qgraphicsview.cpp

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// Copyright (C) 2021 The Qt Company Ltd.
// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR LGPL-3.0-only OR GPL-2.0-only OR GPL-3.0-only
 
static const int QGRAPHICSVIEW_REGION_RECT_THRESHOLD = 50;
 
static const int QGRAPHICSVIEW_PREALLOC_STYLE_OPTIONS = 503; // largest prime < 2^9
 
#include "qgraphicsview.h"
#include "qgraphicsview_p.h"
 
#include "qgraphicsitem.h"
#include "qgraphicsitem_p.h"
#include "qgraphicsscene.h"
#include "qgraphicsscene_p.h"
#include "qgraphicssceneevent.h"
#include "qgraphicswidget.h"
 
#include <QtCore/qdatetime.h>
#include <QtCore/qdebug.h>
#include <QtCore/qmath.h>
#include <QtCore/qscopedvaluerollback.h>
#include <QtWidgets/qapplication.h>
#include <QtGui/qevent.h>
#include <QtWidgets/qlayout.h>
#include <QtGui/qtransform.h>
#include <QtGui/qpainter.h>
#include <QtGui/qpainterpath.h>
#include <QtWidgets/qscrollbar.h>
#include <QtWidgets/qstyleoption.h>
 
#include <private/qevent_p.h>
#include <QtGui/private/qeventpoint_p.h>
 
QT_BEGIN_NAMESPACE
 
bool qt_sendSpontaneousEvent(QObject *receiver, QEvent *event);
 
inline int q_round_bound(qreal d) //### (int)(qreal) INT_MAX != INT_MAX for single precision
{
    if (d <= (qreal) INT_MIN)
        return INT_MIN;
    else if (d >= (qreal) INT_MAX)
        return INT_MAX;
    return d >= 0.0 ? int(d + 0.5) : int(d - int(d-1) + 0.5) + int(d-1);
}
 
void QGraphicsViewPrivate::translateTouchEvent(QGraphicsViewPrivate *d, QTouchEvent *touchEvent)
{
    for (int i = 0; i < touchEvent->pointCount(); ++i) {
        auto &pt = touchEvent->point(i);
        // the scene will set the item local pos, startPos, lastPos, and rect before delivering to
        // an item, but for now those functions are returning the view's local coordinates
        QMutableEventPoint::setScenePosition(pt, d->mapToScene(pt.position()));
        // screenPos, startScreenPos, and lastScreenPos are already set
    }
}
 
QGraphicsViewPrivate::QGraphicsViewPrivate()
    : renderHints(QPainter::TextAntialiasing),
      dragMode(QGraphicsView::NoDrag),
      sceneInteractionAllowed(true), hasSceneRect(false),
      connectedToScene(false),
      useLastMouseEvent(false),
      identityMatrix(true),
      dirtyScroll(true),
      accelerateScrolling(true),
      keepLastCenterPoint(true),
      transforming(false),
      handScrolling(false),
      mustAllocateStyleOptions(false),
      mustResizeBackgroundPixmap(true),
      fullUpdatePending(true),
      hasUpdateClip(false),
      mousePressButton(Qt::NoButton),
      leftIndent(0), topIndent(0),
      alignment(Qt::AlignCenter),
      transformationAnchor(QGraphicsView::AnchorViewCenter), resizeAnchor(QGraphicsView::NoAnchor),
      viewportUpdateMode(QGraphicsView::MinimalViewportUpdate),
      scene(nullptr),
#if QT_CONFIG(rubberband)
      rubberBanding(false),
      rubberBandSelectionMode(Qt::IntersectsItemShape),
      rubberBandSelectionOperation(Qt::ReplaceSelection),
#endif
      handScrollMotions(0),
#ifndef QT_NO_CURSOR
      hasStoredOriginalCursor(false),
#endif
      lastDragDropEvent(nullptr),
      updateSceneSlotReimplementedChecked(false)
{
    styleOptions.reserve(QGRAPHICSVIEW_PREALLOC_STYLE_OPTIONS);
}
 
QGraphicsViewPrivate::~QGraphicsViewPrivate()
{
}
 
void QGraphicsViewPrivate::recalculateContentSize()
{
    Q_Q(QGraphicsView);
 
    const QSize maxSize = q->maximumViewportSize();
    int width = maxSize.width();
    int height = maxSize.height();
    const QRectF viewRect = matrix.mapRect(q->sceneRect());
 
    bool frameOnlyAround = (q->style()->styleHint(QStyle::SH_ScrollView_FrameOnlyAroundContents, nullptr, q));
    if (frameOnlyAround) {
        if (hbarpolicy == Qt::ScrollBarAlwaysOn)
            height -= frameWidth * 2;
        if (vbarpolicy == Qt::ScrollBarAlwaysOn)
            width -= frameWidth * 2;
    }
 
    // Adjust the maximum width and height of the viewport based on the width
    // of visible scroll bars.
    const int scrollBarExtent = q->style()->pixelMetric(QStyle::PM_ScrollBarExtent, nullptr, q)
                              + (frameOnlyAround ? frameWidth * 2 : 0);
 
    // We do not need to subtract the width scrollbars whose policy is
    // Qt::ScrollBarAlwaysOn, this was already done by maximumViewportSize().
    bool useHorizontalScrollBar = (viewRect.width() > width) && hbarpolicy == Qt::ScrollBarAsNeeded;
    bool useVerticalScrollBar = (viewRect.height() > height) && vbarpolicy == Qt::ScrollBarAsNeeded;
    if (useHorizontalScrollBar && vbarpolicy == Qt::ScrollBarAsNeeded) {
        if (viewRect.height() > height - scrollBarExtent)
            useVerticalScrollBar = true;
    }
    if (useVerticalScrollBar && hbarpolicy == Qt::ScrollBarAsNeeded) {
        if (viewRect.width() > width - scrollBarExtent)
            useHorizontalScrollBar = true;
    }
    if (useHorizontalScrollBar)
        height -= scrollBarExtent;
    if (useVerticalScrollBar)
        width -= scrollBarExtent;
 
    // Setting the ranges of these scroll bars can/will cause the values to
    // change, and scrollContentsBy() will be called correspondingly. This
    // will reset the last center point.
    const QPointF savedLastCenterPoint = lastCenterPoint;
 
    // Remember the former indent settings
    const qreal oldLeftIndent = leftIndent;
    const qreal oldTopIndent = topIndent;
 
    // If the whole scene fits horizontally, we center the scene horizontally,
    // and ignore the horizontal scroll bars.
    const int left =  q_round_bound(viewRect.left());
    const int right = q_round_bound(viewRect.right() - width);
    if (left >= right) {
        switch (alignment & Qt::AlignHorizontal_Mask) {
        case Qt::AlignLeft:
            leftIndent = -viewRect.left();
            break;
        case Qt::AlignRight:
            leftIndent = maxSize.width() - viewRect.width() - viewRect.left() - 1;
            break;
        case Qt::AlignHCenter:
        default:
            leftIndent = maxSize.width() / 2 - (viewRect.left() + viewRect.right()) / 2;
            break;
        }
 
        hbar->setRange(0, 0);
    } else {
        leftIndent = 0;
 
        hbar->setRange(left, right);
        hbar->setPageStep(width);
        hbar->setSingleStep(width / 20);
 
        if (oldLeftIndent != 0)
            hbar->setValue(-oldLeftIndent);
    }
 
    // If the whole scene fits vertically, we center the scene vertically, and
    // ignore the vertical scroll bars.
    const int top = q_round_bound(viewRect.top());
    const int bottom = q_round_bound(viewRect.bottom()  - height);
    if (top >= bottom) {
        switch (alignment & Qt::AlignVertical_Mask) {
        case Qt::AlignTop:
            topIndent = -viewRect.top();
            break;
        case Qt::AlignBottom:
            topIndent = maxSize.height() - viewRect.height() - viewRect.top() - 1;
            break;
        case Qt::AlignVCenter:
        default:
            topIndent = maxSize.height() / 2 - (viewRect.top() + viewRect.bottom()) / 2;
            break;
        }
 
        vbar->setRange(0, 0);
    } else {
        topIndent = 0;
 
        vbar->setRange(top, bottom);
        vbar->setPageStep(height);
        vbar->setSingleStep(height / 20);
 
        if (oldTopIndent != 0)
            vbar->setValue(-oldTopIndent);
    }
 
    // Restorethe center point from before the ranges changed.
    lastCenterPoint = savedLastCenterPoint;
 
    // Issue a full update if the indents change.
    // ### If the transform is still the same, we can get away with just a
    // scroll instead.
    if (oldLeftIndent != leftIndent || oldTopIndent != topIndent) {
        dirtyScroll = true;
        updateAll();
    } else if (q->isRightToLeft() && !leftIndent) {
        // In reverse mode, the horizontal scroll always changes after the content
        // size has changed, as the scroll is calculated by summing the min and
        // max values of the range and subtracting the current value. In normal
        // mode the scroll remains unchanged unless the indent has changed.
        dirtyScroll = true;
    }
 
    if (cacheMode & QGraphicsView::CacheBackground) {
        // Invalidate the background pixmap
        mustResizeBackgroundPixmap = true;
    }
}
 
void QGraphicsViewPrivate::centerView(QGraphicsView::ViewportAnchor anchor)
{
    Q_Q(QGraphicsView);
    switch (anchor) {
    case QGraphicsView::AnchorUnderMouse: {
        if (q->underMouse()) {
            // Last scene pos: lastMouseMoveScenePoint
            // Current mouse pos:
            QPointF transformationDiff = q->mapToScene(viewport->rect().center())
                                         - q->mapToScene(viewport->mapFromGlobal(QCursor::pos()));
            q->centerOn(lastMouseMoveScenePoint + transformationDiff);
        } else {
            q->centerOn(lastCenterPoint);
        }
        break;
    }
    case QGraphicsView::AnchorViewCenter:
        q->centerOn(lastCenterPoint);
        break;
    case QGraphicsView::NoAnchor:
        break;
    }
}
 
void QGraphicsViewPrivate::updateLastCenterPoint()
{
    Q_Q(QGraphicsView);
    lastCenterPoint = q->mapToScene(viewport->rect().center());
}
 
qint64 QGraphicsViewPrivate::horizontalScroll() const
{
    if (dirtyScroll)
        const_cast<QGraphicsViewPrivate *>(this)->updateScroll();
    return scrollX;
}
 
qint64 QGraphicsViewPrivate::verticalScroll() const
{
    if (dirtyScroll)
        const_cast<QGraphicsViewPrivate *>(this)->updateScroll();
    return scrollY;
}
 
QRectF QGraphicsViewPrivate::mapRectToScene(const QRect &rect) const
{
    if (dirtyScroll)
        const_cast<QGraphicsViewPrivate *>(this)->updateScroll();
    QRectF scrolled = QRectF(rect.translated(scrollX, scrollY));
    return identityMatrix ? scrolled : matrix.inverted().mapRect(scrolled);
}
 
 
QRectF QGraphicsViewPrivate::mapRectFromScene(const QRectF &rect) const
{
    if (dirtyScroll)
        const_cast<QGraphicsViewPrivate *>(this)->updateScroll();
    return (identityMatrix ? rect : matrix.mapRect(rect)).translated(-scrollX, -scrollY);
}
 
void QGraphicsViewPrivate::updateScroll()
{
    Q_Q(QGraphicsView);
    scrollX = qint64(-leftIndent);
    if (q->isRightToLeft()) {
        if (!leftIndent) {
            scrollX += hbar->minimum();
            scrollX += hbar->maximum();
            scrollX -= hbar->value();
        }
    } else {
        scrollX += hbar->value();
    }
 
    scrollY = qint64(vbar->value() - topIndent);
 
    dirtyScroll = false;
}
 
bool QGraphicsViewPrivate::canStartScrollingAt(const QPoint &startPos) const
{
    Q_Q(const QGraphicsView);
    if (q->dragMode() != QGraphicsView::NoDrag)
        return false;
 
    const QGraphicsItem *childItem = q->itemAt(startPos);
 
    if (!startPos.isNull() && childItem && (childItem->flags() & QGraphicsItem::ItemIsMovable))
        return false;
 
    return QAbstractScrollAreaPrivate::canStartScrollingAt(startPos);
}
 
void QGraphicsViewPrivate::replayLastMouseEvent()
{
    if (!useLastMouseEvent || !scene)
        return;
    QSinglePointEvent *spe = static_cast<QSinglePointEvent *>(&lastMouseEvent);
    mouseMoveEventHandler(static_cast<QMouseEvent *>(spe));
}
 
void QGraphicsViewPrivate::storeMouseEvent(QMouseEvent *event)
{
    useLastMouseEvent = true;
    lastMouseEvent = *event;
}
 
void QGraphicsViewPrivate::mouseMoveEventHandler(QMouseEvent *event)
{
    Q_Q(QGraphicsView);
 
#if QT_CONFIG(rubberband)
    updateRubberBand(event);
#endif
 
    storeMouseEvent(event);
    lastMouseEvent.setAccepted(false);
 
    if (!sceneInteractionAllowed)
        return;
    if (handScrolling)
        return;
    if (!scene)
        return;
 
