); ++i) {
        QGLTexture *tex = m_cache.object(keys.at(i));
        if (tex->id == textureId && tex->context == ctx) {
            tex->options |= QGLContext::MemoryManagedBindOption; // forces a glDeleteTextures() call
            m_cache.remove(keys.at(i));
            return true;
        }
    }
    return false;
}

void QGLTextureCache::removeContextTextures(QGLContext* ctx)
{
    QWriteLocker locker(&m_lock);
    QList<QGLTextureCacheKey> keys = m_cache.keys();
    for (int i = 0; i < keys.size(); ++i) {
        const QGLTextureCacheKey &key = keys.at(i);
        if (m_cache.object(key)->context == ctx)
            m_cache.remove(key);
    }
}

/*
  a hook that removes textures from the cache when a pixmap/image
  is deref'ed
*/
void QGLTextureCache::cleanupTexturesForCacheKey(qint64 cacheKey)
{
    qt_gl_texture_cache()->remove(cacheKey);
}


void QGLTextureCache::cleanupTexturesForPixampData(QPlatformPixmap* pmd)
{
    cleanupTexturesForCacheKey(pmd->cacheKey());
}

void QGLTextureCache::cleanupBeforePixmapDestruction(QPlatformPixmap* pmd)
{
    // Remove any bound textures first:
    cleanupTexturesForPixampData(pmd);
}

QGLTextureCache *QGLTextureCache::instance()
{
    return qt_gl_texture_cache();
}

// DDS format structure
struct DDSFormat {
    quint32 dwSize;
    quint32 dwFlags;
    quint32 dwHeight;
    quint32 dwWidth;
    quint32 dwLinearSize;
    quint32 dummy1;
    quint32 dwMipMapCount;
    quint32 dummy2[11];
    struct {
        quint32 dummy3[2];
        quint32 dwFourCC;
        quint32 dummy4[5];
    } ddsPixelFormat;
};

// compressed texture pixel formats
#define FOURCC_DXT1  0x31545844
#define FOURCC_DXT2  0x32545844
#define FOURCC_DXT3  0x33545844
#define FOURCC_DXT4  0x34545844
#define FOURCC_DXT5  0x35545844

// ####TODO Properly #ifdef this class to use #define symbols actually defined
// by system GL includes
#ifndef GL_COMPRESSED_RGB_S3TC_DXT1_EXT
#define GL_COMPRESSED_RGB_S3TC_DXT1_EXT   0x83F0
#endif

#ifndef GL_COMPRESSED_RGBA_S3TC_DXT1_EXT
#define GL_COMPRESSED_RGBA_S3TC_DXT1_EXT  0x83F1
#endif

#ifndef GL_COMPRESSED_RGBA_S3TC_DXT3_EXT
#define GL_COMPRESSED_RGBA_S3TC_DXT3_EXT 0x83F2
#endif

#ifndef GL_COMPRESSED_RGBA_S3TC_DXT5_EXT
#define GL_COMPRESSED_RGBA_S3TC_DXT5_EXT 0x83F3
#endif

#ifndef GL_GENERATE_MIPMAP_SGIS
#define GL_GENERATE_MIPMAP_SGIS       0x8191
#define GL_GENERATE_MIPMAP_HINT_SGIS  0x8192
#endif

/*!
    \class QGLContext
    \inmodule QtOpenGL

    \brief The QGLContext class encapsulates an OpenGL rendering context.

    An OpenGL rendering context is a complete set of OpenGL state
    variables. The rendering context's \l {QGL::FormatOption} {format}
    is set in the constructor, but it can also be set later with
    setFormat(). The format options that are actually set are returned
    by format(); the options you asked for are returned by
    requestedFormat(). Note that after a QGLContext object has been
    constructed, the actual OpenGL context must be created by
    explicitly calling the \l{create()}
    function. The makeCurrent() function makes this context the
    current rendering context. You can make \e no context current
    using doneCurrent(). The reset() function will reset the context
    and make it invalid.

    You can examine properties of the context with, e.g. isValid(),
    isSharing(), initialized(), windowCreated() and
    overlayTransparentColor().

    If you're using double buffering you can swap the screen contents
    with the off-screen buffer using swapBuffers().

    Please note that QGLContext is not thread safe.
*/

/*!
    \enum QGLContext::BindOption
    \since 4.6

    A set of options to decide how to bind a texture using bindTexture().

    \value NoBindOption Don't do anything, pass the texture straight
    through.

    \value InvertedYBindOption Specifies that the texture should be flipped
    over the X axis so that the texture coordinate 0,0 corresponds to
    the top left corner. Inverting the texture implies a deep copy
    prior to upload.

    \value MipmapBindOption Specifies that bindTexture() should try
    to generate mipmaps.  If the GL implementation supports the \c
    GL_SGIS_generate_mipmap extension, mipmaps will be automatically
    generated for the texture. Mipmap generation is only supported for
    the \c GL_TEXTURE_2D target.

    \value PremultipliedAlphaBindOption Specifies that the image should be
    uploaded with premultiplied alpha and does a conversion accordingly.

    \value LinearFilteringBindOption Specifies that the texture filtering
    should be set to GL_LINEAR. Default is GL_NEAREST. If mipmap is
    also enabled, filtering will be set to GL_LINEAR_MIPMAP_LINEAR.

    \value DefaultBindOption In Qt 4.5 and earlier, bindTexture()
    would mirror the image and automatically generate mipmaps. This
    option helps preserve this default behavior.

    \omitvalue CanFlipNativePixmapBindOption Used by x11 from pixmap to choose
    whether or not it can bind the pixmap upside down or not.

    \omitvalue MemoryManagedBindOption Used by paint engines to
    indicate that the pixmap should be memory managed along side with
    the pixmap/image that it stems from, e.g. installing destruction
    hooks in them.

    \omitvalue TemporarilyCachedBindOption Used by paint engines on some
    platforms to indicate that the pixmap or image texture is possibly
    cached only temporarily and must be destroyed immediately after the use.

    \omitvalue InternalBindOption
*/

/*!
    \obsolete

    Constructs an OpenGL context for the given paint \a device, which
    can be a widget or a pixmap. The \a format specifies several
    display options for the context.

    If the underlying OpenGL/Window system cannot satisfy all the
    features requested in \a format, the nearest subset of features
    will be used. After creation, the format() method will return the
    actual format obtained.

    Note that after a QGLContext object has been constructed, \l
    create() must be called explicitly to create the actual OpenGL
    context. The context will be \l {isValid()}{invalid} if it was not
    possible to obtain a GL context at all.
*/

QGLContext::QGLContext(const QGLFormat &format, QPaintDevice *device)
    : d_ptr(new QGLContextPrivate(this))
{
    Q_D(QGLContext);
    d->init(device, format);
}

/*!
    Constructs an OpenGL context with the given \a format which
    specifies several display options for the context.

    If the underlying OpenGL/Window system cannot satisfy all the
    features requested in \a format, the nearest subset of features
    will be used. After creation, the format() method will return the
    actual format obtained.

    Note that after a QGLContext object has been constructed, \l
    create() must be called explicitly to create the actual OpenGL
    context. The context will be \l {isValid()}{invalid} if it was not
    possible to obtain a GL context at all.

    \sa format(), isValid()
*/
QGLContext::QGLContext(const QGLFormat &format)
    : d_ptr(new QGLContextPrivate(this))
{
    Q_D(QGLContext);
    d->init(0, format);
}

/*!
    Destroys the OpenGL context and frees its resources.
*/

QGLContext::~QGLContext()
{
    // remove any textures cached in this context
    QGLTextureCache::instance()->removeContextTextures(this);

    // clean up resources specific to this context
    d_ptr->cleanup();

    QGLSignalProxy::instance()->emitAboutToDestroyContext(this);
    reset();
}

void QGLContextPrivate::cleanup()
{
}

#define ctx q_ptr
void QGLContextPrivate::setVertexAttribArrayEnabled(int arrayIndex, bool enabled)
{
    Q_Q(QGLContext);
    Q_ASSERT(arrayIndex < QT_GL_VERTEX_ARRAY_TRACKED_COUNT);
#ifdef glEnableVertexAttribArray
    Q_ASSERT(glEnableVertexAttribArray);
#endif

    if (vertexAttributeArraysEnabledState[arrayIndex] && !enabled)
        q->functions()->glDisableVertexAttribArray(arrayIndex);

    if (!vertexAttributeArraysEnabledState[arrayIndex] && enabled)
        q->functions()->glEnableVertexAttribArray(arrayIndex);

    vertexAttributeArraysEnabledState[arrayIndex] = enabled;
}

void QGLContextPrivate::syncGlState()
{
    Q_Q(QGLContext);
#ifdef glEnableVertexAttribArray
    Q_ASSERT(glEnableVertexAttribArray);
#endif
    for (int i = 0; i < QT_GL_VERTEX_ARRAY_TRACKED_COUNT; ++i) {
        if (vertexAttributeArraysEnabledState[i])
            q->functions()->glEnableVertexAttribArray(i);
        else
            q->functions()->glDisableVertexAttribArray(i);
    }

}
#undef ctx

void QGLContextPrivate::swapRegion(const QRegion &)
{
    Q_Q(QGLContext);
    q->swapBuffers();
}

/*!
    \overload

    Reads the compressed texture file \a fileName and generates a 2D GL
    texture from it.

    This function can load DirectDrawSurface (DDS) textures in the
    DXT1, DXT3 and DXT5 DDS formats if the \c GL_ARB_texture_compression
    and \c GL_EXT_texture_compression_s3tc extensions are supported.

    Since 4.6.1, textures in the ETC1 format can be loaded if the
    \c GL_OES_compressed_ETC1_RGB8_texture extension is supported
    and the ETC1 texture has been encapsulated in the PVR container format.
    Also, textures in the PVRTC2 and PVRTC4 formats can be loaded
    if the \c GL_IMG_texture_compression_pvrtc extension is supported.

    \sa deleteTexture()
*/

GLuint QGLContext::bindTexture(const QString &fileName)
{
    QGLTexture texture(this);
    QSize size = texture.bindCompressedTexture(fileName);
    if (!size.isValid())
        return 0;
    return texture.id;
}

static inline QRgb qt_gl_convertToGLFormatHelper(QRgb src_pixel, GLenum texture_format)
{
    if (texture_format == GL_BGRA) {
        if (QSysInfo::ByteOrder == QSysInfo::BigEndian) {
            return ((src_pixel << 24) & 0xff000000)
                   | ((src_pixel >> 24) & 0x000000ff)
                   | ((src_pixel << 8) & 0x00ff0000)
                   | ((src_pixel >> 8) & 0x0000ff00);
        } else {
            return src_pixel;
        }
    } else {  // GL_RGBA
        if (QSysInfo::ByteOrder == QSysInfo::BigEndian) {
            return (src_pixel << 8) | ((src_pixel >> 24) & 0xff);
        } else {
            return ((src_pixel << 16) & 0xff0000)
                   | ((src_pixel >> 16) & 0xff)
                   | (src_pixel & 0xff00ff00);
        }
    }
}

static void convertToGLFormatHelper(QImage &dst, const QImage &img, GLenum texture_format)
{
    Q_ASSERT(dst.depth() == 32);
    Q_ASSERT(img.depth() == 32);

    if (dst.size() != img.size()) {
        int target_width = dst.width();
        int target_height = dst.height();
        qreal sx = target_width / qreal(img.width());
        qreal sy = target_height / qreal(img.height());

        quint32 *dest = (quint32 *) dst.scanLine(0); // NB! avoid detach here
        uchar *srcPixels = (uchar *) img.scanLine(img.height() - 1);
        int sbpl = img.bytesPerLine();
        int dbpl = dst.bytesPerLine();

        int ix = int(0x00010000 / sx);
        int iy = int(0x00010000 / sy);

        quint32 basex = int(0.5 * ix);
        quint32 srcy = int(0.5 * iy);

        // scale, swizzle and mirror in one loop
        while (target_height--) {
            const uint *src = (const quint32 *) (srcPixels - (srcy >> 16) * sbpl);
            int srcx = basex;
            for (int x=0; x<target_width; ++x) {
                dest[x] = qt_gl_convertToGLFormatHelper(src[srcx >> 16], texture_format);
                srcx += ix;
            }
            dest = (quint32 *)(((uchar *) dest) + dbpl);
            srcy += iy;
        }
    } else {
        const int width = img.width();
        const int height = img.height();
        const uint *p = (const uint*) img.scanLine(img.height() - 1);
        uint *q = (uint*) dst.scanLine(0);

        if (texture_format == GL_BGRA) {
            if (QSysInfo::ByteOrder == QSysInfo::BigEndian) {
                // mirror + swizzle
                for (int i=0; i < height; ++i) {
                    const uint *end = p + width;
                    while (p < end) {
                        *q = ((*p << 24) & 0xff000000)
                             | ((*p >> 24) & 0x000000ff)
                             | ((*p << 8) & 0x00ff0000)
                             | ((*p >> 8) & 0x0000ff00);
                        p++;
                        q++;
                    }
                    p -= 2 * width;
                }
            } else {
                const uint bytesPerLine = img.bytesPerLine();
                for (int i=0; i < height; ++i) {
                    memcpy(q, p, bytesPerLine);
                    q += width;
                    p -= width;
                }
            }
        } else {
            if (QSysInfo::ByteOrder == QSysInfo::BigEndian) {
                for (int i=0; i < height; ++i) {
                    const uint *end = p + width;
                    while (p < end) {
                        *q = (*p << 8) | ((*p >> 24) & 0xff);
                        p++;
                        q++;
                    }
                    p -= 2 * width;
                }
            } else {
                for (int i=0; i < height; ++i) {
                    const uint *end = p + width;
                    while (p < end) {
                        *q = ((*p << 16) & 0xff0000) | ((*p >> 16) & 0xff) | (*p & 0xff00ff00);
                        p++;
                        q++;
                    }
                    p -= 2 * width;
                }
            }
        }
    }
}

