qgraphicsscene.cpp

奇趣公司比较新的qt/emd版本

    Returns the topmost visible item at the specified \a position, or 0 if
    there are no items at this position.

    \sa items(), collidingItems()
*/
QGraphicsItem *QGraphicsScene::itemAt(const QPointF &pos) const
{
    QList<QGraphicsItem *> itemsAtPoint = items(pos);
    return itemsAtPoint.isEmpty() ? 0 : itemsAtPoint.first();
}

/*!
    \fn QGraphicsScene::itemAt(qreal x, qreal y) const
    \overload

    Returns the topmost item at the position specified by (\a x, \a
    y), or 0 if there are no items at this position.

    This convenience function is equivalent to calling \c
    {itemAt(QPointF(x, y))}.
*/

/*!
    Returns a list of all currently selected items. The items are
    returned in no particular order.

    \sa setSelectionArea()
*/
QList<QGraphicsItem *> QGraphicsScene::selectedItems() const
{
    Q_D(const QGraphicsScene);

    // Optimization: Lazily removes items that are not selected.
    QGraphicsScene *that = const_cast<QGraphicsScene *>(this);
    QSet<QGraphicsItem *> actuallySelectedSet;
    foreach (QGraphicsItem *item, that->d_func()->selectedItems) {
        if (item->isSelected())
            actuallySelectedSet << item;
    }

    that->d_func()->selectedItems = actuallySelectedSet;

    return d->selectedItems.values();
}

/*!
    Returns the selection area that was previously set with
    setSelectionArea(), or an empty QPainterPath if no selection area has been
    set.

    \sa setSelectionArea()
*/
QPainterPath QGraphicsScene::selectionArea() const
{
    Q_D(const QGraphicsScene);
    return d->selectionArea;
}

/*!
    Sets the selection area to \a path. All items within this area are
    immediately selected, and all items outside are unselected. You can get
    the list of all selected items by calling selectedItems().

    For an item to be selected, it must be marked as \e selectable
    (QGraphicsItem::ItemIsSelectable).

    \sa clearSelection(), selectionArea()
*/
void QGraphicsScene::setSelectionArea(const QPainterPath &path)
{
    setSelectionArea(path, Qt::IntersectsItemShape);
}

/*!
    \overload
    \since 4.3

    Sets the selection area to \a path using \a mode to determine if items are
    included in the selection area.

    \sa clearSelection(), selectionArea()
*/
void QGraphicsScene::setSelectionArea(const QPainterPath &path, Qt::ItemSelectionMode mode)
{
    Q_D(QGraphicsScene);

    // Note: with boolean path operations, we can improve performance here
    // quite a lot by "growing" the old path instead of replacing it. That
    // allows us to only check the intersect area for changes, instead of
    // reevaluating the whole path over again.
    d->selectionArea = path;

    QSet<QGraphicsItem *> unselectItems = d->selectedItems;

    // Disable emitting selectionChanged() for individual items.
    ++d->selectionChanging;
    bool changed = false;

    // Set all items in path to selected.
    foreach (QGraphicsItem *item, items(path, mode)) {
        if (item->flags() & QGraphicsItem::ItemIsSelectable) {
            if (!item->isSelected())
                changed = true;
            unselectItems.remove(item);
            item->setSelected(true);
        }
    }

    // Unselect all items outside path.
    foreach (QGraphicsItem *item, unselectItems) {
        item->setSelected(false);
        changed = true;
    }

    // Reenable emitting selectionChanged() for individual items.
    --d->selectionChanging;

    if (!d->selectionChanging && changed)
        emit selectionChanged();
}

/*!
   Clears the current selection.

   \sa setSelectionArea(), selectedItems()
*/
void QGraphicsScene::clearSelection()
{
    Q_D(QGraphicsScene);

    // Disable emitting selectionChanged
    ++d->selectionChanging;
    bool changed = !d->selectedItems.isEmpty();

    foreach (QGraphicsItem *item, d->selectedItems)
        item->setSelected(false);
    d->selectedItems.clear();

    // Reenable emitting selectionChanged() for individual items.
    --d->selectionChanging;

    if (!d->selectionChanging && changed)
        emit selectionChanged();
}

/*!
    Groups all items in \a items into a new QGraphicsItemGroup, and returns a
    pointer to the group. The group is created with the common ancestor of \a
    items as its parent, and with position (0, 0). The items are all
    reparented to the group, and their positions and transformations are
    mapped to the group. If \a items is empty, this function will return an
    empty top-level QGraphicsItemGroup.

