source: trunk/src/gui/graphicsview/qgraphicsview.cpp@ 396

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//#define QGRAPHICSVIEW_DEBUG

static const int QGRAPHICSVIEW_REGION_RECT_THRESHOLD = 50;

static const int QGRAPHICSVIEW_PREALLOC_STYLE_OPTIONS = 503; // largest prime < 2^9

/*!
    \class QGraphicsView
    \brief The QGraphicsView class provides a widget for displaying the
    contents of a QGraphicsScene.
    \since 4.2
    \ingroup multimedia
    \ingroup graphicsview-api
    \mainclass

    QGraphicsView visualizes the contents of a QGraphicsScene in a scrollable
    viewport. To create a scene with geometrical items, see QGraphicsScene's
    documentation. QGraphicsView is part of \l{The Graphics View Framework}.

    To visualize a scene, you start by constructing a QGraphicsView object,
    passing the address of the scene you want to visualize to QGraphicsView's
    constructor. Alternatively, you can call setScene() to set the scene at a
    later point. After you call show(), the view will by default scroll to the
    center of the scene and display any items that are visible at this
    point. For example:

    \snippet doc/src/snippets/code/src_gui_graphicsview_qgraphicsview.cpp 0

    You can explicitly scroll to any position on the scene by using the
    scroll bars, or by calling centerOn(). By passing a point to centerOn(),
    QGraphicsView will scroll its viewport to ensure that the point is
    centered in the view. An overload is provided for scrolling to a
    QGraphicsItem, in which case QGraphicsView will see to that the center of
    the item is centered in the view. If all you want is to ensure that a
    certain area is visible, (but not necessarily centered,) you can call
    ensureVisible() instead.

    QGraphicsView can be used to visualize a whole scene, or only parts of it.
    The visualized area is by default detected automatically when the view is
    displayed for the first time (by calling
    QGraphicsScene::itemsBoundingRect()). To set the visualized area rectangle
    yourself, you can call setSceneRect(). This will adjust the scroll bars'
    ranges appropriately. Note that although the scene supports a virtually
    unlimited size, the range of the scroll bars will never exceed the range of
    an integer (INT_MIN, INT_MAX). When the scene is larger than the scroll
    bars' values, you can choose to use translate() to navigate the scene
    instead.

    QGraphicsView visualizes the scene by calling render(). By default, the
    items are drawn onto the viewport by using a regular QPainter, and using
    default render hints. To change the default render hints that
    QGraphicsView passes to QPainter when painting items, you can call
    setRenderHints().

    By default, QGraphicsView provides a regular QWidget for the viewport
    widget. You can access this widget by calling viewport(), or you can
    replace it by calling setViewport(). To render using OpenGL, simply call
    setViewport(new QGLWidget). QGraphicsView takes ownership of the viewport
    widget.

    QGraphicsView supports affine transformations, using QMatrix. You can
    either pass a matrix to setMatrix(), or you can call one of the
    convenience functions rotate(), scale(), translate() or shear(). The most
    two common transformations are scaling, which is used to implement
    zooming, and rotation. QGraphicsView keeps the center of the view fixed
    during a transformation.

    You can interact with the items on the scene by using the mouse and
    keyboard. QGraphicsView translates the mouse and key events into \e scene
    events, (events that inherit QGraphicsSceneEvent,), and forward them to
    the visualized scene. In the end, it's the individual item that handles
    the events and reacts to them. For example, if you click on a selectable
    item, the item will typically let the scene know that it has been
    selected, and it will also redraw itself to display a selection
    rectangle. Similiary, if you click and drag the mouse to move a movable
    item, it's the item that handles the mouse moves and moves itself.  Item
    interaction is enabled by default, and you can toggle it by calling
    setInteractive().

    You can also provide your own custom scene interaction, by creating a
    subclass of QGraphicsView, and reimplementing the mouse and key event
    handlers. To simplify how you programmatically interact with items in the
    view, QGraphicsView provides the mapping functions mapToScene() and
    mapFromScene(), and the item accessors items() and itemAt(). These
    functions allow you to map points, rectangles, polygons and paths between
    view coordinates and scene coordinates, and to find items on the scene
    using view coordinates.

    \img graphicsview-view.png

    \sa QGraphicsScene, QGraphicsItem, QGraphicsSceneEvent
*/

/*!
    \enum QGraphicsView::ViewportAnchor

    This enums describe the possible anchors that QGraphicsView can
    use when the user resizes the view or when the view is
    transformed.

    \value NoAnchor No anchor, i.e. the view leaves the scene's
                    position unchanged.
    \value AnchorViewCenter The scene point at the center of the view
                            is used as the anchor.
    \value AnchorUnderMouse The point under the mouse is used as the anchor.

    \sa resizeAnchor, transformationAnchor
*/

/*!
    \enum QGraphicsView::ViewportUpdateMode

    \since 4.3

    This enum describes how QGraphicsView updates its viewport when the scene
    contents change or are exposed.

    \value FullViewportUpdate When any visible part of the scene changes or is
    reexposed, QGraphicsView will update the entire viewport. This approach is
    fastest when QGraphicsView spends more time figuring out what to draw than
    it would spend drawing (e.g., when very many small items are repeatedly
    updated). This is the preferred update mode for viewports that do not
    support partial updates, such as QGLWidget, and for viewports that need to
    disable scroll optimization.

    \value MinimalViewportUpdate QGraphicsView will determine the minimal
    viewport region that requires a redraw, minimizing the time spent drawing
    by avoiding a redraw of areas that have not changed. This is
    QGraphicsView's default mode. Although this approach provides the best
    performance in general, if there are many small visible changes on the
    scene, QGraphicsView might end up spending more time finding the minimal
    approach than it will spend drawing.

    \value SmartViewportUpdate QGraphicsView will attempt to find an optimal
    update mode by analyzing the areas that require a redraw.

    \value BoundingRectViewportUpdate The bounding rectangle of all changes in
    the viewport will be redrawn. This mode has the advantage that
    QGraphicsView searches only one region for changes, minimizing time spent
    determining what needs redrawing. The disadvantage is that areas that have
    not changed also need to be redrawn.

    \value NoViewportUpdate QGraphicsView will never update its viewport when
    the scene changes; the user is expected to control all updates. This mode
    disables all (potentially slow) item visibility testing in QGraphicsView,
    and is suitable for scenes that either require a fixed frame rate, or where
    the viewport is otherwise updated externally.

    \sa viewportUpdateMode
*/

/*!
    \enum QGraphicsView::OptimizationFlag

    \since 4.3

    This enum describes flags that you can enable to improve rendering
    performance in QGraphicsView. By default, none of these flags are set.
    Note that setting a flag usually imposes a side effect, and this effect
    can vary between paint devices and platforms.