    QGraphicsSceneMouseEvent mouseEvent(QEvent::GraphicsSceneMouseMove);
    mouseEvent.setWidget(viewport);
    mouseEvent.setButtonDownScenePos(mousePressButton, mousePressScenePoint);
    mouseEvent.setButtonDownScreenPos(mousePressButton, mousePressScreenPoint);
    mouseEvent.setScenePos(q->mapToScene(event->position().toPoint()));
    mouseEvent.setScreenPos(event->globalPosition().toPoint());
    mouseEvent.setLastScenePos(lastMouseMoveScenePoint);
    mouseEvent.setLastScreenPos(lastMouseMoveScreenPoint);
    mouseEvent.setButtons(event->buttons());
    mouseEvent.setButton(event->button());
    mouseEvent.setModifiers(event->modifiers());
    mouseEvent.setSource(event->source());
    mouseEvent.setFlags(event->flags());
    mouseEvent.setTimestamp(event->timestamp());
    lastMouseMoveScenePoint = mouseEvent.scenePos();
    lastMouseMoveScreenPoint = mouseEvent.screenPos();
    mouseEvent.setAccepted(false);
    if (event->spontaneous())
        qt_sendSpontaneousEvent(scene, &mouseEvent);
    else
        QCoreApplication::sendEvent(scene, &mouseEvent);
 
    // Remember whether the last event was accepted or not.
    lastMouseEvent.setAccepted(mouseEvent.isAccepted());
 
    if (mouseEvent.isAccepted() && mouseEvent.buttons() != 0) {
        // The event was delivered to a mouse grabber; the press is likely to
        // have set a cursor, and we must not change it.
        return;
    }
 
#ifndef QT_NO_CURSOR
    // If all the items ignore hover events, we don't look-up any items
    // in QGraphicsScenePrivate::dispatchHoverEvent, hence the
    // cachedItemsUnderMouse list will be empty. We therefore do the look-up
    // for cursor items here if not all items use the default cursor.
    if (scene->d_func()->allItemsIgnoreHoverEvents && !scene->d_func()->allItemsUseDefaultCursor
        && scene->d_func()->cachedItemsUnderMouse.isEmpty()) {
        scene->d_func()->cachedItemsUnderMouse = scene->d_func()->itemsAtPosition(mouseEvent.screenPos(),
                                                                                  mouseEvent.scenePos(),
                                                                                  mouseEvent.widget());
    }
    // Find the topmost item under the mouse with a cursor.
    for (QGraphicsItem *item : std::as_const(scene->d_func()->cachedItemsUnderMouse)) {
        if (item->isEnabled() && item->hasCursor()) {
            _q_setViewportCursor(item->cursor());
            return;
        }
    }
 
    // No items with cursors found; revert to the view cursor.
    if (hasStoredOriginalCursor) {
        // Restore the original viewport cursor.
        hasStoredOriginalCursor = false;
        viewport->setCursor(originalCursor);
    }
#endif
}
 
#if QT_CONFIG(rubberband)
QRegion QGraphicsViewPrivate::rubberBandRegion(const QWidget *widget, const QRect &rect) const
{
    QStyleHintReturnMask mask;
    QStyleOptionRubberBand option;
    option.initFrom(widget);
    option.rect = rect;
    option.opaque = false;
    option.shape = QRubberBand::Rectangle;
 
    QRegion tmp;
    tmp += rect.adjusted(-1, -1, 1, 1);
    if (widget->style()->styleHint(QStyle::SH_RubberBand_Mask, &option, widget, &mask))
        tmp &= mask.region;
    return tmp;
}
 
void QGraphicsViewPrivate::updateRubberBand(const QMouseEvent *event)
{
    Q_Q(QGraphicsView);
    if (dragMode != QGraphicsView::RubberBandDrag || !sceneInteractionAllowed || !rubberBanding)
        return;
    // Check for enough drag distance
    if ((mousePressViewPoint - event->position().toPoint()).manhattanLength() < QApplication::startDragDistance())
        return;
 
    // Update old rubberband
    if (viewportUpdateMode != QGraphicsView::NoViewportUpdate && !rubberBandRect.isEmpty()) {
        if (viewportUpdateMode != QGraphicsView::FullViewportUpdate)
            q->viewport()->update(rubberBandRegion(q->viewport(), rubberBandRect));
        else
            updateAll();
    }
 
    // Stop rubber banding if the user has let go of all buttons (even
    // if we didn't get the release events).
    if (!event->buttons()) {
        rubberBanding = false;
        rubberBandSelectionOperation = Qt::ReplaceSelection;
        if (!rubberBandRect.isNull()) {
            rubberBandRect = QRect();
            emit q->rubberBandChanged(rubberBandRect, QPointF(), QPointF());
        }
        return;
    }
 
    QRect oldRubberband = rubberBandRect;
 
    // Update rubberband position
    const QPoint mp = q->mapFromScene(mousePressScenePoint);
    const QPoint ep = event->position().toPoint();
    rubberBandRect = QRect(qMin(mp.x(), ep.x()), qMin(mp.y(), ep.y()),
                           qAbs(mp.x() - ep.x()) + 1, qAbs(mp.y() - ep.y()) + 1);
 
    if (rubberBandRect != oldRubberband || lastRubberbandScenePoint != lastMouseMoveScenePoint) {
        lastRubberbandScenePoint = lastMouseMoveScenePoint;
        oldRubberband = rubberBandRect;
        emit q->rubberBandChanged(rubberBandRect, mousePressScenePoint, lastRubberbandScenePoint);
    }
 
    // Update new rubberband
    if (viewportUpdateMode != QGraphicsView::NoViewportUpdate) {
        if (viewportUpdateMode != QGraphicsView::FullViewportUpdate)
            q->viewport()->update(rubberBandRegion(q->viewport(), rubberBandRect));
        else
            updateAll();
    }
            // Set the new selection area
    QPainterPath selectionArea;
    selectionArea.addPolygon(q->mapToScene(rubberBandRect));
    selectionArea.closeSubpath();
    if (scene)
        scene->setSelectionArea(selectionArea, rubberBandSelectionOperation, rubberBandSelectionMode, q->viewportTransform());
}
 
void QGraphicsViewPrivate::clearRubberBand()
{
    Q_Q(QGraphicsView);
    if (dragMode != QGraphicsView::RubberBandDrag || !sceneInteractionAllowed || !rubberBanding)
        return;
 
    if (viewportUpdateMode != QGraphicsView::NoViewportUpdate) {
        if (viewportUpdateMode != QGraphicsView::FullViewportUpdate)
            q->viewport()->update(rubberBandRegion(q->viewport(), rubberBandRect));
        else
            updateAll();
    }
 
    rubberBanding = false;
    rubberBandSelectionOperation = Qt::ReplaceSelection;
    if (!rubberBandRect.isNull()) {
        rubberBandRect = QRect();
        emit q->rubberBandChanged(rubberBandRect, QPointF(), QPointF());
    }
}
#endif
 
#ifndef QT_NO_CURSOR
void QGraphicsViewPrivate::_q_setViewportCursor(const QCursor &cursor)
{
    if (!hasStoredOriginalCursor) {
        hasStoredOriginalCursor = true;
        originalCursor = viewport->cursor();
    }
    viewport->setCursor(cursor);
}
#endif
 
#ifndef QT_NO_CURSOR
void QGraphicsViewPrivate::_q_unsetViewportCursor()
{
    Q_Q(QGraphicsView);
    const auto items = q->items(lastMouseEvent.position().toPoint());
    for (QGraphicsItem *item : items) {
        if (item->isEnabled() && item->hasCursor()) {
            _q_setViewportCursor(item->cursor());
            return;
        }
    }
 
    // Restore the original viewport cursor.
    if (hasStoredOriginalCursor) {
        hasStoredOriginalCursor = false;
        if (dragMode == QGraphicsView::ScrollHandDrag)
            viewport->setCursor(Qt::OpenHandCursor);
        else
            viewport->setCursor(originalCursor);
    }
}
#endif
 
void QGraphicsViewPrivate::storeDragDropEvent(const QGraphicsSceneDragDropEvent *event)
{
    delete lastDragDropEvent;
    lastDragDropEvent = new QGraphicsSceneDragDropEvent(event->type());
    lastDragDropEvent->setScenePos(event->scenePos());
    lastDragDropEvent->setScreenPos(event->screenPos());
    lastDragDropEvent->setButtons(event->buttons());
    lastDragDropEvent->setModifiers(event->modifiers());
    lastDragDropEvent->setPossibleActions(event->possibleActions());
    lastDragDropEvent->setProposedAction(event->proposedAction());
    lastDragDropEvent->setDropAction(event->dropAction());
    lastDragDropEvent->setMimeData(event->mimeData());
    lastDragDropEvent->setWidget(event->widget());
    lastDragDropEvent->setSource(event->source());
    lastDragDropEvent->setTimestamp(event->timestamp());
}
 
void QGraphicsViewPrivate::populateSceneDragDropEvent(QGraphicsSceneDragDropEvent *dest,
                                                      QDropEvent *source)
{
#if QT_CONFIG(draganddrop)
    Q_Q(QGraphicsView);
    dest->setScenePos(q->mapToScene(source->position().toPoint()));
    dest->setScreenPos(q->mapToGlobal(source->position().toPoint()));
    dest->setButtons(source->buttons());
    dest->setModifiers(source->modifiers());
    dest->setPossibleActions(source->possibleActions());
    dest->setProposedAction(source->proposedAction());
    dest->setDropAction(source->dropAction());
    dest->setMimeData(source->mimeData());
    dest->setWidget(viewport);
    dest->setSource(qobject_cast<QWidget *>(source->source()));
#else
    Q_UNUSED(dest);
    Q_UNUSED(source);
#endif
}
 
QRect QGraphicsViewPrivate::mapToViewRect(const QGraphicsItem *item, const QRectF &rect) const
{
    Q_Q(const QGraphicsView);
    if (dirtyScroll)
        const_cast<QGraphicsViewPrivate *>(this)->updateScroll();
 
    if (item->d_ptr->itemIsUntransformable()) {
        QTransform itv = item->deviceTransform(q->viewportTransform());
        return itv.mapRect(rect).toAlignedRect();
    }
 
    // Translate-only
    // COMBINE
    QPointF offset;
    const QGraphicsItem *parentItem = item;
    const QGraphicsItemPrivate *itemd;
    do {
        itemd = parentItem->d_ptr.data();
        if (itemd->transformData)
            break;
        offset += itemd->pos;
    } while ((parentItem = itemd->parent));
 
    QRectF baseRect = rect.translated(offset.x(), offset.y());
    if (!parentItem) {
        if (identityMatrix) {
            baseRect.translate(-scrollX, -scrollY);
            return baseRect.toAlignedRect();
        }
        return matrix.mapRect(baseRect).translated(-scrollX, -scrollY).toAlignedRect();
    }
 
    QTransform tr = parentItem->sceneTransform();
    if (!identityMatrix)
        tr *= matrix;
    QRectF r = tr.mapRect(baseRect);
    r.translate(-scrollX, -scrollY);
    return r.toAlignedRect();
}
 
QRegion QGraphicsViewPrivate::mapToViewRegion(const QGraphicsItem *item, const QRectF &rect) const
{
    Q_Q(const QGraphicsView);
    if (dirtyScroll)
        const_cast<QGraphicsViewPrivate *>(this)->updateScroll();
 
    // Accurate bounding region
    QTransform itv = item->deviceTransform(q->viewportTransform());
    return item->boundingRegion(itv) & itv.mapRect(rect).toAlignedRect();
}
 
void QGraphicsViewPrivate::processPendingUpdates()
{
    if (!scene)
        return;
 
    if (fullUpdatePending) {
        viewport->update();
    } else if (viewportUpdateMode == QGraphicsView::BoundingRectViewportUpdate) {
        viewport->update(dirtyBoundingRect);
    } else {
        viewport->update(dirtyRegion); // Already adjusted in updateRect/Region.
    }
 
    dirtyBoundingRect = QRect();
    dirtyRegion = QRegion();
}
 
static inline bool intersectsViewport(const QRect &r, int width, int height)
{ return !(r.left() > width) && !(r.right() < 0) && !(r.top() >= height) && !(r.bottom() < 0); }
 
static inline bool containsViewport(const QRect &r, int width, int height)
{ return r.left() <= 0 && r.top() <= 0 && r.right() >= width - 1 && r.bottom() >= height - 1; }
 
static inline void QRect_unite(QRect *rect, const QRect &other)
{
    if (rect->isEmpty()) {
        *rect = other;
    } else {
        rect->setCoords(qMin(rect->left(), other.left()), qMin(rect->top(), other.top()),
                        qMax(rect->right(), other.right()), qMax(rect->bottom(), other.bottom()));
    }
}
 
/*
   Calling this function results in update rects being clipped to the item's
   bounding rect. Note that updates prior to this function call is not clipped.
   The clip is removed by passing \nullptr.
*/
void QGraphicsViewPrivate::setUpdateClip(QGraphicsItem *item)
{
    Q_Q(QGraphicsView);
    // We simply ignore the request if the update mode is either FullViewportUpdate
    // or NoViewportUpdate; in that case there's no point in clipping anything.
    if (!item || viewportUpdateMode == QGraphicsView::NoViewportUpdate
        || viewportUpdateMode == QGraphicsView::FullViewportUpdate) {
        hasUpdateClip = false;
        return;
    }
 
