/****************************************************************************
**
** Copyright (C) 2016 The Qt Company Ltd.
** Contact: https://www.qt.io/licensing/
**
** This file is part of the QtWidgets module of the Qt Toolkit.
**
** $QT_BEGIN_LICENSE:LGPL$
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** accordance with the commercial license agreement provided with the
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** information use the contact form at https://www.qt.io/contact-us.
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** Alternatively, this file may be used under the terms of the GNU Lesser
** General Public License version 3 as published by the Free Software
** Foundation and appearing in the file LICENSE.LGPL3 included in the
** packaging of this file. Please review the following information to
** ensure the GNU Lesser General Public License version 3 requirements
** will be met: https://www.gnu.org/licenses/lgpl-3.0.html.
**
** GNU General Public License Usage
** Alternatively, this file may be used under the terms of the GNU
** General Public License version 2.0 or (at your option) the GNU General
** Public license version 3 or any later version approved by the KDE Free
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** Foundation and appearing in the file LICENSE.GPL2 and LICENSE.GPL3
** included in the packaging of this file. Please review the following
** information to ensure the GNU General Public License requirements will
** be met: https://www.gnu.org/licenses/gpl-2.0.html and
** https://www.gnu.org/licenses/gpl-3.0.html.
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** $QT_END_LICENSE$
**
****************************************************************************/


#include "qplatformdefs.h"

#include "qwidgetrepaintmanager_p.h"

#include <QtCore/qglobal.h>
#include <QtCore/qdebug.h>
#include <QtCore/qvarlengtharray.h>
#include <QtGui/qevent.h>
#include <QtWidgets/qapplication.h>
#include <QtGui/qpaintengine.h>
#if QT_CONFIG(graphicsview)
#include <QtWidgets/qgraphicsproxywidget.h>
#endif

#include <private/qwidget_p.h>
#include <private/qapplication_p.h>
#include <private/qpaintengine_raster_p.h>
#if QT_CONFIG(graphicseffect)
#include <private/qgraphicseffect_p.h>
#endif
#include <QtGui/private/qwindow_p.h>
#include <QtGui/private/qhighdpiscaling_p.h>

#include <qpa/qplatformbackingstore.h>

#include <private/qmemory_p.h>

QT_BEGIN_NAMESPACE

#ifndef QT_NO_OPENGL
Q_GLOBAL_STATIC(QPlatformTextureList, qt_dummy_platformTextureList)
#endif

static bool hasPlatformWindow(QWidget *widget)
{
    return widget && widget->windowHandle() && widget->windowHandle()->handle();
}

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

/*!
    Prepares the window surface to paint a\ toClean region of the \a widget.

    The \a toClean region might be clipped by the window surface.
*/
void QWidgetRepaintManager::beginPaint(QRegion &toClean, QBackingStore *backingStore)
{
    // Always flush repainted areas.
    dirtyOnScreen += toClean;

    backingStore->beginPaint(toClean);
}

void QWidgetRepaintManager::endPaint(QBackingStore *backingStore)
{
    backingStore->endPaint();
    flush();
}

/*!
    Returns the region (in top-level coordinates) that needs repaint and/or flush.

    If the widget is non-zero, only the dirty region for the widget is returned
    and the region will be in widget coordinates.
*/
QRegion QWidgetRepaintManager::dirtyRegion(QWidget *widget) const
{
    const bool widgetDirty = widget && widget != tlw;
    const QRect tlwRect(topLevelRect());
    const QRect surfaceGeometry(tlwRect.topLeft(), store->size());
    if (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;

    for (QWidget *w : dirtyOnScreenWidgets) {
        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;
}

/*!
    Returns the static content inside the \a parent if non-zero; otherwise the static content
    for the entire backing store is returned. The content will be clipped to \a withinClipRect
    if non-empty.
*/
QRegion QWidgetRepaintManager::staticContents(QWidget *parent, const QRect &withinClipRect) const
{
    if (!parent && tlw->testAttribute(Qt::WA_StaticContents)) {
        const QSize surfaceGeometry(store->size());
        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;
}

void QWidgetRepaintManager::sendUpdateRequest(QWidget *widget, UpdateTime updateTime)
{
    if (!widget)
        return;