    \value DontClipPainter QGraphicsView sometimes clips the painter when
    rendering the scene contents. This can generally improve performance
    (e.g., rendering only small parts of a large pixmap), and protects against
    rendering mistakes (e.g., drawing outside bounding rectangles, or outside
    the exposed area). In some situations, however, the painter clip can slow
    down rendering; especially when all painting is restricted to inside
    exposed areas. By enabling this flag, QGraphicsView will completely
    disable its implicit clipping. Note that rendering artifacts from using a
    semi-transparent foreground or background brush can occur if clipping is
    disabled.

    \value DontSavePainterState When rendering, QGraphicsView protects the
    painter state (see QPainter::save()) when rendering the background or
    foreground, and when rendering each item. This allows you to leave the
    painter in an altered state (i.e., you can call QPainter::setPen() or
    QPainter::setBrush() without restoring the state after painting). However,
    if the items consistently do restore the state, you should enable this
    flag to prevent QGraphicsView from doing the same.

    \value DontAdjustForAntialiasing Disables QGraphicsView's antialiasing
    auto-adjustment of exposed areas. Items that render antialiased lines on
    the boundaries of their QGraphicsItem::boundingRect() can end up rendering
    parts of the line outside. To prevent rendering artifacts, QGraphicsView
    expands all exposed regions by 2 pixels in all directions. If you enable
    this flag, QGraphicsView will no longer perform these adjustments,
    minimizing the areas that require redrawing, which improves performance. A
    common side effect is that items that do draw with antialiasing can leave
    painting traces behind on the scene as they are moved.
*/

/*!
    \enum QGraphicsView::CacheModeFlag

    This enum describes the flags that you can set for a QGraphicsView's cache
    mode.

    \value CacheNone All painting is done directly onto the viewport.

    \value CacheBackground The background is cached. This affects both custom
    backgrounds, and backgrounds based on the backgroundBrush property. When
    this flag is enabled, QGraphicsView will allocate one pixmap with the full
    size of the viewport.

    \sa cacheMode
*/

/*!
    \enum QGraphicsView::DragMode

    This enum describes the default action for the view when pressing and
    dragging the mouse over the viewport.

    \value NoDrag Nothing happens; the mouse event is ignored.

    \value ScrollHandDrag The cursor changes into a pointing hand, and
    dragging the mouse around will scroll the scrolbars. This mode works both
    in \l{QGraphicsView::interactive}{interactive} and non-interactive mode.

    \value RubberBandDrag A rubber band will appear. Dragging the mouse will
    set the rubber band geometry, and all items covered by the rubber band are
    selected. This mode is disabled for non-interactive views.

    \sa dragMode, QGraphicsScene::setSelectionArea()
*/

#include "qgraphicsview.h"
#include "qgraphicsview_p.h"

#ifndef QT_NO_GRAPHICSVIEW

#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 <QtGui/qapplication.h>
#include <QtGui/qdesktopwidget.h>
#include <QtGui/qevent.h>
#include <QtGui/qlayout.h>
#include <QtGui/qtransform.h>
#include <QtGui/qmatrix.h>
#include <QtGui/qpainter.h>
#include <QtGui/qscrollbar.h>
#include <QtGui/qstyleoption.h>
#ifdef Q_WS_X11
#include <private/qt_x11_p.h>
#endif

QT_BEGIN_NAMESPACE

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);
}

/*!
    \internal
*/
QGraphicsViewPrivate::QGraphicsViewPrivate()
    : renderHints(QPainter::TextAntialiasing),
      dragMode(QGraphicsView::NoDrag),
      sceneInteractionAllowed(true), hasSceneRect(false),
      connectedToScene(false),
      mousePressButton(Qt::NoButton),
      identityMatrix(true),
      dirtyScroll(true),
      accelerateScrolling(true),
      leftIndent(0), topIndent(0),
      lastMouseEvent(QEvent::None, QPoint(), Qt::NoButton, 0, 0),
      useLastMouseEvent(false),
      keepLastCenterPoint(true),
      alignment(Qt::AlignCenter),
      transforming(false),
      transformationAnchor(QGraphicsView::AnchorViewCenter), resizeAnchor(QGraphicsView::NoAnchor),
      viewportUpdateMode(QGraphicsView::MinimalViewportUpdate),
      optimizationFlags(0),
      scene(0),
#ifndef QT_NO_RUBBERBAND
      rubberBanding(false),
      rubberBandSelectionMode(Qt::IntersectsItemShape),
#endif
      handScrolling(false), handScrollMotions(0), cacheMode(0),
      mustAllocateStyleOptions(false),
      mustResizeBackgroundPixmap(true),
#ifndef QT_NO_CURSOR
      hasStoredOriginalCursor(false),
#endif
      lastDragDropEvent(0),
      fullUpdatePending(true),
      dirtyRectCount(0),
      updatingLater(false),
      updateSceneSlotReimplementedChecked(false)
{
    styleOptions.reserve(QGRAPHICSVIEW_PREALLOC_STYLE_OPTIONS);
}

/*!
    \internal
*/
void QGraphicsViewPrivate::recalculateContentSize()
{
    Q_Q(QGraphicsView);

    QSize maxSize = q->maximumViewportSize();
    int width = maxSize.width();
    int height = maxSize.height();
    QRectF viewRect = matrix.mapRect(q->sceneRect());

    bool frameOnlyAround = (q->style()->styleHint(QStyle::SH_ScrollView_FrameOnlyAroundContents, 0, 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.
    int scrollBarExtent = q->style()->pixelMetric(QStyle::PM_ScrollBarExtent, 0, q);
    if (frameOnlyAround)
        scrollBarExtent += frameWidth * 2;

    bool useHorizontalScrollBar = (viewRect.width() > width) && hbarpolicy != Qt::ScrollBarAlwaysOff;
    bool useVerticalScrollBar = (viewRect.height() > height) && vbarpolicy != Qt::ScrollBarAlwaysOff;
    if (useHorizontalScrollBar && !useVerticalScrollBar) {
        if (viewRect.height() > height - scrollBarExtent)
            useVerticalScrollBar = true;
    }
    if (useVerticalScrollBar && !useHorizontalScrollBar) {
        if (viewRect.width() > width - scrollBarExtent)
            useHorizontalScrollBar = true;
    }
    if (useHorizontalScrollBar && hbarpolicy != Qt::ScrollBarAlwaysOn)
        height -= scrollBarExtent;
    if (useVerticalScrollBar && vbarpolicy != Qt::ScrollBarAlwaysOn)
        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.
    QPointF savedLastCenterPoint = lastCenterPoint;

