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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.
        **
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    ** GNU General Public License version 2 as published by the Free Software
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    ** packaging of this file.
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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(50, 50);
        }

        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);

            painter.save();
            transformPainter(painter);
            drawCoordinates(painter);
            painter.restore();
        }

        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:
                    ;
                }
            }
        }