/*! \internal */
QGLTexture *QGLContextPrivate::bindTexture(const QImage &image, GLenum target, GLint format,
                                           QGLContext::BindOptions options)
{
    Q_Q(QGLContext);

    const qint64 key = image.cacheKey();
    QGLTexture *texture = textureCacheLookup(key, target);
    if (texture) {
        if (image.paintingActive()) {
            // A QPainter is active on the image - take the safe route and replace the texture.
            q->deleteTexture(texture->id);
            texture = 0;
        } else {
            glBindTexture(target, texture->id);
            return texture;
        }
    }

    if (!texture)
        texture = bindTexture(image, target, format, key, options);
    // NOTE: bindTexture(const QImage&, GLenum, GLint, const qint64, bool) should never return null
    Q_ASSERT(texture);

    // Enable the cleanup hooks for this image so that the texture cache entry is removed when the
    // image gets deleted:
    QImagePixmapCleanupHooks::enableCleanupHooks(image);

    return texture;
}

// #define QGL_BIND_TEXTURE_DEBUG

// ####TODO Properly #ifdef this file to use #define symbols actually defined
// by OpenGL/ES includes
#ifndef GL_UNSIGNED_INT_8_8_8_8_REV
#define GL_UNSIGNED_INT_8_8_8_8_REV 0x8367
#endif

// map from Qt's ARGB endianness-dependent format to GL's big-endian RGBA layout
static inline void qgl_byteSwapImage(QImage &img, GLenum pixel_type)
{
    const int width = img.width();
    const int height = img.height();

    if (pixel_type == GL_UNSIGNED_INT_8_8_8_8_REV
        || (pixel_type == GL_UNSIGNED_BYTE && QSysInfo::ByteOrder == QSysInfo::LittleEndian))
    {
        for (int i = 0; i < height; ++i) {
            uint *p = (uint *) img.scanLine(i);
            for (int x = 0; x < width; ++x)
                p[x] = ((p[x] << 16) & 0xff0000) | ((p[x] >> 16) & 0xff) | (p[x] & 0xff00ff00);
        }
    } else {
        for (int i = 0; i < height; ++i) {
            uint *p = (uint *) img.scanLine(i);
            for (int x = 0; x < width; ++x)
                p[x] = (p[x] << 8) | ((p[x] >> 24) & 0xff);
        }
    }
}

QGLTexture* QGLContextPrivate::bindTexture(const QImage &image, GLenum target, GLint internalFormat,
                                           const qint64 key, QGLContext::BindOptions options)
{
    Q_Q(QGLContext);

#ifdef QGL_BIND_TEXTURE_DEBUG
    printf("QGLContextPrivate::bindTexture(), imageSize=(%d,%d), internalFormat =0x%x, options=%x, key=%llx\n",
           image.width(), image.height(), internalFormat, int(options), key);
    QTime time;
    time.start();
#endif

#ifndef QT_NO_DEBUG
    // Reset the gl error stack...git
    while (glGetError() != GL_NO_ERROR) ;
#endif

    // Scale the pixmap if needed. GL textures needs to have the
    // dimensions 2^n+2(border) x 2^m+2(border), unless we're using GL
    // 2.0 or use the GL_TEXTURE_RECTANGLE texture target
    int tx_w = qt_next_power_of_two(image.width());
    int tx_h = qt_next_power_of_two(image.height());

    QImage img = image;

    if (!qgl_extensions()->hasOpenGLFeature(QOpenGLFunctions::NPOTTextures)
        && !(QGLFormat::openGLVersionFlags() & QGLFormat::OpenGL_ES_Version_2_0)
        && (target == GL_TEXTURE_2D && (tx_w != image.width() || tx_h != image.height())))
    {
        img = img.scaled(tx_w, tx_h);
#ifdef QGL_BIND_TEXTURE_DEBUG
        printf(" - upscaled to %dx%d (%d ms)\n", tx_w, tx_h, time.elapsed());

#endif
    }

    GLuint filtering = options & QGLContext::LinearFilteringBindOption ? GL_LINEAR : GL_NEAREST;

    GLuint tx_id;
    glGenTextures(1, &tx_id);
    glBindTexture(target, tx_id);
    glTexParameteri(target, GL_TEXTURE_MAG_FILTER, filtering);

    QOpenGLContext *ctx = QOpenGLContext::currentContext();
    bool genMipmap = !ctx->isOpenGLES();
    if (glFormat.directRendering()
        && (qgl_extensions()->hasOpenGLExtension(QOpenGLExtensions::GenerateMipmap))
        && target == GL_TEXTURE_2D
        && (options & QGLContext::MipmapBindOption))
    {
#if !defined(QT_OPENGL_ES_2)
        if (genMipmap) {
            glHint(GL_GENERATE_MIPMAP_HINT_SGIS, GL_NICEST);
            glTexParameteri(target, GL_GENERATE_MIPMAP_SGIS, GL_TRUE);
        } else {
            glHint(GL_GENERATE_MIPMAP_HINT, GL_NICEST);
            genMipmap = true;
        }
#else
        glHint(GL_GENERATE_MIPMAP_HINT, GL_NICEST);
        genMipmap = true;
#endif
        glTexParameteri(target, GL_TEXTURE_MIN_FILTER, options & QGLContext::LinearFilteringBindOption
                        ? GL_LINEAR_MIPMAP_LINEAR : GL_NEAREST_MIPMAP_NEAREST);
#ifdef QGL_BIND_TEXTURE_DEBUG
        printf(" - generating mipmaps (%d ms)\n", time.elapsed());
#endif
    } else {
        glTexParameteri(target, GL_TEXTURE_MIN_FILTER, filtering);
    }

    QImage::Format target_format = img.format();
    bool premul = options & QGLContext::PremultipliedAlphaBindOption;
    bool needsbyteswap = true;
    GLenum externalFormat;
    GLuint pixel_type;
    if (target_format == QImage::Format_RGBA8888
        || target_format == QImage::Format_RGBA8888_Premultiplied
        || target_format == QImage::Format_RGBX8888) {
        externalFormat = GL_RGBA;
        pixel_type = GL_UNSIGNED_BYTE;
        needsbyteswap = false;
    } else if (qgl_extensions()->hasOpenGLExtension(QOpenGLExtensions::BGRATextureFormat)) {
        externalFormat = GL_BGRA;
        needsbyteswap = false;
        if (QGLFormat::openGLVersionFlags() & QGLFormat::OpenGL_Version_1_2)
            pixel_type = GL_UNSIGNED_INT_8_8_8_8_REV;
        else
            pixel_type = GL_UNSIGNED_BYTE;
    } else {
        externalFormat = GL_RGBA;
        pixel_type = GL_UNSIGNED_BYTE;
    }

    switch (target_format) {
    case QImage::Format_ARGB32:
        if (premul) {
            img = img.convertToFormat(target_format = QImage::Format_ARGB32_Premultiplied);
#ifdef QGL_BIND_TEXTURE_DEBUG
            printf(" - converted ARGB32 -> ARGB32_Premultiplied (%d ms) \n", time.elapsed());
#endif
        }
        break;
    case QImage::Format_ARGB32_Premultiplied:
        if (!premul) {
            img = img.convertToFormat(target_format = QImage::Format_ARGB32);
#ifdef QGL_BIND_TEXTURE_DEBUG
            printf(" - converted ARGB32_Premultiplied -> ARGB32 (%d ms)\n", time.elapsed());
#endif
        }
        break;
    case QImage::Format_RGBA8888:
        if (premul) {
            img = img.convertToFormat(target_format = QImage::Format_RGBA8888_Premultiplied);
#ifdef QGL_BIND_TEXTURE_DEBUG
            printf(" - converted RGBA8888 -> RGBA8888_Premultiplied (%d ms) \n", time.elapsed());
#endif
        }
        break;
    case QImage::Format_RGBA8888_Premultiplied:
        if (!premul) {
            img = img.convertToFormat(target_format = QImage::Format_RGBA8888);
#ifdef QGL_BIND_TEXTURE_DEBUG
            printf(" - converted RGBA8888_Premultiplied -> RGBA8888 (%d ms) \n", time.elapsed());
#endif
        }
        break;
    case QImage::Format_RGB16:
        pixel_type = GL_UNSIGNED_SHORT_5_6_5;
        externalFormat = GL_RGB;
        internalFormat = GL_RGB;
        needsbyteswap = false;
        break;
    case QImage::Format_RGB32:
    case QImage::Format_RGBX8888:
        break;
    default:
        // Ideally more formats would be converted directly to an RGBA8888 format,
        // but we are only guaranteed to have a fast conversion to an ARGB format.
        if (img.hasAlphaChannel()) {
            img = img.convertToFormat(premul
                                      ? QImage::Format_ARGB32_Premultiplied
                                      : QImage::Format_ARGB32);
#ifdef QGL_BIND_TEXTURE_DEBUG
            printf(" - converted to 32-bit alpha format (%d ms)\n", time.elapsed());
#endif
        } else {
            img = img.convertToFormat(QImage::Format_RGB32);
#ifdef QGL_BIND_TEXTURE_DEBUG
            printf(" - converted to 32-bit (%d ms)\n", time.elapsed());
#endif
        }
    }

    if (options & QGLContext::InvertedYBindOption) {
        if (img.isDetached()) {
            int ipl = img.bytesPerLine() / 4;
            int h = img.height();
            for (int y=0; y<h/2; ++y) {
                int *a = (int *) img.scanLine(y);
                int *b = (int *) img.scanLine(h - y - 1);
                for (int x=0; x<ipl; ++x)
                    qSwap(a[x], b[x]);
            }
        } else {
            // Create a new image and copy across.  If we use the
            // above in-place code then a full copy of the image is
            // made before the lines are swapped, which processes the
            // data twice.  This version should only do it once.
            img = img.mirrored();
        }
#ifdef QGL_BIND_TEXTURE_DEBUG
            printf(" - flipped bits over y (%d ms)\n", time.elapsed());
#endif
    }

    if (needsbyteswap) {
        // The only case where we end up with a depth different from
        // 32 in the switch above is for the RGB16 case, where we do
        // not need a byteswap.
        Q_ASSERT(img.depth() == 32);
        qgl_byteSwapImage(img, pixel_type);
#ifdef QGL_BIND_TEXTURE_DEBUG
            printf(" - did byte swapping (%d ms)\n", time.elapsed());
#endif
    }
    if (ctx->isOpenGLES()) {
        // OpenGL/ES requires that the internal and external formats be
        // identical.
        internalFormat = externalFormat;
    }
#ifdef QGL_BIND_TEXTURE_DEBUG
    printf(" - uploading, image.format=%d, externalFormat=0x%x, internalFormat=0x%x, pixel_type=0x%x\n",
           img.format(), externalFormat, internalFormat, pixel_type);
#endif

    const QImage &constRef = img; // to avoid detach in bits()...
    glTexImage2D(target, 0, internalFormat, img.width(), img.height(), 0, externalFormat,
                 pixel_type, constRef.bits());
    if (genMipmap && ctx->isOpenGLES())
        q->functions()->glGenerateMipmap(target);
#ifndef QT_NO_DEBUG
    GLenum error = glGetError();
    if (error != GL_NO_ERROR) {
        qWarning(" - texture upload failed, error code 0x%x, enum: %d (%x)\n", error, target, target);
    }
#endif

#ifdef QGL_BIND_TEXTURE_DEBUG
    static int totalUploadTime = 0;
    totalUploadTime += time.elapsed();
    printf(" - upload done in %d ms, (accumulated: %d ms)\n", time.elapsed(), totalUploadTime);
#endif


    // this assumes the size of a texture is always smaller than the max cache size
    int cost = img.width()*img.height()*4/1024;
    QGLTexture *texture = new QGLTexture(q, tx_id, target, options);
    QGLTextureCache::instance()->insert(q, key, texture, cost);

    return texture;
}

QGLTexture *QGLContextPrivate::textureCacheLookup(const qint64 key, GLenum target)
{
    Q_Q(QGLContext);
    QGLTexture *texture = QGLTextureCache::instance()->getTexture(q, key);
    if (texture && texture->target == target
        && (texture->context == q || QGLContext::areSharing(q, texture->context)))
    {
        return texture;
    }
    return 0;
}

/*! \internal */
QGLTexture *QGLContextPrivate::bindTexture(const QPixmap &pixmap, GLenum target, GLint format, QGLContext::BindOptions options)
{
    Q_Q(QGLContext);
    QPlatformPixmap *pd = pixmap.handle();
    Q_UNUSED(pd);

    const qint64 key = pixmap.cacheKey();
    QGLTexture *texture = textureCacheLookup(key, target);
    if (texture) {
        if (pixmap.paintingActive()) {
            // A QPainter is active on the pixmap - take the safe route and replace the texture.
            q->deleteTexture(texture->id);
            texture = 0;
        } else {
            glBindTexture(target, texture->id);
            return texture;
        }
    }

    if (!texture) {
        QImage image;
        QPaintEngine* paintEngine = pixmap.paintEngine();
        if (!paintEngine || paintEngine->type() != QPaintEngine::Raster)
            image = pixmap.toImage();
        else {
            // QRasterPixmapData::toImage() will deep-copy the backing QImage if there's an active QPainter on it.
            // For performance reasons, we don't want that here, so we temporarily redirect the paint engine.
            QPaintDevice* currentPaintDevice = paintEngine->paintDevice();
            paintEngine->setPaintDevice(0);
            image = pixmap.toImage();
            paintEngine->setPaintDevice(currentPaintDevice);
        }