    // Remember the former indent settings
    qreal oldLeftIndent = leftIndent;
    qreal oldTopIndent = topIndent;

    // If the whole scene fits horizontally, we center the scene horizontally,
    // and ignore the horizontal scroll bars.
    int left =  q_round_bound(viewRect.left());
    int right = q_round_bound(viewRect.right() - width);
    if (left >= right) {
        q->horizontalScrollBar()->setRange(0, 0);

        switch (alignment & Qt::AlignHorizontal_Mask) {
        case Qt::AlignLeft:
            leftIndent = -viewRect.left();
            break;
        case Qt::AlignRight:
            leftIndent = width - viewRect.width() - viewRect.left() - 1;
            break;
        case Qt::AlignHCenter:
        default:
            leftIndent = width / 2 - (viewRect.left() + viewRect.right()) / 2;
            break;
        }
    } else {
        q->horizontalScrollBar()->setRange(left, right);
        q->horizontalScrollBar()->setPageStep(width);
        q->horizontalScrollBar()->setSingleStep(width / 20);
        leftIndent = 0;
    }

    // If the whole scene fits vertically, we center the scene vertically, and
    // ignore the vertical scroll bars.
    int top = q_round_bound(viewRect.top());
    int bottom = q_round_bound(viewRect.bottom()  - height);
    if (top >= bottom) {
        q->verticalScrollBar()->setRange(0, 0);

        switch (alignment & Qt::AlignVertical_Mask) {
        case Qt::AlignTop:
            topIndent = -viewRect.top();
            break;
        case Qt::AlignBottom:
            topIndent = height - viewRect.height() - viewRect.top() - 1;
            break;
        case Qt::AlignVCenter:
        default:
            topIndent = height / 2 - (viewRect.top() + viewRect.bottom()) / 2;
            break;
        }
    } else {
        q->verticalScrollBar()->setRange(top, bottom);
        q->verticalScrollBar()->setPageStep(height);
        q->verticalScrollBar()->setSingleStep(height / 20);
        topIndent = 0;
    }

    // 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;
        q->viewport()->update();
    } 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;
    }
}

/*!
    \internal
*/
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(q->viewport()->rect().center())
                                         - q->mapToScene(q->mapFromGlobal(QCursor::pos()));
            q->centerOn(lastMouseMoveScenePoint + transformationDiff);;
        } else {
            q->centerOn(lastCenterPoint);
        }
        break;
    }
    case QGraphicsView::AnchorViewCenter:
        q->centerOn(lastCenterPoint);
        break;
    case QGraphicsView::NoAnchor:
        break;
    }
}

/*!
    \internal
*/
void QGraphicsViewPrivate::updateLastCenterPoint()
{
    Q_Q(QGraphicsView);
    lastCenterPoint = q->mapToScene(q->viewport()->rect().center());
}

/*!
    \internal

    Returns the horizontal scroll value (the X value of the left edge of the
    viewport).
*/
qint64 QGraphicsViewPrivate::horizontalScroll() const
{
    if (dirtyScroll)
        const_cast<QGraphicsViewPrivate *>(this)->updateScroll();
    return scrollX;
}

/*!
    \internal

    Returns the vertical scroll value (the X value of the top edge of the
    viewport).
*/
qint64 QGraphicsViewPrivate::verticalScroll() const
{
    if (dirtyScroll)
        const_cast<QGraphicsViewPrivate *>(this)->updateScroll();
    return scrollY;
}

/*!
    \internal
*/
void QGraphicsViewPrivate::updateScroll()
{
    Q_Q(QGraphicsView);
    scrollX = qint64(-leftIndent);
    if (q->isRightToLeft()) {
        if (!leftIndent) {
            scrollX += q->horizontalScrollBar()->minimum();
            scrollX += q->horizontalScrollBar()->maximum();
            scrollX -= q->horizontalScrollBar()->value();
        }
    } else {
        scrollX += q->horizontalScrollBar()->value();
    }

    scrollY = qint64(q->verticalScrollBar()->value() - topIndent);

    dirtyScroll = false;
}

/*!
    \internal
*/
void QGraphicsViewPrivate::replayLastMouseEvent()
{
    if (!useLastMouseEvent || !scene)
        return;
    mouseMoveEventHandler(&lastMouseEvent);
}

/*!
    \internal
*/
void QGraphicsViewPrivate::storeMouseEvent(QMouseEvent *event)
{
    useLastMouseEvent = true;
    lastMouseEvent = QMouseEvent(QEvent::MouseMove, event->pos(), event->globalPos(),
                                 event->button(), event->buttons(), event->modifiers());
}

void QGraphicsViewPrivate::mouseMoveEventHandler(QMouseEvent *event)
{
    Q_Q(QGraphicsView);

    storeMouseEvent(event);
    lastMouseEvent.setAccepted(false);

    if (!sceneInteractionAllowed)
        return;
    if (handScrolling)
        return;
    if (!scene)
        return;

    QGraphicsSceneMouseEvent mouseEvent(QEvent::GraphicsSceneMouseMove);
    mouseEvent.setWidget(q->viewport());
    mouseEvent.setButtonDownScenePos(mousePressButton, mousePressScenePoint);
    mouseEvent.setButtonDownScreenPos(mousePressButton, mousePressScreenPoint);
    mouseEvent.setScenePos(q->mapToScene(event->pos()));
    mouseEvent.setScreenPos(event->globalPos());
    mouseEvent.setLastScenePos(lastMouseMoveScenePoint);
    mouseEvent.setLastScreenPos(lastMouseMoveScreenPoint);
    mouseEvent.setButtons(event->buttons());
    mouseEvent.setButton(event->button());
    mouseEvent.setModifiers(event->modifiers());
    lastMouseMoveScenePoint = mouseEvent.scenePos();
    lastMouseMoveScreenPoint = mouseEvent.screenPos();
    mouseEvent.setAccepted(false);
    QApplication::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
    // Find the topmost item under the mouse with a cursor.
    foreach (QGraphicsItem *item, scene->d_func()->cachedItemsUnderMouse) {
        if (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;
        q->viewport()->setCursor(originalCursor);
    }
#endif
}

/*!
    \internal
*/
#ifndef QT_NO_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;
    if (widget->style()->styleHint(QStyle::SH_RubberBand_Mask, &option, widget, &mask))
        tmp &= mask.region;
    return tmp;
}
#endif

/*!
    \internal
*/
#ifndef QT_NO_CURSOR
void QGraphicsViewPrivate::_q_setViewportCursor(const QCursor &cursor)
{
    Q_Q(QGraphicsView);
    QWidget *viewport = q->viewport();
    if (!hasStoredOriginalCursor) {
        hasStoredOriginalCursor = true;
        originalCursor = viewport->cursor();
    }
    viewport->setCursor(cursor);
}
#endif

