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# composition.cpp Example File
demos/composition/composition.cpp

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     #include "composition.h"
     #include <QBoxLayout>
     #include <QRadioButton>
     #include <QTimer>
     #include <QDateTime>
     #include <QSlider>
     #include <QMouseEvent>
     #include <math.h>

     CompositionWidget::CompositionWidget(QWidget *parent)
         : QWidget(parent)
     {
         CompositionRenderer *view = new CompositionRenderer(this);

         QGroupBox *mainGroup = new QGroupBox(parent);
         mainGroup->setAttribute(Qt::WA_ContentsPropagated);
         mainGroup->setTitle("Composition Modes");

         QGroupBox *modesGroup = new QGroupBox(mainGroup);
         modesGroup->setAttribute(Qt::WA_ContentsPropagated);
         modesGroup->setTitle("Mode");

         rbClear = new QRadioButton("Clear", modesGroup);
         connect(rbClear, SIGNAL(clicked()), view, SLOT(setClearMode()));
         rbSource = new QRadioButton("Source", modesGroup);
         connect(rbSource, SIGNAL(clicked()), view, SLOT(setSourceMode()));
         rbDest = new QRadioButton("Destination", modesGroup);
         connect(rbDest, SIGNAL(clicked()), view, SLOT(setDestMode()));
         rbSourceOver = new QRadioButton("Source Over", modesGroup);
         connect(rbSourceOver, SIGNAL(clicked()), view, SLOT(setSourceOverMode()));
         rbDestOver = new QRadioButton("Destination Over", modesGroup);
         connect(rbDestOver, SIGNAL(clicked()), view, SLOT(setDestOverMode()));
         rbSourceIn = new QRadioButton("Source In", modesGroup);
         connect(rbSourceIn, SIGNAL(clicked()), view, SLOT(setSourceInMode()));
         rbDestIn = new QRadioButton("Dest In", modesGroup);
         connect(rbDestIn, SIGNAL(clicked()), view, SLOT(setDestInMode()));
         rbSourceOut = new QRadioButton("Source Out", modesGroup);
         connect(rbSourceOut, SIGNAL(clicked()), view, SLOT(setSourceOutMode()));
         rbDestOut = new QRadioButton("Dest Out", modesGroup);
         connect(rbDestOut, SIGNAL(clicked()), view, SLOT(setDestOutMode()));
         rbSourceAtop = new QRadioButton("Source Atop", modesGroup);
         connect(rbSourceAtop, SIGNAL(clicked()), view, SLOT(setSourceAtopMode()));
         rbDestAtop = new QRadioButton("Dest Atop", modesGroup);
         connect(rbDestAtop, SIGNAL(clicked()), view, SLOT(setDestAtopMode()));
         rbXor = new QRadioButton("Xor", modesGroup);
         connect(rbXor, SIGNAL(clicked()), view, SLOT(setXorMode()));

         QGroupBox *circleColorGroup = new QGroupBox(mainGroup);
         circleColorGroup->setAttribute(Qt::WA_ContentsPropagated);
         circleColorGroup->setTitle("Circle color");
         QSlider *circleColorSlider = new QSlider(Qt::Horizontal, circleColorGroup);
         circleColorSlider->setRange(0, 359);
         circleColorSlider->setSizePolicy(QSizePolicy::Preferred, QSizePolicy::Fixed);
         connect(circleColorSlider, SIGNAL(valueChanged(int)), view, SLOT(setCircleColor(int)));

         QGroupBox *circleAlphaGroup = new QGroupBox(mainGroup);
         circleAlphaGroup->setAttribute(Qt::WA_ContentsPropagated);
         circleAlphaGroup->setTitle("Circle alpha");
         QSlider *circleAlphaSlider = new QSlider(Qt::Horizontal, circleAlphaGroup);
         circleAlphaSlider->setRange(0, 255);
         circleAlphaSlider->setSizePolicy(QSizePolicy::Preferred, QSizePolicy::Fixed);
         connect(circleAlphaSlider, SIGNAL(valueChanged(int)), view, SLOT(setCircleAlpha(int)));

