- Qt 5.5
- Qt Widgets
- Plug & Paint Example
- paintarea.cpp Example File
- Qt 5.5.1 Reference Documentation

# paintarea.cpp Example File

tools/plugandpaint/paintarea.cpp

    /****************************************************************************
    **
    ** Copyright (C) 2015 The Qt Company Ltd.
    ** Contact: http://www.qt.io/licensing/
    **
    ** This file is part of the examples of the Qt Toolkit.
    **
    ** $QT_BEGIN_LICENSE:BSD$
    ** You may use this file under the terms of the BSD license as follows:
    **
    ** "Redistribution and use in source and binary forms, with or without
    ** modification, are permitted provided that the following conditions are
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    **     contributors may be used to endorse or promote products derived
    **     from this software without specific prior written permission.
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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;
    #ifndef QT_NO_CURSOR
        setCursor(Qt::CrossCursor);
    #endif
    }

    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();
    #ifndef QT_NO_CURSOR
                unsetCursor();
    #endif
                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));
    }