#ifndef QT_NO_OPENGL
    // Having every repaint() leading to a sync/flush is bad as it causes
    // compositing and waiting for vsync each and every time. Change to
    // UpdateLater, except for approx. once per frame to prevent starvation in
    // case the control does not get back to the event loop.
    QWidget *w = widget->window();
    if (updateTime == UpdateNow && w && w->windowHandle() && QWindowPrivate::get(w->windowHandle())->compositing) {
        int refresh = 60;
        QScreen *ws = w->windowHandle()->screen();
        if (ws)
            refresh = ws->refreshRate();
        QWindowPrivate *wd = QWindowPrivate::get(w->windowHandle());
        if (wd->lastComposeTime.isValid()) {
            const qint64 elapsed = wd->lastComposeTime.elapsed();
            if (elapsed <= qint64(1000.0f / refresh))
                updateTime = UpdateLater;
       }
    }
#endif

    switch (updateTime) {
    case UpdateLater:
        updateRequestSent = true;
        QCoreApplication::postEvent(widget, new QEvent(QEvent::UpdateRequest), Qt::LowEventPriority);
        break;
    case UpdateNow: {
        QEvent event(QEvent::UpdateRequest);
        QCoreApplication::sendEvent(widget, &event);
        break;
        }
    }
}

static inline QRect widgetRectFor(QWidget *, const QRect &r) { return r; }
static inline QRect widgetRectFor(QWidget *widget, const QRegion &) { return widget->rect(); }

/*!
    Marks the region of the widget as dirty (if not already marked as dirty) and
    posts an UpdateRequest event to the top-level widget (if not already posted).

    If updateTime is UpdateNow, the event is sent immediately instead of posted.

    If bufferState is BufferInvalid, all widgets intersecting with the region will be dirty.

    If the widget paints directly on screen, the event is sent to the widget
    instead of the top-level widget, and bufferState is completely ignored.
*/
template <class T>
void QWidgetRepaintManager::markDirty(const T &r, QWidget *widget, UpdateTime updateTime, BufferState bufferState)
{
    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(!r.isEmpty());

#if QT_CONFIG(graphicseffect)
    widget->d_func()->invalidateGraphicsEffectsRecursively();
#endif

    QRect widgetRect = widgetRectFor(widget, r);

    // ---------------------------------------------------------------------------

    if (widget->d_func()->paintOnScreen()) {
        if (widget->d_func()->dirty.isEmpty()) {
            widget->d_func()->dirty = r;
            sendUpdateRequest(widget, updateTime);
            return;
        } else if (qt_region_strictContains(widget->d_func()->dirty, widgetRect)) {
            if (updateTime == UpdateNow)
                sendUpdateRequest(widget, updateTime);
            return; // Already dirty
        }

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

    // ---------------------------------------------------------------------------

    if (QWidgetPrivate::get(widget)->renderToTexture) {
        if (!widget->d_func()->inDirtyList)
            addDirtyRenderToTextureWidget(widget);
        if (!updateRequestSent || updateTime == UpdateNow)
            sendUpdateRequest(tlw, updateTime);
        return;
    }

    // ---------------------------------------------------------------------------

    QRect effectiveWidgetRect = widget->d_func()->effectiveRectFor(widgetRect);
    const QPoint offset = widget->mapTo(tlw, QPoint());
    QRect translatedRect = effectiveWidgetRect.translated(offset);
#if QT_CONFIG(graphicseffect)
    // Graphics effects may exceed window size, clamp
    translatedRect = translatedRect.intersected(QRect(QPoint(), tlw->size()));
#endif
    if (qt_region_strictContains(dirty, translatedRect)) {
        if (updateTime == UpdateNow)
            sendUpdateRequest(tlw, updateTime);
        return; // Already dirty
    }

    // ---------------------------------------------------------------------------

    if (bufferState == BufferInvalid) {
        const bool eventAlreadyPosted = !dirty.isEmpty() || updateRequestSent;
#if QT_CONFIG(graphicseffect)
        if (widget->d_func()->graphicsEffect)
            dirty += widget->d_func()->effectiveRectFor(r).translated(offset);
        else
#endif
            dirty += r.translated(offset);

        if (!eventAlreadyPosted || updateTime == UpdateNow)
            sendUpdateRequest(tlw, updateTime);
        return;
    }

    // ---------------------------------------------------------------------------

    if (dirtyWidgets.isEmpty()) {
        addDirtyWidget(widget, r);
        sendUpdateRequest(tlw, updateTime);
        return;
    }

    // ---------------------------------------------------------------------------

    if (widget->d_func()->inDirtyList) {
        if (!qt_region_strictContains(widget->d_func()->dirty, effectiveWidgetRect)) {
#if QT_CONFIG(graphicseffect)
            if (widget->d_func()->graphicsEffect)
                widget->d_func()->dirty += widget->d_func()->effectiveRectFor(r);
            else
#endif
                widget->d_func()->dirty += r;
        }
    } else {
        addDirtyWidget(widget, r);
    }