        // If the system depth is 16 and the pixmap doesn't have an alpha channel
        // then we convert it to RGB16 in the hope that it gets uploaded as a 16
        // bit texture which is much faster to access than a 32-bit one.
        if (pixmap.depth() == 16 && !image.hasAlphaChannel() )
            image = image.convertToFormat(QImage::Format_RGB16);
        texture = bindTexture(image, target, format, key, options);
    }
    // NOTE: bindTexture(const QImage&, GLenum, GLint, const qint64, bool) should never return null
    Q_ASSERT(texture);

    if (texture->id > 0)
        QImagePixmapCleanupHooks::enableCleanupHooks(pixmap);

    return texture;
}

/*! \internal */
int QGLContextPrivate::maxTextureSize()
{
    if (max_texture_size != -1)
        return max_texture_size;

    glGetIntegerv(GL_MAX_TEXTURE_SIZE, &max_texture_size);

#ifndef QT_OPENGL_ES
    Q_Q(QGLContext);
    if (!q->contextHandle()->isOpenGLES()) {
        GLenum proxy = GL_PROXY_TEXTURE_2D;

        GLint size;
        GLint next = 64;
        glTexImage2D(proxy, 0, GL_RGBA, next, next, 0, GL_RGBA, GL_UNSIGNED_BYTE, 0);
        glGetTexLevelParameteriv(proxy, 0, GL_TEXTURE_WIDTH, &size);
        if (size == 0) {
            return max_texture_size;
        }
        do {
            size = next;
            next = size * 2;

            if (next > max_texture_size)
                break;
            glTexImage2D(proxy, 0, GL_RGBA, next, next, 0, GL_RGBA, GL_UNSIGNED_BYTE, 0);
            glGetTexLevelParameteriv(proxy, 0, GL_TEXTURE_WIDTH, &next);
        } while (next > size);

        max_texture_size = size;
    }
#endif

    return max_texture_size;
}

/*!
  Returns a QGLFunctions object that is initialized for this context.
 */
QGLFunctions *QGLContext::functions() const
{
    QGLContextPrivate *d = const_cast<QGLContextPrivate *>(d_func());
    if (!d->functions) {
        d->functions = new QGLFunctions(this);
        d->functions->initializeGLFunctions(this);
    }
    return d->functions;
}

/*!
  Generates and binds a 2D GL texture to the current context, based
  on \a image. The generated texture id is returned and can be used in
  later \c glBindTexture() calls.

  \overload
*/
GLuint QGLContext::bindTexture(const QImage &image, GLenum target, GLint format)
{
    if (image.isNull())
        return 0;

    Q_D(QGLContext);
    QGLTexture *texture = d->bindTexture(image, target, format, DefaultBindOption);
    return texture->id;
}

/*!
    \since 4.6

    Generates and binds a 2D GL texture to the current context, based
    on \a image. The generated texture id is returned and can be used
    in later \c glBindTexture() calls.

    The \a target parameter specifies the texture target. The default
    target is \c GL_TEXTURE_2D.

    The \a format parameter sets the internal format for the
    texture. The default format is \c GL_RGBA.

    The binding \a options are a set of options used to decide how to
    bind the texture to the context.

    The texture that is generated is cached, so multiple calls to
    bindTexture() with the same QImage will return the same texture
    id.

    Note that we assume default values for the glPixelStore() and
    glPixelTransfer() parameters.

    \sa deleteTexture()
*/
GLuint QGLContext::bindTexture(const QImage &image, GLenum target, GLint format, BindOptions options)
{
    if (image.isNull())
        return 0;

    Q_D(QGLContext);
    QGLTexture *texture = d->bindTexture(image, target, format, options);
    return texture->id;
}

/*! \overload

    Generates and binds a 2D GL texture based on \a pixmap.
*/
GLuint QGLContext::bindTexture(const QPixmap &pixmap, GLenum target, GLint format)
{
    if (pixmap.isNull())
        return 0;

    Q_D(QGLContext);
    QGLTexture *texture = d->bindTexture(pixmap, target, format, DefaultBindOption);
    return texture->id;
}

/*!
  \overload
  \since 4.6

  Generates and binds a 2D GL texture to the current context, based
  on \a pixmap.
*/
GLuint QGLContext::bindTexture(const QPixmap &pixmap, GLenum target, GLint format, BindOptions options)
{
    if (pixmap.isNull())
        return 0;

    Q_D(QGLContext);
    QGLTexture *texture = d->bindTexture(pixmap, target, format, options);
    return texture->id;
}

/*!
    Removes the texture identified by \a id from the texture cache,
    and calls glDeleteTextures() to delete the texture from the
    context.

    \sa bindTexture()
*/
void QGLContext::deleteTexture(GLuint id)
{
    if (QGLTextureCache::instance()->remove(this, id))
        return;
    glDeleteTextures(1, &id);
}

void qt_add_rect_to_array(const QRectF &r, GLfloat *array)
{
    qreal left = r.left();
    qreal right = r.right();
    qreal top = r.top();
    qreal bottom = r.bottom();

    array[0] = left;
    array[1] = top;
    array[2] = right;
    array[3] = top;
    array[4] = right;
    array[5] = bottom;
    array[6] = left;
    array[7] = bottom;
}

void qt_add_texcoords_to_array(qreal x1, qreal y1, qreal x2, qreal y2, GLfloat *array)
{
    array[0] = x1;
    array[1] = y1;
    array[2] = x2;
    array[3] = y1;
    array[4] = x2;
    array[5] = y2;
    array[6] = x1;
    array[7] = y2;
}

#if !defined(QT_OPENGL_ES_2)

static void qDrawTextureRect(const QRectF &target, GLint textureWidth, GLint textureHeight, GLenum textureTarget)
{
    GLfloat tx = 1.0f;
    GLfloat ty = 1.0f;

#ifdef QT_OPENGL_ES
    Q_UNUSED(textureWidth);
    Q_UNUSED(textureHeight);
    Q_UNUSED(textureTarget);
#else
    if (textureTarget != GL_TEXTURE_2D && !QOpenGLContext::currentContext()->isOpenGLES()) {
        if (textureWidth == -1 || textureHeight == -1) {
            glGetTexLevelParameteriv(textureTarget, 0, GL_TEXTURE_WIDTH, &textureWidth);
            glGetTexLevelParameteriv(textureTarget, 0, GL_TEXTURE_HEIGHT, &textureHeight);
        }

        tx = GLfloat(textureWidth);
        ty = GLfloat(textureHeight);
    }
#endif

    GLfloat texCoordArray[4*2] = {
        0, ty, tx, ty, tx, 0, 0, 0
    };

    GLfloat vertexArray[4*2];
    qt_add_rect_to_array(target, vertexArray);

    glVertexPointer(2, GL_FLOAT, 0, vertexArray);
    glTexCoordPointer(2, GL_FLOAT, 0, texCoordArray);

    glEnableClientState(GL_VERTEX_ARRAY);
    glEnableClientState(GL_TEXTURE_COORD_ARRAY);
    glDrawArrays(GL_TRIANGLE_FAN, 0, 4);

    glDisableClientState(GL_VERTEX_ARRAY);
    glDisableClientState(GL_TEXTURE_COORD_ARRAY);
}

#endif // !QT_OPENGL_ES_2

/*!
    \since 4.4

    This function supports the following use cases:

    \list
    \li On OpenGL and OpenGL ES 1.x it draws the given texture, \a textureId,
    to the given target rectangle, \a target, in OpenGL model space. The
    \a textureTarget should be a 2D texture target.
    \li On OpenGL and OpenGL ES 2.x, if a painter is active, not inside a
    beginNativePainting / endNativePainting block, and uses the
    engine with type QPaintEngine::OpenGL2, the function will draw the given
    texture, \a textureId, to the given target rectangle, \a target,
    respecting the current painter state. This will let you draw a texture
    with the clip, transform, render hints, and composition mode set by the
    painter. Note that the texture target needs to be GL_TEXTURE_2D for this
    use case, and that this is the only supported use case under OpenGL ES 2.x.
    \endlist

*/
void QGLContext::drawTexture(const QRectF &target, GLuint textureId, GLenum textureTarget)
{
#if !defined(QT_OPENGL_ES) || defined(QT_OPENGL_ES_2)
     if (d_ptr->active_engine &&
         d_ptr->active_engine->type() == QPaintEngine::OpenGL2) {
         QGL2PaintEngineEx *eng = static_cast<QGL2PaintEngineEx*>(d_ptr->active_engine);
         if (!eng->isNativePaintingActive()) {
            QRectF src(0, 0, target.width(), target.height());
            QSize size(target.width(), target.height());
            if (eng->drawTexture(target, textureId, size, src))
                return;
        }
     }
#endif

#ifndef QT_OPENGL_ES_2
     if (!contextHandle()->isOpenGLES()) {
#ifdef QT_OPENGL_ES
        if (textureTarget != GL_TEXTURE_2D) {
            qWarning("QGLContext::drawTexture(): texture target must be GL_TEXTURE_2D on OpenGL ES");
            return;
        }
#else
        const bool wasEnabled = glIsEnabled(GL_TEXTURE_2D);
        GLint oldTexture;
        glGetIntegerv(GL_TEXTURE_BINDING_2D, &oldTexture);
#endif

        glEnable(textureTarget);
        glBindTexture(textureTarget, textureId);

        qDrawTextureRect(target, -1, -1, textureTarget);

#ifdef QT_OPENGL_ES
        glDisable(textureTarget);
#else
        if (!wasEnabled)
            glDisable(textureTarget);
        glBindTexture(textureTarget, oldTexture);
#endif
        return;
    }
#else
    Q_UNUSED(target);
    Q_UNUSED(textureId);
    Q_UNUSED(textureTarget);
#endif
    qWarning("drawTexture() with OpenGL ES 2.0 requires an active OpenGL2 paint engine");
}

/*!
    \since 4.4

    This function supports the following use cases:

    \list
    \li By default it draws the given texture, \a textureId,
    at the given \a point in OpenGL model space. The
    \a textureTarget should be a 2D texture target.
    \li If a painter is active, not inside a
    beginNativePainting / endNativePainting block, and uses the
    engine with type QPaintEngine::OpenGL2, the function will draw the given
    texture, \a textureId, at the given \a point,
    respecting the current painter state. This will let you draw a texture
    with the clip, transform, render hints, and composition mode set by the
    painter. Note that the texture target needs to be GL_TEXTURE_2D for this
    use case.
    \endlist

    \note This function is not supported under any version of OpenGL ES.
*/
void QGLContext::drawTexture(const QPointF &point, GLuint textureId, GLenum textureTarget)
{
#ifdef QT_OPENGL_ES
    Q_UNUSED(point);
    Q_UNUSED(textureId);
    Q_UNUSED(textureTarget);
#else
    if (!contextHandle()->isOpenGLES()) {
        const bool wasEnabled = glIsEnabled(GL_TEXTURE_2D);
        GLint oldTexture;
        glGetIntegerv(GL_TEXTURE_BINDING_2D, &oldTexture);

        glEnable(textureTarget);
        glBindTexture(textureTarget, textureId);

        GLint textureWidth;
        GLint textureHeight;

        glGetTexLevelParameteriv(textureTarget, 0, GL_TEXTURE_WIDTH, &textureWidth);
        glGetTexLevelParameteriv(textureTarget, 0, GL_TEXTURE_HEIGHT, &textureHeight);

        if (d_ptr->active_engine &&
            d_ptr->active_engine->type() == QPaintEngine::OpenGL2) {
            QGL2PaintEngineEx *eng = static_cast<QGL2PaintEngineEx*>(d_ptr->active_engine);
            if (!eng->isNativePaintingActive()) {
                QRectF dest(point, QSizeF(textureWidth, textureHeight));
                QRectF src(0, 0, textureWidth, textureHeight);
                QSize size(textureWidth, textureHeight);
                if (eng->drawTexture(dest, textureId, size, src))
                    return;
            }
        }

        qDrawTextureRect(QRectF(point, QSizeF(textureWidth, textureHeight)), textureWidth, textureHeight, textureTarget);

        if (!wasEnabled)
            glDisable(textureTarget);
        glBindTexture(textureTarget, oldTexture);
        return;
    }
#endif
    qWarning("drawTexture(const QPointF &point, GLuint textureId, GLenum textureTarget) not supported with OpenGL ES, use rect version instead");
}

/*!
    This function sets the limit for the texture cache to \a size,
    expressed in kilobytes.

    By default, the cache limit is approximately 64 MB.

    \sa textureCacheLimit()
*/
void QGLContext::setTextureCacheLimit(int size)
{
    QGLTextureCache::instance()->setMaxCost(size);
}

/*!
    Returns the current texture cache limit in kilobytes.

    \sa setTextureCacheLimit()
*/
int QGLContext::textureCacheLimit()
{
    return QGLTextureCache::instance()->maxCost();
}


/*!
    \fn QGLFormat QGLContext::format() const

    Returns the frame buffer format that was obtained (this may be a
    subset of what was requested).

    \sa requestedFormat()
*/

/*!
    \fn QGLFormat QGLContext::requestedFormat() const

    Returns the frame buffer format that was originally requested in
    the constructor or setFormat().

    \sa format()
*/

/*!
    Sets a \a format for this context. The context is \l{reset()}{reset}.

    Call create() to create a new GL context that tries to match the
    new format.

