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#include "qrasterbackingstore_p.h"

#include <QtGui/qpainter.h>

QT_BEGIN_NAMESPACE

QRasterBackingStore::QRasterBackingStore(QWindow *window)
    : QPlatformBackingStore(window)
{
}

QRasterBackingStore::~QRasterBackingStore()
{
}

void QRasterBackingStore::resize(const QSize &size, const QRegion &staticContents)
{
    Q_UNUSED(staticContents);

    int windowDevicePixelRatio = window()->devicePixelRatio();
    QSize effectiveBufferSize = size * windowDevicePixelRatio;

    if (m_image.size() == effectiveBufferSize)
        return;

    QImage::Format format = window()->format().hasAlpha() ? QImage::Format_ARGB32_Premultiplied : QImage::Format_RGB32;
    m_image = QImage(effectiveBufferSize, format);
    m_image.setDevicePixelRatio(windowDevicePixelRatio);
    if (format == QImage::Format_ARGB32_Premultiplied)
        m_image.fill(Qt::transparent);
}

QPaintDevice *QRasterBackingStore::paintDevice()
{
    return &m_image;
}

QImage QRasterBackingStore::toImage() const
{
    return m_image;
}

bool QRasterBackingStore::scroll(const QRegion &region, int dx, int dy)
{
    if (window()->surfaceType() != QSurface::RasterSurface)
        return false;

    extern void qt_scrollRectInImage(QImage &, const QRect &, const QPoint &);

    const qreal devicePixelRatio = m_image.devicePixelRatio();
    const QPoint delta(dx * devicePixelRatio, dy * devicePixelRatio);

    for (const QRect &rect : region)
        qt_scrollRectInImage(m_image, QRect(rect.topLeft() * devicePixelRatio, rect.size() * devicePixelRatio), delta);

    return true;
}

void QRasterBackingStore::beginPaint(const QRegion &region)
{
    if (!m_image.hasAlphaChannel())
        return;

    QPainter painter(&m_image);
    painter.setCompositionMode(QPainter::CompositionMode_Source);
    const QColor blank = Qt::transparent;
    for (const QRect &rect : region)
        painter.fillRect(rect, blank);
}

QT_END_NAMESPACE