    // ---------------------------------------------------------------------------

    if (updateTime == UpdateNow)
        sendUpdateRequest(tlw, updateTime);
}
template void QWidgetRepaintManager::markDirty<QRect>(const QRect &, QWidget *, UpdateTime, BufferState);
template void QWidgetRepaintManager::markDirty<QRegion>(const QRegion &, QWidget *, UpdateTime, BufferState);

/*!
    Marks the \a region of the \a widget as dirty on screen. The \a region will be copied from
    the backing store to the \a widget's native parent next time flush() is called.

    Paint on screen widgets are ignored.
*/
void QWidgetRepaintManager::markDirtyOnScreen(const QRegion &region, QWidget *widget, const QPoint &topLevelOffset)
{
    if (!widget || widget->d_func()->paintOnScreen() || region.isEmpty())
        return;

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

    // Alien widgets.
    if (!hasPlatformWindow(widget) && !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 QWidgetRepaintManager::removeDirtyWidget(QWidget *w)
{
    if (!w)
        return;

    dirtyWidgets.removeAll(w);
    dirtyOnScreenWidgets.removeAll(w);
    dirtyRenderToTextureWidgets.removeAll(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);
    }
}

void QWidgetRepaintManager::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 || child->isWindow())
            continue;

        updateLists(child);
    }

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

QWidgetRepaintManager::QWidgetRepaintManager(QWidget *topLevel)
    : tlw(topLevel),
      updateRequestSent(0),
      textureListWatcher(0),
      perfFrames(0)
{
    store = tlw->backingStore();
    Q_ASSERT(store);

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

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

static QVector<QRect> getSortedRectsToScroll(const QRegion &region, int dx, int dy)
{
    QVector<QRect> rects;
    std::copy(region.begin(), region.end(), std::back_inserter(rects));
    if (rects.count() > 1) {
        std::sort(rects.begin(), rects.end(), [=](const QRect &r1, const QRect &r2) {
            if (r1.y() == r2.y()) {
                if (dx > 0)
                    return r1.x() > r2.x();
                return r1.x() < r2.x();
            }
            if (dy > 0)
                return r1.y() > r2.y();
            return r1.y() < r2.y();
        });
    }
    return rects;
}

//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 const bool accelEnv = qEnvironmentVariableIntValue("QT_NO_FAST_MOVE") == 0;

    QWidget *pw = q->parentWidget();
    QPoint toplevelOffset = pw->mapTo(tlw, QPoint());
    QWidgetPrivate *pd = pw->d_func();
    QRect clipR(pd->clipRect());
    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);
    const bool nativeWithTextureChild = textureChildSeen && hasPlatformWindow(q);

    const bool accelerateMove = accelEnv && isOpaque && !nativeWithTextureChild
#if QT_CONFIG(graphicsview)
                          // No accelerate move for proxy widgets.
                          && !tlw->d_func()->extra->proxyWidget
#endif
            ;

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

        QWidgetRepaintManager *wbs = x->repaintManager.get();
        QRegion childExpose(newRect & clipR);
        QRegion overlappedExpose;

        if (sourceRect.isValid()) {
            overlappedExpose = (overlappedRegion(sourceRect) | overlappedRegion(destRect)) & clipR;

            const qreal factor = QHighDpiScaling::factor(q->windowHandle());
            if (overlappedExpose.isEmpty() || qFloor(factor) == factor) {
                const QVector<QRect> rectsToScroll
                        = getSortedRectsToScroll(QRegion(sourceRect) - overlappedExpose, dx, dy);
                for (QRect rect : rectsToScroll) {
                    if (wbs->bltRect(rect, dx, dy, pw)) {
                        childExpose -= rect.translated(dx, dy);
                    }
                }
            }

            childExpose -= overlappedExpose;
        }

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

        const bool childUpdatesEnabled = q->updatesEnabled();
        if (childUpdatesEnabled) {
            if (!overlappedExpose.isEmpty()) {
                overlappedExpose.translate(-data.crect.topLeft());
                invalidateBackingStore(overlappedExpose);
            }
            if (!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;