/*!
    \internal
*/
#ifndef QT_NO_CURSOR
void QGraphicsViewPrivate::_q_unsetViewportCursor()
{
    Q_Q(QGraphicsView);
    foreach (QGraphicsItem *item, q->items(lastMouseEvent.pos())) {
        if (item->hasCursor()) {
            _q_setViewportCursor(item->cursor());
            return;
        }
    }

    // Restore the original viewport cursor.
    hasStoredOriginalCursor = false;
    if (dragMode == QGraphicsView::ScrollHandDrag)
        q->viewport()->setCursor(Qt::OpenHandCursor);
    else
        q->viewport()->setCursor(originalCursor);
}
#endif

/*!
    \internal
*/
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());
}

/*!
    \internal
*/
void QGraphicsViewPrivate::populateSceneDragDropEvent(QGraphicsSceneDragDropEvent *dest,
                                                      QDropEvent *source)
{
#ifndef QT_NO_DRAGANDDROP
    Q_Q(QGraphicsView);
    dest->setScenePos(q->mapToScene(source->pos()));
    dest->setScreenPos(q->mapToGlobal(source->pos()));
    dest->setButtons(source->mouseButtons());
    dest->setModifiers(source->keyboardModifiers());
    dest->setPossibleActions(source->possibleActions());
    dest->setProposedAction(source->proposedAction());
    dest->setDropAction(source->dropAction());
    dest->setMimeData(source->mimeData());
    dest->setWidget(q->viewport());
    dest->setSource(source->source());
#else
    Q_UNUSED(dest)
    Q_UNUSED(source)
#endif
}

/*!
    \internal
*/
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
    QPointF offset;
    const QGraphicsItem *parentItem = item;
    const QGraphicsItemPrivate *itemd;
    do {
        itemd = parentItem->d_ptr;
        if (itemd->hasTransform)
            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();
}

/*!
    \internal
*/
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->sceneTransform() * q->viewportTransform();
    return item->boundingRegion(itv) & itv.mapRect(rect).toAlignedRect();
}

// QRectF::intersects() returns false always if either the source or target
// rectangle's width or height are 0. This works around that problem.
static inline QRectF adjustedItemBoundingRect(const QGraphicsItem *item)
{
    Q_ASSERT(item);
    QRectF boundingRect(item->boundingRect());
    if (!boundingRect.width())
        boundingRect.adjust(-0.00001, 0, 0.00001, 0);
    if (!boundingRect.height())
        boundingRect.adjust(0, -0.00001, 0, 0.00001);
    return boundingRect;
}

/*!
    \internal
*/
void QGraphicsViewPrivate::itemUpdated(QGraphicsItem *item, const QRectF &rect)
{
    if (fullUpdatePending || viewportUpdateMode == QGraphicsView::NoViewportUpdate)
        return;
    if (item->d_ptr->dirty)
        updateLater();

    QRectF updateRect = rect;
    if ((item->d_ptr->flags & QGraphicsItem::ItemClipsChildrenToShape) || item->d_ptr->children.isEmpty()) {
        updateRect &= adjustedItemBoundingRect(item);
        if (updateRect.isEmpty())
            return;
    }

    QGraphicsItem *clipItem = item;
    if (item->d_ptr->ancestorFlags & QGraphicsItemPrivate::AncestorClipsChildren) {
        // Minimize unnecessary redraw.
        QGraphicsItem *parent = item;
        while ((parent = parent->d_ptr->parent)) {
            if (parent->d_ptr->flags & QGraphicsItem::ItemClipsChildrenToShape) {
                // Map update rect to the current parent and itersect with its bounding rect.
                updateRect = clipItem->itemTransform(parent).mapRect(updateRect)
                             & adjustedItemBoundingRect(parent);
                if (updateRect.isEmpty())
                    return;
                clipItem = parent;
            }

            if (!(parent->d_ptr->ancestorFlags & QGraphicsItemPrivate::AncestorClipsChildren))
                break;
        }
    }

    // Map update rect from clipItem coordinates to view coordinates.
    Q_ASSERT(clipItem);
    if (!item->d_ptr->hasBoundingRegionGranularity)
        this->updateRect(mapToViewRect(clipItem, updateRect) & viewport->rect());
    else
        updateRegion(mapToViewRegion(clipItem, updateRect) & viewport->rect());
}

void QGraphicsViewPrivate::updateLater()
{
    Q_Q(QGraphicsView);
    if (updatingLater)
        return;
    updatingLater = true;
    QMetaObject::invokeMethod(q, "_q_updateLaterSlot", Qt::QueuedConnection);
}

void QGraphicsViewPrivate::_q_updateLaterSlot()
{
    Q_Q(QGraphicsView);
    if (!scene)
        return;

    QRect vr = viewport->rect();
    QTransform viewTransform = q->viewportTransform();
    const QList<QGraphicsItem *> &dirtyItems = scene->d_func()->dirtyItems;
    for (int i = 0; i < dirtyItems.size(); ++i) {
        const QGraphicsItem *item = dirtyItems.at(i);
        if (item->d_ptr->discardUpdateRequest(/*ignoreClipping=*/false,
                                              /*ignoreVisibleBit=*/false,
                                              /*ignoreDirtyBit=*/true)) {
            continue;
        }
        QTransform x = item->sceneTransform() * viewTransform;
        updateRect(x.mapRect(item->boundingRect()).toAlignedRect() & vr);
    }

    dirtyRectCount += dirtyRects.size();

    bool noUpdate = !fullUpdatePending && viewportUpdateMode == QGraphicsView::FullViewportUpdate;
    if ((dirtyRectCount > 0 || !dirtyBoundingRect.isEmpty()) && !fullUpdatePending && !noUpdate) {
        if (viewportUpdateMode == QGraphicsView::BoundingRectViewportUpdate
            || (viewportUpdateMode == QGraphicsView::SmartViewportUpdate
                && dirtyRectCount >= QGRAPHICSVIEW_REGION_RECT_THRESHOLD)) {
            if (!(optimizationFlags & QGraphicsView::DontAdjustForAntialiasing)) {
                viewport->update(dirtyBoundingRect.adjusted(-2, -2, 2, 2));
            } else {
                viewport->update(dirtyBoundingRect);
            }
        } else {
            // ### Improve this block, which is very slow for complex regions. We
            // need to strike the balance between having an accurate update
            // region, and running fast. The below approach is the simplest way to
            // create a region from a bunch of rects, but we might want to use
            // other approaches; e.g., a grid of a fixed size representing
            // quadrants of the viewport, which we mark as dirty depending on the
            // rectangles in the list. Perhaps this should go into a
            // QRegion::fromRects(rects, how) function.
            QRegion region;
            if (!(optimizationFlags & QGraphicsView::DontAdjustForAntialiasing)) {
                for (int i = 0; i < dirtyRegions.size(); ++i) {
                    QVector<QRect> rects = dirtyRegions.at(i).rects();
                    for (int j = 0; j < rects.size(); ++j)
                        region += rects.at(j).adjusted(-2, -2, 2, 2);
                }
                for (int i = 0; i < dirtyRects.size(); ++i)
                    region += dirtyRects.at(i).adjusted(-2, -2, 2, 2);
            } else {
                for (int i = 0; i < dirtyRegions.size(); ++i)
                    region += dirtyRegions.at(i);
                for (int i = 0; i < dirtyRects.size(); ++i)
                    region += dirtyRects.at(i);
            }

