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** Alternatively, this file may be used under the terms of the GNU General
** Public License version 3.0 as published by the Free Software Foundation
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** file. Please review the following information to ensure the GNU General
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****************************************************************************/

#include <qbackingstore.h>
#include <qwindow.h>
#include <qpixmap.h>
#include <qplatformbackingstore_qpa.h>

#include <private/qguiapplication_p.h>
#include <private/qwindow_p.h>

QT_BEGIN_NAMESPACE

class QBackingStorePrivate
{
public:
    QBackingStorePrivate(QWindow *w)
        : window(w)
    {
    }

    QWindow *window;
    QPlatformBackingStore *platformBackingStore;
    QRegion staticContents;
    QSize size;
};

/*!
    \class QBackingStore
    \since 5.0

    \brief The QBackingStore class provides the drawing area for top-level windows.
*/


/*!
    \fn void QBackingStore::beginPaint(const QRegion &region)

    This function is called before painting onto the surface begins,
    with the \a region in which the painting will occur.

    \sa endPaint(), paintDevice()
*/

/*!
    \fn void QBackingStore::endPaint(const QRegion &region)

    This function is called after painting onto the surface has ended,
    with the \a region in which the painting was performed.

    \sa beginPaint(), paintDevice()
*/

/*!
    \fn void QBackingStore::flush(QWindow *window, const QRegion &region,
                                  const QPoint &offset)

    Flushes the given \a region from the specified \a window onto the
    screen.

    Note that the \a offset parameter is currently unused.
*/
void QBackingStore::flush(const QRegion &region, QWindow *win, const QPoint &offset)
{
    if (!win)
        win = window();
    d_ptr->platformBackingStore->flush(win, region, offset);
}

/*!
    \fn QPaintDevice* QBackingStore::paintDevice()

    Implement this function to return the appropriate paint device.
*/
QPaintDevice *QBackingStore::paintDevice()
{
    return d_ptr->platformBackingStore->paintDevice();
}

/*!
    Constructs an empty surface for the given top-level \a window.
*/
QBackingStore::QBackingStore(QWindow *window)
    : d_ptr(new QBackingStorePrivate(window))
{
    d_ptr->platformBackingStore = QGuiApplicationPrivate::platformIntegration()->createPlatformBackingStore(window);
}

/*!
    Destroys this surface.
*/
QBackingStore::~QBackingStore()
{
    delete d_ptr->platformBackingStore;
}

/*!
    Returns a pointer to the top-level window associated with this
    surface.
*/
QWindow* QBackingStore::window() const
{
    return d_ptr->window;
}

void QBackingStore::beginPaint(const QRegion &region)
{
    d_ptr->platformBackingStore->beginPaint(region);
}

void QBackingStore::endPaint()
{
    d_ptr->platformBackingStore->endPaint();
}

/*!
      Sets the size of the windowsurface to be \a size.

      \sa size()
*/
void QBackingStore::resize(const QSize &size)
{
    d_ptr->size = size;
    d_ptr->platformBackingStore->resize(size, d_ptr->staticContents);
}

/*!
    Returns the current size of the windowsurface.
*/
QSize QBackingStore::size() const
{
    return d_ptr->size;
}

/*!
    Scrolls the given \a area \a dx pixels to the right and \a dy
    downward; both \a dx and \a dy may be negative.

    Returns true if the area was scrolled successfully; false otherwise.
*/
bool QBackingStore::scroll(const QRegion &area, int dx, int dy)
{
    Q_UNUSED(area);
    Q_UNUSED(dx);
    Q_UNUSED(dy);

    return d_ptr->platformBackingStore->scroll(area, dx, dy);
}

void QBackingStore::setStaticContents(const QRegion &region)
{
    d_ptr->staticContents = region;
}

QRegion QBackingStore::staticContents() const
{
    return d_ptr->staticContents;
}

bool QBackingStore::hasStaticContents() const
{
    return !d_ptr->staticContents.isEmpty();
}

void Q_GUI_EXPORT qt_scrollRectInImage(QImage &img, const QRect &rect, const QPoint &offset)
{
    // make sure we don't detach
    uchar *mem = const_cast<uchar*>(const_cast<const QImage &>(img).bits());

    int lineskip = img.bytesPerLine();
    int depth = img.depth() >> 3;

    const QRect imageRect(0, 0, img.width(), img.height());
    const QRect r = rect & imageRect & imageRect.translated(-offset);
    const QPoint p = rect.topLeft() + offset;

    if (r.isEmpty())
        return;

    const uchar *src;
    uchar *dest;

    if (r.top() < p.y()) {
        src = mem + r.bottom() * lineskip + r.left() * depth;
        dest = mem + (p.y() + r.height() - 1) * lineskip + p.x() * depth;
        lineskip = -lineskip;
    } else {
        src = mem + r.top() * lineskip + r.left() * depth;
        dest = mem + p.y() * lineskip + p.x() * depth;
    }

    const int w = r.width();
    int h = r.height();
    const int bytes = w * depth;

    // overlapping segments?
    if (offset.y() == 0 && qAbs(offset.x()) < w) {
        do {
            ::memmove(dest, src, bytes);
            dest += lineskip;
            src += lineskip;
        } while (--h);
    } else {
        do {
            ::memcpy(dest, src, bytes);
            dest += lineskip;
            src += lineskip;
        } while (--h);
    }
}

QPlatformBackingStore *QBackingStore::handle() const
{
    return d_ptr->platformBackingStore;
}

QT_END_NAMESPACE