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

# renderarea.cpp Example File

painting/basicdrawing/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:
    **
    ** "Redistribution and use in source and binary forms, with or without
    ** modification, are permitted provided that the following conditions are
    ** met:
    **   * Redistributions of source code must retain the above copyright
    **     notice, this list of conditions and the following disclaimer.
    **   * Redistributions in binary form must reproduce the above copyright
    **     notice, this list of conditions and the following disclaimer in
    **     the documentation and/or other materials provided with the
    **     distribution.
    **   * Neither the name of The Qt Company Ltd nor the names of its
    **     contributors may be used to endorse or promote products derived
    **     from this software without specific prior written permission.
    **
    **
    ** THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
    ** "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
    ** LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
    ** A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
    ** OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
    ** SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
    ** LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
    ** DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
    ** THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
    ** (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
    ** OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE."
    **
    ** $QT_END_LICENSE$
    **
    ****************************************************************************/

    #include "renderarea.h"

    #include <QPainter>

    RenderArea::RenderArea(QWidget *parent)
        : QWidget(parent)
    {
        shape = Polygon;
        antialiased = false;
        transformed = false;
        pixmap.load(":/images/qt-logo.png");

        setBackgroundRole(QPalette::Base);
        setAutoFillBackground(true);
    }

    QSize RenderArea::minimumSizeHint() const
    {
        return QSize(100, 100);
    }

    QSize RenderArea::sizeHint() const
    {
        return QSize(400, 200);
    }

    void RenderArea::setShape(Shape shape)
    {
        this->shape = shape;
        update();
    }

    void RenderArea::setPen(const QPen &pen)
    {
        this->pen = pen;
        update();
    }

    void RenderArea::setBrush(const QBrush &brush)
    {
        this->brush = brush;
        update();
    }

    void RenderArea::setAntialiased(bool antialiased)
    {
        this->antialiased = antialiased;
        update();
    }

    void RenderArea::setTransformed(bool transformed)
    {
        this->transformed = transformed;
        update();
    }

    void RenderArea::paintEvent(QPaintEvent * /* event */)
    {
        static const QPoint points[4] = {
            QPoint(10, 80),
            QPoint(20, 10),
            QPoint(80, 30),
            QPoint(90, 70)
        };

        QRect rect(10, 20, 80, 60);

        QPainterPath path;
        path.moveTo(20, 80);
        path.lineTo(20, 30);
        path.cubicTo(80, 0, 50, 50, 80, 80);

        int startAngle = 20 * 16;
        int arcLength = 120 * 16;

        QPainter painter(this);
        painter.setPen(pen);
        painter.setBrush(brush);
        if (antialiased)
            painter.setRenderHint(QPainter::Antialiasing, true);

        for (int x = 0; x < width(); x += 100) {
            for (int y = 0; y < height(); y += 100) {
                painter.save();
                painter.translate(x, y);
                if (transformed) {
                    painter.translate(50, 50);
                    painter.rotate(60.0);
                    painter.scale(0.6, 0.9);
                    painter.translate(-50, -50);
                }

                switch (shape) {
                case Line:
                    painter.drawLine(rect.bottomLeft(), rect.topRight());
                    break;
                case Points:
                    painter.drawPoints(points, 4);
                    break;
                case Polyline:
                    painter.drawPolyline(points, 4);
                    break;
                case Polygon:
                    painter.drawPolygon(points, 4);
                    break;
                case Rect:
                    painter.drawRect(rect);
                    break;
                case RoundedRect:
                    painter.drawRoundedRect(rect, 25, 25, Qt::RelativeSize);
                    break;
                case Ellipse:
                    painter.drawEllipse(rect);
                    break;
                case Arc:
                    painter.drawArc(rect, startAngle, arcLength);
                    break;
                case Chord:
                    painter.drawChord(rect, startAngle, arcLength);
                    break;
                case Pie:
                    painter.drawPie(rect, startAngle, arcLength);
                    break;
                case Path:
                    painter.drawPath(path);
                    break;
                case Text:
                    painter.drawText(rect,
                                     Qt::AlignCenter,
                                     tr("Qt by\nThe Qt Company"));
                    break;
                case Pixmap:
                    painter.drawPixmap(10, 10, pixmap);
                }
                painter.restore();
            }
        }

        painter.setRenderHint(QPainter::Antialiasing, false);
        painter.setPen(palette().dark().color());
        painter.setBrush(Qt::NoBrush);
        painter.drawRect(QRect(0, 0, width() - 1, height() - 1));
    }