qbackingstore.cpp

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#include "qplatformdefs.h"

#include "qbackingstore_p.h"

#include <QtCore/qglobal.h>
#include <QtCore/qdebug.h>
#include <QtCore/qvarlengtharray.h>
#include <QtGui/qevent.h>
#include <QtGui/qapplication.h>
#include <QtGui/qpaintengine.h>
#include <QtGui/qgraphicsproxywidget.h>

#include <private/qwidget_p.h>
#include <private/qwindowsurface_raster_p.h>
#include <private/qapplication_p.h>
#include <private/qpaintengine_raster_p.h>
#include <private/qgraphicseffect_p.h>

#include "qgraphicssystem_p.h"

#ifdef Q_WS_QWS
#include <QtGui/qwsmanager_qws.h>
#include <private/qwsmanager_p.h>
#endif

QT_BEGIN_NAMESPACE

extern QRegion qt_dirtyRegion(QWidget *);

/*
   A version of QRect::intersects() that does not normalize the rects.
*/
static inline bool qRectIntersects(const QRect &r1, const QRect &r2)
{
    return (qMax(r1.left(), r2.left()) <= qMin(r1.right(), r2.right())
            && qMax(r1.top(), r2.top()) <= qMin(r1.bottom(), r2.bottom()));
}

static inline void qt_flush(QWidget *widget, const QRegion &region, QWindowSurface *windowSurface,
                            QWidget *tlw, const QPoint &tlwOffset)
{
    Q_ASSERT(widget);
    Q_ASSERT(!region.isEmpty());
    Q_ASSERT(windowSurface);
    Q_ASSERT(tlw);

#if !defined(QT_NO_PAINT_DEBUG) && !defined(Q_WS_QWS)
    // QWS does flush update in QWindowSurface::flush (because it needs to lock the surface etc).
    static int flushUpdate = qgetenv("QT_FLUSH_UPDATE").toInt();
    if (flushUpdate > 0)
        QWidgetBackingStore::showYellowThing(widget, region, flushUpdate * 10, false);
#endif

    //The performance hit by doing this should be negligible. However, be aware that
    //using this FPS when you have > 1 windowsurface can give you inaccurate FPS
    static bool fpsDebug = qgetenv("QT_DEBUG_FPS").toInt();
    if (fpsDebug) {
        static QTime time = QTime::currentTime();
        static int frames = 0;

        frames++;

        if(time.elapsed() > 5000) {
            double fps = double(frames * 1000) /time.restart();
            fprintf(stderr,"FPS: %.1f\n",fps);
            frames = 0;
        }
    }
    if (widget != tlw)
        windowSurface->flush(widget, region, tlwOffset + widget->mapTo(tlw, QPoint()));
    else
        windowSurface->flush(widget, region, tlwOffset);
}

#ifndef QT_NO_PAINT_DEBUG
#ifdef Q_WS_WIN
static void showYellowThing_win(QWidget *widget, const QRegion &region, int msec)
{
    HBRUSH brush;
    static int i = 0;
    switch (i) {
    case 0:
        brush = CreateSolidBrush(RGB(255, 255, 0));
        break;
    case 1:
        brush = CreateSolidBrush(RGB(255, 200, 55));
        break;
    case 2:
        brush = CreateSolidBrush(RGB(200, 255, 55));
        break;
    case 3:
        brush = CreateSolidBrush(RGB(200, 200, 0));
        break;
    }
    i = (i + 1) & 3;

    HDC hdc = widget->getDC();

    const QVector<QRect> &rects = region.rects();
    foreach (QRect rect, rects) {
        RECT winRect;
        SetRect(&winRect, rect.left(), rect.top(), rect.right(), rect.bottom());
        FillRect(hdc, &winRect, brush);
    }

    widget->releaseDC(hdc);
    ::Sleep(msec);
}
#endif

void QWidgetBackingStore::showYellowThing(QWidget *widget, const QRegion &toBePainted, int msec, bool unclipped)
{
#ifdef Q_WS_QWS
    Q_UNUSED(widget);
    Q_UNUSED(unclipped);
    static QWSYellowSurface surface(true);
    surface.setDelay(msec);
    surface.flush(widget, toBePainted, QPoint());
#else
    QRegion paintRegion = toBePainted;
    QRect widgetRect = widget->rect();

    if (!widget->internalWinId()) {
        QWidget *nativeParent = widget->nativeParentWidget();
        const QPoint offset = widget->mapTo(nativeParent, QPoint(0, 0));
        paintRegion.translate(offset);
        widgetRect.translate(offset);
        widget = nativeParent;
    }

#ifdef Q_WS_WIN
    Q_UNUSED(unclipped);
    showYellowThing_win(widget, paintRegion, msec);
#else
    //flags to fool painter
    bool paintUnclipped = widget->testAttribute(Qt::WA_PaintUnclipped);
    if (unclipped && !widget->d_func()->paintOnScreen())
        widget->setAttribute(Qt::WA_PaintUnclipped);

    const bool setFlag = !widget->testAttribute(Qt::WA_WState_InPaintEvent);
    if (setFlag)
        widget->setAttribute(Qt::WA_WState_InPaintEvent);

    //setup the engine
    QPaintEngine *pe = widget->paintEngine();
    if (pe) {
        pe->setSystemClip(paintRegion);
        {
            QPainter p(widget);
            p.setClipRegion(paintRegion);
            static int i = 0;
            switch (i) {
            case 0:
                p.fillRect(widgetRect, QColor(255,255,0));
                break;
            case 1:
                p.fillRect(widgetRect, QColor(255,200,55));
                break;
            case 2:
                p.fillRect(widgetRect, QColor(200,255,55));
                break;
            case 3:
                p.fillRect(widgetRect, QColor(200,200,0));
                break;
            }
            i = (i+1) & 3;
            p.end();
        }
    }

    if (setFlag)
        widget->setAttribute(Qt::WA_WState_InPaintEvent, false);

    //restore
    widget->setAttribute(Qt::WA_PaintUnclipped, paintUnclipped);

    if (pe)
        pe->setSystemClip(QRegion());

    QApplication::syncX();

#if defined(Q_OS_UNIX)
    ::usleep(1000 * msec);
#endif
#endif // Q_WS_WIN
#endif // Q_WS_QWS
}

bool QWidgetBackingStore::flushPaint(QWidget *widget, const QRegion &rgn)
{
    if (!widget)
        return false;

    int delay = 0;
    if (widget->testAttribute(Qt::WA_WState_InPaintEvent)) {
        static int flushPaintEvent = qgetenv("QT_FLUSH_PAINT_EVENT").toInt();
        if (!flushPaintEvent)
            return false;
        delay = flushPaintEvent;
    } else {
        static int flushPaint = qgetenv("QT_FLUSH_PAINT").toInt();
        if (!flushPaint)
            return false;
        delay = flushPaint;
    }

    QWidgetBackingStore::showYellowThing(widget, rgn, delay * 10, true);
    return true;
}

void QWidgetBackingStore::unflushPaint(QWidget *widget, const QRegion &rgn)
{
    if (widget->d_func()->paintOnScreen() || rgn.isEmpty())
        return;