    // Calculate the clip (item's bounding rect in view coordinates).
    // Optimized version of:
    // QRect clip = item->deviceTransform(q->viewportTransform())
    //              .mapRect(item->boundingRect()).toAlignedRect();
    QRect clip;
    if (item->d_ptr->itemIsUntransformable()) {
        QTransform xform = item->deviceTransform(q->viewportTransform());
        clip = xform.mapRect(item->boundingRect()).toAlignedRect();
    } else if (item->d_ptr->sceneTransformTranslateOnly && identityMatrix) {
        QRectF r(item->boundingRect());
        r.translate(item->d_ptr->sceneTransform.dx() - horizontalScroll(),
                    item->d_ptr->sceneTransform.dy() - verticalScroll());
        clip = r.toAlignedRect();
    } else if (!q->isTransformed()) {
        clip = item->d_ptr->sceneTransform.mapRect(item->boundingRect()).toAlignedRect();
    } else {
        QTransform xform = item->d_ptr->sceneTransform;
        xform *= q->viewportTransform();
        clip = xform.mapRect(item->boundingRect()).toAlignedRect();
    }
 
    if (hasUpdateClip) {
        // Intersect with old clip.
        updateClip &= clip;
    } else {
        updateClip = clip;
        hasUpdateClip = true;
    }
}
 
bool QGraphicsViewPrivate::updateRegion(const QRectF &rect, const QTransform &xform)
{
    if (rect.isEmpty())
        return false;
 
    if (viewportUpdateMode != QGraphicsView::MinimalViewportUpdate
        && viewportUpdateMode != QGraphicsView::SmartViewportUpdate) {
        // No point in updating with QRegion granularity; use the rect instead.
        return updateRectF(xform.mapRect(rect));
    }
 
    // Update mode is either Minimal or Smart, so we have to do a potentially slow operation,
    // which is clearly documented here: QGraphicsItem::setBoundingRegionGranularity.
    const QRegion region = xform.map(QRegion(rect.toAlignedRect()));
    QRect viewRect = region.boundingRect();
    const bool dontAdjustForAntialiasing = optimizationFlags & QGraphicsView::DontAdjustForAntialiasing;
    if (dontAdjustForAntialiasing)
        viewRect.adjust(-1, -1, 1, 1);
    else
        viewRect.adjust(-2, -2, 2, 2);
    if (!intersectsViewport(viewRect, viewport->width(), viewport->height()))
        return false; // Update region for sure outside viewport.
 
    for (QRect viewRect : region) {
        if (dontAdjustForAntialiasing)
            viewRect.adjust(-1, -1, 1, 1);
        else
            viewRect.adjust(-2, -2, 2, 2);
        if (hasUpdateClip)
            viewRect &= updateClip;
        dirtyRegion += viewRect;
    }
 
    return true;
}
 
// NB! Assumes the rect 'r' is already aligned and adjusted for antialiasing.
// For QRectF use updateRectF(const QRectF &) to ensure proper adjustments.
bool QGraphicsViewPrivate::updateRect(const QRect &r)
{
    if (fullUpdatePending || viewportUpdateMode == QGraphicsView::NoViewportUpdate
        || !intersectsViewport(r, viewport->width(), viewport->height())) {
        return false;
    }
 
    switch (viewportUpdateMode) {
    case QGraphicsView::FullViewportUpdate:
        fullUpdatePending = true;
        viewport->update();
        break;
    case QGraphicsView::BoundingRectViewportUpdate:
        if (hasUpdateClip)
            QRect_unite(&dirtyBoundingRect, r & updateClip);
        else
            QRect_unite(&dirtyBoundingRect, r);
        if (containsViewport(dirtyBoundingRect, viewport->width(), viewport->height())) {
            fullUpdatePending = true;
            viewport->update();
        }
        break;
    case QGraphicsView::SmartViewportUpdate: // ### DEPRECATE
    case QGraphicsView::MinimalViewportUpdate:
        if (hasUpdateClip)
            dirtyRegion += r & updateClip;
        else
            dirtyRegion += r;
        break;
    default:
        break;
    }
 
    return true;
}
 
QStyleOptionGraphicsItem *QGraphicsViewPrivate::allocStyleOptionsArray(int numItems)
{
    if (mustAllocateStyleOptions || (numItems > styleOptions.capacity()))
        // too many items, let's allocate on-the-fly
        return new QStyleOptionGraphicsItem[numItems];
 
    // expand only whenever necessary
    if (numItems > styleOptions.size())
        styleOptions.resize(numItems);
 
    mustAllocateStyleOptions = true;
    return styleOptions.data();
}
 
void QGraphicsViewPrivate::freeStyleOptionsArray(QStyleOptionGraphicsItem *array)
{
    mustAllocateStyleOptions = false;
    if (array != styleOptions.data())
        delete [] array;
}
 
extern QPainterPath qt_regionToPath(const QRegion &region);
 
QList<QGraphicsItem *> QGraphicsViewPrivate::findItems(const QRegion &exposedRegion, bool *allItems,
                                                       const QTransform &viewTransform) const
{
    Q_Q(const QGraphicsView);
 
    // Step 1) If all items are contained within the expose region, then
    // return a list of all visible items. ### the scene's growing bounding
    // rect does not take into account untransformable items.
    const QRectF exposedRegionSceneBounds = q->mapToScene(exposedRegion.boundingRect().adjusted(-1, -1, 1, 1))
                                            .boundingRect();
    if (exposedRegionSceneBounds.contains(scene->sceneRect())) {
        Q_ASSERT(allItems);
        *allItems = true;
 
        // All items are guaranteed within the exposed region.
        return scene->items(Qt::AscendingOrder);
    }
 
    // Step 2) If the expose region is a simple rect and the view is only
    // translated or scaled, search for items using
    // QGraphicsScene::items(QRectF).
    bool simpleRectLookup =  exposedRegion.rectCount() == 1 && matrix.type() <= QTransform::TxScale;
    if (simpleRectLookup) {
        return scene->items(exposedRegionSceneBounds,
                            Qt::IntersectsItemBoundingRect,
                            Qt::AscendingOrder, viewTransform);
    }
 
    // If the region is complex or the view has a complex transform, adjust
    // the expose region, convert it to a path, and then search for items
    // using QGraphicsScene::items(QPainterPath);
    QRegion adjustedRegion;
    for (const QRect &r : exposedRegion)
        adjustedRegion += r.adjusted(-1, -1, 1, 1);
 
    const QPainterPath exposedScenePath(q->mapToScene(qt_regionToPath(adjustedRegion)));
    return scene->items(exposedScenePath, Qt::IntersectsItemBoundingRect,
                        Qt::AscendingOrder, viewTransform);
}
 
void QGraphicsViewPrivate::updateInputMethodSensitivity()
{
    Q_Q(QGraphicsView);
    QGraphicsItem *focusItem = nullptr;
    bool enabled = scene && (focusItem = scene->focusItem())
                   && (focusItem->d_ptr->flags & QGraphicsItem::ItemAcceptsInputMethod);
    q->setAttribute(Qt::WA_InputMethodEnabled, enabled);
    q->viewport()->setAttribute(Qt::WA_InputMethodEnabled, enabled);
 
    if (!enabled) {
        q->setInputMethodHints({ });
        return;
    }
 
    QGraphicsProxyWidget *proxy = focusItem->d_ptr->isWidget && focusItem->d_ptr->isProxyWidget()
                                    ? static_cast<QGraphicsProxyWidget *>(focusItem) : nullptr;
    if (!proxy) {
        q->setInputMethodHints(focusItem->inputMethodHints());
    } else if (QWidget *widget = proxy->widget()) {
        if (QWidget *fw = widget->focusWidget())
            widget = fw;
        q->setInputMethodHints(widget->inputMethodHints());
    } else {
        q->setInputMethodHints({ });
    }
}
 
QGraphicsView::QGraphicsView(QWidget *parent)
    : QAbstractScrollArea(*new QGraphicsViewPrivate, parent)
{
    setViewport(nullptr);
    setAcceptDrops(true);
    setBackgroundRole(QPalette::Base);
    // Investigate leaving these disabled by default.
    setAttribute(Qt::WA_InputMethodEnabled);
    viewport()->setAttribute(Qt::WA_InputMethodEnabled);
}
 
QGraphicsView::QGraphicsView(QGraphicsScene *scene, QWidget *parent)
    : QAbstractScrollArea(*new QGraphicsViewPrivate, parent)
{
    setScene(scene);
    setViewport(nullptr);
    setAcceptDrops(true);
    setBackgroundRole(QPalette::Base);
    // Investigate leaving these disabled by default.
    setAttribute(Qt::WA_InputMethodEnabled);
    viewport()->setAttribute(Qt::WA_InputMethodEnabled);
}
 
QGraphicsView::QGraphicsView(QGraphicsViewPrivate &dd, QWidget *parent)
  : QAbstractScrollArea(dd, parent)
{
    setViewport(nullptr);
    setAcceptDrops(true);
    setBackgroundRole(QPalette::Base);
    // Investigate leaving these disabled by default.
    setAttribute(Qt::WA_InputMethodEnabled);
    viewport()->setAttribute(Qt::WA_InputMethodEnabled);
}
 
QGraphicsView::~QGraphicsView()
{
    Q_D(QGraphicsView);
    if (d->scene)
        d->scene->d_func()->views.removeAll(this);
    delete d->lastDragDropEvent;
}
 
QSize QGraphicsView::sizeHint() const
{
    Q_D(const QGraphicsView);
    if (d->scene) {
        QSizeF baseSize = d->matrix.mapRect(sceneRect()).size();
        baseSize += QSizeF(d->frameWidth * 2, d->frameWidth * 2);
        return baseSize.boundedTo((3 * QGuiApplication::primaryScreen()->virtualSize()) / 4).toSize();
    }
    return QAbstractScrollArea::sizeHint();
}
 
QPainter::RenderHints QGraphicsView::renderHints() const
{
    Q_D(const QGraphicsView);
    return d->renderHints;
}
void QGraphicsView::setRenderHints(QPainter::RenderHints hints)
{
    Q_D(QGraphicsView);
    if (hints == d->renderHints)
        return;
    d->renderHints = hints;
    d->updateAll();
}
 
void QGraphicsView::setRenderHint(QPainter::RenderHint hint, bool enabled)
{
    Q_D(QGraphicsView);
    QPainter::RenderHints oldHints = d->renderHints;
    d->renderHints.setFlag(hint, enabled);
    if (oldHints != d->renderHints)
        d->updateAll();
}
 
Qt::Alignment QGraphicsView::alignment() const
{
    Q_D(const QGraphicsView);
    return d->alignment;
}
void QGraphicsView::setAlignment(Qt::Alignment alignment)
{
    Q_D(QGraphicsView);
    if (d->alignment != alignment) {
        d->alignment = alignment;
        d->recalculateContentSize();
    }
}
 
QGraphicsView::ViewportAnchor QGraphicsView::transformationAnchor() const
{
    Q_D(const QGraphicsView);
    return d->transformationAnchor;
}
void QGraphicsView::setTransformationAnchor(ViewportAnchor anchor)
{
    Q_D(QGraphicsView);
    d->transformationAnchor = anchor;
 
    // Ensure mouse tracking is enabled in the case we are using AnchorUnderMouse
    // in order to have up-to-date information for centering the view.
    if (d->transformationAnchor == AnchorUnderMouse)
        d->viewport->setMouseTracking(true);
}
 
QGraphicsView::ViewportAnchor QGraphicsView::resizeAnchor() const
{
    Q_D(const QGraphicsView);
    return d->resizeAnchor;
}
void QGraphicsView::setResizeAnchor(ViewportAnchor anchor)
{
    Q_D(QGraphicsView);
    d->resizeAnchor = anchor;
 
    // Ensure mouse tracking is enabled in the case we are using AnchorUnderMouse
    // in order to have up-to-date information for centering the view.
    if (d->resizeAnchor == AnchorUnderMouse)
        d->viewport->setMouseTracking(true);
}
 
QGraphicsView::ViewportUpdateMode QGraphicsView::viewportUpdateMode() const
{
    Q_D(const QGraphicsView);
    return d->viewportUpdateMode;
}
void QGraphicsView::setViewportUpdateMode(ViewportUpdateMode mode)
{
    Q_D(QGraphicsView);
    d->viewportUpdateMode = mode;
}
 
QGraphicsView::OptimizationFlags QGraphicsView::optimizationFlags() const
{
    Q_D(const QGraphicsView);
    return d->optimizationFlags;
}
void QGraphicsView::setOptimizationFlags(OptimizationFlags flags)
{
    Q_D(QGraphicsView);
    d->optimizationFlags = flags;
}
 
void QGraphicsView::setOptimizationFlag(OptimizationFlag flag, bool enabled)
{
    Q_D(QGraphicsView);
    d->optimizationFlags.setFlag(flag, enabled);
}
 
QGraphicsView::DragMode QGraphicsView::dragMode() const
{
    Q_D(const QGraphicsView);
    return d->dragMode;
}
void QGraphicsView::setDragMode(DragMode mode)
{
    Q_D(QGraphicsView);
    if (d->dragMode == mode)
        return;
 