    QWidgetRepaintManager *wbs = x->repaintManager.get();
    if (!wbs)
        return;

    static const bool accelEnv = qEnvironmentVariableIntValue("QT_NO_FAST_SCROLL") == 0;

    const QRect clipR = clipRect();
    const QRect scrollRect = rect & clipR;
    const bool accelerateScroll = accelEnv && isOpaque && !q_func()->testAttribute(Qt::WA_WState_InPaintEvent);

    if (!accelerateScroll) {
        if (!overlappedRegion(scrollRect.translated(data.crect.topLeft()), true).isEmpty()) {
            QRegion region(scrollRect);
            subtractOpaqueSiblings(region);
            invalidateBackingStore(region);
        }else {
            invalidateBackingStore(scrollRect);
        }
    } else {
        const QPoint toplevelOffset = q->mapTo(tlw, QPoint());
        const QRect destRect = scrollRect.translated(dx, dy) & scrollRect;
        const QRect sourceRect = destRect.translated(-dx, -dy);

        const QRegion overlappedExpose = (overlappedRegion(scrollRect.translated(data.crect.topLeft())))
                .translated(-data.crect.topLeft()) & clipR;
        QRegion childExpose(scrollRect);

        const qreal factor = QHighDpiScaling::factor(q->windowHandle());
        if (overlappedExpose.isEmpty() || qFloor(factor) == factor) {
            const QVector<QRect> rectsToScroll
                    = getSortedRectsToScroll(QRegion(sourceRect) - overlappedExpose, dx, dy);
            for (const QRect &rect : rectsToScroll) {
                if (wbs->bltRect(rect, dx, dy, q)) {
                    childExpose -= rect.translated(dx, dy);
                }
            }
        }

        childExpose -= overlappedExpose;

        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 (!overlappedExpose.isEmpty())
            invalidateBackingStore(overlappedExpose);
        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);
    }
}

#ifndef QT_NO_OPENGL
static void findTextureWidgetsRecursively(QWidget *tlw, QWidget *widget, QPlatformTextureList *widgetTextures, QVector<QWidget *> *nativeChildren)
{
    QWidgetPrivate *wd = QWidgetPrivate::get(widget);
    if (wd->renderToTexture) {
        QPlatformTextureList::Flags flags = wd->textureListFlags();
        const QRect rect(widget->mapTo(tlw, QPoint()), widget->size());
        widgetTextures->appendTexture(widget, wd->textureId(), rect, wd->clipRect(), flags);
    }

    for (int i = 0; i < wd->children.size(); ++i) {
        QWidget *w = qobject_cast<QWidget *>(wd->children.at(i));
        // Stop at native widgets but store them. Stop at hidden widgets too.
        if (w && !w->isWindow() && hasPlatformWindow(w))
            nativeChildren->append(w);
        if (w && !w->isWindow() && !hasPlatformWindow(w) && !w->isHidden() && QWidgetPrivate::get(w)->textureChildSeen)
            findTextureWidgetsRecursively(tlw, w, widgetTextures, nativeChildren);
    }
}

static void findAllTextureWidgetsRecursively(QWidget *tlw, QWidget *widget)
{
    // textureChildSeen does not take native child widgets into account and that's good.
    if (QWidgetPrivate::get(widget)->textureChildSeen) {
        QVector<QWidget *> nativeChildren;
        auto tl = qt_make_unique<QPlatformTextureList>();
        // Look for texture widgets (incl. widget itself) from 'widget' down,
        // but skip subtrees with a parent of a native child widget.
        findTextureWidgetsRecursively(tlw, widget, tl.get(), &nativeChildren);
        // tl may be empty regardless of textureChildSeen if we have native or hidden children.
        if (!tl->isEmpty())
            QWidgetPrivate::get(tlw)->topData()->widgetTextures.push_back(std::move(tl));
        // Native child widgets, if there was any, get their own separate QPlatformTextureList.
        for (QWidget *ncw : qAsConst(nativeChildren)) {
            if (QWidgetPrivate::get(ncw)->textureChildSeen)
                findAllTextureWidgetsRecursively(tlw, ncw);
        }
    }
}

static QPlatformTextureList *widgetTexturesFor(QWidget *tlw, QWidget *widget)
{
    for (const auto &tl : QWidgetPrivate::get(tlw)->topData()->widgetTextures) {
        Q_ASSERT(!tl->isEmpty());
        for (int i = 0; i < tl->count(); ++i) {
            QWidget *w = static_cast<QWidget *>(tl->source(i));
            if ((hasPlatformWindow(w) && w == widget) || (!hasPlatformWindow(w) && w->nativeParentWidget() == widget))
                return tl.get();
        }
    }

