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renderarea.cpp Example File
^{painting/transformations/renderarea.cpp}

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    **
    ** 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
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    ** review the following information:
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    #include <QtGui>

    #include "renderarea.h"

    RenderArea::RenderArea(QWidget *parent)
        : QWidget(parent)
    {
        QFont newFont = font();
        newFont.setPixelSize(12);
        setFont(newFont);

        QFontMetrics fontMetrics(newFont);
        xBoundingRect = fontMetrics.boundingRect(tr("x"));
        yBoundingRect = fontMetrics.boundingRect(tr("y"));
    }

    void RenderArea::setOperations(const QList<Operation> &operations)
    {
        this->operations = operations;
        update();
    }

    void RenderArea::setShape(const QPainterPath &shape)
    {
        this->shape = shape;
        update();
    }

    QSize RenderArea::minimumSizeHint() const
    {
        return QSize(182, 182);
    }

    QSize RenderArea::sizeHint() const
    {
        return QSize(232, 232);
    }

    void RenderArea::paintEvent(QPaintEvent *event)
    {
        QPainter painter(this);
        painter.setRenderHint(QPainter::Antialiasing);
        painter.fillRect(event->rect(), QBrush(Qt::white));

        painter.translate(66, 66);

        painter.save();
        transformPainter(painter);
        drawShape(painter);
        painter.restore();

        drawOutline(painter);

        transformPainter(painter);
        drawCoordinates(painter);
    }

    void RenderArea::drawCoordinates(QPainter &painter)
    {
        painter.setPen(Qt::red);

        painter.drawLine(0, 0, 50, 0);
        painter.drawLine(48, -2, 50, 0);
        painter.drawLine(48, 2, 50, 0);
        painter.drawText(60 - xBoundingRect.width() / 2,
                         0 + xBoundingRect.height() / 2, tr("x"));

        painter.drawLine(0, 0, 0, 50);
        painter.drawLine(-2, 48, 0, 50);
        painter.drawLine(2, 48, 0, 50);
        painter.drawText(0 - yBoundingRect.width() / 2,
                         60 + yBoundingRect.height() / 2, tr("y"));
    }

    void RenderArea::drawOutline(QPainter &painter)
    {
        painter.setPen(Qt::darkGreen);
        painter.setPen(Qt::DashLine);
        painter.setBrush(Qt::NoBrush);
        painter.drawRect(0, 0, 100, 100);
    }

    void RenderArea::drawShape(QPainter &painter)
    {
        painter.fillPath(shape, Qt::blue);
    }

    void RenderArea::transformPainter(QPainter &painter)
    {
        for (int i = 0; i < operations.size(); ++i) {
            switch (operations[i]) {
            case Translate:
                painter.translate(50, 50);
                break;
            case Scale:
                painter.scale(0.75, 0.75);
                break;
            case Rotate:
                painter.rotate(60);
                break;
            case NoTransformation:
            default:
                ;
            }
        }
    }