    QWidget *tlw = widget->window();
    QTLWExtra *tlwExtra = tlw->d_func()->maybeTopData();
    if (!tlwExtra)
        return;

    const QPoint offset = widget->mapTo(tlw, QPoint());
    qt_flush(widget, rgn, tlwExtra->backingStore->windowSurface, tlw, offset);
}
#endif // QT_NO_PAINT_DEBUG

/*
    Moves the whole rect by (dx, dy) in widget's coordinate system.
    Doesn't generate any updates.
*/
bool QWidgetBackingStore::bltRect(const QRect &rect, int dx, int dy, QWidget *widget)
{
    const QPoint pos(tlwOffset + widget->mapTo(tlw, rect.topLeft()));
    const QRect tlwRect(QRect(pos, rect.size()));
    if (fullUpdatePending || dirty.intersects(tlwRect))
        return false; // We don't want to scroll junk.
    return windowSurface->scroll(tlwRect, dx, dy);
}

void QWidgetBackingStore::releaseBuffer()
{
    if (windowSurface)
#if defined(Q_WS_QPA)
        windowSurface->resize(QSize());
#else
        windowSurface->setGeometry(QRect());
#endif
#ifdef Q_BACKINGSTORE_SUBSURFACES
    for (int i = 0; i < subSurfaces.size(); ++i)
        subSurfaces.at(i)->setGeometry(QRect());
#endif
}

void QWidgetBackingStore::beginPaint(QRegion &toClean, QWidget *widget, QWindowSurface *windowSurface,
                                     BeginPaintInfo *returnInfo, bool toCleanIsInTopLevelCoordinates)
{
#ifdef Q_WS_QWS
    QWSWindowSurface *surface = static_cast<QWSWindowSurface *>(windowSurface);
    QWidget *surfaceWidget = surface->window();

    if (!surface->isValid()) {
        // this looks strange but it really just releases the surface
        surface->releaseSurface();
        // the old window surface is deleted in setWindowSurface, which is
        // called from QWindowSurface constructor.
        windowSurface = tlw->d_func()->createDefaultWindowSurface();
        surface = static_cast<QWSWindowSurface *>(windowSurface);
        // createDefaultWindowSurface() will set topdata->windowSurface on the
        // widget to zero. However, if this is a sub-surface, it should point
        // to the widget's sub windowSurface, so we set that here:
        if (!surfaceWidget->isWindow())
            surfaceWidget->d_func()->topData()->windowSurface = windowSurface;
        surface->setGeometry(topLevelRect());
        returnInfo->windowSurfaceRecreated = true;
    }

    const QRegion toCleanUnclipped(toClean);

    if (surfaceWidget->isWindow())
        tlwOffset = surface->painterOffset();
#ifdef Q_BACKINGSTORE_SUBSURFACES
    else if (toCleanIsInTopLevelCoordinates)
        toClean &= surface->clipRegion().translated(surfaceWidget->mapTo(tlw, QPoint()));
    if (!toCleanIsInTopLevelCoordinates && windowSurface == this->windowSurface)
        toClean &= surface->clipRegion().translated(-widget->mapTo(surfaceWidget, QPoint()));
#else
    toClean &= surface->clipRegion();
#endif

    if (toClean.isEmpty()) {
        if (surfaceWidget->isWindow()) {
            dirtyFromPreviousSync += toCleanUnclipped;
            hasDirtyFromPreviousSync = true;
        }

        returnInfo->nothingToPaint = true;
        // Nothing to repaint. However, we might have newly exposed areas on the
        // screen, so we have to make sure those are flushed.
        flush();
        return;
    }

    if (surfaceWidget->isWindow()) {
        if (toCleanUnclipped != toClean) {
            dirtyFromPreviousSync += (toCleanUnclipped - surface->clipRegion());
            hasDirtyFromPreviousSync = true;
        }
        if (hasDirtyFromPreviousSync) {
            dirtyFromPreviousSync -= toClean;
            hasDirtyFromPreviousSync = !dirtyFromPreviousSync.isEmpty();
        }
    }

#endif // Q_WS_QWS

    Q_UNUSED(widget);
    Q_UNUSED(toCleanIsInTopLevelCoordinates);

    // Always flush repainted areas.
    dirtyOnScreen += toClean;

#if defined(Q_WS_QWS) && !defined(Q_BACKINGSTORE_SUBSURFACES)
    toClean.translate(tlwOffset);
#endif

#ifdef QT_NO_PAINT_DEBUG
    windowSurface->beginPaint(toClean);
#else
    returnInfo->wasFlushed = QWidgetBackingStore::flushPaint(tlw, toClean);
    // Avoid deadlock with QT_FLUSH_PAINT: the server will wait for
    // the BackingStore lock, so if we hold that, the server will
    // never release the Communication lock that we are waiting for in
    // sendSynchronousCommand
    if (!returnInfo->wasFlushed)
        windowSurface->beginPaint(toClean);
#endif

    Q_UNUSED(returnInfo);
}

void QWidgetBackingStore::endPaint(const QRegion &cleaned, QWindowSurface *windowSurface,
        BeginPaintInfo *beginPaintInfo)
{
#ifndef QT_NO_PAINT_DEBUG
    if (!beginPaintInfo->wasFlushed)
        windowSurface->endPaint(cleaned);
    else
        QWidgetBackingStore::unflushPaint(tlw, cleaned);
#else
    Q_UNUSED(beginPaintInfo);
    windowSurface->endPaint(cleaned);
#endif

#ifdef Q_BACKINGSTORE_SUBSURFACES
    flush(static_cast<QWSWindowSurface *>(windowSurface)->window(), windowSurface);
#else
    flush();
#endif
}

QRegion QWidgetBackingStore::dirtyRegion(QWidget *widget) const
{
    const bool widgetDirty = widget && widget != tlw;
    const QRect tlwRect(topLevelRect());
#if defined(Q_WS_QPA)
    const QRect surfaceGeometry(tlwRect.topLeft(), windowSurface->size());
#else
    const QRect surfaceGeometry(windowSurface->geometry());
#endif
    if (fullUpdatePending || (surfaceGeometry != tlwRect && surfaceGeometry.size() != tlwRect.size())) {
        if (widgetDirty) {
            const QRect dirtyTlwRect = QRect(QPoint(), tlwRect.size());
            const QPoint offset(widget->mapTo(tlw, QPoint()));
            const QRect dirtyWidgetRect(dirtyTlwRect & widget->rect().translated(offset));
            return dirtyWidgetRect.translated(-offset);
        }
        return QRect(QPoint(), tlwRect.size());
    }

    // Calculate the region that needs repaint.
    QRegion r(dirty);
    for (int i = 0; i < dirtyWidgets.size(); ++i) {
        QWidget *w = dirtyWidgets.at(i);
        if (widgetDirty && w != widget && !widget->isAncestorOf(w))
            continue;
        r += w->d_func()->dirty.translated(w->mapTo(tlw, QPoint()));
    }