    if (QWidgetPrivate::get(widget)->textureChildSeen) {
        // No render-to-texture widgets in the (sub-)tree due to hidden or native
        // children. Returning null results in using the normal backingstore flush path
        // without OpenGL-based compositing. This is very desirable normally. However,
        // some platforms cannot handle switching between the non-GL and GL paths for
        // their windows so it has to be opt-in.
        static bool switchableWidgetComposition =
            QGuiApplicationPrivate::instance()->platformIntegration()
                ->hasCapability(QPlatformIntegration::SwitchableWidgetComposition);
        if (!switchableWidgetComposition)
            return qt_dummy_platformTextureList();
    }

    return 0;
}

// Watches one or more QPlatformTextureLists for changes in the lock state and
// triggers a backingstore sync when all the registered lists turn into
// unlocked state. This is essential when a custom composeAndFlush()
// implementation in a platform plugin is not synchronous and keeps
// holding on to the textures for some time even after returning from there.
QPlatformTextureListWatcher::QPlatformTextureListWatcher(QWidgetRepaintManager *paintManager)
    : m_repaintManager(paintManager)
{
}

void QPlatformTextureListWatcher::watch(QPlatformTextureList *textureList)
{
    connect(textureList, SIGNAL(locked(bool)), SLOT(onLockStatusChanged(bool)));
    m_locked[textureList] = textureList->isLocked();
}

bool QPlatformTextureListWatcher::isLocked() const
{
    foreach (bool v, m_locked) {
        if (v)
            return true;
    }
    return false;
}

void QPlatformTextureListWatcher::onLockStatusChanged(bool locked)
{
    QPlatformTextureList *tl = static_cast<QPlatformTextureList *>(sender());
    m_locked[tl] = locked;
    if (!isLocked())
        m_repaintManager->sync();
}

#else

static QPlatformTextureList *widgetTexturesFor(QWidget *tlw, QWidget *widget)
{
    Q_UNUSED(tlw);
    Q_UNUSED(widget);
    return nullptr;
}

#endif // QT_NO_OPENGL

bool QWidgetPrivate::shouldDiscardSyncRequest() const
{
    Q_Q(const QWidget);
    return !maybeTopData() || !q->testAttribute(Qt::WA_Mapped) || !q->isVisible();
}

bool QWidgetRepaintManager::syncAllowed()
{
#ifndef QT_NO_OPENGL
    QTLWExtra *tlwExtra = tlw->d_func()->maybeTopData();
    if (textureListWatcher && !textureListWatcher->isLocked()) {
        textureListWatcher->deleteLater();
        textureListWatcher = 0;
    } else if (!tlwExtra->widgetTextures.empty()) {
        bool skipSync = false;
        for (const auto &tl : tlwExtra->widgetTextures) {
            if (tl->isLocked()) {
                if (!textureListWatcher)
                    textureListWatcher = new QPlatformTextureListWatcher(this);
                if (!textureListWatcher->isLocked())
                    textureListWatcher->watch(tl.get());
                skipSync = true;
            }
        }
        if (skipSync)  // cannot compose due to widget textures being in use
            return false;
    }
#endif
    return true;
}

/*!
    Synchronizes the \a exposedRegion of the \a exposedWidget with the backing store.

    If there's nothing to repaint, the area is flushed and painting does not occur;
    otherwise the area is marked as dirty on screen and will be flushed right after
    we are done with all painting.
*/
void QWidgetRepaintManager::sync(QWidget *exposedWidget, const QRegion &exposedRegion)
{
    QTLWExtra *tlwExtra = tlw->d_func()->maybeTopData();
    if (!tlw->isVisible() || !tlwExtra || tlwExtra->inTopLevelResize)
        return;

    if (!exposedWidget || !hasPlatformWindow(exposedWidget)
        || !exposedWidget->isVisible() || !exposedWidget->testAttribute(Qt::WA_Mapped)
        || !exposedWidget->updatesEnabled() || exposedRegion.isEmpty()) {
        return;
    }

    // Nothing to repaint.
    if (!isDirty() && store->size().isValid()) {
        QPlatformTextureList *widgetTextures = widgetTexturesFor(tlw, exposedWidget);
        flush(exposedWidget, widgetTextures ? QRegion() : exposedRegion, widgetTextures);
        return;
    }