    QGraphicsScene has ownership of the group item; you do not need to delete
    it. To dismantle (ungroup) a group, call destroyItemGroup().

    \sa destroyItemGroup(), QGraphicsItemGroup::addToGroup()
*/
QGraphicsItemGroup *QGraphicsScene::createItemGroup(const QList<QGraphicsItem *> &items)
{
    // Build a list of the first item's ancestors
    QList<QGraphicsItem *> ancestors;
    int n = 0;
    if (!items.isEmpty()) {
        QGraphicsItem *parent = items.at(n++);
        while ((parent = parent->parentItem()))
            ancestors.append(parent);
    }

    // Find the common ancestor for all items
    QGraphicsItem *commonAncestor = 0;
    if (!ancestors.isEmpty()) {
        while (n < items.size()) {
            int commonIndex = -1;
            QGraphicsItem *parent = items.at(n++);
            do {
                int index = ancestors.indexOf(parent, qMax(0, commonIndex));
                if (index != -1) {
                    commonIndex = index;
                    break;
                }
            } while ((parent = parent->parentItem()));

            if (commonIndex == -1) {
                commonAncestor = 0;
                break;
            }

            commonAncestor = ancestors.at(commonIndex);
        }
    }

    // Create a new group at that level
    QGraphicsItemGroup *group = new QGraphicsItemGroup(commonAncestor);
    if (!commonAncestor)
        addItem(group);
    foreach (QGraphicsItem *item, items)
        group->addToGroup(item);
    return group;
}

/*!
    Reparents all items in \a group to \a group's parent item, then removes \a
    group from the scene, and finally deletes it. The items' positions and
    transformations are mapped from the group to the group's parent.

    \sa createItemGroup(), QGraphicsItemGroup::removeFromGroup()
*/
void QGraphicsScene::destroyItemGroup(QGraphicsItemGroup *group)
{
    foreach (QGraphicsItem *item, group->children())
        group->removeFromGroup(item);
    removeItem(group);
    delete group;
}

/*!
    Adds or moves the item \a item and all its childen to the scene.

    If the item is visible (i.e., QGraphicsItem::isVisible() returns
    true), QGraphicsScene will emit changed() once control goes back
    to the event loop.

    If the item is already in a different scene, it will first be removed from
    its old scene, and then added to this scene as a top-level.

    \sa removeItem(), addEllipse(), addLine(), addPath(), addPixmap(),
    addRect(), addText()
*/
void QGraphicsScene::addItem(QGraphicsItem *item)
{
    Q_D(QGraphicsScene);
    if (!item) {
        qWarning("QGraphicsScene::addItem: cannot add null item");
        return;
    }
    if (item->scene() == this) {
        qWarning("QGraphicsScene::addItem: item has already been added to this scene");
        return;
    }

    // Prevent reusing a recently deleted pointer: purge all removed items
    // from our lists.
    d->purgeRemovedItems();

    // Remove this item from its existing scene
    if (item->d_func()->scene)
        item->d_func()->scene->removeItem(item);

    // Detach this item from its parent if the parent's scene is different
    // from this scene.
    if (QGraphicsItem *itemParent = item->parentItem()) {
        if (itemParent->scene() != this) {
            QVariant variant;
            qVariantSetValue<QGraphicsItem *>(variant, item);
            itemParent->itemChange(QGraphicsItem::ItemChildRemovedChange, variant);
            itemParent->d_func()->children.removeAll(item);
            item->d_func()->parent = 0;
        }
    }

