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# QGraphicsScene Class Reference
[QtGui module]

The QGraphicsScene class provides a surface for managing a large number of 2D graphical items. More...

Inherits QObject.

### Types

- enum ItemIndexMethod { BspTreeIndex, NoIndex }
- enum SceneLayer { ItemLayer, BackgroundLayer, ForegroundLayer, AllLayers }
- class SceneLayers

### Methods

- __init__ (self, QObject parent = None)
- __init__ (self, QRectF sceneRect, QObject parent = None)
- __init__ (self, float x, float y, float width, float height, QObject parent = None)
- QGraphicsEllipseItem addEllipse (self, QRectF rect, QPen pen = QPen(), QBrush brush = QBrush())
- QGraphicsEllipseItem addEllipse (self, float x, float y, float w, float h, QPen pen = QPen(), QBrush brush = QBrush())
- addItem (self, QGraphicsItem item)
- QGraphicsLineItem addLine (self, QLineF line, QPen pen = QPen())
- QGraphicsLineItem addLine (self, float x1, float y1, float x2, float y2, QPen pen = QPen())
- QGraphicsPathItem addPath (self, QPainterPath path, QPen pen = QPen(), QBrush brush = QBrush())
- QGraphicsPixmapItem addPixmap (self, QPixmap pixmap)
- QGraphicsPolygonItem addPolygon (self, QPolygonF polygon, QPen pen = QPen(), QBrush brush = QBrush())
- QGraphicsRectItem addRect (self, QRectF rect, QPen pen = QPen(), QBrush brush = QBrush())
- QGraphicsRectItem addRect (self, float x, float y, float w, float h, QPen pen = QPen(), QBrush brush = QBrush())
- QGraphicsSimpleTextItem addSimpleText (self, QString text, QFont font = QFont())
- QGraphicsTextItem addText (self, QString text, QFont font = QFont())
- advance (self)
- QBrush backgroundBrush (self)
- int bspTreeDepth (self)
- clearFocus (self)
- clearSelection (self)
- QGraphicsItem-list collidingItems (self, QGraphicsItem item, Qt.ItemSelectionMode mode = Qt.IntersectsItemShape)
- contextMenuEvent (self, QGraphicsSceneContextMenuEvent event)
- QGraphicsItemGroup createItemGroup (self, QGraphicsItem-list items)
- destroyItemGroup (self, QGraphicsItemGroup group)
- dragEnterEvent (self, QGraphicsSceneDragDropEvent event)
- dragLeaveEvent (self, QGraphicsSceneDragDropEvent event)
- dragMoveEvent (self, QGraphicsSceneDragDropEvent event)
- drawBackground (self, QPainter painter, QRectF rect)
- drawForeground (self, QPainter painter, QRectF rect)
- drawItems (self, QPainter painter, list items, list options, QWidget widget = None)
- dropEvent (self, QGraphicsSceneDragDropEvent event)
- bool event (self, QEvent event)
- focusInEvent (self, QFocusEvent event)
- QGraphicsItem focusItem (self)
- focusOutEvent (self, QFocusEvent event)
- QBrush foregroundBrush (self)
- bool hasFocus (self)
- float height (self)
- helpEvent (self, QGraphicsSceneHelpEvent event)
- inputMethodEvent (self, QInputMethodEvent event)
- QVariant inputMethodQuery (self, Qt.InputMethodQuery query)
- invalidate (self, QRectF rect = QRectF(), SceneLayers layers = QGraphicsScene.AllLayers)
- invalidate (self, float x, float y, float w, float h, SceneLayers layers = QGraphicsScene.AllLayers)
- QGraphicsItem itemAt (self, QPointF pos)
- QGraphicsItem itemAt (self, float x, float y)
- ItemIndexMethod itemIndexMethod (self)
- QGraphicsItem-list items (self)
- QGraphicsItem-list items (self, QPointF pos)
- QGraphicsItem-list items (self, QRectF rect, Qt.ItemSelectionMode mode = Qt.IntersectsItemShape)
- QGraphicsItem-list items (self, QPolygonF polygon, Qt.ItemSelectionMode mode = Qt.IntersectsItemShape)
- QGraphicsItem-list items (self, QPainterPath path, Qt.ItemSelectionMode mode = Qt.IntersectsItemShape)
- QGraphicsItem-list items (self, float x, float y, float w, float h, Qt.ItemSelectionMode mode = Qt.IntersectsItemShape)
- QRectF itemsBoundingRect (self)
- keyPressEvent (self, QKeyEvent event)
- keyReleaseEvent (self, QKeyEvent event)
- mouseDoubleClickEvent (self, QGraphicsSceneMouseEvent event)
- QGraphicsItem mouseGrabberItem (self)
- mouseMoveEvent (self, QGraphicsSceneMouseEvent event)
- mousePressEvent (self, QGraphicsSceneMouseEvent event)
- mouseReleaseEvent (self, QGraphicsSceneMouseEvent event)
- removeItem (self, QGraphicsItem item)
- render (self, QPainter painter, QRectF target = QRectF(), QRectF source = QRectF(), Qt.AspectRatioMode aspectRatioMode = Qt.KeepAspectRatio)
- QRectF sceneRect (self)
- QGraphicsItem-list selectedItems (self)
- QPainterPath selectionArea (self)
- setBackgroundBrush (self, QBrush brush)
- setBspTreeDepth (self, int depth)
- setFocus (self, Qt.FocusReason focusReason = Qt.OtherFocusReason)
- setFocusItem (self, QGraphicsItem item, Qt.FocusReason focusReason = Qt.OtherFocusReason)
- setForegroundBrush (self, QBrush brush)
- setItemIndexMethod (self, ItemIndexMethod method)
- setSceneRect (self, QRectF rect)
- setSceneRect (self, float x, float y, float w, float h)
- setSelectionArea (self, QPainterPath path)
- setSelectionArea (self, QPainterPath path, Qt.ItemSelectionMode)
- update (self, QRectF rect = QRectF())
- update (self, float x, float y, float w, float h)
- QGraphicsView-list views (self)
- wheelEvent (self, QGraphicsSceneWheelEvent event)
- float width (self)