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

    if (syncAllowed())
        doSync();
}

/*!
    Synchronizes the backing store, i.e. dirty areas are repainted and flushed.
*/
void QWidgetRepaintManager::sync()
{
    updateRequestSent = false;
    if (qt_widget_private(tlw)->shouldDiscardSyncRequest()) {
        // 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();
        }
        return;
    }

    if (syncAllowed())
        doSync();
}

void QWidgetRepaintManager::doSync()
{
    const bool updatesDisabled = !tlw->updatesEnabled();
    bool repaintAllWidgets = false;

    const bool inTopLevelResize = tlw->d_func()->maybeTopData()->inTopLevelResize;
    const QRect tlwRect(topLevelRect());
    const QRect surfaceGeometry(tlwRect.topLeft(), store->size());
    if ((inTopLevelResize || surfaceGeometry.size() != tlwRect.size()) && !updatesDisabled) {
        if (hasStaticContents() && !store->size().isEmpty() ) {
            // 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;
            store->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;
        }
    }

    if (inTopLevelResize || surfaceGeometry.size() != tlwRect.size())
        store->resize(tlwRect.size());

    if (updatesDisabled)
        return;

    // 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);

        // Make a copy of the widget's dirty region, to restore it in case there is an opaque
        // render-to-texture child that completely covers the widget, because otherwise the
        // render-to-texture child won't be visible, due to its parent widget not being redrawn
        // with a proper blending mask.
        const QRegion dirtyBeforeSubtractedOpaqueChildren = wd->dirty;

        // Scrolled and moved widgets must draw all children.
        if (!wd->isScrolled && !wd->isMoved)
            wd->subtractOpaqueChildren(wd->dirty, w->rect());

        if (wd->dirty.isEmpty() && wd->textureChildSeen)
            wd->dirty = dirtyBeforeSubtractedOpaqueChildren;

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

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

#if QT_CONFIG(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();

#ifndef QT_NO_OPENGL
    // Find all render-to-texture child widgets (including self).
    // The search is cut at native widget boundaries, meaning that each native child widget
    // has its own list for the subtree below it.
    QTLWExtra *tlwExtra = tlw->d_func()->topData();
    tlwExtra->widgetTextures.clear();
    findAllTextureWidgetsRecursively(tlw, tlw);
    qt_window_private(tlw->windowHandle())->compositing = false; // will get updated in flush()
#endif

    if (toClean.isEmpty()) {
        // Nothing to repaint. However renderToTexture widgets are handled
        // specially, they are not in the regular dirty list, in order to
        // prevent triggering unnecessary backingstore painting when only the
        // OpenGL content changes. Check if we have such widgets in the special
        // dirty list.
        QVarLengthArray<QWidget *, 16> paintPending;
        const int numPaintPending = dirtyRenderToTextureWidgets.count();
        paintPending.reserve(numPaintPending);
        for (int i = 0; i < numPaintPending; ++i) {
            QWidget *w = dirtyRenderToTextureWidgets.at(i);
            paintPending << w;
            resetWidget(w);
        }
        dirtyRenderToTextureWidgets.clear();
        for (int i = 0; i < numPaintPending; ++i) {
            QWidget *w = paintPending[i];
            w->d_func()->sendPaintEvent(w->rect());
            if (w != tlw) {
                QWidget *npw = w->nativeParentWidget();
                if (hasPlatformWindow(w) || (npw && npw != tlw)) {
                    if (!hasPlatformWindow(w))
                        w = npw;
                    QWidgetPrivate *wPrivate = w->d_func();
                    if (!wPrivate->needsFlush)
                        wPrivate->needsFlush = new QRegion;
                    appendDirtyOnScreenWidget(w);
                }
            }
        }

        // 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. We also need to composite the renderToTexture widgets.
        flush();

        return;
    }

#ifndef QT_NO_OPENGL
    for (const auto &tl : tlwExtra->widgetTextures) {
        for (int i = 0; i < tl->count(); ++i) {
            QWidget *w = static_cast<QWidget *>(tl->source(i));
            if (dirtyRenderToTextureWidgets.contains(w)) {
                const QRect rect = tl->geometry(i); // mapped to the tlw already
                // Set a flag to indicate that the paint event for this
                // render-to-texture widget must not to be optimized away.
                w->d_func()->renderToTextureReallyDirty = 1;
                dirty += rect;
                toClean += rect;
            }
        }
    }
    for (int i = 0; i < dirtyRenderToTextureWidgets.count(); ++i)
        resetWidget(dirtyRenderToTextureWidgets.at(i));
    dirtyRenderToTextureWidgets.clear();
#endif