    \snippet code/src_opengl_qgl.cpp 7

    \sa format(), reset(), create()
*/

void QGLContext::setFormat(const QGLFormat &format)
{
    Q_D(QGLContext);
    reset();
    d->glFormat = d->reqFormat = format;
}

/*!
    \internal
*/
void QGLContext::setDevice(QPaintDevice *pDev)
{
    Q_D(QGLContext);
    // Do not touch the valid flag here. The context is either a new one and
    // valid is not yet set or it is adapted from a valid QOpenGLContext in which
    // case it must remain valid.
    d->paintDevice = pDev;
    if (d->paintDevice && (d->paintDevice->devType() != QInternal::Widget
                           && d->paintDevice->devType() != QInternal::Pixmap
                           && d->paintDevice->devType() != QInternal::Pbuffer)) {
        qWarning("QGLContext: Unsupported paint device type");
    }
}

/*!
    \fn bool QGLContext::isValid() const

    Returns \c true if a GL rendering context has been successfully
    created; otherwise returns \c false.
*/

/*!
    \fn void QGLContext::setValid(bool valid)
    \internal

    Forces the GL rendering context to be valid.
*/

/*!
    \fn bool QGLContext::isSharing() const

    Returns \c true if this context is sharing its GL context with
    another QGLContext, otherwise false is returned. Note that context
    sharing might not be supported between contexts with different
    formats.
*/

/*!
    Returns \c true if \a context1 and \a context2 are sharing their
    GL resources such as textures, shader programs, etc;
    otherwise returns \c false.

    \since 4.6
*/
bool QGLContext::areSharing(const QGLContext *context1, const QGLContext *context2)
{
    if (!context1 || !context2)
        return false;
    return context1->d_ptr->group == context2->d_ptr->group;
}

/*!
    \fn bool QGLContext::deviceIsPixmap() const

    Returns \c true if the paint device of this context is a pixmap;
    otherwise returns \c false.

    Since Qt 5 the paint device is never actually a pixmap. renderPixmap() is
    however still simulated using framebuffer objects and readbacks, and this
    function will return \c true in this case.
*/

/*!
    \fn bool QGLContext::windowCreated() const

    Returns \c true if a window has been created for this context;
    otherwise returns \c false.

    \sa setWindowCreated()
*/

/*!
    \fn void QGLContext::setWindowCreated(bool on)

    If \a on is true the context has had a window created for it. If
    \a on is false no window has been created for the context.

    \sa windowCreated()
*/

/*!
    \fn uint QGLContext::colorIndex(const QColor& c) const

    \internal

    Returns a colormap index for the color c, in ColorIndex mode. Used
    by qglColor() and qglClearColor().
*/


/*!
    \fn bool QGLContext::initialized() const

    Returns \c true if this context has been initialized, i.e. if
    QGLWidget::initializeGL() has been performed on it; otherwise
    returns \c false.

    \sa setInitialized()
*/

/*!
    \fn void QGLContext::setInitialized(bool on)

    If \a on is true the context has been initialized, i.e.
    QGLContext::setInitialized() has been called on it. If \a on is
    false the context has not been initialized.

    \sa initialized()
*/

/*!
    \fn const QGLContext* QGLContext::currentContext()

    Returns the current context, i.e. the context to which any OpenGL
    commands will currently be directed. Returns 0 if no context is
    current.

    \sa makeCurrent()
*/

/*!
    \fn QColor QGLContext::overlayTransparentColor() const

    If this context is a valid context in an overlay plane, returns
    the plane's transparent color. Otherwise returns an \l{QColor::isValid()}{invalid} color.

    The returned color's \l{QColormap::pixel()}{pixel} value is
    the index of the transparent color in the colormap of the overlay
    plane. (Naturally, the color's RGB values are meaningless.)

    The returned QColor object will generally work as expected only
    when passed as the argument to QGLWidget::qglColor() or
    QGLWidget::qglClearColor(). Under certain circumstances it can
    also be used to draw transparent graphics with a QPainter. See the
    examples/opengl/overlay_x11 example for details.
*/


/*!
    Creates the GL context. Returns \c true if it was successful in
    creating a valid GL rendering context on the paint device
    specified in the constructor; otherwise returns \c false (i.e. the
    context is invalid).

    If the OpenGL implementation on your system does not support the requested
    version of OpenGL context, then QGLContext will try to create the closest
    matching version. The actual created context properties can be queried
    using the QGLFormat returned by the format() function. For example, if
    you request a context that supports OpenGL 4.3 Core profile but the driver
    and/or hardware only supports version 3.2 Core profile contexts then you will
    get a 3.2 Core profile context.

    After successful creation, format() returns the set of features of
    the created GL rendering context.

    If \a shareContext points to a valid QGLContext, this method will
    try to establish OpenGL display list and texture object sharing
    between this context and the \a shareContext. Note that this may
    fail if the two contexts have different \l {format()} {formats}.
    Use isSharing() to see if sharing is in effect.

    \warning Implementation note: initialization of C++ class
    members usually takes place in the class constructor. QGLContext
    is an exception because it must be simple to customize. The
    virtual functions chooseContext() (and chooseVisual() for X11) can
    be reimplemented in a subclass to select a particular context. The
    problem is that virtual functions are not properly called during
    construction (even though this is correct C++) because C++
    constructs class hierarchies from the bottom up. For this reason
    we need a create() function.

    \sa chooseContext(), format(), isValid()
*/

bool QGLContext::create(const QGLContext* shareContext)
{
    Q_D(QGLContext);
    if (!d->paintDevice && !d->guiGlContext)
        return false;

    reset();
    d->valid = chooseContext(shareContext);
    if (d->valid && d->paintDevice && d->paintDevice->devType() == QInternal::Widget) {
        QWidgetPrivate *wd = qt_widget_private(static_cast<QWidget *>(d->paintDevice));
        wd->usesDoubleBufferedGLContext = d->glFormat.doubleBuffer();
    }
    return d->valid;
}

bool QGLContext::isValid() const
{
    Q_D(const QGLContext);
    return d->valid;
}

void QGLContext::setValid(bool valid)
{
    Q_D(QGLContext);
    d->valid = valid;
}

bool QGLContext::isSharing() const
{
    Q_D(const QGLContext);
    return d->group->isSharing();
}

QGLFormat QGLContext::format() const
{
    Q_D(const QGLContext);
    return d->glFormat;
}

QGLFormat QGLContext::requestedFormat() const
{
    Q_D(const QGLContext);
    return d->reqFormat;
}

 QPaintDevice* QGLContext::device() const
{
    Q_D(const QGLContext);
    return d->paintDevice;
}

bool QGLContext::deviceIsPixmap() const
{
    Q_D(const QGLContext);
    return !d->readback_target_size.isEmpty();
}


bool QGLContext::windowCreated() const
{
    Q_D(const QGLContext);
    return d->crWin;
}


void QGLContext::setWindowCreated(bool on)
{
    Q_D(QGLContext);
    d->crWin = on;
}

bool QGLContext::initialized() const
{
    Q_D(const QGLContext);
    return d->initDone;
}

void QGLContext::setInitialized(bool on)
{
    Q_D(QGLContext);
    d->initDone = on;
}

const QGLContext* QGLContext::currentContext()
{
    if (const QOpenGLContext *threadContext = QOpenGLContext::currentContext()) {
        return QGLContext::fromOpenGLContext(const_cast<QOpenGLContext *>(threadContext));
    }
    return 0;
}

void QGLContextPrivate::setCurrentContext(QGLContext *context)
{
    Q_UNUSED(context);
}

/*!
    Moves the QGLContext to the given \a thread.

    Enables calling swapBuffers() and makeCurrent() on the context in
    the given thread.
*/
void QGLContext::moveToThread(QThread *thread)
{
    Q_D(QGLContext);
    if (d->guiGlContext)
        d->guiGlContext->moveToThread(thread);
}

/*!
    \fn bool QGLContext::chooseContext(const QGLContext* shareContext = 0)

    This semi-internal function is called by create(). It creates a
    system-dependent OpenGL handle that matches the format() of \a
    shareContext as closely as possible, returning true if successful
    or false if a suitable handle could not be found.

    On Windows, it calls the virtual function choosePixelFormat(),
    which finds a matching pixel format identifier. On X11, it calls
    the virtual function chooseVisual() which finds an appropriate X
    visual. On other platforms it may work differently.
*/

/*!
    \fn void QGLContext::reset()

    Resets the context and makes it invalid.

    \sa create(), isValid()
*/


/*!
    \fn void QGLContext::makeCurrent()

    Makes this context the current OpenGL rendering context. All GL
    functions you call operate on this context until another context
    is made current.

    In some very rare cases the underlying call may fail. If this
    occurs an error message is output to stderr.

    If you call this from a thread other than the main UI thread,
    make sure you've first pushed the context to the relevant thread
    from the UI thread using moveToThread().
*/


/*!
    \fn void QGLContext::swapBuffers() const

    Call this to finish a frame of OpenGL rendering, and make sure to
    call makeCurrent() again before you begin a new frame.
*/


/*!
    \fn void QGLContext::doneCurrent()

    Makes no GL context the current context. Normally, you do not need
    to call this function; QGLContext calls it as necessary.
*/


/*!
    \fn QPaintDevice* QGLContext::device() const

    Returns the paint device set for this context.

    \sa QGLContext::QGLContext()
*/


/*****************************************************************************
  QGLWidget implementation
 *****************************************************************************/


/*!
    \class QGLWidget
    \inmodule QtOpenGL

    \brief The QGLWidget class is a widget for rendering OpenGL graphics.

    QGLWidget provides functionality for displaying OpenGL graphics
    integrated into a Qt application. It is very simple to use. You
    inherit from it and use the subclass like any other QWidget,
    except that you have the choice between using QPainter and
    standard OpenGL rendering commands.

    QGLWidget provides three convenient virtual functions that you can
    reimplement in your subclass to perform the typical OpenGL tasks:

    \list
    \li paintGL() - Renders the OpenGL scene. Gets called whenever the widget
    needs to be updated.
    \li resizeGL() - Sets up the OpenGL viewport, projection, etc. Gets
    called whenever the widget has been resized (and also when it
    is shown for the first time because all newly created widgets get a
    resize event automatically).
    \li initializeGL() - Sets up the OpenGL rendering context, defines display
    lists, etc. Gets called once before the first time resizeGL() or
    paintGL() is called.
    \endlist

    Here is a rough outline of how a QGLWidget subclass might look:

    \snippet code/src_opengl_qgl.cpp 8

    If you need to trigger a repaint from places other than paintGL()
    (a typical example is when using \l{QTimer}{timers} to
    animate scenes), you should call the widget's updateGL() function.

    Your widget's OpenGL rendering context is made current when
    paintGL(), resizeGL(), or initializeGL() is called. If you need to
    call the standard OpenGL API functions from other places (e.g. in
    your widget's constructor or in your own paint functions), you
    must call makeCurrent() first.

    QGLWidget provides functions for requesting a new display
    \l{QGLFormat}{format} and you can also create widgets with
    customized rendering \l{QGLContext}{contexts}.

    You can also share OpenGL display lists between QGLWidget objects (see
    the documentation of the QGLWidget constructors for details).

    Note that under Windows, the QGLContext belonging to a QGLWidget
    has to be recreated when the QGLWidget is reparented. This is
    necessary due to limitations on the Windows platform. This will
    most likely cause problems for users that have subclassed and
    installed their own QGLContext on a QGLWidget. It is possible to
    work around this issue by putting the QGLWidget inside a dummy
    widget and then reparenting the dummy widget, instead of the
    QGLWidget. This will side-step the issue altogether, and is what
    we recommend for users that need this kind of functionality.

    On Mac OS X, when Qt is built with Cocoa support, a QGLWidget
    can't have any sibling widgets placed ontop of itself. This is due
    to limitations in the Cocoa API and is not supported by Apple.

    \section1 Overlays

    The QGLWidget creates a GL overlay context in addition to the
    normal context if overlays are supported by the underlying system.

    If you want to use overlays, you specify it in the
    \l{QGLFormat}{format}. (Note: Overlay must be requested in the format
    passed to the QGLWidget constructor.) Your GL widget should also
    implement some or all of these virtual methods:

    \list
    \li paintOverlayGL()
    \li resizeOverlayGL()
    \li initializeOverlayGL()
    \endlist

    These methods work in the same way as the normal paintGL() etc.
    functions, except that they will be called when the overlay
    context is made current. You can explicitly make the overlay
    context current by using makeOverlayCurrent(), and you can access
    the overlay context directly (e.g. to ask for its transparent
    color) by calling overlayContext().

    On X servers in which the default visual is in an overlay plane,
    non-GL Qt windows can also be used for overlays.

    \section1 Painting Techniques

    As described above, subclass QGLWidget to render pure 3D content in the
    following way:

    \list
    \li Reimplement the QGLWidget::initializeGL() and QGLWidget::resizeGL() to
       set up the OpenGL state and provide a perspective transformation.
    \li Reimplement QGLWidget::paintGL() to paint the 3D scene, calling only
       OpenGL functions to draw on the widget.
    \endlist

    It is also possible to draw 2D graphics onto a QGLWidget subclass, it is necessary
    to reimplement QGLWidget::paintEvent() and do the following:

    \list
    \li Construct a QPainter object.
    \li Initialize it for use on the widget with the QPainter::begin() function.
    \li Draw primitives using QPainter's member functions.
    \li Call QPainter::end() to finish painting.
    \endlist

    Overpainting 2D content on top of 3D content takes a little more effort.
    One approach to doing this is shown in the
    \l{Overpainting Example}{Overpainting} example.