### Qt Signals

- void changed (const QList<QRectF>&)
- void sceneRectChanged (const QRectF&)
- void selectionChanged ()

## Detailed Description

The QGraphicsScene class provides a surface for managing a large number of 2D graphical items.

The class serves as a container for QGraphicsItems. It is used together with QGraphicsView for visualizing graphical items, such as lines, rectangles, text, or even custom items, on a 2D surface. QGraphicsScene is part of The Graphics View Framework.

QGraphicsScene also provides functionality that lets you efficiently determine both the location of items, and for determining what items are visible within an arbitrary area on the scene. With the QGraphicsView widget, you can either visualize the whole scene, or zoom in and view only parts of the scene.

Example:

     QGraphicsScene scene;
     scene.addText("Hello, world!");

     QGraphicsView view(&scene);
     view.show();

Note that QGraphicsScene has no visual appearance of its own; it only manages the items. You need to create a QGraphicsView widget to visualize the scene.

To add items to a scene, you start off by constructing a QGraphicsScene object. Then, you have two options: either add your existing QGraphicsItem objects by calling addItem(), or you can call one of the convenience functions addEllipse(), addLine(), addPath(), addPixmap(), addPolygon(), addRect(), or addText(), which all return a pointer to the newly added item. You can then visualize the scene using QGraphicsView. When the scene changes, (e.g., when an item moves or is transformed) QGraphicsScene emits the changed() signal. To remove an item, call removeItem().