#if QT_CONFIG(rubberband)
    d->clearRubberBand();
#endif
 
#ifndef QT_NO_CURSOR
    if (d->dragMode == ScrollHandDrag)
        viewport()->unsetCursor();
#endif
 
    // If dragMode is unset while dragging, e.g. via a keyEvent, we
    // don't unset the handScrolling state. When enabling scrolling
    // again the mouseMoveEvent will automatically start scrolling,
    // without a mousePress
    if (d->dragMode == ScrollHandDrag && mode == NoDrag && d->handScrolling)
        d->handScrolling = false;
 
    d->dragMode = mode;
 
#ifndef QT_NO_CURSOR
    if (d->dragMode == ScrollHandDrag) {
        // Forget the stored viewport cursor when we enter scroll hand drag mode.
        d->hasStoredOriginalCursor = false;
        viewport()->setCursor(Qt::OpenHandCursor);
    }
#endif
}
 
#if QT_CONFIG(rubberband)
Qt::ItemSelectionMode QGraphicsView::rubberBandSelectionMode() const
{
    Q_D(const QGraphicsView);
    return d->rubberBandSelectionMode;
}
void QGraphicsView::setRubberBandSelectionMode(Qt::ItemSelectionMode mode)
{
    Q_D(QGraphicsView);
    d->rubberBandSelectionMode = mode;
}
 
QRect QGraphicsView::rubberBandRect() const
{
    Q_D(const QGraphicsView);
    if (d->dragMode != QGraphicsView::RubberBandDrag || !d->sceneInteractionAllowed || !d->rubberBanding)
        return QRect();
 
    return d->rubberBandRect;
}
#endif
 
QGraphicsView::CacheMode QGraphicsView::cacheMode() const
{
    Q_D(const QGraphicsView);
    return d->cacheMode;
}
void QGraphicsView::setCacheMode(CacheMode mode)
{
    Q_D(QGraphicsView);
    if (mode == d->cacheMode)
        return;
    d->cacheMode = mode;
    resetCachedContent();
}
 
void QGraphicsView::resetCachedContent()
{
    Q_D(QGraphicsView);
    if (d->cacheMode == CacheNone)
        return;
 
    if (d->cacheMode & CacheBackground) {
        // Background caching is enabled.
        d->mustResizeBackgroundPixmap = true;
        d->updateAll();
    } else if (d->mustResizeBackgroundPixmap) {
        // Background caching is disabled.
        // Cleanup, free some resources.
        d->mustResizeBackgroundPixmap = false;
        d->backgroundPixmap = QPixmap();
        d->backgroundPixmapExposed = QRegion();
    }
}
 
void QGraphicsView::invalidateScene(const QRectF &rect, QGraphicsScene::SceneLayers layers)
{
    Q_D(QGraphicsView);
    if ((layers & QGraphicsScene::BackgroundLayer) && !d->mustResizeBackgroundPixmap) {
        QRect viewRect = mapFromScene(rect).boundingRect();
        if (viewport()->rect().intersects(viewRect)) {
            // The updated background area is exposed; schedule this area for
            // redrawing.
            d->backgroundPixmapExposed += viewRect;
            if (d->scene)
                d->scene->update(rect);
        }
    }
}
 
bool QGraphicsView::isInteractive() const
{
    Q_D(const QGraphicsView);
    return d->sceneInteractionAllowed;
}
void QGraphicsView::setInteractive(bool allowed)
{
    Q_D(QGraphicsView);
    d->sceneInteractionAllowed = allowed;
}
 
QGraphicsScene *QGraphicsView::scene() const
{
    Q_D(const QGraphicsView);
    return d->scene;
}
 
void QGraphicsView::setScene(QGraphicsScene *scene)
{
    Q_D(QGraphicsView);
    if (d->scene == scene)
        return;
 
    // Always update the viewport when the scene changes.
    d->updateAll();
 
    // Remove the previously assigned scene.
    if (d->scene) {
        disconnect(d->scene, SIGNAL(changed(QList<QRectF>)),
                   this, SLOT(updateScene(QList<QRectF>)));
        disconnect(d->scene, SIGNAL(sceneRectChanged(QRectF)),
                   this, SLOT(updateSceneRect(QRectF)));
        d->scene->d_func()->removeView(this);
        d->connectedToScene = false;
 
        if (isActiveWindow() && isVisible()) {
            QEvent windowDeactivate(QEvent::WindowDeactivate);
            QCoreApplication::sendEvent(d->scene, &windowDeactivate);
        }
        if (hasFocus())
            d->scene->clearFocus();
    }
 
    // Assign the new scene and update the contents (scrollbars, etc.)).
    if ((d->scene = scene)) {
        connect(d->scene, SIGNAL(sceneRectChanged(QRectF)),
                this, SLOT(updateSceneRect(QRectF)));
        d->updateSceneSlotReimplementedChecked = false;
        d->scene->d_func()->addView(this);
        d->recalculateContentSize();
        d->lastCenterPoint = sceneRect().center();
        d->keepLastCenterPoint = true;
        // We are only interested in mouse tracking if items accept
        // hover events or use non-default cursors.
        if (!d->scene->d_func()->allItemsIgnoreHoverEvents
            || !d->scene->d_func()->allItemsUseDefaultCursor) {
            d->viewport->setMouseTracking(true);
        }
 
        // enable touch events if any items is interested in them
        if (!d->scene->d_func()->allItemsIgnoreTouchEvents)
            d->viewport->setAttribute(Qt::WA_AcceptTouchEvents);
 
        if (isActiveWindow() && isVisible()) {
            QEvent windowActivate(QEvent::WindowActivate);
            QCoreApplication::sendEvent(d->scene, &windowActivate);
        }
    } else {
        d->recalculateContentSize();
    }
 
    d->updateInputMethodSensitivity();
 
    if (d->scene && hasFocus())
        d->scene->setFocus();
}
 
QRectF QGraphicsView::sceneRect() const
{
    Q_D(const QGraphicsView);
    if (d->hasSceneRect)
        return d->sceneRect;
    if (d->scene)
        return d->scene->sceneRect();
    return QRectF();
}
void QGraphicsView::setSceneRect(const QRectF &rect)
{
    Q_D(QGraphicsView);
    d->hasSceneRect = !rect.isNull();
    d->sceneRect = rect;
    d->recalculateContentSize();
}
 
void QGraphicsView::rotate(qreal angle)
{
    Q_D(QGraphicsView);
    QTransform matrix = d->matrix;
    matrix.rotate(angle);
    setTransform(matrix);
}
 
void QGraphicsView::scale(qreal sx, qreal sy)
{
    Q_D(QGraphicsView);
    QTransform matrix = d->matrix;
    matrix.scale(sx, sy);
    setTransform(matrix);
}
 
void QGraphicsView::shear(qreal sh, qreal sv)
{
    Q_D(QGraphicsView);
    QTransform matrix = d->matrix;
    matrix.shear(sh, sv);
    setTransform(matrix);
}
 
void QGraphicsView::translate(qreal dx, qreal dy)
{
    Q_D(QGraphicsView);
    QTransform matrix = d->matrix;
    matrix.translate(dx, dy);
    setTransform(matrix);
}
 
void QGraphicsView::centerOn(const QPointF &pos)
{
    Q_D(QGraphicsView);
    qreal width = viewport()->width();
    qreal height = viewport()->height();
    QPointF viewPoint = d->matrix.map(pos);
    QPointF oldCenterPoint = pos;
 
    if (!d->leftIndent) {
        if (isRightToLeft()) {
            qint64 horizontal = 0;
            horizontal += horizontalScrollBar()->minimum();
            horizontal += horizontalScrollBar()->maximum();
            horizontal -= int(viewPoint.x() - width / 2.0);
            horizontalScrollBar()->setValue(horizontal);
        } else {
            horizontalScrollBar()->setValue(int(viewPoint.x() - width / 2.0));
        }
    }
    if (!d->topIndent)
        verticalScrollBar()->setValue(int(viewPoint.y() - height / 2.0));
    d->lastCenterPoint = oldCenterPoint;
}
 
void QGraphicsView::centerOn(const QGraphicsItem *item)
{
    centerOn(item->sceneBoundingRect().center());
}
 
void QGraphicsView::ensureVisible(const QRectF &rect, int xmargin, int ymargin)
{
    Q_D(QGraphicsView);
    qreal width = viewport()->width();
    qreal height = viewport()->height();
    QRectF viewRect = d->matrix.mapRect(rect);
 
    qreal left = d->horizontalScroll();
    qreal right = left + width;
    qreal top = d->verticalScroll();
    qreal bottom = top + height;
 
    if (viewRect.left() <= left + xmargin) {
        // need to scroll from the left
        if (!d->leftIndent)
            horizontalScrollBar()->setValue(int(viewRect.left() - xmargin - 0.5));
    }
    if (viewRect.right() >= right - xmargin) {
        // need to scroll from the right
        if (!d->leftIndent)
            horizontalScrollBar()->setValue(int(viewRect.right() - width + xmargin + 0.5));
    }
    if (viewRect.top() <= top + ymargin) {
        // need to scroll from the top
        if (!d->topIndent)
            verticalScrollBar()->setValue(int(viewRect.top() - ymargin - 0.5));
    }
    if (viewRect.bottom() >= bottom - ymargin) {
        // need to scroll from the bottom
        if (!d->topIndent)
            verticalScrollBar()->setValue(int(viewRect.bottom() - height + ymargin + 0.5));
    }
}
 
void QGraphicsView::ensureVisible(const QGraphicsItem *item, int xmargin, int ymargin)
{
    ensureVisible(item->sceneBoundingRect(), xmargin, ymargin);
}
 
void QGraphicsView::fitInView(const QRectF &rect, Qt::AspectRatioMode aspectRatioMode)
{
    Q_D(QGraphicsView);
    if (!d->scene || rect.isNull())
        return;
 
    // Reset the view scale to 1:1.
    QRectF unity = d->matrix.mapRect(QRectF(0, 0, 1, 1));
    if (unity.isEmpty())
        return;
    scale(1 / unity.width(), 1 / unity.height());
 
    // Find the ideal x / y scaling ratio to fit \a rect in the view.
    int margin = 2;
    QRectF viewRect = viewport()->rect().adjusted(margin, margin, -margin, -margin);
    if (viewRect.isEmpty())
        return;
    QRectF sceneRect = d->matrix.mapRect(rect);
    if (sceneRect.isEmpty())
        return;
    qreal xratio = viewRect.width() / sceneRect.width();
    qreal yratio = viewRect.height() / sceneRect.height();
 
    // Respect the aspect ratio mode.
    switch (aspectRatioMode) {
    case Qt::KeepAspectRatio:
        xratio = yratio = qMin(xratio, yratio);
        break;
    case Qt::KeepAspectRatioByExpanding:
        xratio = yratio = qMax(xratio, yratio);
        break;
    case Qt::IgnoreAspectRatio:
        break;
    }
 
    // Scale and center on the center of \a rect.
    scale(xratio, yratio);
    centerOn(rect.center());
}
 
void QGraphicsView::fitInView(const QGraphicsItem *item, Qt::AspectRatioMode aspectRatioMode)
{
    QPainterPath path = item->isClipped() ? item->clipPath() : item->shape();
    if (item->d_ptr->hasTranslateOnlySceneTransform()) {
        path.translate(item->d_ptr->sceneTransform.dx(), item->d_ptr->sceneTransform.dy());
        fitInView(path.boundingRect(), aspectRatioMode);
    } else {
        fitInView(item->d_ptr->sceneTransform.map(path).boundingRect(), aspectRatioMode);
    }
}
 
void QGraphicsView::render(QPainter *painter, const QRectF &target, const QRect &source,
                           Qt::AspectRatioMode aspectRatioMode)
{
    // ### Switch to using the recursive rendering algorithm instead.
 