            viewport->update(region);
        }
    }

    dirtyRegions.clear();
    dirtyRects.clear();
    dirtyRectCount = 0;
    dirtyBoundingRect = QRect();
    updatingLater = false;
}

void QGraphicsViewPrivate::updateAll()
{
    Q_Q(QGraphicsView);
    q->viewport()->update();
    fullUpdatePending = true;
    dirtyRectCount = 0;
    dirtyBoundingRect = QRect();
    updatingLater = false;
}

void QGraphicsViewPrivate::updateRegion(const QRegion &r)
{
    if (r.isEmpty())
        return;

    Q_Q(QGraphicsView);

    // Rect intersects viewport - update everything?
    switch (viewportUpdateMode) {
    case QGraphicsView::FullViewportUpdate:
        fullUpdatePending = true;
        q->viewport()->update();
        break;
    case QGraphicsView::BoundingRectViewportUpdate:
        dirtyBoundingRect |= r.boundingRect();
        if (dirtyBoundingRect == q->viewport()->rect()) {
            fullUpdatePending = true;
            q->viewport()->update();
        } else {
            updateLater();
        }
        break;
    case QGraphicsView::SmartViewportUpdate:
        dirtyBoundingRect |= r.boundingRect();
        if ((dirtyRectCount + r.numRects()) < QGRAPHICSVIEW_REGION_RECT_THRESHOLD)
            dirtyRegions << r;
        dirtyRectCount += r.numRects();
        updateLater();
        break;
    case QGraphicsView::MinimalViewportUpdate:
        dirtyRegions << r;
        dirtyRectCount += r.numRects();
        updateLater();
        break;
    case QGraphicsView::NoViewportUpdate:
        // Unreachable
        break;
    }

    // Compress the regions...
    if (dirtyRectCount > QGRAPHICSVIEW_REGION_RECT_THRESHOLD && dirtyRegions.size() > 1) {
        QRegion masterRegion;
        for (int i=0; i<dirtyRegions.size(); ++i) {
            masterRegion |= dirtyRegions.at(i);
        }
        dirtyRectCount = masterRegion.numRects();
        dirtyRegions.clear();
        dirtyRegions << masterRegion;
    }
}

void QGraphicsViewPrivate::updateRect(const QRect &r)
{
    if (r.isEmpty())
        return;

    Q_Q(QGraphicsView);

    // Rect intersects viewport - update everything?
    switch (viewportUpdateMode) {
    case QGraphicsView::FullViewportUpdate:
        fullUpdatePending = true;
        q->viewport()->update();
        break;
    case QGraphicsView::BoundingRectViewportUpdate:
        dirtyBoundingRect |= r;
        if (dirtyBoundingRect == q->viewport()->rect()) {
            fullUpdatePending = true;
            q->viewport()->update();
        } else {
            updateLater();
        }
        break;
    case QGraphicsView::SmartViewportUpdate:
        dirtyBoundingRect |= r;
        if ((dirtyRectCount + dirtyRects.size()) < QGRAPHICSVIEW_REGION_RECT_THRESHOLD)
            dirtyRects << r;
        updateLater();
        break;
    case QGraphicsView::MinimalViewportUpdate:
        dirtyRects << r;
        updateLater();
        break;
    case QGraphicsView::NoViewportUpdate:
        // Unreachable
        break;
    }
}

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
{
    Q_Q(const QGraphicsView);
    const QPainterPath exposedPath(qt_regionToPath(exposedRegion));
    const QPainterPath exposedScenePath(q->mapToScene(exposedPath));

    if (exposedScenePath.contains(scene->d_func()->growingItemsBoundingRect)) {
        Q_ASSERT(allItems);
        *allItems = true;

        // All items are guaranteed within the exposed region, don't bother using the index.
        QList<QGraphicsItem *> itemList(scene->items());
        int i = 0;
        while (i < itemList.size()) {
            // But we only want to include items that are visible
            if (!itemList.at(i)->isVisible())
                itemList.removeAt(i);
            else
                ++i;
        }

        // Sort the items.
        QGraphicsScenePrivate::sortItems(&itemList, Qt::DescendingOrder, scene->d_func()->sortCacheEnabled);
        return itemList;
    }

    if (scene->d_func()->largestUntransformableItem.isNull()) {
        if (exposedRegion.numRects() == 1 && matrix.type() <= QTransform::TxScale) {
            return scene->d_func()->items_helper(exposedScenePath.controlPointRect(),
                                                 Qt::IntersectsItemBoundingRect,
                                                 Qt::DescendingOrder);
        }
        return scene->d_func()->items_helper(exposedScenePath,
                                             Qt::IntersectsItemBoundingRect,
                                             Qt::DescendingOrder);
    }

    // NB! Path must be in viewport coordinates.
    return itemsInArea(exposedPath, Qt::IntersectsItemBoundingRect, Qt::DescendingOrder);
}

void QGraphicsViewPrivate::generateStyleOptions(const QList<QGraphicsItem *> &itemList,
                                                QGraphicsItem **itemArray,
                                                QStyleOptionGraphicsItem *styleOptionArray,
                                                const QTransform &worldTransform,
                                                bool allItems,
                                                const QRegion &exposedRegion) const
{
    // Two unit vectors.
    QLineF v1(0, 0, 1, 0);
    QLineF v2(0, 0, 0, 1);
    QTransform itemToViewportTransform;
    QRectF brect;
    QTransform reverseMap;

    for (int i = 0; i < itemList.size(); ++i) {
        QGraphicsItem *item = itemArray[i] = itemList[i];