    // Append the region that needs flush.
    r += dirtyOnScreen;

    if (dirtyOnScreenWidgets) { // Only in use with native child widgets.
        for (int i = 0; i < dirtyOnScreenWidgets->size(); ++i) {
            QWidget *w = dirtyOnScreenWidgets->at(i);
            if (widgetDirty && w != widget && !widget->isAncestorOf(w))
                continue;
            QWidgetPrivate *wd = w->d_func();
            Q_ASSERT(wd->needsFlush);
            r += wd->needsFlush->translated(w->mapTo(tlw, QPoint()));
        }
    }

    if (widgetDirty) {
        // Intersect with the widget geometry and translate to its coordinates.
        const QPoint offset(widget->mapTo(tlw, QPoint()));
        r &= widget->rect().translated(offset);
        r.translate(-offset);
    }
    return r;
}

QRegion QWidgetBackingStore::staticContents(QWidget *parent, const QRect &withinClipRect) const
{
    if (!parent && tlw->testAttribute(Qt::WA_StaticContents)) {
#if defined(Q_WS_QPA)
        const QSize surfaceGeometry(windowSurface->size());
#else
        const QRect surfaceGeometry(windowSurface->geometry());
#endif
        QRect surfaceRect(0, 0, surfaceGeometry.width(), surfaceGeometry.height());
        if (!withinClipRect.isEmpty())
            surfaceRect &= withinClipRect;
        return QRegion(surfaceRect);
    }

    QRegion region;
    if (parent && parent->d_func()->children.isEmpty())
        return region;

    const bool clipToRect = !withinClipRect.isEmpty();
    const int count = staticWidgets.count();
    for (int i = 0; i < count; ++i) {
        QWidget *w = staticWidgets.at(i);
        QWidgetPrivate *wd = w->d_func();
        if (!wd->isOpaque || !wd->extra || wd->extra->staticContentsSize.isEmpty()
            || !w->isVisible() || (parent && !parent->isAncestorOf(w))) {
            continue;
        }

        QRect rect(0, 0, wd->extra->staticContentsSize.width(), wd->extra->staticContentsSize.height());
        const QPoint offset = w->mapTo(parent ? parent : tlw, QPoint());
        if (clipToRect)
            rect &= withinClipRect.translated(-offset);
        if (rect.isEmpty())
            continue;

        rect &= wd->clipRect();
        if (rect.isEmpty())
            continue;

        QRegion visible(rect);
        wd->clipToEffectiveMask(visible);
        if (visible.isEmpty())
            continue;
        wd->subtractOpaqueSiblings(visible, 0, /*alsoNonOpaque=*/true);

        visible.translate(offset);
        region += visible;
    }

    return region;
}

static inline void sendUpdateRequest(QWidget *widget, bool updateImmediately)
{
    if (!widget)
        return;

    if (updateImmediately) {
        QEvent event(QEvent::UpdateRequest);
        QApplication::sendEvent(widget, &event);
    } else {
        QApplication::postEvent(widget, new QEvent(QEvent::UpdateRequest), Qt::LowEventPriority);
    }
}

void QWidgetBackingStore::markDirty(const QRegion &rgn, QWidget *widget, bool updateImmediately,
                                    bool invalidateBuffer)
{
    Q_ASSERT(tlw->d_func()->extra);
    Q_ASSERT(tlw->d_func()->extra->topextra);
    Q_ASSERT(!tlw->d_func()->extra->topextra->inTopLevelResize);
    Q_ASSERT(widget->isVisible() && widget->updatesEnabled());
    Q_ASSERT(widget->window() == tlw);
    Q_ASSERT(!rgn.isEmpty());

#ifndef QT_NO_GRAPHICSEFFECT
    widget->d_func()->invalidateGraphicsEffectsRecursively();
#endif //QT_NO_GRAPHICSEFFECT

    if (widget->d_func()->paintOnScreen()) {
        if (widget->d_func()->dirty.isEmpty()) {
            widget->d_func()->dirty = rgn;
            sendUpdateRequest(widget, updateImmediately);
            return;
        } else if (qt_region_strictContains(widget->d_func()->dirty, widget->rect())) {
            if (updateImmediately)
                sendUpdateRequest(widget, updateImmediately);
            return; // Already dirty.
        }

        const bool eventAlreadyPosted = !widget->d_func()->dirty.isEmpty();
        widget->d_func()->dirty += rgn;
        if (!eventAlreadyPosted || updateImmediately)
            sendUpdateRequest(widget, updateImmediately);
        return;
    }

    if (fullUpdatePending) {
        if (updateImmediately)
            sendUpdateRequest(tlw, updateImmediately);
        return;
    }

    if (!windowSurface->hasFeature(QWindowSurface::PartialUpdates)) {
        fullUpdatePending = true;
        sendUpdateRequest(tlw, updateImmediately);
        return;
    }

    const QPoint offset = widget->mapTo(tlw, QPoint());
    const QRect widgetRect = widget->d_func()->effectiveRectFor(widget->rect());
    if (qt_region_strictContains(dirty, widgetRect.translated(offset))) {
        if (updateImmediately)
            sendUpdateRequest(tlw, updateImmediately);
        return; // Already dirty.
    }

    if (invalidateBuffer) {
        const bool eventAlreadyPosted = !dirty.isEmpty();
#ifndef QT_NO_GRAPHICSEFFECT
        if (widget->d_func()->graphicsEffect)
            dirty += widget->d_func()->effectiveRectFor(rgn.boundingRect()).translated(offset);
        else
#endif //QT_NO_GRAPHICSEFFECT
            dirty += rgn.translated(offset);
        if (!eventAlreadyPosted || updateImmediately)
            sendUpdateRequest(tlw, updateImmediately);
        return;
    }

    if (dirtyWidgets.isEmpty()) {
        addDirtyWidget(widget, rgn);
        sendUpdateRequest(tlw, updateImmediately);
        return;
    }

    if (widget->d_func()->inDirtyList) {
        if (!qt_region_strictContains(widget->d_func()->dirty, widgetRect)) {
#ifndef QT_NO_GRAPHICSEFFECT
            if (widget->d_func()->graphicsEffect)
                widget->d_func()->dirty += widget->d_func()->effectiveRectFor(rgn.boundingRect());
            else
#endif //QT_NO_GRAPHICSEFFECT
                widget->d_func()->dirty += rgn;
        }
    } else {
        addDirtyWidget(widget, rgn);
    }

    if (updateImmediately)
        sendUpdateRequest(tlw, updateImmediately);
}

void QWidgetBackingStore::markDirty(const QRect &rect, QWidget *widget, bool updateImmediately,
                                    bool invalidateBuffer)
{
    Q_ASSERT(tlw->d_func()->extra);
    Q_ASSERT(tlw->d_func()->extra->topextra);
    Q_ASSERT(!tlw->d_func()->extra->topextra->inTopLevelResize);
    Q_ASSERT(widget->isVisible() && widget->updatesEnabled());
    Q_ASSERT(widget->window() == tlw);
    Q_ASSERT(!rect.isEmpty());