    \section1 Threading

    As of Qt version 4.8, support for doing threaded GL rendering has
    been improved. There are three scenarios that we currently support:
    \list
    \li 1. Buffer swapping in a thread.

    Swapping buffers in a double buffered context may be a
    synchronous, locking call that may be a costly operation in some
    GL implementations. Especially so on embedded devices. It's not
    optimal to have the CPU idling while the GPU is doing a buffer
    swap. In those cases it is possible to do the rendering in the
    main thread and do the actual buffer swap in a separate
    thread. This can be done with the following steps:

    1. Call doneCurrent() in the main thread when the rendering is
    finished.

    2. Call QGLContext::moveToThread(swapThread) to transfer ownership
    of the context to the swapping thread.

    3. Notify the swapping thread that it can grab the context.

    4. Make the rendering context current in the swapping thread with
    makeCurrent() and then call swapBuffers().

    5. Call doneCurrent() in the swapping thread.

    6. Call QGLContext::moveToThread(qApp->thread()) and notify the
    main thread that swapping is done.

    Doing this will free up the main thread so that it can continue
    with, for example, handling UI events or network requests. Even if
    there is a context swap involved, it may be preferable compared to
    having the main thread wait while the GPU finishes the swap
    operation. Note that this is highly implementation dependent.

    \li 2. Texture uploading in a thread.

    Doing texture uploads in a thread may be very useful for
    applications handling large amounts of images that needs to be
    displayed, like for instance a photo gallery application. This is
    supported in Qt through the existing bindTexture() API. A simple
    way of doing this is to create two sharing QGLWidgets. One is made
    current in the main GUI thread, while the other is made current in
    the texture upload thread. The widget in the uploading thread is
    never shown, it is only used for sharing textures with the main
    thread. For each texture that is bound via bindTexture(), notify
    the main thread so that it can start using the texture.

    \li 3. Using QPainter to draw into a QGLWidget in a thread.

    In Qt 4.8, it is possible to draw into a QGLWidget using a
    QPainter in a separate thread. Note that this is also possible for
    QGLPixelBuffers and QGLFramebufferObjects. Since this is only
    supported in the GL 2 paint engine, OpenGL 2.0 or OpenGL ES 2.0 is
    required.

    QGLWidgets can only be created in the main GUI thread. This means
    a call to doneCurrent() is necessary to release the GL context
    from the main thread, before the widget can be drawn into by
    another thread. You then need to call QGLContext::moveToThread()
    to transfer ownership of the context to the thread in which you
    want to make it current.
    Also, the main GUI thread will dispatch resize and
    paint events to a QGLWidget when the widget is resized, or parts
    of it becomes exposed or needs redrawing. It is therefore
    necessary to handle those events because the default
    implementations inside QGLWidget will try to make the QGLWidget's
    context current, which again will interfere with any threads
    rendering into the widget. Reimplement QGLWidget::paintEvent() and
    QGLWidget::resizeEvent() to notify the rendering thread that a
    resize or update is necessary, and be careful not to call the base
    class implementation. If you are rendering an animation, it might
    not be necessary to handle the paint event at all since the
    rendering thread is doing regular updates. Then it would be enough
    to reimplement QGLWidget::paintEvent() to do nothing.

    \endlist

    As a general rule when doing threaded rendering: be aware that
    binding and releasing contexts in different threads have to be
    synchronized by the user. A GL rendering context can only be
    current in one thread at any time. If you try to open a QPainter
    on a QGLWidget and the widget's rendering context is current in
    another thread, it will fail.

    In addition to this, rendering using raw GL calls in a separate
    thread is supported.

    \e{OpenGL is a trademark of Silicon Graphics, Inc. in the United States and other
    countries.}

    \sa QGLPixelBuffer, {Hello GL Example}, {2D Painting Example}, {Overpainting Example},
        {Grabber Example}
*/

/*!
    Constructs an OpenGL widget with a \a parent widget.

    The \l{QGLFormat::defaultFormat()}{default format} is
    used. The widget will be \l{isValid()}{invalid} if the
    system has no \l{QGLFormat::hasOpenGL()}{OpenGL support}.

    The \a parent and widget flag, \a f, arguments are passed
    to the QWidget constructor.

    If \a shareWidget is a valid QGLWidget, this widget will share
    OpenGL display lists and texture objects with \a shareWidget. But
    if \a shareWidget and this widget have different \l {format()}
    {formats}, sharing might not be possible. You can check whether
    sharing is in effect by calling isSharing().

    The initialization of OpenGL rendering state, etc. should be done
    by overriding the initializeGL() function, rather than in the
    constructor of your QGLWidget subclass.

    \sa QGLFormat::defaultFormat(), {Textures Example}
*/

QGLWidget::QGLWidget(QWidget *parent, const QGLWidget* shareWidget, Qt::WindowFlags f)
    : QWidget(*(new QGLWidgetPrivate), parent, f | Qt::MSWindowsOwnDC)
{
    Q_D(QGLWidget);
    setAttribute(Qt::WA_PaintOnScreen);
    setAttribute(Qt::WA_NoSystemBackground);
    setAutoFillBackground(true); // for compatibility
    d->init(new QGLContext(QGLFormat::defaultFormat(), this), shareWidget);
}

/*!
  \internal
 */
QGLWidget::QGLWidget(QGLWidgetPrivate &dd, const QGLFormat &format, QWidget *parent, const QGLWidget *shareWidget, Qt::WindowFlags f)
    : QWidget(dd, parent, f | Qt::MSWindowsOwnDC)
{
    Q_D(QGLWidget);
    setAttribute(Qt::WA_PaintOnScreen);
    setAttribute(Qt::WA_NoSystemBackground);
    setAutoFillBackground(true); // for compatibility
    d->init(new QGLContext(format, this), shareWidget);

}


/*!
    Constructs an OpenGL widget with parent \a parent.

    The \a format argument specifies the desired
    \l{QGLFormat}{rendering options}.
    If the underlying OpenGL/Window system
    cannot satisfy all the features requested in \a format, the
    nearest subset of features will be used. After creation, the
    format() method will return the actual format obtained.

    The widget will be \l{isValid()}{invalid} if the system
    has no \l{QGLFormat::hasOpenGL()}{OpenGL support}.

    The \a parent and widget flag, \a f, arguments are passed
    to the QWidget constructor.

    If \a shareWidget is a valid QGLWidget, this widget will share
    OpenGL display lists and texture objects with \a shareWidget. But
    if \a shareWidget and this widget have different \l {format()}
    {formats}, sharing might not be possible. You can check whether
    sharing is in effect by calling isSharing().

    The initialization of OpenGL rendering state, etc. should be done
    by overriding the initializeGL() function, rather than in the
    constructor of your QGLWidget subclass.

    \sa QGLFormat::defaultFormat(), isValid()
*/

QGLWidget::QGLWidget(const QGLFormat &format, QWidget *parent, const QGLWidget* shareWidget,
                     Qt::WindowFlags f)
    : QWidget(*(new QGLWidgetPrivate), parent, f | Qt::MSWindowsOwnDC)
{
    Q_D(QGLWidget);
    setAttribute(Qt::WA_PaintOnScreen);
    setAttribute(Qt::WA_NoSystemBackground);
    setAutoFillBackground(true); // for compatibility
    d->init(new QGLContext(format, this), shareWidget);
}

/*!
    Constructs an OpenGL widget with parent \a parent.

    The \a context argument is a pointer to the QGLContext that
    you wish to be bound to this widget. This allows you to pass in
    your own QGLContext sub-classes.

    The widget will be \l{isValid()}{invalid} if the system
    has no \l{QGLFormat::hasOpenGL()}{OpenGL support}.

    The \a parent and widget flag, \a f, arguments are passed
    to the QWidget constructor.

    If \a shareWidget is a valid QGLWidget, this widget will share
    OpenGL display lists and texture objects with \a shareWidget. But
    if \a shareWidget and this widget have different \l {format()}
    {formats}, sharing might not be possible. You can check whether
    sharing is in effect by calling isSharing().

    The initialization of OpenGL rendering state, etc. should be done
    by overriding the initializeGL() function, rather than in the
    constructor of your QGLWidget subclass.

    \sa QGLFormat::defaultFormat(), isValid()
*/
QGLWidget::QGLWidget(QGLContext *context, QWidget *parent, const QGLWidget *shareWidget,
                     Qt::WindowFlags f)
    : QWidget(*(new QGLWidgetPrivate), parent, f | Qt::MSWindowsOwnDC)
{
    Q_D(QGLWidget);
    setAttribute(Qt::WA_PaintOnScreen);
    setAttribute(Qt::WA_NoSystemBackground);
    setAutoFillBackground(true); // for compatibility
    d->init(context, shareWidget);
}

/*!
    Destroys the widget.
*/

QGLWidget::~QGLWidget()
{
    Q_D(QGLWidget);
    delete d->glcx;
    d->glcx = 0;
    d->cleanupColormaps();
}

/*!
    \fn QGLFormat QGLWidget::format() const

    Returns the format of the contained GL rendering context.
*/

/*!
    \fn bool QGLWidget::doubleBuffer() const

    Returns \c true if the contained GL rendering context has double
    buffering; otherwise returns \c false.

    \sa QGLFormat::doubleBuffer()
*/

/*!
    \fn void QGLWidget::setAutoBufferSwap(bool on)

    If \a on is true automatic GL buffer swapping is switched on;
    otherwise it is switched off.

    If \a on is true and the widget is using a double-buffered format,
    the background and foreground GL buffers will automatically be
    swapped after each paintGL() call.

    The buffer auto-swapping is on by default.

    \sa autoBufferSwap(), doubleBuffer(), swapBuffers()
*/

/*!
    \fn bool QGLWidget::autoBufferSwap() const

    Returns \c true if the widget is doing automatic GL buffer swapping;
    otherwise returns \c false.

    \sa setAutoBufferSwap()
*/

/*!
    \fn QFunctionPointer QGLContext::getProcAddress(const QString &proc) const

    Returns a function pointer to the GL extension function passed in
    \a proc. 0 is returned if a pointer to the function could not be
    obtained.
*/

/*!
    \fn bool QGLWidget::isValid() const

    Returns \c true if the widget has a valid GL rendering context;
    otherwise returns \c false. A widget will be invalid if the system
    has no \l{QGLFormat::hasOpenGL()}{OpenGL support}.
*/

bool QGLWidget::isValid() const
{
    Q_D(const QGLWidget);
    return d->glcx && d->glcx->isValid();
}

/*!
    \fn bool QGLWidget::isSharing() const

    Returns \c true if this widget's GL context is shared with another GL
    context, otherwise false is returned. Context sharing might not be
    possible if the widgets use different formats.

    \sa format()
*/

bool QGLWidget::isSharing() const
{
    Q_D(const QGLWidget);
    return d->glcx->isSharing();
}

/*!
    \fn void QGLWidget::makeCurrent()

    Makes this widget the current widget for OpenGL operations, i.e.
    makes the widget's rendering context the current OpenGL rendering
    context.
*/

void QGLWidget::makeCurrent()
{
    Q_D(QGLWidget);
    d->glcx->makeCurrent();
}

/*!
    \fn void QGLWidget::doneCurrent()

    Makes no GL context the current context. Normally, you do not need
    to call this function; QGLContext calls it as necessary. However,
    it may be useful in multithreaded environments.
*/

void QGLWidget::doneCurrent()
{
    Q_D(QGLWidget);
    d->glcx->doneCurrent();
}

/*!
    \fn void QGLWidget::swapBuffers()

    Swaps the screen contents with an off-screen buffer. This only
    works if the widget's format specifies double buffer mode.

    Normally, there is no need to explicitly call this function
    because it is done automatically after each widget repaint, i.e.
    each time after paintGL() has been executed.

    \sa doubleBuffer(), setAutoBufferSwap(), QGLFormat::setDoubleBuffer()
*/

void QGLWidget::swapBuffers()
{
    Q_D(QGLWidget);
    d->glcx->swapBuffers();
}


/*!
    \fn const QGLContext* QGLWidget::overlayContext() const

    Returns the overlay context of this widget, or 0 if this widget
    has no overlay.

    \sa context()
*/



/*!
    \fn void QGLWidget::makeOverlayCurrent()

    Makes the overlay context of this widget current. Use this if you
    need to issue OpenGL commands to the overlay context outside of
    initializeOverlayGL(), resizeOverlayGL(), and paintOverlayGL().

    Does nothing if this widget has no overlay.

    \sa makeCurrent()
*/


/*!
  \obsolete

  Sets a new format for this widget.

  If the underlying OpenGL/Window system cannot satisfy all the
  features requested in \a format, the nearest subset of features will
  be used. After creation, the format() method will return the actual
  rendering context format obtained.

  The widget will be assigned a new QGLContext, and the initializeGL()
  function will be executed for this new context before the first
  resizeGL() or paintGL().

  This method will try to keep display list and texture object sharing
  in effect with other QGLWidget objects, but changing the format might make
  sharing impossible. Use isSharing() to see if sharing is still in
  effect.

  \sa format(), isSharing(), isValid()
*/

void QGLWidget::setFormat(const QGLFormat &format)
{
    setContext(new QGLContext(format,this));
}




/*!
    \fn QGLContext *QGLWidget::context() const

    Returns the context of this widget.

    It is possible that the context is not valid (see isValid()), for
    example, if the underlying hardware does not support the format
    attributes that were requested.
*/

/*!
  \fn void QGLWidget::setContext(QGLContext *context,
                                 const QGLContext* shareContext,
                                 bool deleteOldContext)
  \obsolete

  Sets a new context for this widget. The QGLContext \a context must
  be created using \e new. QGLWidget will delete \a context when
  another context is set or when the widget is destroyed.