        QStyleOptionGraphicsItem &option = styleOptionArray[i];
        brect = item->boundingRect();
        option.state = QStyle::State_None;
        option.rect = brect.toRect();
        option.exposedRect = QRectF();
        if (item->d_ptr->selected)
            option.state |= QStyle::State_Selected;
        if (item->d_ptr->enabled)
            option.state |= QStyle::State_Enabled;
        if (item->hasFocus())
            option.state |= QStyle::State_HasFocus;
        if (scene->d_func()->hoverItems.contains(item))
            option.state |= QStyle::State_MouseOver;
        if (item == scene->mouseGrabberItem())
            option.state |= QStyle::State_Sunken;

        // Calculate a simple level-of-detail metric.
        // ### almost identical code in QGraphicsScene::render()
        //     and QGraphicsView::render() - consider refactoring
        if (item->d_ptr->itemIsUntransformable()) {
            itemToViewportTransform = item->deviceTransform(worldTransform);
        } else {
            itemToViewportTransform = item->sceneTransform() * worldTransform;
        }

        if (itemToViewportTransform.type() <= QTransform::TxTranslate) {
            // Translation and rotation only? The LOD is 1.
            option.levelOfDetail = 1;
        } else {
            // LOD is the transformed area of a 1x1 rectangle.
            option.levelOfDetail = qSqrt(itemToViewportTransform.map(v1).length() * itemToViewportTransform.map(v2).length());
        }
        option.matrix = itemToViewportTransform.toAffine(); //### discards perspective

        if (!allItems) {
            // Determine the item's exposed area
            reverseMap = itemToViewportTransform.inverted();
            foreach (const QRect &rect, exposedRegion.rects()) {
                option.exposedRect |= reverseMap.mapRect(QRectF(rect.adjusted(-1, -1, 1, 1)));
                if (option.exposedRect.contains(brect))
                    break;
            }
            option.exposedRect &= brect;
        } else {
            // The whole item is exposed
            option.exposedRect = brect;
        }
    }
}

/*!
    Constructs a QGraphicsView. \a parent is passed to QWidget's constructor.
*/
QGraphicsView::QGraphicsView(QWidget *parent)
    : QAbstractScrollArea(*new QGraphicsViewPrivate, parent)
{
    setViewport(0);
    setAcceptDrops(true);
    setBackgroundRole(QPalette::Base);

    // ### Ideally this would be enabled/disabled depending on whether any
    // widgets in the current scene enabled input methods. We could do that
    // using a simple reference count. The same goes for acceptDrops and mouse
    // tracking.
    setAttribute(Qt::WA_InputMethodEnabled);
}

/*!
    Constructs a QGraphicsView and sets the visualized scene to \a
    scene. \a parent is passed to QWidget's constructor.
*/
QGraphicsView::QGraphicsView(QGraphicsScene *scene, QWidget *parent)
    : QAbstractScrollArea(*new QGraphicsViewPrivate, parent)
{
    setScene(scene);
    setViewport(0);
    setAcceptDrops(true);
    setBackgroundRole(QPalette::Base);
    setAttribute(Qt::WA_InputMethodEnabled);
}

/*!
  \internal
 */
QGraphicsView::QGraphicsView(QGraphicsViewPrivate &dd, QWidget *parent)
  : QAbstractScrollArea(dd, parent)
{
    setViewport(0);
    setAcceptDrops(true);
    setBackgroundRole(QPalette::Base);
    setAttribute(Qt::WA_InputMethodEnabled);
}

/*!
    Destructs the QGraphicsView object.
*/
QGraphicsView::~QGraphicsView()
{
    Q_D(QGraphicsView);
    if (d->scene)
        d->scene->d_func()->views.removeAll(this);
    delete d->lastDragDropEvent;
}

/*!
    \reimp
*/
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 * QApplication::desktop()->size()) / 4).toSize();
    }
    return QAbstractScrollArea::sizeHint();
}

/*!
    \property QGraphicsView::renderHints
    \brief the default render hints for the view

    These hints are
    used to initialize QPainter before each visible item is drawn. QPainter
    uses render hints to toggle rendering features such as antialiasing and
    smooth pixmap transformation.

    QPainter::TextAntialiasing is enabled by default.

    Example:

    \snippet doc/src/snippets/code/src_gui_graphicsview_qgraphicsview.cpp 1
*/
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;
    viewport()->update();
}

/*!
    If \a enabled is true, the render hint \a hint is enabled; otherwise it
    is disabled.

    \sa renderHints
*/
void QGraphicsView::setRenderHint(QPainter::RenderHint hint, bool enabled)
{
    Q_D(QGraphicsView);
    QPainter::RenderHints oldHints = d->renderHints;
    if (enabled)
        d->renderHints |= hint;
    else
        d->renderHints &= ~hint;
    if (oldHints != d->renderHints)
        viewport()->update();
}

/*!
    \property QGraphicsView::alignment
    \brief the alignment of the scene in the view when the whole
    scene is visible.

    If the whole scene is visible in the view, (i.e., there are no visible
    scroll bars,) the view's alignment will decide where the scene will be
    rendered in the view. For example, if the alignment is Qt::AlignCenter,
    which is default, the scene will be centered in the view, and if the
    alignment is (Qt::AlignLeft | Qt::AlignTop), the scene will be rendered in
    the top-left corner of the view.
*/
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();
    }
}

/*!
    \property QGraphicsView::transformationAnchor
    \brief how the view should position the scene during transformations.

    QGraphicsView uses this property to decide how to position the scene in
    the viewport when the transformation matrix changes, and the coordinate
    system of the view is transformed. The default behavior, AnchorViewCenter,
    ensures that the scene point at the center of the view remains unchanged
    during transformations (e.g., when rotating, the scene will appear to
    rotate around the center of the view).

    Note that the effect of this property is noticeable when only a part of the
    scene is visible (i.e., when there are scroll bars). Otherwise, if the
    whole scene fits in the view, QGraphicsScene uses the view \l alignment to
    position the scene in the view.

    \sa alignment, resizeAnchor
*/
QGraphicsView::ViewportAnchor QGraphicsView::transformationAnchor() const
{
    Q_D(const QGraphicsView);
    return d->transformationAnchor;
}
void QGraphicsView::setTransformationAnchor(ViewportAnchor anchor)
{
    Q_D(QGraphicsView);
    d->transformationAnchor = anchor;
}

/*!
    \property QGraphicsView::resizeAnchor
    \brief how the view should position the scene when the view is resized.

    QGraphicsView uses this property to decide how to position the scene in
    the viewport when the viewport widget's size changes. The default
    behavior, NoAnchor, leaves the scene's position unchanged during a resize;
    the top-left corner of the view will appear to be anchored while resizing.

    Note that the effect of this property is noticeable when only a part of the
    scene is visible (i.e., when there are scroll bars). Otherwise, if the
    whole scene fits in the view, QGraphicsScene uses the view \l alignment to
    position the scene in the view.