#if QT_CONFIG(graphicsview)
    if (tlw->d_func()->extra->proxyWidget) {
        updateStaticContentsSize();
        dirty = QRegion();
        updateRequestSent = false;
        for (const QRect &rect : toClean)
            tlw->d_func()->extra->proxyWidget->update(rect);
        return;
    }
#endif

    beginPaint(toClean, store);

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

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

        QWidgetPrivate::DrawWidgetFlags 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);

        QPoint offset;
        if (w != tlw)
            offset += w->mapTo(tlw, QPoint());
        wd->drawWidget(store->paintDevice(), toBePainted, offset, flags, 0, this);
    }

    // Paint the rest with composition.
    if (repaintAllWidgets || !dirtyCopy.isEmpty()) {
        QWidgetPrivate::DrawWidgetFlags flags = QWidgetPrivate::DrawAsRoot | QWidgetPrivate::DrawRecursive;
        tlw->d_func()->drawWidget(store->paintDevice(), dirtyCopy, QPoint(), flags, 0, this);
    }

    endPaint(store);
}

/*!
    Flushes the contents of the backing store into the top-level widget.
    If the \a widget is non-zero, the content is flushed to the \a widget.
*/
void QWidgetRepaintManager::flush(QWidget *widget)
{
    const bool hasDirtyOnScreenWidgets = !dirtyOnScreenWidgets.isEmpty();
    bool flushed = false;

    // Flush the region in dirtyOnScreen.
    if (!dirtyOnScreen.isEmpty()) {
        QWidget *target = widget ? widget : tlw;
        flush(target, dirtyOnScreen, widgetTexturesFor(tlw, tlw));
        dirtyOnScreen = QRegion();
        flushed = true;
    }

    // Render-to-texture widgets are not in dirtyOnScreen so flush if we have not done it above.
    if (!flushed && !hasDirtyOnScreenWidgets) {
#ifndef QT_NO_OPENGL
        if (!tlw->d_func()->topData()->widgetTextures.empty()) {
            QPlatformTextureList *widgetTextures = widgetTexturesFor(tlw, tlw);
            if (widgetTextures) {
                QWidget *target = widget ? widget : tlw;
                flush(target, QRegion(), widgetTextures);
            }
        }
#endif
    }

    if (!hasDirtyOnScreenWidgets)
        return;

    for (QWidget *w : qExchange(dirtyOnScreenWidgets, {})) {
        QWidgetPrivate *wd = w->d_func();
        Q_ASSERT(wd->needsFlush);
        QPlatformTextureList *widgetTexturesForNative = wd->textureChildSeen ? widgetTexturesFor(tlw, w) : 0;
        flush(w, *wd->needsFlush, widgetTexturesForNative);
        *wd->needsFlush = QRegion();
    }
}

/*
    Flushes the contents of the backingstore into the screen area of \a widget.

    \a region is the region to be updated in \a widget coordinates.
 */
void QWidgetRepaintManager::flush(QWidget *widget, const QRegion &region, QPlatformTextureList *widgetTextures)
{
#ifdef QT_NO_OPENGL
    Q_UNUSED(widgetTextures);
    Q_ASSERT(!region.isEmpty());
#else
    Q_ASSERT(!region.isEmpty() || widgetTextures);
#endif
    Q_ASSERT(widget);
    Q_ASSERT(tlw);

    if (tlw->testAttribute(Qt::WA_DontShowOnScreen) || widget->testAttribute(Qt::WA_DontShowOnScreen))
        return;

    // Foreign Windows do not have backing store content and must not be flushed
    if (QWindow *widgetWindow = widget->windowHandle()) {
        if (widgetWindow->type() == Qt::ForeignWindow)
            return;
    }

    static bool fpsDebug = qEnvironmentVariableIntValue("QT_DEBUG_FPS");
    if (fpsDebug) {
        if (!perfFrames++)
            perfTime.start();
        if (perfTime.elapsed() > 5000) {
            double fps = double(perfFrames * 1000) / perfTime.restart();
            qDebug("FPS: %.1f\n", fps);
            perfFrames = 0;
        }
    }

    QPoint offset;
    if (widget != tlw)
        offset += widget->mapTo(tlw, QPoint());