         QPushButton *showSourceButton = new QPushButton(mainGroup);
         showSourceButton->setText("Show Source");
     #ifdef QT_OPENGL_SUPPORT
         QPushButton *enableOpenGLButton = new QPushButton(mainGroup);
         enableOpenGLButton->setText("Use OpenGL");
         enableOpenGLButton->setCheckable(true);
         enableOpenGLButton->setChecked(view->usesOpenGL());

         if (!QGLFormat::hasOpenGL() || !QGLPixelBuffer::hasOpenGLPbuffers())
             enableOpenGLButton->hide();
     #endif
         QPushButton *whatsThisButton = new QPushButton(mainGroup);
         whatsThisButton->setText("What's This?");
         whatsThisButton->setCheckable(true);

         QPushButton *animateButton = new QPushButton(mainGroup);
         animateButton->setText("Animated");
         animateButton->setCheckable(true);
         animateButton->setChecked(true);

         QHBoxLayout *viewLayout = new QHBoxLayout(this);
         viewLayout->addWidget(view);
         viewLayout->addWidget(mainGroup);

         QVBoxLayout *mainGroupLayout = new QVBoxLayout(mainGroup);
         mainGroupLayout->addWidget(circleColorGroup);
         mainGroupLayout->addWidget(circleAlphaGroup);
         mainGroupLayout->addWidget(modesGroup);
         mainGroupLayout->addStretch();
         mainGroupLayout->addWidget(animateButton);
         mainGroupLayout->addWidget(whatsThisButton);
         mainGroupLayout->addWidget(showSourceButton);
     #ifdef QT_OPENGL_SUPPORT
         mainGroupLayout->addWidget(enableOpenGLButton);
     #endif

         QVBoxLayout *modesLayout = new QVBoxLayout(modesGroup);
         modesLayout->addWidget(rbClear);
         modesLayout->addWidget(rbSource);
         modesLayout->addWidget(rbDest);
         modesLayout->addWidget(rbSourceOver);
         modesLayout->addWidget(rbDestOver);
         modesLayout->addWidget(rbSourceIn);
         modesLayout->addWidget(rbDestIn);
         modesLayout->addWidget(rbSourceOut);
         modesLayout->addWidget(rbDestOut);
         modesLayout->addWidget(rbSourceAtop);
         modesLayout->addWidget(rbDestAtop);
         modesLayout->addWidget(rbXor);

         QVBoxLayout *circleColorLayout = new QVBoxLayout(circleColorGroup);
         circleColorLayout->addWidget(circleColorSlider);

         QVBoxLayout *circleAlphaLayout = new QVBoxLayout(circleAlphaGroup);
         circleAlphaLayout->addWidget(circleAlphaSlider);

         view->loadDescription(":res/composition.html");
         view->loadSourceFile(":res/composition.cpp");

         connect(whatsThisButton, SIGNAL(clicked(bool)), view, SLOT(setDescriptionEnabled(bool)));
         connect(view, SIGNAL(descriptionEnabledChanged(bool)), whatsThisButton, SLOT(setChecked(bool)));
         connect(showSourceButton, SIGNAL(clicked()), view, SLOT(showSource()));
     #ifdef QT_OPENGL_SUPPORT
         connect(enableOpenGLButton, SIGNAL(clicked(bool)), view, SLOT(enableOpenGL(bool)));
     #endif
         connect(animateButton, SIGNAL(toggled(bool)), view, SLOT(setAnimationEnabled(bool)));

         circleColorSlider->setValue(270);
         circleAlphaSlider->setValue(200);
         rbSourceOut->animateClick();

         setWindowTitle(tr("Composition Modes"));
     }

     void CompositionWidget::nextMode()
     {
         /*
           if (!m_animation_enabled)
           return;
           if (rbClear->isChecked()) rbSource->animateClick();
           if (rbSource->isChecked()) rbDest->animateClick();
           if (rbDest->isChecked()) rbSourceOver->animateClick();
           if (rbSourceOver->isChecked()) rbDestOver->animateClick();
           if (rbDestOver->isChecked()) rbSourceIn->animateClick();
           if (rbSourceIn->isChecked()) rbDestIn->animateClick();
           if (rbDestIn->isChecked()) rbSourceOut->animateClick();
           if (rbSourceOut->isChecked()) rbDestOut->animateClick();
           if (rbDestOut->isChecked()) rbSourceAtop->animateClick();
           if (rbSourceAtop->isChecked()) rbDestAtop->animateClick();
           if (rbDestAtop->isChecked()) rbXor->animateClick();
           if (rbXor->isChecked()) rbClear->animateClick();
         */
     }