    \sa alignment, transformationAnchor, Qt::WNorthWestGravity
*/
QGraphicsView::ViewportAnchor QGraphicsView::resizeAnchor() const
{
    Q_D(const QGraphicsView);
    return d->resizeAnchor;
}
void QGraphicsView::setResizeAnchor(ViewportAnchor anchor)
{
    Q_D(QGraphicsView);
    d->resizeAnchor = anchor;
}

/*!
    \property QGraphicsView::viewportUpdateMode
    \brief how the viewport should update its contents.

    \since 4.3

    QGraphicsView uses this property to decide how to update areas of the
    scene that have been reexposed or changed. Usually you do not need to
    modify this property, but there are some cases where doing so can improve
    rendering performance. See the ViewportUpdateMode documentation for
    specific details.

    The default value is MinimalViewportUpdate, where QGraphicsView will
    update as small an area of the viewport as possible when the contents
    change.

    \sa ViewportUpdateMode, cacheMode
*/
QGraphicsView::ViewportUpdateMode QGraphicsView::viewportUpdateMode() const
{
    Q_D(const QGraphicsView);
    return d->viewportUpdateMode;
}
void QGraphicsView::setViewportUpdateMode(ViewportUpdateMode mode)
{
    Q_D(QGraphicsView);
    d->viewportUpdateMode = mode;
}

/*!
    \property QGraphicsView::optimizationFlags
    \brief flags that can be used to tune QGraphicsView's performance.

    \since 4.3

    QGraphicsView uses clipping, extra bounding rect adjustments, and certain
    other aids to improve rendering quality and performance for the common
    case graphics scene. However, depending on the target platform, the scene,
    and the viewport in use, some of these operations can degrade performance.

    The effect varies from flag to flag; see the OptimizationFlags
    documentation for details.

    By default, no optimization flags are enabled.

    \sa setOptimizationFlag()
*/
QGraphicsView::OptimizationFlags QGraphicsView::optimizationFlags() const
{
    Q_D(const QGraphicsView);
    return d->optimizationFlags;
}
void QGraphicsView::setOptimizationFlags(OptimizationFlags flags)
{
    Q_D(QGraphicsView);
    d->optimizationFlags = flags;
}

/*!
    Enables \a flag if \a enabled is true; otherwise disables \a flag.

    \sa optimizationFlags
*/
void QGraphicsView::setOptimizationFlag(OptimizationFlag flag, bool enabled)
{
    Q_D(QGraphicsView);
    if (enabled)
        d->optimizationFlags |= flag;
    else
        d->optimizationFlags &= ~flag;
}

/*!
    \property QGraphicsView::dragMode
    \brief the behavior for dragging the mouse over the scene while
    the left mouse button is pressed.

    This property defines what should happen when the user clicks on the scene
    background and drags the mouse (e.g., scrolling the viewport contents
    using a pointing hand cursor, or selecting multiple items with a rubber
    band). The default value, NoDrag, does nothing.

    This behavior only affects mouse clicks that are not handled by any item.
    You can define a custom behavior by creating a subclass of QGraphicsView
    and reimplementing mouseMoveEvent().
*/
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;

#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
}

#ifndef QT_NO_RUBBERBAND
/*!
    \property QGraphicsView::rubberBandSelectionMode
    \brief the behavior for selecting items with a rubber band selection rectangle.
    \since 4.3

    This property defines how items are selected when using the RubberBandDrag
    drag mode.

    The default value is Qt::IntersectsItemShape; all items whose shape
    intersects with or is contained by the rubber band are selected.

    \sa dragMode, items()
*/
Qt::ItemSelectionMode QGraphicsView::rubberBandSelectionMode() const
{
    Q_D(const QGraphicsView);
    return d->rubberBandSelectionMode;
}
void QGraphicsView::setRubberBandSelectionMode(Qt::ItemSelectionMode mode)
{
    Q_D(QGraphicsView);
    d->rubberBandSelectionMode = mode;
}
#endif

/*!
    \property QGraphicsView::cacheMode
    \brief which parts of the view are cached

    QGraphicsView can cache pre-rendered content in a QPixmap, which is then
    drawn onto the viewport. The purpose of such caching is to speed up the
    total rendering time for areas that are slow to render.  Texture, gradient
    and alpha blended backgrounds, for example, can be notibly slow to render;
    especially with a transformed view. The CacheBackground flag enables
    caching of the view's background. For example:

    \snippet doc/src/snippets/code/src_gui_graphicsview_qgraphicsview.cpp 2

    The cache is invalidated every time the view is transformed. However, when
    scrolling, only partial invalidation is required.

    By default, nothing is cached.

    \sa resetCachedContent(), QPixmapCache
*/
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();
}

/*!
    Resets any cached content. Calling this function will clear
    QGraphicsView's cache. If the current cache mode is \l CacheNone, this
    function does nothing.

    This function is called automatically for you when the backgroundBrush or
    QGraphicsScene::backgroundBrush properties change; you only need to call
    this function if you have reimplemented QGraphicsScene::drawBackground()
    or QGraphicsView::drawBackground() to draw a custom background, and need
    to trigger a full redraw.

    \sa cacheMode()
*/
void QGraphicsView::resetCachedContent()
{
    Q_D(QGraphicsView);
    if (d->cacheMode == CacheNone)
        return;

    if (d->cacheMode & CacheBackground) {
        // Background caching is enabled.
        d->mustResizeBackgroundPixmap = true;
        viewport()->update();
    } else if (d->mustResizeBackgroundPixmap) {
        // Background caching is disabled.
        // Cleanup, free some resources.
        d->mustResizeBackgroundPixmap = false;
        d->backgroundPixmap = QPixmap();
        d->backgroundPixmapExposed = QRegion();
    }
}

/*!
    Invalidates and schedules a redraw of \a layers inside \a rect. \a rect is
    in scene coordinates. Any cached content for \a layers inside \a rect is
    unconditionally invalidated and redrawn.

    You can call this function to notify QGraphicsView of changes to the
    background or the foreground of the scene. It is commonly used for scenes
    with tile-based backgrounds to notify changes when QGraphicsView has
    enabled background caching.

    Note that QGraphicsView currently supports background caching only (see
    QGraphicsView::CacheBackground). This function is equivalent to calling update() if any
    layer but QGraphicsScene::BackgroundLayer is passed.

    \sa QGraphicsScene::invalidate(), update()
*/
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);
        }
    }
}

/*!
    \property QGraphicsView::interactive
    \brief whether the view allowed scene interaction.

    If enabled, this view is set to allow scene interaction. Otherwise, this
    view will not allow interaction, and any mouse or key events are ignored
    (i.e., it will act as a read-only view).

