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# paintarea.cpp Example File
tools/plugandpaint/paintarea.cpp

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        **
        ** This file is part of the documentation of the Qt Toolkit.
        **
        ** This file may be distributed and/or modified under the terms of the
    ** GNU General Public License version 2 as published by the Free Software
    ** Foundation and appearing in the file LICENSE.GPL included in the
    ** packaging of this file.
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    ** information about Qt Commercial License Agreements.
    ** See http://www.trolltech.com/gpl/ for GPL licensing information.
    **
    ** Contact info@trolltech.com if any conditions of this licensing are
    ** not clear to you.
        **
        ** This file is provided AS IS with NO WARRANTY OF ANY KIND, INCLUDING THE
        ** WARRANTY OF DESIGN, MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
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        #include <QtGui>

        #include "interfaces.h"
        #include "paintarea.h"

        PaintArea::PaintArea(QWidget *parent)
            : QWidget(parent)
        {
            setAttribute(Qt::WA_StaticContents);
            setAttribute(Qt::WA_NoBackground);

            theImage = QImage(500, 400, QImage::Format_RGB32);
            theImage.fill(qRgb(255, 255, 255));
            color = Qt::blue;
            thickness = 3;
            brushInterface = 0;
            lastPos = QPoint(-1, -1);
        }

        bool PaintArea::openImage(const QString &fileName)
        {
            QImage image;
            if (!image.load(fileName))
                return false;

            setImage(image);
            return true;
        }

        bool PaintArea::saveImage(const QString &fileName, const char *fileFormat)
        {
            return theImage.save(fileName, fileFormat);
        }

        void PaintArea::setImage(const QImage &image)
        {
            theImage = image.convertToFormat(QImage::Format_RGB32);
            update();
            updateGeometry();
        }

        void PaintArea::insertShape(const QPainterPath &path)
        {
            pendingPath = path;
            setCursor(Qt::CrossCursor);
        }

        void PaintArea::setBrushColor(const QColor &color)
        {
            this->color = color;
        }

        void PaintArea::setBrushWidth(int width)
        {
            thickness = width;
        }

        void PaintArea::setBrush(BrushInterface *brushInterface, const QString &brush)
        {
            this->brushInterface = brushInterface;
            this->brush = brush;
        }

        QSize PaintArea::sizeHint() const
        {
            return theImage.size();
        }

        void PaintArea::paintEvent(QPaintEvent * /* event */)
        {
            QPainter painter(this);
            painter.drawImage(QPoint(0, 0), theImage);
        }

        void PaintArea::mousePressEvent(QMouseEvent *event)
        {
            if (event->button() == Qt::LeftButton) {
                if (!pendingPath.isEmpty()) {
                    QPainter painter(&theImage);
                    setupPainter(painter);

                    QRectF boundingRect = pendingPath.boundingRect();
                    QLinearGradient gradient(boundingRect.topRight(),
                                             boundingRect.bottomLeft());
                    gradient.setColorAt(0.0, QColor(color.red(), color.green(),
                                                    color.blue(), 63));
                    gradient.setColorAt(1.0, QColor(color.red(), color.green(),
                                                    color.blue(), 191));
                    painter.setBrush(gradient);
                    painter.translate(event->pos() - boundingRect.center());
                    painter.drawPath(pendingPath);

                    pendingPath = QPainterPath();
                    unsetCursor();
                    update();
                } else {
                    if (brushInterface) {
                        QPainter painter(&theImage);
                        setupPainter(painter);
                        QRect rect = brushInterface->mousePress(brush, painter,
                                                                event->pos());
                        update(rect);
                    }

                    lastPos = event->pos();
                }
            }
        }

        void PaintArea::mouseMoveEvent(QMouseEvent *event)
        {
            if ((event->buttons() & Qt::LeftButton) && lastPos != QPoint(-1, -1)) {
                if (brushInterface) {
                    QPainter painter(&theImage);
                    setupPainter(painter);
                    QRect rect = brushInterface->mouseMove(brush, painter, lastPos,
                                                           event->pos());
                    update(rect);
                }

                lastPos = event->pos();
            }
        }

        void PaintArea::mouseReleaseEvent(QMouseEvent *event)
        {
            if (event->button() == Qt::LeftButton && lastPos != QPoint(-1, -1)) {
                if (brushInterface) {
                    QPainter painter(&theImage);
                    setupPainter(painter);
                    QRect rect = brushInterface->mouseRelease(brush, painter,
                                                              event->pos());
                    update(rect);
                }

                lastPos = QPoint(-1, -1);
            }
        }

        void PaintArea::setupPainter(QPainter &painter)
        {
            painter.setRenderHint(QPainter::Antialiasing, true);
            painter.setPen(QPen(color, thickness, Qt::SolidLine, Qt::RoundCap,
                           Qt::RoundJoin));
        }