#ifndef QT_NO_GRAPHICSEFFECT
    widget->d_func()->invalidateGraphicsEffectsRecursively();
#endif //QT_NO_GRAPHICSEFFECT

    if (widget->d_func()->paintOnScreen()) {
        if (widget->d_func()->dirty.isEmpty()) {
            widget->d_func()->dirty = QRegion(rect);
            sendUpdateRequest(widget, updateImmediately);
            return;
        } else if (qt_region_strictContains(widget->d_func()->dirty, rect)) {
            if (updateImmediately)
                sendUpdateRequest(widget, updateImmediately);
            return; // Already dirty.
        }

        const bool eventAlreadyPosted = !widget->d_func()->dirty.isEmpty();
        widget->d_func()->dirty += rect;
        if (!eventAlreadyPosted || updateImmediately)
            sendUpdateRequest(widget, updateImmediately);
        return;
    }

    if (fullUpdatePending) {
        if (updateImmediately)
            sendUpdateRequest(tlw, updateImmediately);
        return;
    }

    if (!windowSurface->hasFeature(QWindowSurface::PartialUpdates)) {
        fullUpdatePending = true;
        sendUpdateRequest(tlw, updateImmediately);
        return;
    }

    const QRect widgetRect = widget->d_func()->effectiveRectFor(rect);
    const QRect translatedRect(widgetRect.translated(widget->mapTo(tlw, QPoint())));
    if (qt_region_strictContains(dirty, translatedRect)) {
        if (updateImmediately)
            sendUpdateRequest(tlw, updateImmediately);
        return; // Already dirty
    }

    if (invalidateBuffer) {
        const bool eventAlreadyPosted = !dirty.isEmpty();
        dirty += translatedRect;
        if (!eventAlreadyPosted || updateImmediately)
            sendUpdateRequest(tlw, updateImmediately);
        return;
    }

    if (dirtyWidgets.isEmpty()) {
        addDirtyWidget(widget, rect);
        sendUpdateRequest(tlw, updateImmediately);
        return;
    }

    if (widget->d_func()->inDirtyList) {
        if (!qt_region_strictContains(widget->d_func()->dirty, widgetRect))
            widget->d_func()->dirty += widgetRect;
    } else {
        addDirtyWidget(widget, rect);
    }

    if (updateImmediately)
        sendUpdateRequest(tlw, updateImmediately);
}

void QWidgetBackingStore::markDirtyOnScreen(const QRegion &region, QWidget *widget, const QPoint &topLevelOffset)
{
    if (!widget || widget->d_func()->paintOnScreen() || region.isEmpty())
        return;

#if defined(Q_WS_QWS) || defined(Q_WS_MAC)
    if (!widget->testAttribute(Qt::WA_WState_InPaintEvent))
        dirtyOnScreen += region.translated(topLevelOffset);
    return;
#endif

    // Top-level.
    if (widget == tlw) {
        if (!widget->testAttribute(Qt::WA_WState_InPaintEvent))
            dirtyOnScreen += region;
        return;
    }

    // Alien widgets.
    if (!widget->internalWinId() && !widget->isWindow()) {
        QWidget *nativeParent = widget->nativeParentWidget();        // Alien widgets with the top-level as the native parent (common case).
        if (nativeParent == tlw) {
            if (!widget->testAttribute(Qt::WA_WState_InPaintEvent))
                dirtyOnScreen += region.translated(topLevelOffset);
            return;
        }

        // Alien widgets with native parent != tlw.
        QWidgetPrivate *nativeParentPrivate = nativeParent->d_func();
        if (!nativeParentPrivate->needsFlush)
            nativeParentPrivate->needsFlush = new QRegion;
        const QPoint nativeParentOffset = widget->mapTo(nativeParent, QPoint());
        *nativeParentPrivate->needsFlush += region.translated(nativeParentOffset);
        appendDirtyOnScreenWidget(nativeParent);
        return;
    }

    // Native child widgets.
    QWidgetPrivate *widgetPrivate = widget->d_func();
    if (!widgetPrivate->needsFlush)
        widgetPrivate->needsFlush = new QRegion;
    *widgetPrivate->needsFlush += region;
    appendDirtyOnScreenWidget(widget);
}

void QWidgetBackingStore::removeDirtyWidget(QWidget *w)
{
    if (!w)
        return;

    dirtyWidgetsRemoveAll(w);
    dirtyOnScreenWidgetsRemoveAll(w);
    resetWidget(w);

    QWidgetPrivate *wd = w->d_func();
    const int n = wd->children.count();
    for (int i = 0; i < n; ++i) {
        if (QWidget *child = qobject_cast<QWidget*>(wd->children.at(i)))
            removeDirtyWidget(child);
    }
}

#if defined(Q_WS_QWS) && !defined(QT_NO_QWS_MANAGER)
bool QWidgetBackingStore::hasDirtyWindowDecoration() const
{
    QTLWExtra *tlwExtra = tlw->d_func()->maybeTopData();
    if (tlwExtra && tlwExtra->qwsManager)
        return !tlwExtra->qwsManager->d_func()->dirtyRegions.isEmpty();
    return false;
}

void QWidgetBackingStore::paintWindowDecoration()
{
    if (!hasDirtyWindowDecoration())
        return;

    QDecoration &decoration = QApplication::qwsDecoration();
    const QRect decorationRect = tlw->rect();
    QRegion decorationRegion = decoration.region(tlw, decorationRect);

    QWSManagerPrivate *managerPrivate = tlw->d_func()->topData()->qwsManager->d_func();
    const bool doClipping = !managerPrivate->entireDecorationNeedsRepaint
                            && !managerPrivate->dirtyClip.isEmpty();

    if (doClipping) {
        decorationRegion &= static_cast<QWSWindowSurface *>(windowSurface)->clipRegion();
        decorationRegion &= managerPrivate->dirtyClip;
    }

    if (decorationRegion.isEmpty())
        return;

    //### The QWS decorations do not always paint the pixels they promise to paint.
    // This causes painting problems with QWSMemorySurface. Since none of the other
    // window surfaces actually use the region, passing an empty region is a safe
    // workaround.

    windowSurface->beginPaint(QRegion());

    QPaintEngine *engine = windowSurface->paintDevice()->paintEngine();
    Q_ASSERT(engine);
    const QRegion oldSystemClip(engine->systemClip());
    engine->setSystemClip(decorationRegion.translated(tlwOffset));

    QPainter painter(windowSurface->paintDevice());
    painter.setFont(QApplication::font());
    painter.translate(tlwOffset);

    const int numDirty = managerPrivate->dirtyRegions.size();
    for (int i = 0; i < numDirty; ++i) {
        const int area = managerPrivate->dirtyRegions.at(i);

        QRegion clipRegion = decoration.region(tlw, decorationRect, area);
        if (!clipRegion.isEmpty()) {
            // Decoration styles changes the clip and assumes the old clip is non-empty,
            // so we have to set it, but in theory it shouldn't be required.
            painter.setClipRegion(clipRegion);
            decoration.paint(&painter, tlw, area, managerPrivate->dirtyStates.at(i));
        }
    }
    markDirtyOnScreen(decorationRegion, tlw, QPoint());

    painter.end();
    windowSurface->endPaint(decorationRegion);
    managerPrivate->clearDirtyRegions();
    engine->setSystemClip(oldSystemClip);
}
#endif

void QWidgetBackingStore::updateLists(QWidget *cur)
{
    if (!cur)
        return;

    QList<QObject*> children = cur->children();
    for (int i = 0; i < children.size(); ++i) {
        QWidget *child = qobject_cast<QWidget*>(children.at(i));
        if (!child)
            continue;

        updateLists(child);
    }

    if (cur->testAttribute(Qt::WA_StaticContents))
        addStaticWidget(cur);