    Q_D(QGraphicsView);
    if (!d->scene || !(painter && painter->isActive()))
        return;
 
    // Default source rect = viewport rect
    QRect sourceRect = source;
    if (source.isNull())
        sourceRect = viewport()->rect();
 
    // Default target rect = device rect
    QRectF targetRect = target;
    if (target.isNull()) {
        if (painter->device()->devType() == QInternal::Picture)
            targetRect = sourceRect;
        else
            targetRect.setRect(0, 0, painter->device()->width(), painter->device()->height());
    }
 
    // Find the ideal x / y scaling ratio to fit \a source into \a target.
    qreal xratio = targetRect.width() / sourceRect.width();
    qreal yratio = targetRect.height() / sourceRect.height();
 
    // Scale according to the aspect ratio mode.
    switch (aspectRatioMode) {
    case Qt::KeepAspectRatio:
        xratio = yratio = qMin(xratio, yratio);
        break;
    case Qt::KeepAspectRatioByExpanding:
        xratio = yratio = qMax(xratio, yratio);
        break;
    case Qt::IgnoreAspectRatio:
        break;
    }
 
    // Find all items to draw, and reverse the list (we want to draw
    // in reverse order).
    QPolygonF sourceScenePoly = mapToScene(sourceRect.adjusted(-1, -1, 1, 1));
    QList<QGraphicsItem *> itemList = d->scene->items(sourceScenePoly,
                                                      Qt::IntersectsItemBoundingRect);
    QGraphicsItem **itemArray = new QGraphicsItem *[itemList.size()];
    int numItems = itemList.size();
    for (int i = 0; i < numItems; ++i)
        itemArray[numItems - i - 1] = itemList.at(i);
    itemList.clear();
 
    // Setup painter matrix.
    QTransform moveMatrix = QTransform::fromTranslate(-d->horizontalScroll(), -d->verticalScroll());
    QTransform painterMatrix = d->matrix * moveMatrix;
    painterMatrix *= QTransform()
                     .translate(targetRect.left(), targetRect.top())
                     .scale(xratio, yratio)
                     .translate(-sourceRect.left(), -sourceRect.top());
 
    // Generate the style options
    QStyleOptionGraphicsItem *styleOptionArray = d->allocStyleOptionsArray(numItems);
    for (int i = 0; i < numItems; ++i)
        itemArray[i]->d_ptr->initStyleOption(&styleOptionArray[i], painterMatrix, targetRect.toRect());
 
    painter->save();
 
    // Clip in device coordinates to avoid QRegion transformations.
    painter->setClipRect(targetRect);
    QPainterPath path;
    path.addPolygon(sourceScenePoly);
    path.closeSubpath();
    painter->setClipPath(painterMatrix.map(path), Qt::IntersectClip);
 
    // Transform the painter.
    painter->setTransform(painterMatrix, true);
 
    // Render the scene.
    QRectF sourceSceneRect = sourceScenePoly.boundingRect();
    drawBackground(painter, sourceSceneRect);
    drawItems(painter, numItems, itemArray, styleOptionArray);
    drawForeground(painter, sourceSceneRect);
 
    delete [] itemArray;
    d->freeStyleOptionsArray(styleOptionArray);
 
    painter->restore();
}
 
QList<QGraphicsItem *> QGraphicsView::items() const
{
    Q_D(const QGraphicsView);
    if (!d->scene)
        return QList<QGraphicsItem *>();
    return d->scene->items();
}
 
QList<QGraphicsItem *> QGraphicsView::items(const QPoint &pos) const
{
    Q_D(const QGraphicsView);
    if (!d->scene)
        return QList<QGraphicsItem *>();
    // ### Unify these two, and use the items(QPointF) version in
    // QGraphicsScene instead. The scene items function could use the viewport
    // transform to map the point to a rect/polygon.
    if ((d->identityMatrix || d->matrix.type() <= QTransform::TxScale)) {
        // Use the rect version
        QTransform xinv = viewportTransform().inverted();
        return d->scene->items(xinv.mapRect(QRectF(pos.x(), pos.y(), 1, 1)),
                               Qt::IntersectsItemShape,
                               Qt::DescendingOrder,
                               viewportTransform());
    }
    // Use the polygon version
    return d->scene->items(mapToScene(pos.x(), pos.y(), 1, 1),
                           Qt::IntersectsItemShape,
                           Qt::DescendingOrder,
                           viewportTransform());
}
 
QList<QGraphicsItem *> QGraphicsView::items(const QRect &rect, Qt::ItemSelectionMode mode) const
{
    Q_D(const QGraphicsView);
    if (!d->scene)
        return QList<QGraphicsItem *>();
    return d->scene->items(mapToScene(rect), mode, Qt::DescendingOrder, viewportTransform());
}
 
QList<QGraphicsItem *> QGraphicsView::items(const QPolygon &polygon, Qt::ItemSelectionMode mode) const
{
    Q_D(const QGraphicsView);
    if (!d->scene)
        return QList<QGraphicsItem *>();
    return d->scene->items(mapToScene(polygon), mode, Qt::DescendingOrder, viewportTransform());
}
 
QList<QGraphicsItem *> QGraphicsView::items(const QPainterPath &path, Qt::ItemSelectionMode mode) const
{
    Q_D(const QGraphicsView);
    if (!d->scene)
        return QList<QGraphicsItem *>();
    return d->scene->items(mapToScene(path), mode, Qt::DescendingOrder, viewportTransform());
}
 
QGraphicsItem *QGraphicsView::itemAt(const QPoint &pos) const
{
    Q_D(const QGraphicsView);
    if (!d->scene)
        return nullptr;
    const QList<QGraphicsItem *> itemsAtPos = items(pos);
    return itemsAtPos.isEmpty() ? 0 : itemsAtPos.first();
}
 
QPointF QGraphicsView::mapToScene(const QPoint &point) const
{
    Q_D(const QGraphicsView);
    QPointF p = point;
    p.rx() += d->horizontalScroll();
    p.ry() += d->verticalScroll();
    return d->identityMatrix ? p : d->matrix.inverted().map(p);
}
 
QPolygonF QGraphicsView::mapToScene(const QRect &rect) const
{
    Q_D(const QGraphicsView);
    if (!rect.isValid())
        return QPolygonF();
 
    QPointF scrollOffset(d->horizontalScroll(), d->verticalScroll());
    QRect r = rect.adjusted(0, 0, 1, 1);
    QPointF tl = scrollOffset + r.topLeft();
    QPointF tr = scrollOffset + r.topRight();
    QPointF br = scrollOffset + r.bottomRight();
    QPointF bl = scrollOffset + r.bottomLeft();
 
    QPolygonF poly(4);
    if (!d->identityMatrix) {
        QTransform x = d->matrix.inverted();
        poly[0] = x.map(tl);
        poly[1] = x.map(tr);
        poly[2] = x.map(br);
        poly[3] = x.map(bl);
    } else {
        poly[0] = tl;
        poly[1] = tr;
        poly[2] = br;
        poly[3] = bl;
    }
    return poly;
}
 
QPolygonF QGraphicsView::mapToScene(const QPolygon &polygon) const
{
    QPolygonF poly;
    poly.reserve(polygon.size());
    for (const QPoint &point : polygon)
        poly << mapToScene(point);
    return poly;
}
 
QPainterPath QGraphicsView::mapToScene(const QPainterPath &path) const
{
    Q_D(const QGraphicsView);
    QTransform matrix = QTransform::fromTranslate(d->horizontalScroll(), d->verticalScroll());
    matrix *= d->matrix.inverted();
    return matrix.map(path);
}
 
QPoint QGraphicsView::mapFromScene(const QPointF &point) const
{
    Q_D(const QGraphicsView);
    QPointF p = d->identityMatrix ? point : d->matrix.map(point);
    p.rx() -= d->horizontalScroll();
    p.ry() -= d->verticalScroll();
    return p.toPoint();
}
 
QPolygon QGraphicsView::mapFromScene(const QRectF &rect) const
{
    Q_D(const QGraphicsView);
    QPointF tl;
    QPointF tr;
    QPointF br;
    QPointF bl;
    if (!d->identityMatrix) {
        const QTransform &x = d->matrix;
        tl = x.map(rect.topLeft());
        tr = x.map(rect.topRight());
        br = x.map(rect.bottomRight());
        bl = x.map(rect.bottomLeft());
    } else {
        tl = rect.topLeft();
        tr = rect.topRight();
        br = rect.bottomRight();
        bl = rect.bottomLeft();
    }
    QPointF scrollOffset(d->horizontalScroll(), d->verticalScroll());
    tl -= scrollOffset;
    tr -= scrollOffset;
    br -= scrollOffset;
    bl -= scrollOffset;
 
    QPolygon poly(4);
    poly[0] = tl.toPoint();
    poly[1] = tr.toPoint();
    poly[2] = br.toPoint();
    poly[3] = bl.toPoint();
    return poly;
}
 
QPolygon QGraphicsView::mapFromScene(const QPolygonF &polygon) const
{
    QPolygon poly;
    poly.reserve(polygon.size());
    for (const QPointF &point : polygon)
        poly << mapFromScene(point);
    return poly;
}
 
QPainterPath QGraphicsView::mapFromScene(const QPainterPath &path) const
{
    Q_D(const QGraphicsView);
    QTransform matrix = d->matrix;
    matrix *= QTransform::fromTranslate(-d->horizontalScroll(), -d->verticalScroll());
    return matrix.map(path);
}
 
QVariant QGraphicsView::inputMethodQuery(Qt::InputMethodQuery query) const
{
    Q_D(const QGraphicsView);
    if (!d->scene)
        return QVariant();
 
    QVariant value = d->scene->inputMethodQuery(query);
    if (value.userType() == QMetaType::QRectF)
        value = d->mapRectFromScene(value.toRectF());
    else if (value.userType() == QMetaType::QPointF)
        value = mapFromScene(value.toPointF());
    else if (value.userType() == QMetaType::QRect)
        value = d->mapRectFromScene(value.toRect()).toRect();
    else if (value.userType() == QMetaType::QPoint)
        value = mapFromScene(value.toPoint());
    return value;
}
 
QBrush QGraphicsView::backgroundBrush() const
{
    Q_D(const QGraphicsView);
    return d->backgroundBrush;
}
void QGraphicsView::setBackgroundBrush(const QBrush &brush)
{
    Q_D(QGraphicsView);
    d->backgroundBrush = brush;
    d->updateAll();
 
    if (d->cacheMode & CacheBackground) {
        // Invalidate the background pixmap
        d->mustResizeBackgroundPixmap = true;
    }
}
 
QBrush QGraphicsView::foregroundBrush() const
{
    Q_D(const QGraphicsView);
    return d->foregroundBrush;
}
void QGraphicsView::setForegroundBrush(const QBrush &brush)
{
    Q_D(QGraphicsView);
    d->foregroundBrush = brush;
    d->updateAll();
}
 
void QGraphicsView::updateScene(const QList<QRectF> &rects)
{
    // ### Note: Since 4.5, this slot is only called if the user explicitly
    // establishes a connection between the scene and the view, as the scene
    // and view are no longer connected. We need to keep it working (basically
    // leave it as it is), but the new delivery path is through
    // QGraphicsScenePrivate::itemUpdate().
    Q_D(QGraphicsView);
    if (d->fullUpdatePending || d->viewportUpdateMode == QGraphicsView::NoViewportUpdate)
        return;
 
    // Extract and reset dirty scene rect info.
    QList<QRect> dirtyViewportRects;
    dirtyViewportRects.reserve(d->dirtyRegion.rectCount() + rects.size());
    for (const QRect &dirtyRect : d->dirtyRegion)
        dirtyViewportRects += dirtyRect;
    d->dirtyRegion = QRegion();
    d->dirtyBoundingRect = QRect();
 
    bool fullUpdate = !d->accelerateScrolling || d->viewportUpdateMode == QGraphicsView::FullViewportUpdate;
    bool boundingRectUpdate = (d->viewportUpdateMode == QGraphicsView::BoundingRectViewportUpdate)
                              || (d->viewportUpdateMode == QGraphicsView::SmartViewportUpdate
                                  && ((dirtyViewportRects.size() + rects.size()) >= QGRAPHICSVIEW_REGION_RECT_THRESHOLD));
 
    QRegion updateRegion;
    QRect boundingRect;
    QRect viewportRect = viewport()->rect();
    bool redraw = false;
    QTransform transform = viewportTransform();
 
    // Convert scene rects to viewport rects.
    for (const QRectF &rect : rects) {
        QRect xrect = transform.mapRect(rect).toAlignedRect();
        if (!(d->optimizationFlags & DontAdjustForAntialiasing))
            xrect.adjust(-2, -2, 2, 2);
        else
            xrect.adjust(-1, -1, 1, 1);
        if (!viewportRect.intersects(xrect))
            continue;
        dirtyViewportRects << xrect;
    }
 
    for (const QRect &rect : std::as_const(dirtyViewportRects)) {
        // Add the exposed rect to the update region. In rect update
        // mode, we only count the bounding rect of items.
        if (!boundingRectUpdate) {
            updateRegion += rect;
        } else {
            boundingRect |= rect;
        }
        redraw = true;
        if (fullUpdate) {
            // If fullUpdate is true and we found a visible dirty rect,
            // we're done.
            break;
        }
    }
 
    if (!redraw)
        return;
 
    if (fullUpdate)
        viewport()->update();
    else if (boundingRectUpdate)
        viewport()->update(boundingRect);
    else
        viewport()->update(updateRegion);
}
 
void QGraphicsView::updateSceneRect(const QRectF &rect)
{
    Q_D(QGraphicsView);
    if (!d->hasSceneRect) {
        d->sceneRect = rect;
        d->recalculateContentSize();
    }
}
 
void QGraphicsView::setupViewport(QWidget *widget)
{
    Q_D(QGraphicsView);
 
    if (!widget) {
        qWarning("QGraphicsView::setupViewport: cannot initialize null widget");
        return;
    }
 
    const bool isGLWidget = widget->inherits("QOpenGLWidget");
 
    d->accelerateScrolling = !(isGLWidget);
 
    widget->setFocusPolicy(Qt::StrongFocus);
 
    if (isGLWidget)
        d->stereoEnabled = QWidgetPrivate::get(widget)->isStereoEnabled();
 
    if (!isGLWidget) {
        // autoFillBackground enables scroll acceleration.
        widget->setAutoFillBackground(true);
    }
 