    // Add the item to this scene
    item->d_func()->scene = qVariantValue<QGraphicsScene *>(item->itemChange(QGraphicsItem::ItemSceneChange,
                                                                             qVariantFromValue<QGraphicsScene *>(this)));
    if (d->indexMethod != QGraphicsScene::NoIndex) {
        // Indexing requires sceneBoundingRect(), but because \a item might
        // not be completely constructed at this point, we need to store it in
        // a temporary list and schedule an indexing for later.
        d->unindexedItems << item;
        item->d_func()->index = -1;
        d->startIndexTimer();
    } else {
        // No index: We can insert the item directly.
        if (!d->freeItemIndexes.isEmpty()) {
            int newIndex = d->freeItemIndexes.takeLast();
            Q_ASSERT_X(d->indexedItems[newIndex] == 0, "QGraphicsItem::addItem",
                       "An index marked as free was still occupied");
            d->indexedItems[newIndex] = item;
            item->d_func()->index = newIndex;
        } else {
            item->d_func()->index = d->indexedItems.size();
            d->indexedItems << item;
        }
    }

    // Add to list of items that require an update. We cannot assume that the
    // item is fully constructed, so calling item->update() can lead to a pure
    // virtual function call to boundingRect().
    if (!d->updateAll) {
        if (d->pendingUpdateItems.isEmpty())
            QTimer::singleShot(0, this, SLOT(_q_updateLater()));
        d->pendingUpdateItems << item;
    }

    // Disable selectionChanged() for individual items
    ++d->selectionChanging;
    int oldSelectedItemSize = d->selectedItems.size();

    // Update selection lists
    if (item->isSelected())
        d->selectedItems << item;

    // Add all children recursively
    foreach (QGraphicsItem *child, item->children())
        addItem(child);

    // Reenable selectionChanged() for individual items
    --d->selectionChanging;
    if (!d->selectionChanging && d->selectedItems.size() != oldSelectedItemSize)
        emit selectionChanged();
}

/*!
    Creates and adds an ellipse item to the scene, and returns the item
    pointer. The geometry of the ellipse is defined by \a rect, and it's pen
    and brush are initialized to \a pen and \a brush.

    Note that the item's geometry is provided in item coordinates, and its
    position is initialized to (0, 0).

    If the item is visible (i.e., QGraphicsItem::isVisible() returns true),
    QGraphicsScene will emit changed() once control goes back to the event
    loop.

    \sa addLine(), addPath(), addPixmap(), addRect(), addText(), addItem()
*/
QGraphicsEllipseItem *QGraphicsScene::addEllipse(const QRectF &rect, const QPen &pen, const QBrush &brush)
{
    QGraphicsEllipseItem *item = new QGraphicsEllipseItem(rect);
    item->setPen(pen);
    item->setBrush(brush);
    addItem(item);
    return item;
}

/*!
    \fn QGraphicsEllipseItem *QGraphicsScene::addEllipse(qreal x, qreal y, qreal w, qreal h, const QPen &pen, const QBrush &brush)
    \since 4.3

    This convenience function is equivalent to calling addEllipse(QRectF(\a x,
    \a y, \a w, \a h), \a pen, \a brush).
*/

/*!
    Creates and adds a line item to the scene, and returns the item
    pointer. The geometry of the line is defined by \a line, and it's pen
    is initialized to \a pen.

    Note that the item's geometry is provided in item coordinates, and its
    position is initialized to (0, 0).

    If the item is visible (i.e., QGraphicsItem::isVisible() returns true),
    QGraphicsScene will emit changed() once control goes back to the event
    loop.

    \sa addEllipse(), addPath(), addPixmap(), addRect(), addText(), addItem()
*/
QGraphicsLineItem *QGraphicsScene::addLine(const QLineF &line, const QPen &pen)
{
    QGraphicsLineItem *item = new QGraphicsLineItem(line);
    item->setPen(pen);
    addItem(item);
    return item;
}

/*!
    \fn QGraphicsLineItem *QGraphicsScene::addLine(qreal x1, qreal y1, qreal x2, qreal y2, const QPen &pen)
    \since 4.3

    This convenience function is equivalent to calling addLine(QLineF(\a x1,
    \a y1, \a x2, \a y2), \a pen).
*/

/*!