#ifdef Q_BACKINGSTORE_SUBSURFACES
    QTLWExtra *extra = cur->d_func()->maybeTopData();
    if (extra && extra->windowSurface && cur != tlw)
        subSurfaces.append(extra->windowSurface);
#endif
}

QWidgetBackingStore::QWidgetBackingStore(QWidget *topLevel)
    : tlw(topLevel), dirtyOnScreenWidgets(0), hasDirtyFromPreviousSync(false)
    , fullUpdatePending(0)
{
    windowSurface = tlw->windowSurface();
    if (!windowSurface)
        windowSurface = topLevel->d_func()->createDefaultWindowSurface();

    // The QWindowSurface constructor will call QWidget::setWindowSurface(),
    // but automatically created surfaces should not be added to the topdata.
#ifdef Q_BACKINGSTORE_SUBSURFACES
    Q_ASSERT(topLevel->d_func()->topData()->windowSurface == windowSurface);
#endif
    topLevel->d_func()->topData()->windowSurface = 0;

    // Ensure all existing subsurfaces and static widgets are added to their respective lists.
    updateLists(topLevel);
}

QWidgetBackingStore::~QWidgetBackingStore()
{
    for (int c = 0; c < dirtyWidgets.size(); ++c) {
        resetWidget(dirtyWidgets.at(c));
    }

    delete windowSurface;
    windowSurface = 0;
    delete dirtyOnScreenWidgets;
    dirtyOnScreenWidgets = 0;
}

//parent's coordinates; move whole rect; update parent and widget
//assume the screen blt has already been done, so we don't need to refresh that part
void QWidgetPrivate::moveRect(const QRect &rect, int dx, int dy)
{
    Q_Q(QWidget);
    if (!q->isVisible() || (dx == 0 && dy == 0))
        return;

    QWidget *tlw = q->window();
    QTLWExtra* x = tlw->d_func()->topData();
    if (x->inTopLevelResize)
        return;

    static int accelEnv = -1;
    if (accelEnv == -1) {
        accelEnv = qgetenv("QT_NO_FAST_MOVE").toInt() == 0;
    }

    QWidget *pw = q->parentWidget();
    QPoint toplevelOffset = pw->mapTo(tlw, QPoint());
    QWidgetPrivate *pd = pw->d_func();
    QRect clipR(pd->clipRect());
#ifdef Q_WS_QWS
    QWidgetBackingStore *wbs = x->backingStore.data();
    QWSWindowSurface *surface = static_cast<QWSWindowSurface*>(wbs->windowSurface);
    clipR = clipR.intersected(surface->clipRegion().translated(-toplevelOffset).boundingRect());
#endif
    const QRect newRect(rect.translated(dx, dy));
    QRect destRect = rect.intersected(clipR);
    if (destRect.isValid())
        destRect = destRect.translated(dx, dy).intersected(clipR);
    const QRect sourceRect(destRect.translated(-dx, -dy));
    const QRect parentRect(rect & clipR);

    bool accelerateMove = accelEnv && isOpaque
#ifndef QT_NO_GRAPHICSVIEW
                          // No accelerate move for proxy widgets.
                          && !tlw->d_func()->extra->proxyWidget
#endif
                          && !isOverlapped(sourceRect) && !isOverlapped(destRect);

    if (!accelerateMove) {
        QRegion parentR(effectiveRectFor(parentRect));
        if (!extra || !extra->hasMask) {
            parentR -= newRect;
        } else {
            // invalidateBuffer() excludes anything outside the mask
            parentR += newRect & clipR;
        }
        pd->invalidateBuffer(parentR);
        invalidateBuffer((newRect & clipR).translated(-data.crect.topLeft()));
    } else {

        QWidgetBackingStore *wbs = x->backingStore.data();
        QRegion childExpose(newRect & clipR);

        if (sourceRect.isValid() && wbs->bltRect(sourceRect, dx, dy, pw))
            childExpose -= destRect;

        if (!pw->updatesEnabled())
            return;

        const bool childUpdatesEnabled = q->updatesEnabled();
        if (childUpdatesEnabled && !childExpose.isEmpty()) {
            childExpose.translate(-data.crect.topLeft());
            wbs->markDirty(childExpose, q);
            isMoved = true;
        }

        QRegion parentExpose(parentRect);
        parentExpose -= newRect;
        if (extra && extra->hasMask)
            parentExpose += QRegion(newRect) - extra->mask.translated(data.crect.topLeft());

        if (!parentExpose.isEmpty()) {
            wbs->markDirty(parentExpose, pw);
            pd->isMoved = true;
        }

        if (childUpdatesEnabled) {
            QRegion needsFlush(sourceRect);
            needsFlush += destRect;
            wbs->markDirtyOnScreen(needsFlush, pw, toplevelOffset);
        }
    }
}

//widget's coordinates; scroll within rect;  only update widget
void QWidgetPrivate::scrollRect(const QRect &rect, int dx, int dy)
{
    Q_Q(QWidget);
    QWidget *tlw = q->window();
    QTLWExtra* x = tlw->d_func()->topData();
    if (x->inTopLevelResize)
        return;

    QWidgetBackingStore *wbs = x->backingStore.data();
    if (!wbs)
        return;

    static int accelEnv = -1;
    if (accelEnv == -1) {
        accelEnv = qgetenv("QT_NO_FAST_SCROLL").toInt() == 0;
    }

    QRect scrollRect = rect & clipRect();
    bool overlapped = false;
    bool accelerateScroll = accelEnv && isOpaque
                            && !(overlapped = isOverlapped(scrollRect.translated(data.crect.topLeft())));

#if defined(Q_WS_QWS)
    QWSWindowSurface *surface;
    surface = static_cast<QWSWindowSurface*>(wbs->windowSurface);

    if (accelerateScroll && !surface->isBuffered()) {
        const QRegion surfaceClip = surface->clipRegion();
        const QRegion outsideClip = QRegion(rect) - surfaceClip;
        if (!outsideClip.isEmpty()) {
            const QVector<QRect> clipped = (surfaceClip & rect).rects();
            if (clipped.size() < 8) {
                for (int i = 0; i < clipped.size(); ++i)
                    this->scrollRect(clipped.at(i), dx, dy);
                return;
            } else {
                accelerateScroll = false;
            }
        }
    }
#endif // Q_WS_QWS

    if (!accelerateScroll) {
        if (overlapped) {
            QRegion region(scrollRect);
            subtractOpaqueSiblings(region);
            invalidateBuffer(region);
        }else {
            invalidateBuffer(scrollRect);
        }
    } else {
        const QPoint toplevelOffset = q->mapTo(tlw, QPoint());
#ifdef Q_WS_QWS
        QWSWindowSurface *surface = static_cast<QWSWindowSurface*>(wbs->windowSurface);
        const QRegion clip = surface->clipRegion().translated(-toplevelOffset) & scrollRect;
        const QRect clipBoundingRect = clip.boundingRect();
        scrollRect &= clipBoundingRect;
#endif
        const QRect destRect = scrollRect.translated(dx, dy) & scrollRect;
        const QRect sourceRect = destRect.translated(-dx, -dy);