    QRegion effectiveRegion = region;
#ifndef QT_NO_OPENGL
    const bool compositionWasActive = widget->d_func()->renderToTextureComposeActive;
    if (!widgetTextures) {
        widget->d_func()->renderToTextureComposeActive = false;
        // Detect the case of falling back to the normal flush path when no
        // render-to-texture widgets are visible anymore. We will force one
        // last flush to go through the OpenGL-based composition to prevent
        // artifacts. The next flush after this one will use the normal path.
        if (compositionWasActive)
            widgetTextures = qt_dummy_platformTextureList;
    } else {
        widget->d_func()->renderToTextureComposeActive = true;
    }
    // When changing the composition status, make sure the dirty region covers
    // the entire widget.  Just having e.g. the shown/hidden render-to-texture
    // widget's area marked as dirty is incorrect when changing flush paths.
    if (compositionWasActive != widget->d_func()->renderToTextureComposeActive)
        effectiveRegion = widget->rect();

    // re-test since we may have been forced to this path via the dummy texture list above
    if (widgetTextures) {
        qt_window_private(tlw->windowHandle())->compositing = true;
        widget->window()->d_func()->sendComposeStatus(widget->window(), false);
        // A window may have alpha even when the app did not request
        // WA_TranslucentBackground. Therefore the compositor needs to know whether the app intends
        // to rely on translucency, in order to decide if it should clear to transparent or opaque.
        const bool translucentBackground = widget->testAttribute(Qt::WA_TranslucentBackground);
        store->handle()->composeAndFlush(widget->windowHandle(), effectiveRegion, offset,
                                                widgetTextures, translucentBackground);
        widget->window()->d_func()->sendComposeStatus(widget->window(), true);
    } else
#endif
        store->flush(effectiveRegion, widget->windowHandle(), offset);
}

/*!
    Invalidates the backing store when the widget is resized.
    Static areas are never invalidated unless absolutely needed.
*/
void QWidgetPrivate::invalidateBackingStore_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;
        QWidgetRepaintManager *bs = 0;
        if (offset.isNull() && (bs = maybeRepaintManager()))
            staticChildren = bs->staticContents(q, oldWidgetRect);
        const bool hasStaticChildren = !staticChildren.isEmpty();

        if (hasStaticChildren) {
            QRegion dirty(newWidgetRect);
            dirty -= staticChildren;
            invalidateBackingStore(dirty);
        } else {
            // Entire widget needs repaint.
            invalidateBackingStore(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()->invalidateBackingStore(parentExpose);
        } else {
            if (hasStaticChildren && !graphicsEffect) {
                QRegion parentExpose(QRect(oldPos, oldSize));
                parentExpose -= data.crect; // Offset is unchanged, safe to do this.
                q->parentWidget()->d_func()->invalidateBackingStore(parentExpose);
            } else {
                q->parentWidget()->d_func()->invalidateBackingStore(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;
        invalidateBackingStore(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()->invalidateBackingStore(parentExpose);
    } else {
        QRegion parentExpose(oldRect);
        parentExpose -= data.crect;
        q->parentWidget()->d_func()->invalidateBackingStore(parentExpose);
    }
}

/*!
    Invalidates the \a r (in widget's coordinates) of the backing store, i.e.
    all widgets intersecting with the region will be repainted when the backing
    store is synced.
*/
template <class T>
void QWidgetPrivate::invalidateBackingStore(const T &r)
{
    if (r.isEmpty())
        return;

    if (QCoreApplication::closingDown())
        return;

    Q_Q(QWidget);
    if (!q->isVisible() || !q->updatesEnabled())
        return;

    QTLWExtra *tlwExtra = q->window()->d_func()->maybeTopData();
    if (!tlwExtra || tlwExtra->inTopLevelResize || !tlwExtra->backingStore)
        return;

    T clipped(r);
    clipped &= clipRect();
    if (clipped.isEmpty())
        return;

    if (!graphicsEffect && extra && extra->hasMask) {
        QRegion masked(extra->mask);
        masked &= clipped;
        if (masked.isEmpty())
            return;

        tlwExtra->repaintManager->markDirty(masked, q,
            QWidgetRepaintManager::UpdateLater, QWidgetRepaintManager::BufferInvalid);
    } else {
        tlwExtra->repaintManager->markDirty(clipped, q,
            QWidgetRepaintManager::UpdateLater, QWidgetRepaintManager::BufferInvalid);
    }
}
// Needed by tst_QWidget
template Q_AUTOTEST_EXPORT void QWidgetPrivate::invalidateBackingStore<QRect>(const QRect &r);

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

    if (shouldDiscardSyncRequest())
        return;

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

    QPaintEngine *engine = q->paintEngine();

    // 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);

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

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

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


QT_END_NAMESPACE

#include "moc_qwidgetrepaintmanager_p.cpp"