QGraphicsScene uses an indexing algorithm to manage the location of items efficiently. By default, a BSP (Binary Space Partitioning) tree is used; an algorithm suitable for large scenes where most items remain static (i.e., do not move around). You can choose to disable this index by calling setItemIndexMethod(). For more information about the available indexing algorithms, see the itemIndexMethod property.

The scene's bounding rect is set by calling setSceneRect(). Items can be placed at any position on the scene, and the size of the scene is by default unlimited. The scene rect is used only for internal bookkeeping, maintaining the scene's item index. If the scene rect is unset, QGraphicsScene will use the bounding area of all items, as returned by itemsBoundingRect(), as the scene rect. However, itemsBoundingRect() is a relatively time consuming function, as it operates by collecting positional information for every item on the scene. Because of this, you should always set the scene rect when operating on large scenes.

One of QGraphicsScene's greatest strengths is its ability to efficiently determine the location of items. Even with millions of items on the scene, the items() functions can determine the location of an item within few milliseconds. There are several overloads to items(): one that finds items at a certain position, one that finds items inside or intersecting with a polygon or a rectangle, and more. The list of returned items is sorted by stacking order, with the topmost item being the first item in the list. For convenience, there is also an itemAt() function that returns the topmost item at a given position.

QGraphicsScene maintains selection information for the scene. To select items, call setSelectionArea(), and to clear the current selection, call clearSelection(). Call selectedItems() to get the list of all selected items.

### Event Handling and Propagation

Another responsibility that QGraphicsScene has, is to propagate events from QGraphicsView. To send an event to a scene, you construct an event that inherits QEvent, and then send it using, for example, QApplication.sendEvent(). event() is responsible for dispatching the event to the individual items. Some common events are handled by convenience event handlers. For example, key press events are handled by keyPressEvent(), and mouse press events are handled by mousePressEvent().

Key events are delivered to the focus item. To set the focus item, you can either call setFocusItem(), passing an item that accepts focus, or the item itself can call QGraphicsItem.setFocus(). Call focusItem() to get the current focus item. For compatibility with widgets, the scene also maintains its own focus information. By default, the scene does not have focus, and all key events are discarded. If setFocus() is called, or if an item on the scene gains focus, the scene automatically gains focus. If the scene has focus, hasFocus() will return true, and key events will be forwarded to the focus item, if any. If the scene loses focus, (i.e., someone calls clearFocus(),) while an item has focus, the scene will maintain its item focus information, and once the scene regains focus, it will make sure the last focus item regains focus.

For mouse-over effects, QGraphicsScene dispatches hover events. If an item accepts hover events (see QGraphicsItem.acceptsHoverEvents()), it will receive a GraphicsSceneHoverEnter event when the mouse enters its area. As the mouse continues moving inside the item's area, QGraphicsScene will send it GraphicsSceneHoverMove events. When the mouse leaves the item's area, the item will receive a GraphicsSceneHoverLeave event.

All mouse events are delivered to the current mouse grabber item. An item becomes the scene's mouse grabber if it accepts mouse events (see QGraphicsItem.acceptedMouseButtons()) and it receives a mouse press. It stays the mouse grabber until it receives a mouse release when no other mouse buttons are pressed. You can call mouseGrabberItem() to determine what item is currently grabbing the mouse.

See also QGraphicsItem and QGraphicsView.

## Type Documentation

### QGraphicsScene.ItemIndexMethod

This enum describes the indexing algorithms QGraphicsScene provides for managing positional information about items on the scene.

Constant | Value | Description
--- | --- | ---
`QGraphicsScene.BspTreeIndex` | `0` | A Binary Space Partitioning tree is applied. All QGraphicsScene's item location algorithms are of an order close to logarithmic complexity, by making use of binary search. Adding, moving and removing items is logarithmic. This approach is best for static scenes (i.e., scenes where most items do not move).
`QGraphicsScene.NoIndex` | `-1` | No index is applied. Item location is of linear complexity, as all items on the scene are searched. Adding, moving and removing items, however, is done in constant time. This approach is ideal for dynamic scenes, where many items are added, moved or removed continuously.