  If \a context is invalid, QGLContext::create() is performed on
  it. The initializeGL() function will then be executed for the new
  context before the first resizeGL() or paintGL().

  If \a context is invalid, this method will try to keep display list
  and texture object sharing in effect, or (if \a shareContext points
  to a valid context) start display list and texture object sharing
  with that context, but sharing might be impossible if the two
  contexts have different \l {format()} {formats}. Use isSharing() to
  see whether sharing is in effect.

  If \a deleteOldContext is true (the default), the existing context
  will be deleted. You may use false here if you have kept a pointer
  to the old context (as returned by context()), and want to restore
  that context later.

  \note This function is obsolete and should no longer be used. If you were
  using it to recreate the context for a QGLWidget, you should instead create a
  new QGLWidget or use the QOpenGLContext API in conjunction with QWindow.
  There is currently no officially supported way to substitute QGLWidget's
  context with your own implementation of QGLContext.

  \sa context(), isSharing()
*/



/*!
    \fn void QGLWidget::updateGL()

    Updates the widget by calling glDraw().
*/

void QGLWidget::updateGL()
{
    Q_D(QGLWidget);
    const bool targetIsOffscreen = !d->glcx->d_ptr->readback_target_size.isEmpty();
    if (updatesEnabled() && (testAttribute(Qt::WA_Mapped) || targetIsOffscreen))
        glDraw();
}


/*!
    \fn void QGLWidget::updateOverlayGL()

    Updates the widget's overlay (if any). Will cause the virtual
    function paintOverlayGL() to be executed.

    The widget's rendering context will become the current context and
    initializeGL() will be called if it hasn't already been called.
*/


/*!
    This virtual function is called once before the first call to
    paintGL() or resizeGL(), and then once whenever the widget has
    been assigned a new QGLContext. Reimplement it in a subclass.

    This function should set up any required OpenGL context rendering
    flags, defining display lists, etc.

    There is no need to call makeCurrent() because this has already
    been done when this function is called.
*/

void QGLWidget::initializeGL()
{
}


/*!
    This virtual function is called whenever the widget needs to be
    painted. Reimplement it in a subclass.

    There is no need to call makeCurrent() because this has already
    been done when this function is called.
*/

void QGLWidget::paintGL()
{
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
}


/*!
    \fn void QGLWidget::resizeGL(int width , int height)

    This virtual function is called whenever the widget has been
    resized. The new size is passed in \a width and \a height.
    Reimplement it in a subclass.

    There is no need to call makeCurrent() because this has already
    been done when this function is called.
*/

void QGLWidget::resizeGL(int, int)
{
}



/*!
    This virtual function is used in the same manner as initializeGL()
    except that it operates on the widget's overlay context instead of
    the widget's main context. This means that initializeOverlayGL()
    is called once before the first call to paintOverlayGL() or
    resizeOverlayGL(). Reimplement it in a subclass.

    This function should set up any required OpenGL context rendering
    flags, defining display lists, etc. for the overlay context.

    There is no need to call makeOverlayCurrent() because this has
    already been done when this function is called.
*/

void QGLWidget::initializeOverlayGL()
{
}


/*!
    This virtual function is used in the same manner as paintGL()
    except that it operates on the widget's overlay context instead of
    the widget's main context. This means that paintOverlayGL() is
    called whenever the widget's overlay needs to be painted.
    Reimplement it in a subclass.

    There is no need to call makeOverlayCurrent() because this has
    already been done when this function is called.
*/

void QGLWidget::paintOverlayGL()
{
}


/*!
    \fn void QGLWidget::resizeOverlayGL(int width , int height)

    This virtual function is used in the same manner as paintGL()
    except that it operates on the widget's overlay context instead of
    the widget's main context. This means that resizeOverlayGL() is
    called whenever the widget has been resized. The new size is
    passed in \a width and \a height. Reimplement it in a subclass.

    There is no need to call makeOverlayCurrent() because this has
    already been done when this function is called.
*/

void QGLWidget::resizeOverlayGL(int, int)
{
}

/*!
    \fn void QGLWidget::paintEvent(QPaintEvent *event)

    Handles paint events passed in the \a event parameter. Will cause
    the virtual paintGL() function to be called.

    The widget's rendering context will become the current context and
    initializeGL() will be called if it hasn't already been called.
*/

void QGLWidget::paintEvent(QPaintEvent *)
{
    if (updatesEnabled()) {
        glDraw();
        updateOverlayGL();
    }
}


/*!
    \fn void QGLWidget::resizeEvent(QResizeEvent *event)

    Handles resize events that are passed in the \a event parameter.
    Calls the virtual function resizeGL().
*/


/*!
    Renders the current scene on a pixmap and returns the pixmap.

    You can use this method on both visible and invisible QGLWidget objects.

    Internally the function renders into a framebuffer object and performs pixel
    readback. This has a performance penalty, meaning that this function is not
    suitable to be called at a high frequency.

    After creating and binding the framebuffer object, the function will call
    initializeGL(), resizeGL(), and paintGL(). On the next normal update
    initializeGL() and resizeGL() will be triggered again since the size of the
    destination pixmap and the QGLWidget's size may differ.

    The size of the pixmap will be \a w pixels wide and \a h pixels high unless
    one of these parameters is 0 (the default), in which case the pixmap will
    have the same size as the widget.

    Care must be taken when using framebuffer objects in paintGL() in
    combination with this function. To switch back to the default framebuffer,
    use QGLFramebufferObject::bindDefault(). Binding FBO 0 is wrong since
    renderPixmap() uses a custom framebuffer instead of the one provided by the
    windowing system.

    \a useContext is ignored. Historically this parameter enabled the usage of
    the existing GL context. This is not supported anymore since additional
    contexts are never created.

    Overlays are not rendered onto the pixmap.

    If the GL rendering context and the desktop have different bit
    depths, the result will most likely look surprising.

    Note that the creation of display lists, modifications of the view
    frustum etc. should be done from within initializeGL(). If this is
    not done, the temporary QGLContext will not be initialized
    properly, and the rendered pixmap may be incomplete/corrupted.
*/

QPixmap QGLWidget::renderPixmap(int w, int h, bool useContext)
{
    Q_UNUSED(useContext);
    Q_D(QGLWidget);

    QSize sz = size();
    if ((w > 0) && (h > 0))
        sz = QSize(w, h);

    QPixmap pm;
    if (d->glcx->isValid()) {
        d->glcx->makeCurrent();
        QGLFramebufferObject fbo(sz, QGLFramebufferObject::CombinedDepthStencil);
        fbo.bind();
        d->glcx->setInitialized(false);
        uint prevDefaultFbo = d->glcx->d_ptr->default_fbo;
        d->glcx->d_ptr->default_fbo = fbo.handle();
        d->glcx->d_ptr->readback_target_size = sz;
        updateGL();
        fbo.release();
        pm = QPixmap::fromImage(fbo.toImage());
        d->glcx->d_ptr->default_fbo = prevDefaultFbo;
        d->glcx->setInitialized(false);
        d->glcx->d_ptr->readback_target_size = QSize();
    }

    return pm;
}

/*!
    Returns an image of the frame buffer. If \a withAlpha is true the
    alpha channel is included.

    Depending on your hardware, you can explicitly select which color
    buffer to grab with a glReadBuffer() call before calling this
    function.

    On QNX the back buffer is not preserved when swapBuffers() is called. The back buffer
    where this function reads from, might thus not contain the same content as the front buffer.
    In order to retrieve what is currently visible on the screen, swapBuffers()
    has to be executed prior to this function call.
*/
QImage QGLWidget::grabFrameBuffer(bool withAlpha)
{
    makeCurrent();
    QImage res;
    qreal pixelRatio = devicePixelRatio();
    int w = pixelRatio * width();
    int h = pixelRatio * height();
    if (format().rgba())
        res = qt_gl_read_frame_buffer(QSize(w, h), format().alpha(), withAlpha);
    res.setDevicePixelRatio(pixelRatio);
    return res;
}



/*!
    Initializes OpenGL for this widget's context. Calls the virtual
    function initializeGL().
*/

void QGLWidget::glInit()
{
    Q_D(QGLWidget);
    if (!isValid())
        return;
    makeCurrent();
    initializeGL();
    d->glcx->setInitialized(true);
}


/*!
    Executes the virtual function paintGL().

    The widget's rendering context will become the current context and
    initializeGL() will be called if it hasn't already been called.
*/

void QGLWidget::glDraw()
{
    Q_D(QGLWidget);
    if (!isValid())
        return;
    makeCurrent();
#ifndef QT_OPENGL_ES
    if (d->glcx->deviceIsPixmap() && !d->glcx->contextHandle()->isOpenGLES())
        glDrawBuffer(GL_FRONT);
#endif
    QSize readback_target_size = d->glcx->d_ptr->readback_target_size;
    if (!d->glcx->initialized()) {
        glInit();
        const qreal scaleFactor = (window() && window()->windowHandle()) ?
            window()->windowHandle()->devicePixelRatio() : 1.0;
        int w, h;
        if (readback_target_size.isEmpty()) {
            w = d->glcx->device()->width() * scaleFactor;
            h = d->glcx->device()->height() * scaleFactor;
        } else {
            w = readback_target_size.width();
            h = readback_target_size.height();
        }
        resizeGL(w, h); // New context needs this "resize"
    }
    paintGL();
    if (doubleBuffer() && readback_target_size.isEmpty()) {
        if (d->autoSwap)
            swapBuffers();
    } else {
        glFlush();
    }
}

/*!
    Convenience function for specifying a drawing color to OpenGL.
    Calls glColor4 (in RGBA mode) or glIndex (in color-index mode)
    with the color \a c. Applies to this widgets GL context.

    \note This function is not supported on OpenGL/ES 2.0 systems.

    \sa qglClearColor(), QGLContext::currentContext(), QColor
*/

void QGLWidget::qglColor(const QColor& c) const
{
#if !defined(QT_OPENGL_ES_2)
#ifdef QT_OPENGL_ES
    glColor4f(c.redF(), c.greenF(), c.blueF(), c.alphaF());
#else
    Q_D(const QGLWidget);
    const QGLContext *ctx = QGLContext::currentContext();
    if (ctx && !ctx->contextHandle()->isOpenGLES()) {
        if (ctx->format().rgba())
            glColor4f(c.redF(), c.greenF(), c.blueF(), c.alphaF());
        else if (!d->cmap.isEmpty()) { // QGLColormap in use?
            int i = d->cmap.find(c.rgb());
            if (i < 0)
                i = d->cmap.findNearest(c.rgb());
            glIndexi(i);
        } else
            glIndexi(ctx->colorIndex(c));
    }
#endif //QT_OPENGL_ES
#else
    Q_UNUSED(c);
#endif //QT_OPENGL_ES_2
}

/*!
    Convenience function for specifying the clearing color to OpenGL.
    Calls glClearColor (in RGBA mode) or glClearIndex (in color-index
    mode) with the color \a c. Applies to this widgets GL context.

    \sa qglColor(), QGLContext::currentContext(), QColor
*/

void QGLWidget::qglClearColor(const QColor& c) const
{
#ifdef QT_OPENGL_ES
    glClearColor(c.redF(), c.greenF(), c.blueF(), c.alphaF());
#else
    Q_D(const QGLWidget);
    const QGLContext *ctx = QGLContext::currentContext();
    if (ctx && !ctx->contextHandle()->isOpenGLES()) {
        if (ctx->format().rgba())
            glClearColor(c.redF(), c.greenF(), c.blueF(), c.alphaF());
        else if (!d->cmap.isEmpty()) { // QGLColormap in use?
            int i = d->cmap.find(c.rgb());
            if (i < 0)
                i = d->cmap.findNearest(c.rgb());
            glClearIndex(i);
        } else {
            glClearIndex(ctx->colorIndex(c));
        }
    } else {
        glClearColor(c.redF(), c.greenF(), c.blueF(), c.alphaF());
    }
#endif
}


/*!
    Converts the image \a img into the unnamed format expected by
    OpenGL functions such as glTexImage2D(). The returned image is not
    usable as a QImage, but QImage::width(), QImage::height() and
    QImage::bits() may be used with OpenGL. The GL format used is
    \c GL_RGBA.

    \omit ###

    \l opengl/texture example
    The following few lines are from the texture example. Most of the
    code is irrelevant, so we just quote the relevant bits:

    \quotefromfile opengl/texture/gltexobj.cpp
    \skipto tex1
    \printline tex1
    \printline gllogo.bmp

    We create \e tex1 (and another variable) for OpenGL, and load a real
    image into \e buf.

    \skipto convertToGLFormat
    \printline convertToGLFormat

    A few lines later, we convert \e buf into OpenGL format and store it
    in \e tex1.

    \skipto glTexImage2D
    \printline glTexImage2D
    \printline tex1.bits

    Note the dimension restrictions for texture images as described in
    the glTexImage2D() documentation. The width must be 2^m + 2*border
    and the height 2^n + 2*border where m and n are integers and
    border is either 0 or 1.

    Another function in the same example uses \e tex1 with OpenGL.

    \endomit
*/

QImage QGLWidget::convertToGLFormat(const QImage& img)
{
    QImage res(img.size(), QImage::Format_ARGB32);
    convertToGLFormatHelper(res, img.convertToFormat(QImage::Format_ARGB32), GL_RGBA);
    return res;
}


/*!
    \fn QGLColormap & QGLWidget::colormap() const

    Returns the colormap for this widget.

