- Qt 5.5
- Qt GUI
- Raster Window Example
- rasterwindow.cpp Example File
- Qt 5.5.1 Reference Documentation

# rasterwindow.cpp Example File

rasterwindow/rasterwindow.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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    ** modification, are permitted provided that the following conditions are
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    **     from this software without specific prior written permission.
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    #include "rasterwindow.h"

    RasterWindow::RasterWindow(QWindow *parent)
        : QWindow(parent)
        , m_update_pending(false)
    {
        m_backingStore = new QBackingStore(this);
        create();

        setGeometry(100, 100, 300, 200);

    }

    bool RasterWindow::event(QEvent *event)
    {
        if (event->type() == QEvent::UpdateRequest) {
            m_update_pending = false;
            renderNow();
            return true;
        }
        return QWindow::event(event);
    }

    void RasterWindow::renderLater()
    {
        if (!m_update_pending) {
            m_update_pending = true;
            QCoreApplication::postEvent(this, new QEvent(QEvent::UpdateRequest));
        }
    }

    void RasterWindow::resizeEvent(QResizeEvent *resizeEvent)
    {
        m_backingStore->resize(resizeEvent->size());
        if (isExposed())
            renderNow();
    }

    void RasterWindow::exposeEvent(QExposeEvent *)
    {
        if (isExposed()) {
            renderNow();
        }
    }

    void RasterWindow::renderNow()
    {
        if (!isExposed())
            return;

        QRect rect(0, 0, width(), height());
        m_backingStore->beginPaint(rect);

        QPaintDevice *device = m_backingStore->paintDevice();
        QPainter painter(device);

        painter.fillRect(0, 0, width(), height(), Qt::white);
        render(&painter);

        m_backingStore->endPaint();
        m_backingStore->flush(rect);
    }

    void RasterWindow::render(QPainter *painter)
    {
        painter->drawText(QRectF(0, 0, width(), height()), Qt::AlignCenter, QStringLiteral("QWindow"));
    }