See also setItemIndexMethod() and bspTreeDepth.

### QGraphicsScene.SceneLayer

This enum describes the rendering layers in a QGraphicsScene. When QGraphicsScene draws the scene contents, it renders each of these layers separately, in order.

Each layer represents a flag that can be OR'ed together when calling functions such as invalidate() or QGraphicsView.invalidateScene().

Constant | Value | Description
--- | --- | ---
`QGraphicsScene.ItemLayer` | `0x1` | The item layer. QGraphicsScene renders all items are in this layer by calling the virtual function drawItems(). The item layer is drawn after the background layer, but before the foreground layer.
`QGraphicsScene.BackgroundLayer` | `0x2` | The background layer. QGraphicsScene renders the scene's background in this layer by calling the virtual function drawBackground(). The background layer is drawn first of all layers.
`QGraphicsScene.ForegroundLayer` | `0x4` | The foreground layer. QGraphicsScene renders the scene's foreground in this layer by calling the virtual function drawForeground(). The foreground layer is drawn last of all layers.
`QGraphicsScene.AllLayers` | `0xffff` | All layers; this value represents a combination of all three layers.

This enum was introduced in Qt 4.3.

The SceneLayers type is a typedef for QFlags<SceneLayer>. It stores an OR combination of SceneLayer values.

See also invalidate() and QGraphicsView.invalidateScene().

## Method Documentation

### QGraphicsScene.__init__ (self, QObject parent = None)

The parent argument, if not None, causes self to be owned by Qt instead of PyQt.

Constructs a QGraphicsScene object. The parent parameter is passed to QObject's constructor.

### QGraphicsScene.__init__ (self, QRectF sceneRect, QObject parent = None)

The parent argument, if not None, causes self to be owned by Qt instead of PyQt.

Constructs a QGraphicsScene object, using sceneRect for its scene rectangle. The parent parameter is passed to QObject's constructor.

See also sceneRect.

### QGraphicsScene.__init__ (self, float x, float y, float width, float height, QObject parent = None)

The parent argument, if not None, causes self to be owned by Qt instead of PyQt.

Constructs a QGraphicsScene object, using the rectangle specified by (x, y), and the given width and height for its scene rectangle. The parent parameter is passed to QObject's constructor.

See also sceneRect.

### QGraphicsEllipseItem QGraphicsScene.addEllipse (self, QRectF rect, QPen pen = QPen(), QBrush brush = QBrush())

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

See also addLine(), addPath(), addPixmap(), addRect(), addText(), and addItem().

### QGraphicsEllipseItem QGraphicsScene.addEllipse (self, float x, float y, float w, float h, QPen pen = QPen(), QBrush brush = QBrush())

This is an overloaded member function, provided for convenience.

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

This function was introduced in Qt 4.3.

### QGraphicsScene.addItem (self, QGraphicsItem item)

The item argument has it's ownership transferred to Qt.

Adds or moves the item 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.

See also removeItem(), addEllipse(), addLine(), addPath(), addPixmap(), addRect(), and addText().

### QGraphicsLineItem QGraphicsScene.addLine (self, QLineF line, QPen pen = QPen())

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

See also addEllipse(), addPath(), addPixmap(), addRect(), addText(), and addItem().

### QGraphicsLineItem QGraphicsScene.addLine (self, float x1, float y1, float x2, float y2, QPen pen = QPen())

This is an overloaded member function, provided for convenience.

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

This function was introduced in Qt 4.3.

### QGraphicsPathItem QGraphicsScene.addPath (self, QPainterPath path, QPen pen = QPen(), QBrush brush = QBrush())

Creates and adds a path item to the scene, and returns the item pointer. The geometry of the path is defined by path, and it's pen and brush are initialized to pen and 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.

See also addEllipse(), addLine(), addPixmap(), addRect(), addText(), and addItem().