    Usually it is only top-level widgets that can have different
    colormaps installed. Asking for the colormap of a child widget
    will return the colormap for the child's top-level widget.

    If no colormap has been set for this widget, the QGLColormap
    returned will be empty.

    \sa setColormap(), QGLColormap::isEmpty()
*/

/*!
    \fn void QGLWidget::setColormap(const QGLColormap & cmap)

    Set the colormap for this widget to \a cmap. Usually it is only
    top-level widgets that can have colormaps installed.

    \sa colormap()
*/

#ifndef QT_OPENGL_ES

static void qt_save_gl_state()
{
    glPushClientAttrib(GL_CLIENT_ALL_ATTRIB_BITS);
    glPushAttrib(GL_ALL_ATTRIB_BITS);
    glMatrixMode(GL_TEXTURE);
    glPushMatrix();
    glLoadIdentity();
    glMatrixMode(GL_PROJECTION);
    glPushMatrix();
    glMatrixMode(GL_MODELVIEW);
    glPushMatrix();

    glShadeModel(GL_FLAT);
    glDisable(GL_CULL_FACE);
    glDisable(GL_LIGHTING);
    glDisable(GL_STENCIL_TEST);
    glDisable(GL_DEPTH_TEST);
    glEnable(GL_BLEND);
    glBlendFunc(GL_ONE, GL_ONE_MINUS_SRC_ALPHA);
}

static void qt_restore_gl_state()
{
    glMatrixMode(GL_TEXTURE);
    glPopMatrix();
    glMatrixMode(GL_PROJECTION);
    glPopMatrix();
    glMatrixMode(GL_MODELVIEW);
    glPopMatrix();
    glPopAttrib();
    glPopClientAttrib();
}

static void qt_gl_draw_text(QPainter *p, int x, int y, const QString &str,
                            const QFont &font)
{
    GLfloat color[4];
    glGetFloatv(GL_CURRENT_COLOR, &color[0]);

    QColor col;
    col.setRgbF(color[0], color[1], color[2],color[3]);
    QPen old_pen = p->pen();
    QFont old_font = p->font();

    p->setPen(col);
    p->setFont(font);
    p->drawText(x, y, str);

    p->setPen(old_pen);
    p->setFont(old_font);
}

#endif // !QT_OPENGL_ES

/*!
   Renders the string \a str into the GL context of this widget.

   \a x and \a y are specified in window coordinates, with the origin
   in the upper left-hand corner of the window. If \a font is not
   specified, the currently set application font will be used to
   render the string. To change the color of the rendered text you can
   use the glColor() call (or the qglColor() convenience function),
   just before the renderText() call.

   \note This function clears the stencil buffer.

   \note This function is not supported on OpenGL/ES systems.

   \note This function temporarily disables depth-testing when the
   text is drawn.

   \note This function can only be used inside a
   QPainter::beginNativePainting()/QPainter::endNativePainting() block
   if a painter is active on the QGLWidget.

   \l{Overpainting Example}{Overpaint} with QPainter::drawText() instead.
*/

void QGLWidget::renderText(int x, int y, const QString &str, const QFont &font)
{
#ifndef QT_OPENGL_ES
    Q_D(QGLWidget);
    if (!d->glcx->contextHandle()->isOpenGLES()) {
        Q_D(QGLWidget);
        if (str.isEmpty() || !isValid())
            return;

        GLint view[4];
        bool use_scissor_testing = glIsEnabled(GL_SCISSOR_TEST);
        if (!use_scissor_testing)
            glGetIntegerv(GL_VIEWPORT, &view[0]);
        int width = d->glcx->device()->width();
        int height = d->glcx->device()->height();
        bool auto_swap = autoBufferSwap();

        QPaintEngine *engine = paintEngine();

        qt_save_gl_state();

        QPainter *p;
        bool reuse_painter = false;
        if (engine->isActive()) {
            reuse_painter = true;
            p = engine->painter();

            glDisable(GL_DEPTH_TEST);
            glViewport(0, 0, width, height);
        } else {
            setAutoBufferSwap(false);
            // disable glClear() as a result of QPainter::begin()
            d->disable_clear_on_painter_begin = true;
            p = new QPainter(this);
        }

        QRect viewport(view[0], view[1], view[2], view[3]);
        if (!use_scissor_testing && viewport != rect()) {
            // if the user hasn't set a scissor box, we set one that
            // covers the current viewport
            glScissor(view[0], view[1], view[2], view[3]);
            glEnable(GL_SCISSOR_TEST);
        } else if (use_scissor_testing) {
            // use the scissor box set by the user
            glEnable(GL_SCISSOR_TEST);
        }

        qt_gl_draw_text(p, x, y, str, font);

        if (!reuse_painter) {
            p->end();
            delete p;
            setAutoBufferSwap(auto_swap);
            d->disable_clear_on_painter_begin = false;
        }

        qt_restore_gl_state();

        return;
    }
#else // QT_OPENGL_ES
    Q_UNUSED(x);
    Q_UNUSED(y);
    Q_UNUSED(str);
    Q_UNUSED(font);
#endif
    qWarning("QGLWidget::renderText is not supported under OpenGL/ES");
}

/*! \overload

    \a x, \a y and \a z are specified in scene or object coordinates
    relative to the currently set projection and model matrices. This
    can be useful if you want to annotate models with text labels and
    have the labels move with the model as it is rotated etc.

    \note This function is not supported on OpenGL/ES systems.

    \note If depth testing is enabled before this function is called,
    then the drawn text will be depth-tested against the models that
    have already been drawn in the scene.  Use \c{glDisable(GL_DEPTH_TEST)}
    before calling this function to annotate the models without
    depth-testing the text.

    \note This function can only be used inside a
    QPainter::beginNativePainting()/QPainter::endNativePainting() block
    if a painter is active on the QGLWidget.

    \l{Overpainting Example}{Overpaint} with QPainter::drawText() instead.
*/
void QGLWidget::renderText(double x, double y, double z, const QString &str, const QFont &font)
{
#ifndef QT_OPENGL_ES
    Q_D(QGLWidget);
    if (!d->glcx->contextHandle()->isOpenGLES()) {
        Q_D(QGLWidget);
        if (str.isEmpty() || !isValid())
            return;

        bool auto_swap = autoBufferSwap();

        int width = d->glcx->device()->width();
        int height = d->glcx->device()->height();
        GLdouble model[4 * 4], proj[4 * 4];
        GLint view[4];
        glGetDoublev(GL_MODELVIEW_MATRIX, &model[0]);
        glGetDoublev(GL_PROJECTION_MATRIX, &proj[0]);
        glGetIntegerv(GL_VIEWPORT, &view[0]);
        GLdouble win_x = 0, win_y = 0, win_z = 0;
        qgluProject(x, y, z, &model[0], &proj[0], &view[0],
                    &win_x, &win_y, &win_z);
        win_y = height - win_y; // y is inverted

        QPaintEngine *engine = paintEngine();

        QPainter *p;
        bool reuse_painter = false;
        bool use_depth_testing = glIsEnabled(GL_DEPTH_TEST);
        bool use_scissor_testing = glIsEnabled(GL_SCISSOR_TEST);

        qt_save_gl_state();

        if (engine->isActive()) {
            reuse_painter = true;
            p = engine->painter();
        } else {
            setAutoBufferSwap(false);
            // disable glClear() as a result of QPainter::begin()
            d->disable_clear_on_painter_begin = true;
            p = new QPainter(this);
        }

        QRect viewport(view[0], view[1], view[2], view[3]);
        if (!use_scissor_testing && viewport != rect()) {
            glScissor(view[0], view[1], view[2], view[3]);
            glEnable(GL_SCISSOR_TEST);
        } else if (use_scissor_testing) {
            glEnable(GL_SCISSOR_TEST);
        }
        glViewport(0, 0, width, height);
        glAlphaFunc(GL_GREATER, 0.0);
        glEnable(GL_ALPHA_TEST);
        if (use_depth_testing)
            glEnable(GL_DEPTH_TEST);

        // The only option in Qt 5 is the shader-based OpenGL 2 paint engine.
        // Setting fixed pipeline transformations is futile. Instead, pass the
        // extra values directly and let the engine figure the matrices out.
        static_cast<QGL2PaintEngineEx *>(p->paintEngine())->setTranslateZ(-win_z);

        qt_gl_draw_text(p, qRound(win_x), qRound(win_y), str, font);

        static_cast<QGL2PaintEngineEx *>(p->paintEngine())->setTranslateZ(0);

        if (!reuse_painter) {
            p->end();
            delete p;
            setAutoBufferSwap(auto_swap);
            d->disable_clear_on_painter_begin = false;
        }

        qt_restore_gl_state();

        return;
    }
#else // QT_OPENGL_ES
    Q_UNUSED(x);
    Q_UNUSED(y);
    Q_UNUSED(z);
    Q_UNUSED(str);
    Q_UNUSED(font);
#endif
    qWarning("QGLWidget::renderText is not supported under OpenGL/ES");
}

QGLFormat QGLWidget::format() const
{
    Q_D(const QGLWidget);
    return d->glcx->format();
}

QGLContext *QGLWidget::context() const
{
    Q_D(const QGLWidget);
    return d->glcx;
}

bool QGLWidget::doubleBuffer() const
{
    Q_D(const QGLWidget);
    return d->glcx->d_ptr->glFormat.testOption(QGL::DoubleBuffer);
}

void QGLWidget::setAutoBufferSwap(bool on)
{
    Q_D(QGLWidget);
    d->autoSwap = on;
}

bool QGLWidget::autoBufferSwap() const
{
    Q_D(const QGLWidget);
    return d->autoSwap;
}

/*!
    Calls QGLContext:::bindTexture(\a image, \a target, \a format) on the currently
    set context.

    \sa deleteTexture()
*/
GLuint QGLWidget::bindTexture(const QImage &image, GLenum target, GLint format)
{
    if (image.isNull())
        return 0;

    Q_D(QGLWidget);
    return d->glcx->bindTexture(image, target, format, QGLContext::DefaultBindOption);
}

/*!
  \overload
  \since 4.6

  The binding \a options are a set of options used to decide how to
  bind the texture to the context.
 */
GLuint QGLWidget::bindTexture(const QImage &image, GLenum target, GLint format, QGLContext::BindOptions options)
{
    if (image.isNull())
        return 0;

    Q_D(QGLWidget);
    return d->glcx->bindTexture(image, target, format, options);
}


/*!
    Calls QGLContext:::bindTexture(\a pixmap, \a target, \a format) on the currently
    set context.

    \sa deleteTexture()
*/
GLuint QGLWidget::bindTexture(const QPixmap &pixmap, GLenum target, GLint format)
{
    if (pixmap.isNull())
        return 0;

    Q_D(QGLWidget);
    return d->glcx->bindTexture(pixmap, target, format, QGLContext::DefaultBindOption);
}

/*!
  \overload
  \since 4.6

  Generates and binds a 2D GL texture to the current context, based
  on \a pixmap. The generated texture id is returned and can be used in

  The binding \a options are a set of options used to decide how to
  bind the texture to the context.
 */
GLuint QGLWidget::bindTexture(const QPixmap &pixmap, GLenum target, GLint format,
                              QGLContext::BindOptions options)
{
    Q_D(QGLWidget);
    return d->glcx->bindTexture(pixmap, target, format, options);
}

/*! \overload

    Calls QGLContext::bindTexture(\a fileName) on the currently set context.

    \sa deleteTexture()
*/
GLuint QGLWidget::bindTexture(const QString &fileName)
{
    Q_D(QGLWidget);
    return d->glcx->bindTexture(fileName);
}

/*!
    Calls QGLContext::deleteTexture(\a id) on the currently set
    context.