    // We are only interested in mouse tracking if items
    // accept hover events or use non-default cursors or if
    // AnchorUnderMouse is used as transformation or resize anchor.
    if ((d->scene && (!d->scene->d_func()->allItemsIgnoreHoverEvents
                     || !d->scene->d_func()->allItemsUseDefaultCursor))
        || d->transformationAnchor == AnchorUnderMouse
        || d->resizeAnchor == AnchorUnderMouse) {
        widget->setMouseTracking(true);
    }
 
    // enable touch events if any items is interested in them
    if (d->scene && !d->scene->d_func()->allItemsIgnoreTouchEvents)
        widget->setAttribute(Qt::WA_AcceptTouchEvents);
 
#ifndef QT_NO_GESTURES
    if (d->scene) {
        const auto gestures = d->scene->d_func()->grabbedGestures.keys();
        for (Qt::GestureType gesture : gestures)
            widget->grabGesture(gesture);
    }
#endif
 
    widget->setAcceptDrops(acceptDrops());
}
 
bool QGraphicsView::event(QEvent *event)
{
    Q_D(QGraphicsView);
 
    if (d->sceneInteractionAllowed) {
        switch (event->type()) {
        case QEvent::ShortcutOverride:
            if (d->scene)
                return QCoreApplication::sendEvent(d->scene, event);
            break;
        case QEvent::KeyPress:
            if (d->scene) {
                QKeyEvent *k = static_cast<QKeyEvent *>(event);
                if (k->key() == Qt::Key_Tab || k->key() == Qt::Key_Backtab) {
                    // Send the key events to the scene. This will invoke the
                    // scene's tab focus handling, and if the event is
                    // accepted, we return (prevent further event delivery),
                    // and the base implementation will call QGraphicsView's
                    // focusNextPrevChild() function. If the event is ignored,
                    // we fall back to standard tab focus handling.
                    QCoreApplication::sendEvent(d->scene, event);
                    if (event->isAccepted())
                        return true;
                    // Ensure the event doesn't propagate just because the
                    // scene ignored it. If the event propagates, then tab
                    // handling will be called twice (this and parent).
                    event->accept();
                }
            }
            break;
        default:
            break;
        }
    }
 
    return QAbstractScrollArea::event(event);
}
 
bool QGraphicsView::viewportEvent(QEvent *event)
{
    Q_D(QGraphicsView);
    if (!d->scene)
        return QAbstractScrollArea::viewportEvent(event);
 
    switch (event->type()) {
    case QEvent::Enter:
        QCoreApplication::sendEvent(d->scene, event);
        break;
    case QEvent::WindowActivate:
        QCoreApplication::sendEvent(d->scene, event);
        break;
    case QEvent::WindowDeactivate:
        // ### This is a temporary fix for until we get proper mouse
        // grab events. mouseGrabberItem should be set to 0 if we lose
        // the mouse grab.
        // Remove all popups when the scene loses focus.
        if (!d->scene->d_func()->popupWidgets.isEmpty())
            d->scene->d_func()->removePopup(d->scene->d_func()->popupWidgets.constFirst());
        QCoreApplication::sendEvent(d->scene, event);
        break;
    case QEvent::Show:
        if (d->scene && isActiveWindow()) {
            QEvent windowActivate(QEvent::WindowActivate);
            QCoreApplication::sendEvent(d->scene, &windowActivate);
        }
        break;
    case QEvent::Hide:
        // spontaneous event will generate a WindowDeactivate.
        if (!event->spontaneous() && d->scene && isActiveWindow()) {
            QEvent windowDeactivate(QEvent::WindowDeactivate);
            QCoreApplication::sendEvent(d->scene, &windowDeactivate);
        }
        break;
    case QEvent::Leave: {
        // ### This is a temporary fix for until we get proper mouse grab
        // events. activeMouseGrabberItem should be set to 0 if we lose the
        // mouse grab.
        if ((QApplication::activePopupWidget() && QApplication::activePopupWidget() != window())
            || (QApplication::activeModalWidget() && QApplication::activeModalWidget() != window())
            || (QApplication::activeWindow() != window())) {
            if (!d->scene->d_func()->popupWidgets.isEmpty())
                d->scene->d_func()->removePopup(d->scene->d_func()->popupWidgets.constFirst());
        }
        d->useLastMouseEvent = false;
        QGraphicsSceneEvent leaveEvent(QEvent::GraphicsSceneLeave);
        leaveEvent.setWidget(viewport());
        QCoreApplication::sendEvent(d->scene, &leaveEvent);
        event->setAccepted(leaveEvent.isAccepted());
        break;
    }
#if QT_CONFIG(tooltip)
    case QEvent::ToolTip: {
        QHelpEvent *toolTip = static_cast<QHelpEvent *>(event);
        QGraphicsSceneHelpEvent helpEvent(QEvent::GraphicsSceneHelp);
        helpEvent.setWidget(viewport());
        helpEvent.setScreenPos(toolTip->globalPos());
        helpEvent.setScenePos(mapToScene(toolTip->pos()));
        QCoreApplication::sendEvent(d->scene, &helpEvent);
        toolTip->setAccepted(helpEvent.isAccepted());
        return true;
    }
#endif
    case QEvent::Paint:
        // Reset full update
        d->fullUpdatePending = false;
        d->dirtyScrollOffset = QPoint();
        if (d->scene) {
            // Check if this view reimplements the updateScene slot; if it
            // does, we can't do direct update delivery and have to fall back
            // to connecting the changed signal.
            if (!d->updateSceneSlotReimplementedChecked) {
                d->updateSceneSlotReimplementedChecked = true;
                const QMetaObject *mo = metaObject();
                if (mo != &QGraphicsView::staticMetaObject) {
                    if (mo->indexOfSlot("updateScene(QList<QRectF>)")
                        != QGraphicsView::staticMetaObject.indexOfSlot("updateScene(QList<QRectF>)")) {
                        connect(d->scene, SIGNAL(changed(QList<QRectF>)),
                                this, SLOT(updateScene(QList<QRectF>)));
                    }
                }
            }
        }
        break;
    case QEvent::TouchBegin:
    case QEvent::TouchUpdate:
    case QEvent::TouchEnd:
    {
        if (!isEnabled())
            return false;
 
        if (d->scene && d->sceneInteractionAllowed) {
            // Convert and deliver the touch event to the scene.
            QTouchEvent *touchEvent = static_cast<QTouchEvent *>(event);
            QMutableTouchEvent::from(touchEvent)->setTarget(viewport());
            QGraphicsViewPrivate::translateTouchEvent(d, touchEvent);
            QCoreApplication::sendEvent(d->scene, touchEvent);
        } else {
            event->ignore();
        }
 
        return true;
    }
#ifndef QT_NO_GESTURES
    case QEvent::Gesture:
    case QEvent::GestureOverride:
    {
        if (!isEnabled())
            return false;
 
        if (d->scene && d->sceneInteractionAllowed) {
            QGestureEvent *gestureEvent = static_cast<QGestureEvent *>(event);
            gestureEvent->setWidget(viewport());
            QCoreApplication::sendEvent(d->scene, gestureEvent);
        }
        return true;
    }
#endif // QT_NO_GESTURES
    default:
        break;
    }
 
    return QAbstractScrollArea::viewportEvent(event);
}
 
#ifndef QT_NO_CONTEXTMENU
void QGraphicsView::contextMenuEvent(QContextMenuEvent *event)
{
    Q_D(QGraphicsView);
    if (!d->scene || !d->sceneInteractionAllowed)
        return;
 
    d->mousePressViewPoint = event->pos();
    d->mousePressScenePoint = mapToScene(d->mousePressViewPoint);
    d->mousePressScreenPoint = event->globalPos();
    d->lastMouseMoveScenePoint = d->mousePressScenePoint;
    d->lastMouseMoveScreenPoint = d->mousePressScreenPoint;
 
    QGraphicsSceneContextMenuEvent contextEvent(QEvent::GraphicsSceneContextMenu);
    contextEvent.setWidget(viewport());
    contextEvent.setScenePos(d->mousePressScenePoint);
    contextEvent.setScreenPos(d->mousePressScreenPoint);
    contextEvent.setModifiers(event->modifiers());
    contextEvent.setReason((QGraphicsSceneContextMenuEvent::Reason)(event->reason()));
    contextEvent.setAccepted(event->isAccepted());
    contextEvent.setTimestamp(event->timestamp());
    QCoreApplication::sendEvent(d->scene, &contextEvent);
    event->setAccepted(contextEvent.isAccepted());
}
#endif // QT_NO_CONTEXTMENU
 
#if QT_CONFIG(draganddrop)
void QGraphicsView::dropEvent(QDropEvent *event)
{
    Q_D(QGraphicsView);
    if (!d->scene || !d->sceneInteractionAllowed)
        return;
 
    // Generate a scene event.
    QGraphicsSceneDragDropEvent sceneEvent(QEvent::GraphicsSceneDrop);
    d->populateSceneDragDropEvent(&sceneEvent, event);
 
    // Send it to the scene.
    QCoreApplication::sendEvent(d->scene, &sceneEvent);
 
    // Accept the originating event if the scene accepted the scene event.
    event->setAccepted(sceneEvent.isAccepted());
    if (sceneEvent.isAccepted())
        event->setDropAction(sceneEvent.dropAction());
 
    delete d->lastDragDropEvent;
    d->lastDragDropEvent = nullptr;
}
 
void QGraphicsView::dragEnterEvent(QDragEnterEvent *event)
{
    Q_D(QGraphicsView);
    if (!d->scene || !d->sceneInteractionAllowed)
        return;
 
    // Disable replaying of mouse move events.
    d->useLastMouseEvent = false;
 
    // Generate a scene event.
    QGraphicsSceneDragDropEvent sceneEvent(QEvent::GraphicsSceneDragEnter);
    d->populateSceneDragDropEvent(&sceneEvent, event);
 
    // Store it for later use.
    d->storeDragDropEvent(&sceneEvent);
 
    // Send it to the scene.
    QCoreApplication::sendEvent(d->scene, &sceneEvent);
 
    // Accept the originating event if the scene accepted the scene event.
    if (sceneEvent.isAccepted()) {
        event->setAccepted(true);
        event->setDropAction(sceneEvent.dropAction());
    }
}
 
void QGraphicsView::dragLeaveEvent(QDragLeaveEvent *event)
{
    Q_D(QGraphicsView);
    if (!d->scene || !d->sceneInteractionAllowed)
        return;
    if (!d->lastDragDropEvent) {
        qWarning("QGraphicsView::dragLeaveEvent: drag leave received before drag enter");
        return;
    }
 
    // Generate a scene event.
    QGraphicsSceneDragDropEvent sceneEvent(QEvent::GraphicsSceneDragLeave);
    sceneEvent.setScenePos(d->lastDragDropEvent->scenePos());
    sceneEvent.setScreenPos(d->lastDragDropEvent->screenPos());
    sceneEvent.setButtons(d->lastDragDropEvent->buttons());
    sceneEvent.setModifiers(d->lastDragDropEvent->modifiers());
    sceneEvent.setPossibleActions(d->lastDragDropEvent->possibleActions());
    sceneEvent.setProposedAction(d->lastDragDropEvent->proposedAction());
    sceneEvent.setDropAction(d->lastDragDropEvent->dropAction());
    sceneEvent.setMimeData(d->lastDragDropEvent->mimeData());
    sceneEvent.setWidget(d->lastDragDropEvent->widget());
    sceneEvent.setSource(d->lastDragDropEvent->source());
    delete d->lastDragDropEvent;
    d->lastDragDropEvent = nullptr;
 
    // Send it to the scene.
    QCoreApplication::sendEvent(d->scene, &sceneEvent);
 
    // Accept the originating event if the scene accepted the scene event.
    if (sceneEvent.isAccepted())
        event->setAccepted(true);
}
 
void QGraphicsView::dragMoveEvent(QDragMoveEvent *event)
{
    Q_D(QGraphicsView);
    if (!d->scene || !d->sceneInteractionAllowed)
        return;
 
    // Generate a scene event.
    QGraphicsSceneDragDropEvent sceneEvent(QEvent::GraphicsSceneDragMove);
    d->populateSceneDragDropEvent(&sceneEvent, event);
 
    // Store it for later use.
    d->storeDragDropEvent(&sceneEvent);
 
    // Send it to the scene.
    QCoreApplication::sendEvent(d->scene, &sceneEvent);
 