### QGraphicsPixmapItem QGraphicsScene.addPixmap (self, QPixmap pixmap)

Creates and adds a pixmap item to the scene, and returns the item pointer. The pixmap is defined by pixmap.

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.

See also addEllipse(), addLine(), addPath(), addRect(), addText(), and addItem().

### QGraphicsPolygonItem QGraphicsScene.addPolygon (self, QPolygonF polygon, QPen pen = QPen(), QBrush brush = QBrush())

Creates and adds a polygon item to the scene, and returns the item pointer. The polygon is defined by polygon, and it's pen and brush are initialized to pen and 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.

See also addEllipse(), addLine(), addPath(), addRect(), addText(), and addItem().

### QGraphicsRectItem QGraphicsScene.addRect (self, QRectF rect, QPen pen = QPen(), QBrush brush = QBrush())

Creates and adds a rectangle item to the scene, and returns the item pointer. The geometry of the rectangle is defined by rect, and it's pen and brush are initialized to pen and 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.

See also addEllipse(), addLine(), addPixmap(), addPixmap(), addText(), and addItem().

### QGraphicsRectItem QGraphicsScene.addRect (self, float x, float y, float w, float h, QPen pen = QPen(), QBrush brush = QBrush())

This is an overloaded member function, provided for convenience.

This convenience function is equivalent to calling addRect(QRectF(x, y, w, h), pen, brush).

This function was introduced in Qt 4.3.

### QGraphicsSimpleTextItem QGraphicsScene.addSimpleText (self, QString text, QFont font = QFont())

Creates and adds a QGraphicsSimpleTextItem to the scene, and returns the item pointer. The text string is initialized to text, and it's font is initialized to font.

The item's 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.

See also addEllipse(), addLine(), addPixmap(), addPixmap(), addRect(), and addItem().

### QGraphicsTextItem QGraphicsScene.addText (self, QString text, QFont font = QFont())

Creates and adds a text item to the scene, and returns the item pointer. The text string is initialized to text, and it's font is initialized to font.

The item's 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.

See also addEllipse(), addLine(), addPixmap(), addPixmap(), addRect(), and addItem().

### QGraphicsScene.advance (self)

This method is also a Qt slot with the C++ signature `void advance()`.

This slot advances the scene by one step, by calling QGraphicsItem.advance() for all items on the scene. This is done in two phases: in the first phase, all items are notified that the scene is about to change, and in the second phase all items are notified that they can move. In the first phase, QGraphicsItem.advance() is called passing a value of 0 as an argument, and 1 is passed in the second phase.

See also QGraphicsItem.advance(), QGraphicsItemAnimation, and QTimeLine.

### QBrush QGraphicsScene.backgroundBrush (self)

### int QGraphicsScene.bspTreeDepth (self)

### QGraphicsScene.clearFocus (self)

Clears focus from the scene. If any item has focus when this function is called, it will lose focus, and regain focus again once the scene regains focus.

A scene that does not have focus ignores key events.

See also hasFocus(), setFocus(), and setFocusItem().

### QGraphicsScene.clearSelection (self)

Clears the current selection.

See also setSelectionArea() and selectedItems().

### QGraphicsItem-list QGraphicsScene.collidingItems (self, QGraphicsItem item, Qt.ItemSelectionMode mode = Qt.IntersectsItemShape)

Returns a list of all items that collide with item. Collisions are determined by calling QGraphicsItem.collidesWithItem(); the collision detection is determined by mode. By default, all items whose shape intersects item or is contained inside item's shape are returned.

The items are returned in descending Z order (i.e., the first item in the list is the top-most item, and the last item is the bottom-most item).

See also items(), itemAt(), and QGraphicsItem.collidesWithItem().

### QGraphicsScene.contextMenuEvent (self, QGraphicsSceneContextMenuEvent event)

This event handler, for event contextMenuEvent, can be reimplemented in a subclass to receive context menu events. The default implementation forwards the event to the item at the scene position provided by the event.