        QRegion childExpose(scrollRect);
        if (sourceRect.isValid()) {
            if (wbs->bltRect(sourceRect, dx, dy, q))
                childExpose -= destRect;
        }

        if (inDirtyList) {
            if (rect == q->rect()) {
                dirty.translate(dx, dy);
            } else {
                QRegion dirtyScrollRegion = dirty.intersected(scrollRect);
                if (!dirtyScrollRegion.isEmpty()) {
                    dirty -= dirtyScrollRegion;
                    dirtyScrollRegion.translate(dx, dy);
                    dirty += dirtyScrollRegion;
                }
            }
        }

        if (!q->updatesEnabled())
            return;

        if (!childExpose.isEmpty()) {
            wbs->markDirty(childExpose, q);
            isScrolled = true;
        }

        // Instead of using native scroll-on-screen, we copy from
        // backingstore, giving only one screen update for each
        // scroll, and a solid appearance
        wbs->markDirtyOnScreen(destRect, q, toplevelOffset);
    }
}

static inline bool discardSyncRequest(QWidget *tlw, QTLWExtra *tlwExtra)
{
    if (!tlw || !tlwExtra)
        return true;

#ifdef Q_WS_X11
    // Delay the sync until we get an Expose event from X11 (initial show).
    // Qt::WA_Mapped is set to true, but the actual mapping has not yet occurred.
    // However, we must repaint immediately regardless of the state if someone calls repaint().
    if (tlwExtra->waitingForMapNotify && !tlwExtra->inRepaint)
        return true;
#endif

    if (!tlw->testAttribute(Qt::WA_Mapped))
        return true;

    if (!tlw->isVisible()
#ifndef Q_WS_X11
        // If we're minimized on X11, WA_Mapped will be false and we
        // will return in the case above. Some window managers on X11
        // sends us the PropertyNotify to change the minimized state
        // *AFTER* we've received the expose event, which is baaad.
        || tlw->isMinimized()
#endif
        )
        return true;

    return false;
}

void QWidgetBackingStore::sync(QWidget *exposedWidget, const QRegion &exposedRegion)
{
    QTLWExtra *tlwExtra = tlw->d_func()->maybeTopData();
    if (discardSyncRequest(tlw, tlwExtra) || tlwExtra->inTopLevelResize)
        return;

    if (!exposedWidget || !exposedWidget->internalWinId() || !exposedWidget->isVisible()
        || !exposedWidget->updatesEnabled() || exposedRegion.isEmpty()) {
        return;
    }

    // If there's no preserved contents support we always need
    // to do a full repaint before flushing
    if (!windowSurface->hasFeature(QWindowSurface::PreservedContents))
        fullUpdatePending = true;

    // Nothing to repaint.
    if (!isDirty()) {
        qt_flush(exposedWidget, exposedRegion, windowSurface, tlw, tlwOffset);
        return;
    }

    if (exposedWidget != tlw)
        markDirtyOnScreen(exposedRegion, exposedWidget, exposedWidget->mapTo(tlw, QPoint()));
    else
        markDirtyOnScreen(exposedRegion, exposedWidget, QPoint());
    sync();
}

void QWidgetBackingStore::sync()
{
    QTLWExtra *tlwExtra = tlw->d_func()->maybeTopData();
    if (discardSyncRequest(tlw, tlwExtra)) {
        // If the top-level is minimized, it's not visible on the screen so we can delay the
        // update until it's shown again. In order to do that we must keep the dirty states.
        // These will be cleared when we receive the first expose after showNormal().
        // However, if the widget is not visible (isVisible() returns false), everything will
        // be invalidated once the widget is shown again, so clear all dirty states.
        if (!tlw->isVisible()) {
            dirty = QRegion();
            for (int i = 0; i < dirtyWidgets.size(); ++i)
                resetWidget(dirtyWidgets.at(i));
            dirtyWidgets.clear();
            fullUpdatePending = false;
        }
        return;
    }

    const bool updatesDisabled = !tlw->updatesEnabled();
    bool repaintAllWidgets = false;

    const bool inTopLevelResize = tlwExtra->inTopLevelResize;
    const QRect tlwRect(topLevelRect());
#ifdef  Q_WS_QPA
    const QRect surfaceGeometry(tlwRect.topLeft(), windowSurface->size());
#else
    const QRect surfaceGeometry(windowSurface->geometry());
#endif
    if ((fullUpdatePending || inTopLevelResize || surfaceGeometry.size() != tlwRect.size()) && !updatesDisabled) {
        if (hasStaticContents()) {
            // Repaint existing dirty area and newly visible area.
            const QRect clipRect(0, 0, surfaceGeometry.width(), surfaceGeometry.height());
            const QRegion staticRegion(staticContents(0, clipRect));
            QRegion newVisible(0, 0, tlwRect.width(), tlwRect.height());
            newVisible -= staticRegion;
            dirty += newVisible;
            windowSurface->setStaticContents(staticRegion);
        } else {
            // Repaint everything.
            dirty = QRegion(0, 0, tlwRect.width(), tlwRect.height());
            for (int i = 0; i < dirtyWidgets.size(); ++i)
                resetWidget(dirtyWidgets.at(i));
            dirtyWidgets.clear();
            repaintAllWidgets = true;
        }
    }

#ifdef Q_WS_QPA
    if (inTopLevelResize || surfaceGeometry.size() != tlwRect.size())
        windowSurface->resize(tlwRect.size());
#else
    if (inTopLevelResize || surfaceGeometry != tlwRect)
        windowSurface->setGeometry(tlwRect);
#endif

    if (updatesDisabled)
        return;

    if (hasDirtyFromPreviousSync)
        dirty += dirtyFromPreviousSync;

    // Contains everything that needs repaint.
    QRegion toClean(dirty);

    // Loop through all update() widgets and remove them from the list before they are
    // painted (in case someone calls update() in paintEvent). If the widget is opaque
    // and does not have transparent overlapping siblings, append it to the
    // opaqueNonOverlappedWidgets list and paint it directly without composition.
    QVarLengthArray<QWidget *, 32> opaqueNonOverlappedWidgets;
    for (int i = 0; i < dirtyWidgets.size(); ++i) {
        QWidget *w = dirtyWidgets.at(i);
        QWidgetPrivate *wd = w->d_func();
        if (wd->data.in_destructor)
            continue;

        // Clip with mask() and clipRect().
        wd->dirty &= wd->clipRect();
        wd->clipToEffectiveMask(wd->dirty);

        // Subtract opaque siblings and children.
        bool hasDirtySiblingsAbove = false;
        // We know for sure that the widget isn't overlapped if 'isMoved' is true.
        if (!wd->isMoved)
            wd->subtractOpaqueSiblings(wd->dirty, &hasDirtySiblingsAbove);
        // Scrolled and moved widgets must draw all children.
        if (!wd->isScrolled && !wd->isMoved)
            wd->subtractOpaqueChildren(wd->dirty, w->rect());

        if (wd->dirty.isEmpty()) {
            resetWidget(w);
            continue;
        }

        const QRegion widgetDirty(w != tlw ? wd->dirty.translated(w->mapTo(tlw, QPoint()))
                                           : wd->dirty);
        toClean += widgetDirty;