     CompositionRenderer::CompositionRenderer(QWidget *parent)
         : ArthurFrame(parent)
     {
         m_animation_enabled = true;
         m_image = QImage(":res/flower_2.png");
         m_circle_alpha = 127;
         m_circle_hue = 255;
         m_current_object = NoObject;
         m_composition_mode = QPainter::CompositionMode_SourceOut;

         m_circle_pos = QPoint(200, 100);

         setSizePolicy(QSizePolicy::Expanding, QSizePolicy::Expanding);
     #ifdef QT_OPENGL_SUPPORT
         m_pbuffer = 0;
         m_pbuffer_size = 1024;
     #endif
     }

     QRectF rectangle_around(const QPointF &p, const QSizeF &size = QSize(250, 200))
     {
         QRectF rect(p, size);
         rect.translate(-size.width()/2, -size.height()/2);
         return rect;
     }

     void CompositionRenderer::updateCirclePos()
     {
         if (m_current_object != NoObject)
             return;
         QDateTime dt = QDateTime::currentDateTime();
         qreal t = (dt.toTime_t() * 1000 + dt.time().msec()) / 1000.0;

         qreal x = width() / 2.0 + (cos(t) + sin(-t*2)) * width() / 2.0;
         qreal y = height() / 2.0 + (sin(t) + cos(t * 3)) * height() / 2.0;

         m_circle_pos = QLineF(m_circle_pos, QPointF(x, y)).pointAt(0.01);
     }

     void CompositionRenderer::drawBase(QPainter &p)
     {
         p.setPen(Qt::NoPen);

         QLinearGradient rect_gradient(0, 0, 0, height());
         rect_gradient.setColorAt(0, Qt::red);
         rect_gradient.setColorAt(.17, Qt::yellow);
         rect_gradient.setColorAt(.33, Qt::green);
         rect_gradient.setColorAt(.50, Qt::cyan);
         rect_gradient.setColorAt(.66, Qt::blue);
         rect_gradient.setColorAt(.81, Qt::magenta);
         rect_gradient.setColorAt(1, Qt::red);
         p.setBrush(rect_gradient);
         p.drawRect(width() / 2, 0, width() / 2, height());

         QLinearGradient alpha_gradient(0, 0, width(), 0);
         alpha_gradient.setColorAt(0, Qt::white);
         alpha_gradient.setColorAt(0.2, Qt::white);
         alpha_gradient.setColorAt(0.5, Qt::transparent);
         alpha_gradient.setColorAt(0.8, Qt::white);
         alpha_gradient.setColorAt(1, Qt::white);

         p.setCompositionMode(QPainter::CompositionMode_DestinationIn);
         p.setBrush(alpha_gradient);
         p.drawRect(0, 0, width(), height());

         p.setCompositionMode(QPainter::CompositionMode_DestinationOver);

         p.setPen(Qt::NoPen);
         p.setRenderHint(QPainter::SmoothPixmapTransform);
         p.drawImage(rect(), m_image);
     }

     void CompositionRenderer::drawSource(QPainter &p)
     {
         p.setPen(Qt::NoPen);
         p.setRenderHint(QPainter::Antialiasing);
         p.setCompositionMode(m_composition_mode);

         QRectF circle_rect = rectangle_around(m_circle_pos);
         QColor color = QColor::fromHsvF(m_circle_hue / 360.0, 1, 1, m_circle_alpha / 255.0);
         QLinearGradient circle_gradient(circle_rect.topLeft(), circle_rect.bottomRight());
         circle_gradient.setColorAt(0, color.light());
         circle_gradient.setColorAt(0.5, color);
         circle_gradient.setColorAt(1, color.dark());
         p.setBrush(circle_gradient);

         p.drawEllipse(circle_rect);
     }

     void CompositionRenderer::paint(QPainter *painter)
     {
         if (m_animation_enabled)
             updateCirclePos();

