Qt 4.3: paintarea.cpp Example File (tools/plugandpaint/paintarea.cpp)

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

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

     #include <QPainter>
     #include <QMouseEvent>

     PaintArea::PaintArea(QWidget *parent) :
         QWidget(parent),
         theImage(500, 400, QImage::Format_RGB32),
         color(Qt::blue),
         thickness(3),
         brushInterface(0),
         lastPos(-1, -1)
     {
         setAttribute(Qt::WA_StaticContents);
         setAttribute(Qt::WA_NoBackground);

         theImage.fill(qRgb(255, 255, 255));
     }

     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);

                 const 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);
                     const 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);
                 const 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));
     }