#ifndef QT_NO_GRAPHICSVIEW
        if (tlw->d_func()->extra->proxyWidget) {
            resetWidget(w);
            continue;
        }
#endif

        if (!hasDirtySiblingsAbove && wd->isOpaque && !dirty.intersects(widgetDirty.boundingRect())) {
            opaqueNonOverlappedWidgets.append(w);
        } else {
            resetWidget(w);
            dirty += widgetDirty;
        }
    }
    dirtyWidgets.clear();

    fullUpdatePending = false;

    if (toClean.isEmpty()) {
        // Nothing to repaint. However, we might have newly exposed areas on the
        // screen if this function was called from sync(QWidget *, QRegion)), so
        // we have to make sure those are flushed.
        flush();
        return;
    }

#ifndef QT_NO_GRAPHICSVIEW
    if (tlw->d_func()->extra->proxyWidget) {
        updateStaticContentsSize();
        dirty = QRegion();
        const QVector<QRect> rects(toClean.rects());
        for (int i = 0; i < rects.size(); ++i)
            tlw->d_func()->extra->proxyWidget->update(rects.at(i));
        return;
    }
#endif

#ifndef Q_BACKINGSTORE_SUBSURFACES
    BeginPaintInfo beginPaintInfo;
    beginPaint(toClean, tlw, windowSurface, &beginPaintInfo);
    if (beginPaintInfo.nothingToPaint) {
        for (int i = 0; i < opaqueNonOverlappedWidgets.size(); ++i)
            resetWidget(opaqueNonOverlappedWidgets[i]);
        dirty = QRegion();
        return;
    }
#endif

    // Must do this before sending any paint events because
    // the size may change in the paint event.
    updateStaticContentsSize();
    const QRegion dirtyCopy(dirty);
    dirty = QRegion();

    // Paint opaque non overlapped widgets.
    for (int i = 0; i < opaqueNonOverlappedWidgets.size(); ++i) {
        QWidget *w = opaqueNonOverlappedWidgets[i];
        QWidgetPrivate *wd = w->d_func();

        int flags = QWidgetPrivate::DrawRecursive;
        // Scrolled and moved widgets must draw all children.
        if (!wd->isScrolled && !wd->isMoved)
            flags |= QWidgetPrivate::DontDrawOpaqueChildren;
        if (w == tlw)
            flags |= QWidgetPrivate::DrawAsRoot;

        QRegion toBePainted(wd->dirty);
        resetWidget(w);

#ifdef Q_BACKINGSTORE_SUBSURFACES
        QWindowSurface *subSurface = w->windowSurface();
        BeginPaintInfo beginPaintInfo;

        QPoint off = w->mapTo(tlw, QPoint());
        toBePainted.translate(off);
        beginPaint(toBePainted, w, subSurface, &beginPaintInfo, true);
        toBePainted.translate(-off);

        if (beginPaintInfo.nothingToPaint)
            continue;

        if (beginPaintInfo.windowSurfaceRecreated) {
            // Eep the window surface has changed. The old one may have been
            // deleted, in which case we will segfault on the call to
            // painterOffset() below. Use the new window surface instead.
            subSurface = w->windowSurface();
        }

        QPoint offset(tlwOffset);
        if (subSurface == windowSurface)
            offset += w->mapTo(tlw, QPoint());
        else
            offset = static_cast<QWSWindowSurface*>(subSurface)->painterOffset();
        wd->drawWidget(subSurface->paintDevice(), toBePainted, offset, flags, 0, this);

        endPaint(toBePainted, subSurface, &beginPaintInfo);
#else
        QPoint offset(tlwOffset);
        if (w != tlw)
            offset += w->mapTo(tlw, QPoint());
        wd->drawWidget(windowSurface->paintDevice(), toBePainted, offset, flags, 0, this);
#endif
    }

    // Paint the rest with composition.
#ifndef Q_BACKINGSTORE_SUBSURFACES
    if (repaintAllWidgets || !dirtyCopy.isEmpty()) {
        const int flags = QWidgetPrivate::DrawAsRoot | QWidgetPrivate::DrawRecursive;
        tlw->d_func()->drawWidget(windowSurface->paintDevice(), dirtyCopy, tlwOffset, flags, 0, this);
    }

    endPaint(toClean, windowSurface, &beginPaintInfo);
#else
    if (!repaintAllWidgets && dirtyCopy.isEmpty())
        return; // Nothing more to paint.

    QList<QWindowSurface *> surfaceList(subSurfaces);
    surfaceList.prepend(windowSurface);
    const QRect dirtyBoundingRect(dirtyCopy.boundingRect());

    // Loop through all window surfaces (incl. the top-level surface) and
    // repaint those intersecting with the bounding rect of the dirty region.
    for (int i = 0; i < surfaceList.size(); ++i) {
        QWindowSurface *subSurface = surfaceList.at(i);
        QWidget *w = subSurface->window();
        QWidgetPrivate *wd = w->d_func();

        const QRect clipRect = wd->clipRect().translated(w->mapTo(tlw, QPoint()));
        if (!qRectIntersects(dirtyBoundingRect, clipRect))
            continue;

        toClean = dirtyCopy;
        BeginPaintInfo beginPaintInfo;
        beginPaint(toClean, w, subSurface, &beginPaintInfo);
        if (beginPaintInfo.nothingToPaint)
            continue;

        if (beginPaintInfo.windowSurfaceRecreated) {
            // Eep the window surface has changed. The old one may have been
            // deleted, in which case we will segfault on the call to
            // painterOffset() below. Use the new window surface instead.
            subSurface = w->windowSurface();
        }

        int flags = QWidgetPrivate::DrawRecursive;
        if (w == tlw)
            flags |= QWidgetPrivate::DrawAsRoot;
        const QPoint painterOffset = static_cast<QWSWindowSurface*>(subSurface)->painterOffset();
        wd->drawWidget(subSurface->paintDevice(), toClean, painterOffset, flags, 0, this);

        endPaint(toClean, subSurface, &beginPaintInfo);
    }
#endif
}

void QWidgetBackingStore::flush(QWidget *widget, QWindowSurface *surface)
{
#if defined(Q_WS_QWS) && !defined(QT_NO_QWS_MANAGER)
    paintWindowDecoration();
#endif

    if (!dirtyOnScreen.isEmpty()) {
        QWidget *target = widget ? widget : tlw;
        QWindowSurface *source = surface ? surface : windowSurface;
        qt_flush(target, dirtyOnScreen, source, tlw, tlwOffset);
        dirtyOnScreen = QRegion();
    }

    if (!dirtyOnScreenWidgets || dirtyOnScreenWidgets->isEmpty())
        return;

    for (int i = 0; i < dirtyOnScreenWidgets->size(); ++i) {
        QWidget *w = dirtyOnScreenWidgets->at(i);
        QWidgetPrivate *wd = w->d_func();
        Q_ASSERT(wd->needsFlush);
        qt_flush(w, *wd->needsFlush, windowSurface, tlw, tlwOffset);
        *wd->needsFlush = QRegion();
    }
    dirtyOnScreenWidgets->clear();
}

