- Qt 5.5
- Qt Widgets
- Transformations Example
- renderarea.cpp Example File
- Qt 5.5.1 Reference Documentation

# renderarea.cpp Example File

painting/transformations/renderarea.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:
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    **     from this software without specific prior written permission.
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    #include "renderarea.h"

    #include <QPainter>
    #include <QPaintEvent>

    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:
                ;
            }
        }
    }