    \sa bindTexture()
*/
void QGLWidget::deleteTexture(GLuint id)
{
    Q_D(QGLWidget);
    d->glcx->deleteTexture(id);
}

/*!
    \since 4.4

    Calls the corresponding QGLContext::drawTexture() with
    \a target, \a textureId, and \a textureTarget for this
    widget's context.
*/
void QGLWidget::drawTexture(const QRectF &target, GLuint textureId, GLenum textureTarget)
{
    Q_D(QGLWidget);
    d->glcx->drawTexture(target, textureId, textureTarget);
}

/*!
    \since 4.4

    Calls the corresponding QGLContext::drawTexture() with
    \a point, \a textureId, and \a textureTarget for this
    widget's context.
*/
void QGLWidget::drawTexture(const QPointF &point, GLuint textureId, GLenum textureTarget)
{
    Q_D(QGLWidget);
    d->glcx->drawTexture(point, textureId, textureTarget);
}

Q_GLOBAL_STATIC(QGLEngineThreadStorage<QGL2PaintEngineEx>, qt_gl_2_engine)

Q_OPENGL_EXPORT QPaintEngine* qt_qgl_paint_engine()
{
    return qt_gl_2_engine()->engine();
}

/*!
    \internal

    Returns the GL widget's paint engine.
*/
QPaintEngine *QGLWidget::paintEngine() const
{
    return qt_qgl_paint_engine();
}

/*
  This is the shared initialization for all platforms. Called from QGLWidgetPrivate::init()
*/
void QGLWidgetPrivate::initContext(QGLContext *context, const QGLWidget* shareWidget)
{
    Q_Q(QGLWidget);

    glDevice.setWidget(q);

    glcx = 0;
    autoSwap = true;

    if (context && !context->device())
        context->setDevice(q);
    q->setContext(context, shareWidget ? shareWidget->context() : 0);

    if (!glcx)
        glcx = new QGLContext(QGLFormat::defaultFormat(), q);
}

Q_GLOBAL_STATIC(QString, qt_gl_lib_name)

void qt_set_gl_library_name(const QString& name)
{
    qt_gl_lib_name()->operator=(name);
}

const QString qt_gl_library_name()
{
    if (qt_gl_lib_name()->isNull()) {
# if defined(QT_OPENGL_ES_2)
        return QLatin1String("GLESv2");
# else
        return QLatin1String("GL");
# endif
    }
    return *qt_gl_lib_name();
}

void QGLContextGroup::addShare(const QGLContext *context, const QGLContext *share) {
    Q_ASSERT(context && share);
    if (context->d_ptr->group == share->d_ptr->group)
        return;

    // Make sure 'context' is not already shared with another group of contexts.
    Q_ASSERT(context->d_ptr->group->m_refs.load() == 1);

    // Free 'context' group resources and make it use the same resources as 'share'.
    QGLContextGroup *group = share->d_ptr->group;
    delete context->d_ptr->group;
    context->d_ptr->group = group;
    group->m_refs.ref();

    // Maintain a list of all the contexts in each group of sharing contexts.
    // The list is empty if the "share" context wasn't sharing already.
    if (group->m_shares.isEmpty())
        group->m_shares.append(share);
    group->m_shares.append(context);
}

void QGLContextGroup::removeShare(const QGLContext *context) {
    // Remove the context from the group.
    QGLContextGroup *group = context->d_ptr->group;
    if (group->m_shares.isEmpty())
        return;
    group->m_shares.removeAll(context);

    // Update context group representative.
    Q_ASSERT(group->m_shares.size() != 0);
    if (group->m_context == context)
        group->m_context = group->m_shares[0];

    // If there is only one context left, then make the list empty.
    if (group->m_shares.size() == 1)
        group->m_shares.clear();
}

QSize QGLTexture::bindCompressedTexture
    (const QString& fileName, const char *format)
{
    QFile file(fileName);
    if (!file.open(QIODevice::ReadOnly))
        return QSize();
    QByteArray contents = file.readAll();
    file.close();
    return bindCompressedTexture
        (contents.constData(), contents.size(), format);
}

// PVR header format for container files that store textures compressed
// with the ETC1, PVRTC2, and PVRTC4 encodings.  Format information from the
// PowerVR SDK at http://www.imgtec.com/powervr/insider/powervr-sdk.asp
// "PVRTexTool Reference Manual, version 1.11f".
struct PvrHeader
{
    quint32 headerSize;
    quint32 height;
    quint32 width;
    quint32 mipMapCount;
    quint32 flags;
    quint32 dataSize;
    quint32 bitsPerPixel;
    quint32 redMask;
    quint32 greenMask;
    quint32 blueMask;
    quint32 alphaMask;
    quint32 magic;
    quint32 surfaceCount;
};

#define PVR_MAGIC               0x21525650      // "PVR!" in little-endian

#define PVR_FORMAT_MASK         0x000000FF
#define PVR_FORMAT_PVRTC2       0x00000018
#define PVR_FORMAT_PVRTC4       0x00000019
#define PVR_FORMAT_ETC1         0x00000036

#define PVR_HAS_MIPMAPS         0x00000100
#define PVR_TWIDDLED            0x00000200
#define PVR_NORMAL_MAP          0x00000400
#define PVR_BORDER_ADDED        0x00000800
#define PVR_CUBE_MAP            0x00001000
#define PVR_FALSE_COLOR_MIPMAPS 0x00002000
#define PVR_VOLUME_TEXTURE      0x00004000
#define PVR_ALPHA_IN_TEXTURE    0x00008000
#define PVR_VERTICAL_FLIP       0x00010000

#ifndef GL_COMPRESSED_RGB_PVRTC_4BPPV1_IMG
#define GL_COMPRESSED_RGB_PVRTC_4BPPV1_IMG      0x8C00
#define GL_COMPRESSED_RGB_PVRTC_2BPPV1_IMG      0x8C01
#define GL_COMPRESSED_RGBA_PVRTC_4BPPV1_IMG     0x8C02
#define GL_COMPRESSED_RGBA_PVRTC_2BPPV1_IMG     0x8C03
#endif

#ifndef GL_ETC1_RGB8_OES
#define GL_ETC1_RGB8_OES                        0x8D64
#endif

bool QGLTexture::canBindCompressedTexture
    (const char *buf, int len, const char *format, bool *hasAlpha)
{
    if (QSysInfo::ByteOrder != QSysInfo::LittleEndian) {
        // Compressed texture loading only supported on little-endian
        // systems such as x86 and ARM at the moment.
        return false;
    }
    if (!format) {
        // Auto-detect the format from the header.
        if (len >= 4 && !qstrncmp(buf, "DDS ", 4)) {
            *hasAlpha = true;
            return true;
        } else if (len >= 52 && !qstrncmp(buf + 44, "PVR!", 4)) {
            const PvrHeader *pvrHeader =
                reinterpret_cast<const PvrHeader *>(buf);
            *hasAlpha = (pvrHeader->alphaMask != 0);
            return true;
        }
    } else {
        // Validate the format against the header.
        if (!qstricmp(format, "DDS")) {
            if (len >= 4 && !qstrncmp(buf, "DDS ", 4)) {
                *hasAlpha = true;
                return true;
            }
        } else if (!qstricmp(format, "PVR") || !qstricmp(format, "ETC1")) {
            if (len >= 52 && !qstrncmp(buf + 44, "PVR!", 4)) {
                const PvrHeader *pvrHeader =
                    reinterpret_cast<const PvrHeader *>(buf);
                *hasAlpha = (pvrHeader->alphaMask != 0);
                return true;
            }
        }
    }
    return false;
}

#define ctx QGLContext::currentContext()

QSize QGLTexture::bindCompressedTexture
    (const char *buf, int len, const char *format)
{
    if (QSysInfo::ByteOrder != QSysInfo::LittleEndian) {
        // Compressed texture loading only supported on little-endian
        // systems such as x86 and ARM at the moment.
        return QSize();
    }
    if (!format) {
        // Auto-detect the format from the header.
        if (len >= 4 && !qstrncmp(buf, "DDS ", 4))
            return bindCompressedTextureDDS(buf, len);
        else if (len >= 52 && !qstrncmp(buf + 44, "PVR!", 4))
            return bindCompressedTexturePVR(buf, len);
    } else {
        // Validate the format against the header.
        if (!qstricmp(format, "DDS")) {
            if (len >= 4 && !qstrncmp(buf, "DDS ", 4))
                return bindCompressedTextureDDS(buf, len);
        } else if (!qstricmp(format, "PVR") || !qstricmp(format, "ETC1")) {
            if (len >= 52 && !qstrncmp(buf + 44, "PVR!", 4))
                return bindCompressedTexturePVR(buf, len);
        }
    }
    return QSize();
}

QSize QGLTexture::bindCompressedTextureDDS(const char *buf, int len)
{
    // We only support 2D texture loading at present.
    if (target != GL_TEXTURE_2D)
        return QSize();

    // Bail out if the necessary extension is not present.
    if (!qgl_extensions()->hasOpenGLExtension(QOpenGLExtensions::DDSTextureCompression)) {
        qWarning("QGLContext::bindTexture(): DDS texture compression is not supported.");
        return QSize();
    }

    const DDSFormat *ddsHeader = reinterpret_cast<const DDSFormat *>(buf + 4);
    if (!ddsHeader->dwLinearSize) {
        qWarning("QGLContext::bindTexture(): DDS image size is not valid.");
        return QSize();
    }

    int blockSize = 16;
    GLenum format;

    switch(ddsHeader->ddsPixelFormat.dwFourCC) {
    case FOURCC_DXT1:
        format = GL_COMPRESSED_RGBA_S3TC_DXT1_EXT;
        blockSize = 8;
        break;
    case FOURCC_DXT3:
        format = GL_COMPRESSED_RGBA_S3TC_DXT3_EXT;
        break;
    case FOURCC_DXT5:
        format = GL_COMPRESSED_RGBA_S3TC_DXT5_EXT;
        break;
    default:
        qWarning("QGLContext::bindTexture(): DDS image format not supported.");
        return QSize();
    }

    const GLubyte *pixels =
        reinterpret_cast<const GLubyte *>(buf + ddsHeader->dwSize + 4);

    glGenTextures(1, &id);
    glBindTexture(GL_TEXTURE_2D, id);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);

    int size;
    int offset = 0;
    int available = len - int(ddsHeader->dwSize + 4);
    int w = ddsHeader->dwWidth;
    int h = ddsHeader->dwHeight;

    // load mip-maps
    for(int i = 0; i < (int) ddsHeader->dwMipMapCount; ++i) {
        if (w == 0) w = 1;
        if (h == 0) h = 1;

        size = ((w+3)/4) * ((h+3)/4) * blockSize;
        if (size > available)
            break;
        qgl_extensions()->glCompressedTexImage2D(GL_TEXTURE_2D, i, format, w, h, 0,
                               size, pixels + offset);
        offset += size;
        available -= size;

        // half size for each mip-map level
        w = w/2;
        h = h/2;
    }

    // DDS images are not inverted.
    options &= ~QGLContext::InvertedYBindOption;

    return QSize(ddsHeader->dwWidth, ddsHeader->dwHeight);
}

QSize QGLTexture::bindCompressedTexturePVR(const char *buf, int len)
{
    // We only support 2D texture loading at present.  Cube maps later.
    if (target != GL_TEXTURE_2D)
        return QSize();

    // Determine which texture format we will be loading.
    const PvrHeader *pvrHeader = reinterpret_cast<const PvrHeader *>(buf);
    GLenum textureFormat;
    quint32 minWidth, minHeight;
    switch (pvrHeader->flags & PVR_FORMAT_MASK) {
    case PVR_FORMAT_PVRTC2:
        if (pvrHeader->alphaMask)
            textureFormat = GL_COMPRESSED_RGBA_PVRTC_2BPPV1_IMG;
        else
            textureFormat = GL_COMPRESSED_RGB_PVRTC_2BPPV1_IMG;
        minWidth = 16;
        minHeight = 8;
        break;

    case PVR_FORMAT_PVRTC4:
        if (pvrHeader->alphaMask)
            textureFormat = GL_COMPRESSED_RGBA_PVRTC_4BPPV1_IMG;
        else
            textureFormat = GL_COMPRESSED_RGB_PVRTC_4BPPV1_IMG;
        minWidth = 8;
        minHeight = 8;
        break;

    case PVR_FORMAT_ETC1:
        textureFormat = GL_ETC1_RGB8_OES;
        minWidth = 4;
        minHeight = 4;
        break;

    default:
        qWarning("QGLContext::bindTexture(): PVR image format 0x%x not supported.", int(pvrHeader->flags & PVR_FORMAT_MASK));
        return QSize();
    }

    // Bail out if the necessary extension is not present.
    if (textureFormat == GL_ETC1_RGB8_OES) {
        if (!qgl_extensions()->hasOpenGLExtension(QOpenGLExtensions::ETC1TextureCompression)) {
            qWarning("QGLContext::bindTexture(): ETC1 texture compression is not supported.");
            return QSize();
        }
    } else {
        if (!qgl_extensions()->hasOpenGLExtension(QOpenGLExtensions::PVRTCTextureCompression)) {
            qWarning("QGLContext::bindTexture(): PVRTC texture compression is not supported.");
            return QSize();
        }
    }

    // Boundary check on the buffer size.
    quint32 bufferSize = pvrHeader->headerSize + pvrHeader->dataSize;
    if (bufferSize > quint32(len)) {
        qWarning("QGLContext::bindTexture(): PVR image size is not valid.");
        return QSize();
    }

    // Create the texture.
    glPixelStorei(GL_UNPACK_ALIGNMENT, 1);
    glGenTextures(1, &id);
    glBindTexture(GL_TEXTURE_2D, id);
    if (pvrHeader->mipMapCount) {
        if ((options & QGLContext::LinearFilteringBindOption) != 0) {
            glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
            glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR_MIPMAP_LINEAR);
        } else {
            glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
            glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST_MIPMAP_NEAREST);
        }
    } else if ((options & QGLContext::LinearFilteringBindOption) != 0) {
        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
    } else {
        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
    }

    // Load the compressed mipmap levels.
    const GLubyte *buffer =
        reinterpret_cast<const GLubyte *>(buf + pvrHeader->headerSize);
    bufferSize = pvrHeader->dataSize;
    quint32 level = 0;
    quint32 width = pvrHeader->width;
    quint32 height = pvrHeader->height;
    while (bufferSize > 0 && level <= pvrHeader->mipMapCount) {
        quint32 size =
            (qMax(width, minWidth) * qMax(height, minHeight) *
             pvrHeader->bitsPerPixel) / 8;
        if (size > bufferSize)
            break;
        qgl_extensions()->glCompressedTexImage2D(GL_TEXTURE_2D, GLint(level), textureFormat,
                               GLsizei(width), GLsizei(height), 0,
                               GLsizei(size), buffer);
        width /= 2;
        height /= 2;
        buffer += size;
        ++level;
    }

    // Restore the default pixel alignment for later texture uploads.
    glPixelStorei(GL_UNPACK_ALIGNMENT, 4);

    // Set the invert flag for the texture.  The "vertical flip"
    // flag in PVR is the opposite sense to our sense of inversion.
    if ((pvrHeader->flags & PVR_VERTICAL_FLIP) != 0)
        options &= ~QGLContext::InvertedYBindOption;
    else
        options |= QGLContext::InvertedYBindOption;

    return QSize(pvrHeader->width, pvrHeader->height);
}

#undef ctx

QT_END_NAMESPACE