     #ifdef QT_OPENGL_SUPPORT
         if (usesOpenGL()) {

             int new_pbuf_size = m_pbuffer_size;
             if (size().width() > m_pbuffer_size ||
                 size().height() > m_pbuffer_size)
                 new_pbuf_size *= 2;

             if (size().width() < m_pbuffer_size/2 &&
                 size().height() < m_pbuffer_size/2)
                 new_pbuf_size /= 2;

             if (!m_pbuffer || new_pbuf_size != m_pbuffer_size) {
                 if (m_pbuffer) {
                     m_pbuffer->deleteTexture(m_base_tex);
                     m_pbuffer->deleteTexture(m_compositing_tex);
                     delete m_pbuffer;
                 }

                 m_pbuffer = new QGLPixelBuffer(QSize(new_pbuf_size, new_pbuf_size), QGLFormat::defaultFormat(), glWidget());
                 m_pbuffer->makeCurrent();
                 m_base_tex = m_pbuffer->generateDynamicTexture();
                 m_compositing_tex = m_pbuffer->generateDynamicTexture();
                 m_pbuffer_size = new_pbuf_size;
             }

             if (size() != m_previous_size) {
                 m_previous_size = size();
                 QPainter p(m_pbuffer);
                 p.setCompositionMode(QPainter::CompositionMode_Source);
                 p.fillRect(QRect(0, 0, m_pbuffer->width(), m_pbuffer->height()), Qt::transparent);
                 drawBase(p);
                 m_pbuffer->updateDynamicTexture(m_base_tex);
             }

             qreal x_fraction = width()/float(m_pbuffer->width());
             qreal y_fraction = height()/float(m_pbuffer->height());

             {
                 QPainter p(m_pbuffer);
                 p.setCompositionMode(QPainter::CompositionMode_Source);
                 p.fillRect(QRect(0, 0, m_pbuffer->width(), m_pbuffer->height()), Qt::transparent);

                 p.save();
                 glBindTexture(GL_TEXTURE_2D, m_base_tex);
                 glEnable(GL_TEXTURE_2D);
                 glColor4f(1.,1.,1.,1.);

                 glBegin(GL_QUADS);
                 {
                     glTexCoord2f(0, 1.0);
                     glVertex2f(0, 0);

                     glTexCoord2f(x_fraction, 1.0);
                     glVertex2f(width(), 0);

                     glTexCoord2f(x_fraction, 1.0-y_fraction);
                     glVertex2f(width(), height());

                     glTexCoord2f(0, 1.0-y_fraction);
                     glVertex2f(0, height());
                 }
                 glEnd();

                 glDisable(GL_TEXTURE_2D);
                 p.restore();

                 drawSource(p);
                 m_pbuffer->updateDynamicTexture(m_compositing_tex);
             }

             glWidget()->makeCurrent();
             glBindTexture(GL_TEXTURE_2D, m_compositing_tex);
             glEnable(GL_TEXTURE_2D);
             glColor4f(1.,1.,1.,1.);
             glBegin(GL_QUADS);
             {
                 glTexCoord2f(0, 1.0);
                 glVertex2f(0, 0);

                 glTexCoord2f(x_fraction, 1.0);
                 glVertex2f(width(), 0);

                 glTexCoord2f(x_fraction, 1.0-y_fraction);
                 glVertex2f(width(), height());

                 glTexCoord2f(0, 1.0-y_fraction);
                 glVertex2f(0, height());
             }
             glEnd();
             glDisable(GL_TEXTURE_2D);
         } else
     #endif
         {
             // using a QImage
             if (m_buffer.size() != size()) {
                 m_buffer = QImage(size(), QImage::Format_ARGB32_Premultiplied);
                 m_base_buffer = QImage(size(), QImage::Format_ARGB32_Premultiplied);

                 m_base_buffer.fill(0);

                 QPainter p(&m_base_buffer);

                 drawBase(p);
             }

             memcpy(m_buffer.bits(), m_base_buffer.bits(), m_buffer.numBytes());

             {
                 QPainter p(&m_buffer);
                 drawSource(p);
             }

             painter->drawImage(0, 0, m_buffer);
         }

         if (m_animation_enabled)
             update();
     }

     void CompositionRenderer::mousePressEvent(QMouseEvent *e)
     {
         setDescriptionEnabled(false);

         QRectF circle = rectangle_around(m_circle_pos);

         if (circle.contains(e->pos())) {
             m_current_object = Circle;
             m_offset = circle.center() - e->pos();
         } else {
             m_current_object = NoObject;
         }
     }

     void CompositionRenderer::mouseMoveEvent(QMouseEvent *e)
     {
         if (m_current_object == Circle) setCirclePos(e->pos() + m_offset);
     }

     void CompositionRenderer::mouseReleaseEvent(QMouseEvent *)
     {
         m_current_object = NoObject;
     }