Qt 4.0: scribblearea.cpp Example File (widgets/scribble/scribblearea.cpp)

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# scribblearea.cpp Example File
widgets/scribble/scribblearea.cpp

        /****************************************************************************
        **
        ** Copyright (C) 2005-2005 Trolltech AS. All rights reserved.
        **
        ** This file is part of the documentation of the Qt Toolkit.
        **
        ** This file may be used under the terms of the GNU General Public
    ** License version 2.0 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 GNU
    ** General Public Licensing requirements will be met:
    ** http://www.trolltech.com/products/qt/opensource.html
    **
    ** If you are unsure which license is appropriate for your use, please
    ** review the following information:
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        **
        ** This file is provided AS IS with NO WARRANTY OF ANY KIND, INCLUDING THE
        ** WARRANTY OF DESIGN, MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
        **
        ****************************************************************************/

        #include <QtGui>

        #include "scribblearea.h"

        ScribbleArea::ScribbleArea(QWidget *parent)
            : QWidget(parent)
        {
            setAttribute(Qt::WA_StaticContents);
            modified = false;
            scribbling = false;
            myPenWidth = 1;
            myPenColor = Qt::blue;
        }

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

            QSize newSize = loadedImage.size().expandedTo(size());
            resizeImage(&loadedImage, newSize);
            image = loadedImage;
            modified = false;
            update();
            return true;
        }

        bool ScribbleArea::saveImage(const QString &fileName, const char *fileFormat)
        {
            QImage visibleImage = image;
            resizeImage(&visibleImage, size());

            if (visibleImage.save(fileName, fileFormat)) {
                modified = false;
                return true;
            } else {
                return false;
            }
        }

        void ScribbleArea::setPenColor(const QColor &newColor)
        {
            myPenColor = newColor;
        }

        void ScribbleArea::setPenWidth(int newWidth)
        {
            myPenWidth = newWidth;
        }

        void ScribbleArea::clearImage()
        {
            image.fill(qRgb(255, 255, 255));
            modified = true;
            update();
        }

        void ScribbleArea::mousePressEvent(QMouseEvent *event)
        {
            if (event->button() == Qt::LeftButton) {
                lastPoint = event->pos();
                scribbling = true;
            }
        }

        void ScribbleArea::mouseMoveEvent(QMouseEvent *event)
        {
            if ((event->buttons() & Qt::LeftButton) && scribbling)
                drawLineTo(event->pos());
        }

        void ScribbleArea::mouseReleaseEvent(QMouseEvent *event)
        {
            if (event->button() == Qt::LeftButton && scribbling) {
                drawLineTo(event->pos());
                scribbling = false;
            }
        }

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

        void ScribbleArea::resizeEvent(QResizeEvent *event)
        {
            if (width() > image.width() || height() > image.height()) {
                int newWidth = qMax(width() + 128, image.width());
                int newHeight = qMax(height() + 128, image.height());
                resizeImage(&image, QSize(newWidth, newHeight));
                update();
            }
            QWidget::resizeEvent(event);
        }

        void ScribbleArea::drawLineTo(const QPoint &endPoint)
        {
            QPainter painter(&image);
            painter.setPen(QPen(myPenColor, myPenWidth, Qt::SolidLine, Qt::RoundCap,
                                Qt::RoundJoin));
            painter.drawLine(lastPoint, endPoint);
            modified = true;

            int rad = myPenWidth / 2;
            update(QRect(lastPoint, endPoint).normalized()
                                             .adjusted(-rad, -rad, +rad, +rad));
            lastPoint = endPoint;
        }

        void ScribbleArea::resizeImage(QImage *image, const QSize &newSize)
        {
            if (image->size() == newSize)
                return;

            QImage newImage(newSize, QImage::Format_RGB32);
            newImage.fill(qRgb(255, 255, 255));
            QPainter painter(&newImage);
            painter.drawImage(QPoint(0, 0), *image);
            *image = newImage;
        }