    By default, this property is true.
*/
bool QGraphicsView::isInteractive() const
{
    Q_D(const QGraphicsView);
    return d->sceneInteractionAllowed;
}
void QGraphicsView::setInteractive(bool allowed)
{
    Q_D(QGraphicsView);
    d->sceneInteractionAllowed = allowed;
}

/*!
    Returns a pointer to the scene that is currently visualized in the
    view. If no scene is currently visualized, 0 is returned.

    \sa setScene()
*/
QGraphicsScene *QGraphicsView::scene() const
{
    Q_D(const QGraphicsView);
    return d->scene;
}

/*!
    Sets the current scene to \a scene. If \a scene is already being
    viewed, this function does nothing.

    When a scene is set on a view, the QGraphicsScene::changed() signal
    is automatically connected to this view's updateScene() slot, and the
    view's scroll bars are adjusted to fit the size of the scene.
*/
void QGraphicsView::setScene(QGraphicsScene *scene)
{
    Q_D(QGraphicsView);
    if (d->scene == scene)
        return;

    // Always update the viewport when the scene changes.
    viewport()->update();

    // 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()->views.removeAll(this);
    }

    // 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()->views << this;
        d->recalculateContentSize();
        d->lastCenterPoint = sceneRect().center();
        d->keepLastCenterPoint = true;
    } else {
        d->recalculateContentSize();
    }
}

/*!
    \property QGraphicsView::sceneRect
    \brief the area of the scene visualized by this view.

    The scene rectangle defines the extent of the scene, and in the view's case,
    this means the area of the scene that you can navigate using the scroll
    bars.

    If unset, or if a null QRectF is set, this property has the same value as
    QGraphicsScene::sceneRect, and it changes with
    QGraphicsScene::sceneRect. Otherwise, the view's scene rect is unaffected
    by the scene.

    Note that, although the scene supports a virtually unlimited size, the
    range of the scroll bars will never exceed the range of an integer
    (INT_MIN, INT_MAX). When the scene is larger than the scroll bars' values,
    you can choose to use translate() to navigate the scene instead.

    By default, this property contains a rectangle at the origin with zero
    width and height.

    \sa QGraphicsScene::sceneRect
*/
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();
}

/*!
    Returns the current transformation matrix for the view. If no current
    transformation is set, the identity matrix is returned.

    \sa setMatrix(), rotate(), scale(), shear(), translate()
*/
QMatrix QGraphicsView::matrix() const
{
    Q_D(const QGraphicsView);
    return d->matrix.toAffine();
}

/*!
    Sets the view's current transformation matrix to \a matrix.

    If \a combine is true, then \a matrix is combined with the current matrix;
    otherwise, \a matrix \e replaces the current matrix. \a combine is false
    by default.

    The transformation matrix tranforms the scene into view coordinates. Using
    the default transformation, provided by the identity matrix, one pixel in
    the view represents one unit in the scene (e.g., a 10x10 rectangular item
    is drawn using 10x10 pixels in the view). If a 2x2 scaling matrix is
    applied, the scene will be drawn in 1:2 (e.g., a 10x10 rectangular item is
    then drawn using 20x20 pixels in the view).

    Example:

    \snippet doc/src/snippets/code/src_gui_graphicsview_qgraphicsview.cpp 3

    To simplify interation with items using a transformed view, QGraphicsView
    provides mapTo... and mapFrom... functions that can translate between
    scene and view coordinates. For example, you can call mapToScene() to map
    a view coordinate to a floating point scene coordinate, or mapFromScene()
    to map from floating point scene coordinates to view coordinates.

    \sa matrix(), rotate(), scale(), shear(), translate()
*/
void QGraphicsView::setMatrix(const QMatrix &matrix, bool combine)
{
    setTransform(QTransform(matrix), combine);
}

/*!
    Resets the view transformation matrix to the identity matrix.
*/
void QGraphicsView::resetMatrix()
{
    resetTransform();
}

/*!
    Rotates the current view transformation \a angle degrees clockwise.

    \sa setMatrix(), matrix(), scale(), shear(), translate()
*/
void QGraphicsView::rotate(qreal angle)
{
    Q_D(QGraphicsView);
    QTransform matrix = d->matrix;
    matrix.rotate(angle);
    setTransform(matrix);
}

/*!
    Scales the current view transformation by (\a sx, \a sy).

    \sa setMatrix(), matrix(), rotate(), shear(), translate()
*/
void QGraphicsView::scale(qreal sx, qreal sy)
{
    Q_D(QGraphicsView);
    QTransform matrix = d->matrix;
    matrix.scale(sx, sy);
    setTransform(matrix);
}

/*!
    Shears the current view transformation by (\a sh, \a sv).

    \sa setMatrix(), matrix(), rotate(), scale(), translate()
*/
void QGraphicsView::shear(qreal sh, qreal sv)
{
    Q_D(QGraphicsView);
    QTransform matrix = d->matrix;
    matrix.shear(sh, sv);
    setTransform(matrix);
}

/*!
    Translates the current view transformation by (\a dx, \a dy).

    \sa setMatrix(), matrix(), rotate(), shear()
*/
void QGraphicsView::translate(qreal dx, qreal dy)
{
    Q_D(QGraphicsView);
    QTransform matrix = d->matrix;
    matrix.translate(dx, dy);
    setTransform(matrix);
}

/*!
    Scrolls the contents of the viewport to ensure that the scene
    coordinate \a pos, is centered in the view.

    Because \a pos is a floating point coordinate, and the scroll bars operate
    on integer coordinates, the centering is only an approximation.

    \note If the item is close to or outside the border, it will be visible
    in the view, but not centered.

    \sa ensureVisible()
*/
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;
}

/*!
    \fn QGraphicsView::centerOn(qreal x, qreal y)
    \overload

    This function is provided for convenience. It's equivalent to calling
    centerOn(QPointF(\a x, \a y)).
*/

/*!
    \overload

    Scrolls the contents of the viewport to ensure that \a item
    is centered in the view.

    \sa ensureVisible()
*/
void QGraphicsView::centerOn(const QGraphicsItem *item)
{
    centerOn(item->sceneBoundingRect().center());
}

/*!
    Scrolls the contents of the viewport so that the scene rectangle \a rect
    is visible, with margins specified in pixels by \a xmargin and \a
    ymargin. If the specified rect cannot be reached, the contents are
    scrolled to the nearest valid position. The default value for both margins
    is 50 pixels.

    \sa centerOn()
*/
void QGraphicsView::ensureVisible(const QRectF &rect, int xmargin, int ymargin)
{
    Q_D(QGraphicsView);
    Q_UNUSED(xmargin);
    Q_UNUSED(ymargin);
    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