static inline bool discardInvalidateBufferRequest(QWidget *widget, QTLWExtra *tlwExtra)
{
    Q_ASSERT(widget);
    if (QApplication::closingDown())
        return true;

    if (!tlwExtra || tlwExtra->inTopLevelResize || !tlwExtra->backingStore)
        return true;

    if (!widget->isVisible() || !widget->updatesEnabled())
        return true;

    return false;
}

void QWidgetPrivate::invalidateBuffer_resizeHelper(const QPoint &oldPos, const QSize &oldSize)
{
    Q_Q(QWidget);
    Q_ASSERT(!q->isWindow());
    Q_ASSERT(q->parentWidget());

    const bool staticContents = q->testAttribute(Qt::WA_StaticContents);
    const bool sizeDecreased = (data.crect.width() < oldSize.width())
                               || (data.crect.height() < oldSize.height());

    const QPoint offset(data.crect.x() - oldPos.x(), data.crect.y() - oldPos.y());
    const bool parentAreaExposed = !offset.isNull() || sizeDecreased;
    const QRect newWidgetRect(q->rect());
    const QRect oldWidgetRect(0, 0, oldSize.width(), oldSize.height());

    if (!staticContents || graphicsEffect) {
        QRegion staticChildren;
        QWidgetBackingStore *bs = 0;
        if (offset.isNull() && (bs = maybeBackingStore()))
            staticChildren = bs->staticContents(q, oldWidgetRect);
        const bool hasStaticChildren = !staticChildren.isEmpty();

        if (hasStaticChildren) {
            QRegion dirty(newWidgetRect);
            dirty -= staticChildren;
            invalidateBuffer(dirty);
        } else {
            // Entire widget needs repaint.
            invalidateBuffer(newWidgetRect);
        }

        if (!parentAreaExposed)
            return;

        // Invalidate newly exposed area of the parent.
        if (!graphicsEffect && extra && extra->hasMask) {
            QRegion parentExpose(extra->mask.translated(oldPos));
            parentExpose &= QRect(oldPos, oldSize);
            if (hasStaticChildren)
                parentExpose -= data.crect; // Offset is unchanged, safe to do this.
            q->parentWidget()->d_func()->invalidateBuffer(parentExpose);
        } else {
            if (hasStaticChildren && !graphicsEffect) {
                QRegion parentExpose(QRect(oldPos, oldSize));
                parentExpose -= data.crect; // Offset is unchanged, safe to do this.
                q->parentWidget()->d_func()->invalidateBuffer(parentExpose);
            } else {
                q->parentWidget()->d_func()->invalidateBuffer(effectiveRectFor(QRect(oldPos, oldSize)));
            }
        }
        return;
    }

    // Move static content to its new position.
    if (!offset.isNull()) {
        if (sizeDecreased) {
            const QSize minSize(qMin(oldSize.width(), data.crect.width()),
                                qMin(oldSize.height(), data.crect.height()));
            moveRect(QRect(oldPos, minSize), offset.x(), offset.y());
        } else {
            moveRect(QRect(oldPos, oldSize), offset.x(), offset.y());
        }
    }

    // Invalidate newly visible area of the widget.
    if (!sizeDecreased || !oldWidgetRect.contains(newWidgetRect)) {
        QRegion newVisible(newWidgetRect);
        newVisible -= oldWidgetRect;
        invalidateBuffer(newVisible);
    }

    if (!parentAreaExposed)
        return;

    // Invalidate newly exposed area of the parent.
    const QRect oldRect(oldPos, oldSize);
    if (extra && extra->hasMask) {
        QRegion parentExpose(oldRect);
        parentExpose &= extra->mask.translated(oldPos);
        parentExpose -= (extra->mask.translated(data.crect.topLeft()) & data.crect);
        q->parentWidget()->d_func()->invalidateBuffer(parentExpose);
    } else {
        QRegion parentExpose(oldRect);
        parentExpose -= data.crect;
        q->parentWidget()->d_func()->invalidateBuffer(parentExpose);
    }
}

void QWidgetPrivate::invalidateBuffer(const QRegion &rgn)
{
    Q_Q(QWidget);

    QTLWExtra *tlwExtra = q->window()->d_func()->maybeTopData();
    if (discardInvalidateBufferRequest(q, tlwExtra) || rgn.isEmpty())
        return;

    QRegion wrgn(rgn);
    wrgn &= clipRect();
    if (!graphicsEffect && extra && extra->hasMask)
        wrgn &= extra->mask;
    if (wrgn.isEmpty())
        return;

    tlwExtra->backingStore->markDirty(wrgn, q, false, true);
}

void QWidgetPrivate::invalidateBuffer(const QRect &rect)
{
    Q_Q(QWidget);

    QTLWExtra *tlwExtra = q->window()->d_func()->maybeTopData();
    if (discardInvalidateBufferRequest(q, tlwExtra) || rect.isEmpty())
        return;

    QRect wRect(rect);
    wRect &= clipRect();
    if (wRect.isEmpty())
        return;

    if (graphicsEffect || !extra || !extra->hasMask) {
        tlwExtra->backingStore->markDirty(wRect, q, false, true);
        return;
    }

    QRegion wRgn(extra->mask);
    wRgn &= wRect;
    if (wRgn.isEmpty())
        return;

    tlwExtra->backingStore->markDirty(wRgn, q, false, true);
}

void QWidgetPrivate::repaint_sys(const QRegion &rgn)
{
    if (data.in_destructor)
        return;

    Q_Q(QWidget);
    if (q->testAttribute(Qt::WA_StaticContents)) {
        if (!extra)
            createExtra();
        extra->staticContentsSize = data.crect.size();
    }

#ifdef Q_WS_QPA //Don't even call q->p
    QPaintEngine *engine = 0;
#else
    QPaintEngine *engine = q->paintEngine();
#endif
    // QGLWidget does not support partial updates if:
    // 1) The context is double buffered
    // 2) The context is single buffered and auto-fill background is enabled.
    const bool noPartialUpdateSupport = (engine && (engine->type() == QPaintEngine::OpenGL
                                                || engine->type() == QPaintEngine::OpenGL2))
                                        && (usesDoubleBufferedGLContext || q->autoFillBackground());
    QRegion toBePainted(noPartialUpdateSupport ? q->rect() : rgn);

#ifdef Q_WS_MAC
    // No difference between update() and repaint() on the Mac.
    update_sys(toBePainted);
    return;
#endif

    toBePainted &= clipRect();
    clipToEffectiveMask(toBePainted);
    if (toBePainted.isEmpty())
        return; // Nothing to repaint.

#ifndef QT_NO_PAINT_DEBUG
    bool flushed = QWidgetBackingStore::flushPaint(q, toBePainted);
#endif

    drawWidget(q, toBePainted, QPoint(), QWidgetPrivate::DrawAsRoot | QWidgetPrivate::DrawPaintOnScreen, 0);

#ifndef QT_NO_PAINT_DEBUG
    if (flushed)
        QWidgetBackingStore::unflushPaint(q, toBePainted);
#endif

    if (!q->testAttribute(Qt::WA_PaintOutsidePaintEvent) && q->paintingActive())
        qWarning("QWidget::repaint: It is dangerous to leave painters active on a widget outside of the PaintEvent");
}


QT_END_NAMESPACE