    // Ignore the originating event if the scene ignored the scene event.
    event->setAccepted(sceneEvent.isAccepted());
    if (sceneEvent.isAccepted())
        event->setDropAction(sceneEvent.dropAction());
}
#endif // QT_CONFIG(draganddrop)
 
void QGraphicsView::focusInEvent(QFocusEvent *event)
{
    Q_D(QGraphicsView);
    d->updateInputMethodSensitivity();
    QAbstractScrollArea::focusInEvent(event);
    if (d->scene)
        QCoreApplication::sendEvent(d->scene, event);
    // Pass focus on if the scene cannot accept focus.
    if (!d->scene || !event->isAccepted())
        QAbstractScrollArea::focusInEvent(event);
}
 
bool QGraphicsView::focusNextPrevChild(bool next)
{
    return QAbstractScrollArea::focusNextPrevChild(next);
}
 
void QGraphicsView::focusOutEvent(QFocusEvent *event)
{
    Q_D(QGraphicsView);
    QAbstractScrollArea::focusOutEvent(event);
    if (d->scene)
        QCoreApplication::sendEvent(d->scene, event);
}
 
void QGraphicsView::keyPressEvent(QKeyEvent *event)
{
    Q_D(QGraphicsView);
    if (!d->scene || !d->sceneInteractionAllowed) {
        QAbstractScrollArea::keyPressEvent(event);
        return;
    }
    QCoreApplication::sendEvent(d->scene, event);
    if (!event->isAccepted())
        QAbstractScrollArea::keyPressEvent(event);
}
 
void QGraphicsView::keyReleaseEvent(QKeyEvent *event)
{
    Q_D(QGraphicsView);
    if (!d->scene || !d->sceneInteractionAllowed)
        return;
    QCoreApplication::sendEvent(d->scene, event);
    if (!event->isAccepted())
        QAbstractScrollArea::keyReleaseEvent(event);
}
 
void QGraphicsView::mouseDoubleClickEvent(QMouseEvent *event)
{
    Q_D(QGraphicsView);
    if (!d->scene || !d->sceneInteractionAllowed)
        return;
 
    d->storeMouseEvent(event);
    d->mousePressViewPoint = event->position().toPoint();
    d->mousePressScenePoint = mapToScene(d->mousePressViewPoint);
    d->mousePressScreenPoint = event->globalPosition().toPoint();
    d->lastMouseMoveScenePoint = d->mousePressScenePoint;
    d->lastMouseMoveScreenPoint = d->mousePressScreenPoint;
    d->mousePressButton = event->button();
 
    QGraphicsSceneMouseEvent mouseEvent(QEvent::GraphicsSceneMouseDoubleClick);
    mouseEvent.setWidget(viewport());
    mouseEvent.setButtonDownScenePos(d->mousePressButton, d->mousePressScenePoint);
    mouseEvent.setButtonDownScreenPos(d->mousePressButton, d->mousePressScreenPoint);
    mouseEvent.setScenePos(mapToScene(d->mousePressViewPoint));
    mouseEvent.setScreenPos(d->mousePressScreenPoint);
    mouseEvent.setLastScenePos(d->lastMouseMoveScenePoint);
    mouseEvent.setLastScreenPos(d->lastMouseMoveScreenPoint);
    mouseEvent.setButtons(event->buttons());
    mouseEvent.setAccepted(false);
    mouseEvent.setButton(event->button());
    mouseEvent.setModifiers(event->modifiers());
    mouseEvent.setSource(event->source());
    mouseEvent.setFlags(event->flags());
    mouseEvent.setTimestamp(event->timestamp());
    if (event->spontaneous())
        qt_sendSpontaneousEvent(d->scene, &mouseEvent);
    else
        QCoreApplication::sendEvent(d->scene, &mouseEvent);
 
    // Update the original mouse event accepted state.
    const bool isAccepted = mouseEvent.isAccepted();
    event->setAccepted(isAccepted);
 
    // Update the last mouse event accepted state.
    d->lastMouseEvent.setAccepted(isAccepted);
}
 
void QGraphicsView::mousePressEvent(QMouseEvent *event)
{
    Q_D(QGraphicsView);
 
    // Store this event for replaying, finding deltas, and for
    // scroll-dragging; even in non-interactive mode, scroll hand dragging is
    // allowed, so we store the event at the very top of this function.
    d->storeMouseEvent(event);
    d->lastMouseEvent.setAccepted(false);
 
    if (d->sceneInteractionAllowed) {
        // Store some of the event's button-down data.
        d->mousePressViewPoint = event->position().toPoint();
        d->mousePressScenePoint = mapToScene(d->mousePressViewPoint);
        d->mousePressScreenPoint = event->globalPosition().toPoint();
        d->lastMouseMoveScenePoint = d->mousePressScenePoint;
        d->lastMouseMoveScreenPoint = d->mousePressScreenPoint;
        d->mousePressButton = event->button();
 
        if (d->scene) {
            // Convert and deliver the mouse event to the scene.
            QGraphicsSceneMouseEvent mouseEvent(QEvent::GraphicsSceneMousePress);
            mouseEvent.setWidget(viewport());
            mouseEvent.setButtonDownScenePos(d->mousePressButton, d->mousePressScenePoint);
            mouseEvent.setButtonDownScreenPos(d->mousePressButton, d->mousePressScreenPoint);
            mouseEvent.setScenePos(d->mousePressScenePoint);
            mouseEvent.setScreenPos(d->mousePressScreenPoint);
            mouseEvent.setLastScenePos(d->lastMouseMoveScenePoint);
            mouseEvent.setLastScreenPos(d->lastMouseMoveScreenPoint);
            mouseEvent.setButtons(event->buttons());
            mouseEvent.setButton(event->button());
            mouseEvent.setModifiers(event->modifiers());
            mouseEvent.setSource(event->source());
            mouseEvent.setFlags(event->flags());
            mouseEvent.setAccepted(false);
            mouseEvent.setTimestamp(event->timestamp());
            if (event->spontaneous())
                qt_sendSpontaneousEvent(d->scene, &mouseEvent);
            else
                QCoreApplication::sendEvent(d->scene, &mouseEvent);
 
            // Update the original mouse event accepted state.
            bool isAccepted = mouseEvent.isAccepted();
            event->setAccepted(isAccepted);
 
            // Update the last mouse event accepted state.
            d->lastMouseEvent.setAccepted(isAccepted);
 
            if (isAccepted)
                return;
        }
    }
 
#if QT_CONFIG(rubberband)
    if (d->dragMode == QGraphicsView::RubberBandDrag && !d->rubberBanding) {
        if (d->sceneInteractionAllowed) {
            // Rubberbanding is only allowed in interactive mode.
            event->accept();
            d->rubberBanding = true;
            d->rubberBandRect = QRect();
            if (d->scene) {
                bool extendSelection = (event->modifiers() & Qt::ControlModifier) != 0;
 
                if (extendSelection) {
                    d->rubberBandSelectionOperation = Qt::AddToSelection;
                } else {
                    d->rubberBandSelectionOperation = Qt::ReplaceSelection;
                    d->scene->clearSelection();
                }
            }
        }
    } else
#endif
        if (d->dragMode == QGraphicsView::ScrollHandDrag && event->button() == Qt::LeftButton) {
            // Left-button press in scroll hand mode initiates hand scrolling.
            event->accept();
            d->handScrolling = true;
            d->handScrollMotions = 0;
#ifndef QT_NO_CURSOR
            viewport()->setCursor(Qt::ClosedHandCursor);
#endif
        }
}
 
void QGraphicsView::mouseMoveEvent(QMouseEvent *event)
{
    Q_D(QGraphicsView);
 
    if (d->dragMode == QGraphicsView::ScrollHandDrag) {
        if (d->handScrolling) {
            QScrollBar *hBar = horizontalScrollBar();
            QScrollBar *vBar = verticalScrollBar();
            QPoint delta = event->position().toPoint() - d->lastMouseEvent.position().toPoint();
            hBar->setValue(hBar->value() + (isRightToLeft() ? delta.x() : -delta.x()));
            vBar->setValue(vBar->value() - delta.y());
 
            // Detect how much we've scrolled to disambiguate scrolling from
            // clicking.
            ++d->handScrollMotions;
        }
    }
 
    d->mouseMoveEventHandler(event);
}
 
void QGraphicsView::mouseReleaseEvent(QMouseEvent *event)
{
    Q_D(QGraphicsView);
 
#if QT_CONFIG(rubberband)
    if (d->dragMode == QGraphicsView::RubberBandDrag && d->sceneInteractionAllowed && !event->buttons()) {
        d->clearRubberBand();
    } else
#endif
    if (d->dragMode == QGraphicsView::ScrollHandDrag && event->button() == Qt::LeftButton) {
#ifndef QT_NO_CURSOR
        // Restore the open hand cursor. ### There might be items
        // under the mouse that have a valid cursor at this time, so
        // we could repeat the steps from mouseMoveEvent().
        viewport()->setCursor(Qt::OpenHandCursor);
#endif
        d->handScrolling = false;
 
        if (d->scene && d->sceneInteractionAllowed && !d->lastMouseEvent.isAccepted() && d->handScrollMotions <= 6) {
            // If we've detected very little motion during the hand drag, and
            // no item accepted the last event, we'll interpret that as a
            // click to the scene, and reset the selection.
            d->scene->clearSelection();
        }
    }
 
    d->storeMouseEvent(event);
 
    if (!d->sceneInteractionAllowed)
        return;
 
    if (!d->scene)
        return;
 
    QGraphicsSceneMouseEvent mouseEvent(QEvent::GraphicsSceneMouseRelease);
    mouseEvent.setWidget(viewport());
    mouseEvent.setButtonDownScenePos(d->mousePressButton, d->mousePressScenePoint);
    mouseEvent.setButtonDownScreenPos(d->mousePressButton, d->mousePressScreenPoint);
    mouseEvent.setScenePos(mapToScene(event->position().toPoint()));
    mouseEvent.setScreenPos(event->globalPosition().toPoint());
    mouseEvent.setLastScenePos(d->lastMouseMoveScenePoint);
    mouseEvent.setLastScreenPos(d->lastMouseMoveScreenPoint);
    mouseEvent.setButtons(event->buttons());
    mouseEvent.setButton(event->button());
    mouseEvent.setModifiers(event->modifiers());
    mouseEvent.setSource(event->source());
    mouseEvent.setFlags(event->flags());
    mouseEvent.setAccepted(false);
    mouseEvent.setTimestamp(event->timestamp());
    if (event->spontaneous())
        qt_sendSpontaneousEvent(d->scene, &mouseEvent);
    else
        QCoreApplication::sendEvent(d->scene, &mouseEvent);
 
    // Update the last mouse event selected state.
    d->lastMouseEvent.setAccepted(mouseEvent.isAccepted());
 
#ifndef QT_NO_CURSOR
    if (mouseEvent.isAccepted() && mouseEvent.buttons() == 0 && viewport()->testAttribute(Qt::WA_SetCursor)) {
        // The last mouse release on the viewport will trigger clearing the cursor.
        d->_q_unsetViewportCursor();
    }
#endif
}
 
#if QT_CONFIG(wheelevent)
void QGraphicsView::wheelEvent(QWheelEvent *event)
{
    Q_D(QGraphicsView);
    if (!d->scene || !d->sceneInteractionAllowed) {
        QAbstractScrollArea::wheelEvent(event);
        return;
    }
 
    event->ignore();
 
    QGraphicsSceneWheelEvent wheelEvent(QEvent::GraphicsSceneWheel);
    wheelEvent.setWidget(viewport());
    wheelEvent.setScenePos(mapToScene(event->position().toPoint()));
    wheelEvent.setScreenPos(event->globalPosition().toPoint());
    wheelEvent.setButtons(event->buttons());
    wheelEvent.setModifiers(event->modifiers());
    const bool horizontal = qAbs(event->angleDelta().x()) > qAbs(event->angleDelta().y());
    wheelEvent.setDelta(horizontal ? event->angleDelta().x() : event->angleDelta().y());
    wheelEvent.setPixelDelta(event->pixelDelta());
    wheelEvent.setPhase(event->phase());
    wheelEvent.setInverted(event->isInverted());
    wheelEvent.setOrientation(horizontal ? Qt::Horizontal : Qt::Vertical);
    wheelEvent.setAccepted(false);
    wheelEvent.setTimestamp(event->timestamp());
    QCoreApplication::sendEvent(d->scene, &wheelEvent);
    event->setAccepted(wheelEvent.isAccepted());
    if (!event->isAccepted())
        QAbstractScrollArea::wheelEvent(event);
}
#endif // QT_CONFIG(wheelevent)
 
void QGraphicsView::paintEvent(QPaintEvent *event)
{
    Q_D(QGraphicsView);
    if (!d->scene) {
        QAbstractScrollArea::paintEvent(event);
        return;
    }
 
    // Set up painter state protection.
    d->scene->d_func()->painterStateProtection = !(d->optimizationFlags & DontSavePainterState);
 
    // Determine the exposed region
    d->exposedRegion = event->region();
    QRectF exposedSceneRect = mapToScene(d->exposedRegion.boundingRect()).boundingRect();
 
    // Set up the painter
    QPainter painter(viewport());
#if QT_CONFIG(rubberband)
    if (d->rubberBanding && !d->rubberBandRect.isEmpty())
        painter.save();
#endif
    // Set up render hints
    painter.setRenderHints(painter.renderHints(), false);
    painter.setRenderHints(d->renderHints, true);
 
    // Set up viewport transform
    const bool viewTransformed = isTransformed();
    if (viewTransformed)
        painter.setWorldTransform(viewportTransform());
    const QTransform viewTransform = painter.worldTransform();
 
    const auto actuallyDraw = [&]() {
        // Draw background
        if (d->cacheMode & CacheBackground) {
            // Recreate the background pixmap, and flag the whole background as
            // exposed.
            if (d->mustResizeBackgroundPixmap) {
                const qreal dpr = d->viewport->devicePixelRatio();
                d->backgroundPixmap = QPixmap(viewport()->size() * dpr);
                d->backgroundPixmap.setDevicePixelRatio(dpr);
                QBrush bgBrush = viewport()->palette().brush(viewport()->backgroundRole());
                if (!bgBrush.isOpaque())
                    d->backgroundPixmap.fill(Qt::transparent);
                QPainter p(&d->backgroundPixmap);
                p.fillRect(0, 0, d->backgroundPixmap.width(), d->backgroundPixmap.height(), bgBrush);
                d->backgroundPixmapExposed = QRegion(viewport()->rect());
                d->mustResizeBackgroundPixmap = false;
            }
 
            // Redraw exposed areas
            if (!d->backgroundPixmapExposed.isEmpty()) {
                QPainter backgroundPainter(&d->backgroundPixmap);
                backgroundPainter.setClipRegion(d->backgroundPixmapExposed, Qt::ReplaceClip);
                if (viewTransformed)
                    backgroundPainter.setTransform(viewTransform);
                QRectF backgroundExposedSceneRect = mapToScene(d->backgroundPixmapExposed.boundingRect()).boundingRect();
                drawBackground(&backgroundPainter, backgroundExposedSceneRect);
                d->backgroundPixmapExposed = QRegion();
            }
 
            // Blit the background from the background pixmap
            if (viewTransformed) {
                painter.setWorldTransform(QTransform());
                painter.drawPixmap(QPoint(), d->backgroundPixmap);
                painter.setWorldTransform(viewTransform);
            } else {
                painter.drawPixmap(QPoint(), d->backgroundPixmap);
            }
        } else {
            if (!(d->optimizationFlags & DontSavePainterState))
                painter.save();
 
            drawBackground(&painter, exposedSceneRect);
            if (!(d->optimizationFlags & DontSavePainterState))
                painter.restore();
        }
 
        // Items
        if (!(d->optimizationFlags & IndirectPainting)) {
            const quint32 oldRectAdjust = d->scene->d_func()->rectAdjust;
            if (d->optimizationFlags & QGraphicsView::DontAdjustForAntialiasing)
                d->scene->d_func()->rectAdjust = 1;
            else
                d->scene->d_func()->rectAdjust = 2;
            d->scene->d_func()->drawItems(&painter, viewTransformed ? &viewTransform : nullptr,
                                          &d->exposedRegion, viewport());
            d->scene->d_func()->rectAdjust = oldRectAdjust;
            // Make sure the painter's world transform is restored correctly when
            // drawing without painter state protection (DontSavePainterState).
            // We only change the worldTransform() so there's no need to do a full-blown
            // save() and restore(). Also note that we don't have to do this in case of
            // IndirectPainting (the else branch), because in that case we always save()
            // and restore() in QGraphicsScene::drawItems().
            if (!d->scene->d_func()->painterStateProtection)
                painter.setOpacity(1.0);
            painter.setWorldTransform(viewTransform);
        } else {
            // Make sure we don't have unpolished items before we draw
            if (!d->scene->d_func()->unpolishedItems.isEmpty())
                d->scene->d_func()->_q_polishItems();
            // We reset updateAll here (after we've issued polish events)
            // so that we can discard update requests coming from polishEvent().
            d->scene->d_func()->updateAll = false;
 
            // Find all exposed items
            bool allItems = false;
            QList<QGraphicsItem *> itemList = d->findItems(d->exposedRegion, &allItems, viewTransform);
            if (!itemList.isEmpty()) {
                // Generate the style options.
                const int numItems = itemList.size();
                QGraphicsItem **itemArray = &itemList[0]; // Relies on QList internals, but is perfectly valid.
                QStyleOptionGraphicsItem *styleOptionArray = d->allocStyleOptionsArray(numItems);
                QTransform transform(Qt::Uninitialized);
                for (int i = 0; i < numItems; ++i) {
                    QGraphicsItem *item = itemArray[i];
                    QGraphicsItemPrivate *itemd = item->d_ptr.data();
                    itemd->initStyleOption(&styleOptionArray[i], viewTransform, d->exposedRegion, allItems);
                    // Cache the item's area in view coordinates.
                    // Note that we have to do this here in case the base class implementation
                    // (QGraphicsScene::drawItems) is not called. If it is, we'll do this
                    // operation twice, but that's the price one has to pay for using indirect
                    // painting :-/.
                    const QRectF brect = adjustedItemEffectiveBoundingRect(item);
                    if (!itemd->itemIsUntransformable()) {
                        transform = item->sceneTransform();
                        if (viewTransformed)
                            transform *= viewTransform;
                    } else {
                        transform = item->deviceTransform(viewTransform);
                    }
                    itemd->paintedViewBoundingRects.insert(d->viewport, transform.mapRect(brect).toRect());
                }
                // Draw the items.
                drawItems(&painter, numItems, itemArray, styleOptionArray);
                d->freeStyleOptionsArray(styleOptionArray);
            }
        }
 
        // Foreground
        drawForeground(&painter, exposedSceneRect);
 
    #if QT_CONFIG(rubberband)
        // Rubberband
        if (d->rubberBanding && !d->rubberBandRect.isEmpty()) {
            painter.restore();
            QStyleOptionRubberBand option;
            option.initFrom(viewport());
            option.rect = d->rubberBandRect;
            option.shape = QRubberBand::Rectangle;
 
            QStyleHintReturnMask mask;
            if (viewport()->style()->styleHint(QStyle::SH_RubberBand_Mask, &option, viewport(), &mask)) {
                // painter clipping for masked rubberbands
                painter.setClipRegion(mask.region, Qt::IntersectClip);
            }
 
            viewport()->style()->drawControl(QStyle::CE_RubberBand, &option, &painter, viewport());
        }
    #endif
    };
 
    actuallyDraw();
 
    // For stereo we want to draw everything twice, once to each buffer
    if (d->stereoEnabled) {
        QWidgetPrivate* w = QWidgetPrivate::get(viewport());
        if (w->toggleStereoTargetBuffer()) {
            actuallyDraw();
            w->toggleStereoTargetBuffer();
        }
    }
 
    painter.end();
 
    // Restore painter state protection.
    d->scene->d_func()->painterStateProtection = true;
}
 
void QGraphicsView::resizeEvent(QResizeEvent *event)
{
    Q_D(QGraphicsView);
    // Save the last center point - the resize may scroll the view, which
    // changes the center point.
    QPointF oldLastCenterPoint = d->lastCenterPoint;
 
    QAbstractScrollArea::resizeEvent(event);
    d->recalculateContentSize();
 
    // Restore the center point again.
    if (d->resizeAnchor == NoAnchor && !d->keepLastCenterPoint) {
        d->updateLastCenterPoint();
    } else {
        d->lastCenterPoint = oldLastCenterPoint;
    }
    d->centerView(d->resizeAnchor);
    d->keepLastCenterPoint = false;
 
    if (d->cacheMode & CacheBackground) {
        // Invalidate the background pixmap
        d->mustResizeBackgroundPixmap = true;
    }
}
 
void QGraphicsView::scrollContentsBy(int dx, int dy)
{
    Q_D(QGraphicsView);
    d->dirtyScroll = true;
    if (d->transforming)
        return;
    if (isRightToLeft())
        dx = -dx;
 
    if (d->viewportUpdateMode != QGraphicsView::NoViewportUpdate) {
        if (d->viewportUpdateMode != QGraphicsView::FullViewportUpdate) {
            if (d->accelerateScrolling) {
#if QT_CONFIG(rubberband)
                // Update new and old rubberband regions
                if (!d->rubberBandRect.isEmpty()) {
                    QRegion rubberBandRegion(d->rubberBandRegion(viewport(), d->rubberBandRect));
                    rubberBandRegion += rubberBandRegion.translated(-dx, -dy);
                    viewport()->update(rubberBandRegion);
                }
#endif
                d->dirtyScrollOffset.rx() += dx;
                d->dirtyScrollOffset.ry() += dy;
                d->dirtyRegion.translate(dx, dy);
                viewport()->scroll(dx, dy);
            } else {
                d->updateAll();
            }
        } else {
            d->updateAll();
        }
    }
 
    d->updateLastCenterPoint();
 
    if (d->cacheMode & CacheBackground) {
        // Below, QPixmap::scroll() works in device pixels, while the delta values
        // and backgroundPixmapExposed are in device independent pixels.
        const qreal dpr = d->backgroundPixmap.devicePixelRatio();
        const qreal inverseDpr = qreal(1) / dpr;
 
        // Scroll the background pixmap
        QRegion exposed;
        if (!d->backgroundPixmap.isNull())
            d->backgroundPixmap.scroll(dx * dpr, dy * dpr, d->backgroundPixmap.rect(), &exposed);
 
        // Invalidate the background pixmap
        d->backgroundPixmapExposed.translate(dx, dy);
        const QRegion exposedScaled = QTransform::fromScale(inverseDpr, inverseDpr).map(exposed);
        d->backgroundPixmapExposed += exposedScaled;
    }
 
    // Always replay on scroll.
    if (d->sceneInteractionAllowed)
        d->replayLastMouseEvent();
}
 
void QGraphicsView::showEvent(QShowEvent *event)
{
    Q_D(QGraphicsView);
    d->recalculateContentSize();
    d->centerView(d->transformationAnchor);
    QAbstractScrollArea::showEvent(event);
}
 
void QGraphicsView::inputMethodEvent(QInputMethodEvent *event)
{
    Q_D(QGraphicsView);
    if (d->scene)
        QCoreApplication::sendEvent(d->scene, event);
}
 
void QGraphicsView::drawBackground(QPainter *painter, const QRectF &rect)
{
    Q_D(QGraphicsView);
    if (d->scene && d->backgroundBrush.style() == Qt::NoBrush) {
        d->scene->drawBackground(painter, rect);
        return;
    }
 
    const bool wasAa = painter->testRenderHint(QPainter::Antialiasing);
    if (wasAa)
        painter->setRenderHints(QPainter::Antialiasing, false);
    painter->fillRect(rect, d->backgroundBrush);
    if (wasAa)
        painter->setRenderHints(QPainter::Antialiasing, true);
}
 
void QGraphicsView::drawForeground(QPainter *painter, const QRectF &rect)
{
    Q_D(QGraphicsView);
    if (d->scene && d->foregroundBrush.style() == Qt::NoBrush) {
        d->scene->drawForeground(painter, rect);
        return;
    }
 
    painter->fillRect(rect, d->foregroundBrush);
}
 
void QGraphicsView::drawItems(QPainter *painter, int numItems,
                              QGraphicsItem *items[],
                              const QStyleOptionGraphicsItem options[])
{
    Q_D(QGraphicsView);
    if (d->scene) {
        QWidget *widget = painter->device() == viewport() ? viewport() : nullptr;
        d->scene->drawItems(painter, numItems, items, options, widget);
    }
}
 
QTransform QGraphicsView::transform() const
{
    Q_D(const QGraphicsView);
    return d->matrix;
}
 
QTransform QGraphicsView::viewportTransform() const
{
    Q_D(const QGraphicsView);
    QTransform moveMatrix = QTransform::fromTranslate(-d->horizontalScroll(), -d->verticalScroll());
    return d->identityMatrix ? moveMatrix : d->matrix * moveMatrix;
}
 
bool QGraphicsView::isTransformed() const
{
    Q_D(const QGraphicsView);
    return !d->identityMatrix || d->horizontalScroll() || d->verticalScroll();
}
 
void QGraphicsView::setTransform(const QTransform &matrix, bool combine )
{
    Q_D(QGraphicsView);
    QTransform oldMatrix = d->matrix;
    if (!combine)
        d->matrix = matrix;
    else
        d->matrix = matrix * d->matrix;
    if (oldMatrix == d->matrix)
        return;
 
    d->identityMatrix = d->matrix.isIdentity();
    d->transforming = true;
    if (d->scene) {
        d->recalculateContentSize();
        d->centerView(d->transformationAnchor);
    } else {
        d->updateLastCenterPoint();
    }
 
    if (d->sceneInteractionAllowed)
        d->replayLastMouseEvent();
    d->transforming = false;
 
    // Any matrix operation requires a full update.
    d->updateAll();
}
 
void QGraphicsView::resetTransform()
{
    setTransform(QTransform());
}
 
QPointF QGraphicsViewPrivate::mapToScene(const QPointF &point) const
{
    QPointF p = point;
    p.rx() += horizontalScroll();
    p.ry() += verticalScroll();
    return identityMatrix ? p : matrix.inverted().map(p);
}
 
QRectF QGraphicsViewPrivate::mapToScene(const QRectF &rect) const
{
    QPointF scrollOffset(horizontalScroll(), verticalScroll());
    QPointF tl = scrollOffset + rect.topLeft();
    QPointF tr = scrollOffset + rect.topRight();
    QPointF br = scrollOffset + rect.bottomRight();
    QPointF bl = scrollOffset + rect.bottomLeft();
 
    QPolygonF poly(4);
    if (!identityMatrix) {
        QTransform x = matrix.inverted();
        poly[0] = x.map(tl);
        poly[1] = x.map(tr);
        poly[2] = x.map(br);
        poly[3] = x.map(bl);
    } else {
        poly[0] = tl;
        poly[1] = tr;
        poly[2] = br;
        poly[3] = bl;
    }
    return poly.boundingRect();
}
 
QT_END_NAMESPACE
 
#include "moc_qgraphicsview.cpp"