See also QGraphicsItem.contextMenuEvent().

### QGraphicsItemGroup QGraphicsScene.createItemGroup (self, QGraphicsItem-list items)

The items argument has it's ownership transferred to Qt.

Groups all items in items into a new QGraphicsItemGroup, and returns a pointer to the group. The group is created with the common ancestor of 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 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().

See also destroyItemGroup() and QGraphicsItemGroup.addToGroup().

### QGraphicsScene.destroyItemGroup (self, QGraphicsItemGroup group)

The group argument has it's ownership transferred to Qt.

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

See also createItemGroup() and QGraphicsItemGroup.removeFromGroup().

### QGraphicsScene.dragEnterEvent (self, QGraphicsSceneDragDropEvent event)

This event handler, for event event, can be reimplemented in a subclass to receive drag enter events for the scene.

The default implementation accepts the event and prepares the scene to accept drag move events.

See also QGraphicsItem.dragEnterEvent(), dragMoveEvent(), dragLeaveEvent(), and dropEvent().

### QGraphicsScene.dragLeaveEvent (self, QGraphicsSceneDragDropEvent event)

This event handler, for event event, can be reimplemented in a subclass to receive drag leave events for the scene.

See also QGraphicsItem.dragLeaveEvent(), dragEnterEvent(), dragMoveEvent(), and dropEvent().

### QGraphicsScene.dragMoveEvent (self, QGraphicsSceneDragDropEvent event)

This event handler, for event event, can be reimplemented in a subclass to receive drag move events for the scene.

See also QGraphicsItem.dragMoveEvent(), dragEnterEvent(), dragLeaveEvent(), and dropEvent().

### QGraphicsScene.drawBackground (self, QPainter painter, QRectF rect)

Draws the background of the scene using painter, before any items and the foreground are drawn. Reimplement this function to provide a custom background for the scene.

All painting is done in scene coordinates. The rect parameter is the exposed rectangle.

See also drawForeground() and drawItems().

### QGraphicsScene.drawForeground (self, QPainter painter, QRectF rect)

Draws the foreground of the scene using painter, after the background and all items have been drawn. Reimplement this function to provide a custom foreground for the scene.

All painting is done in scene coordinates. The rect parameter is the exposed rectangle.

See also drawBackground() and drawItems().

### QGraphicsScene.drawItems (self, QPainter painter, list items, list options, QWidget widget = None)

Paints the given items using the provided painter, after the background has been drawn, and before the foreground has been drawn. All painting is done in scene coordinates. Before drawing each item, the painter must be transformed using QGraphicsItem.sceneMatrix().

The options parameter is the list of style option objects for each item in items. The numItems parameter is the number of items in items and options in options. The widget parameter is optional; if specified, it should point to the widget that is being painted on.

The default implementation prepares the painter matrix, and calls QGraphicsItem.paint() on all items. Reimplement this function to provide custom painting of all items for the scene; gaining complete control over how each item is drawn. In some cases this can increase drawing performance significantly.

Example:

     void CustomScene.drawItems(QPainter *painter, int numItems,
                                 QGraphicsItem *items[],
                                 const QStyleOptionGraphicsItem options[],
                                 QWidget *widget)
     {
         for (int i = 0; i < numItems; ++i) {
              // Draw the item
              painter->save();
              painter->setMatrix(items[i]->sceneMatrix(), true);
              items[i]->paint(painter, &options[i], widget);
              painter->restore();
          }
     }

See also drawBackground() and drawForeground().

### QGraphicsScene.dropEvent (self, QGraphicsSceneDragDropEvent event)

This event handler, for event event, can be reimplemented in a subclass to receive drop events for the scene.

See also QGraphicsItem.dropEvent(), dragEnterEvent(), dragMoveEvent(), and dragLeaveEvent().

### bool QGraphicsScene.event (self, QEvent event)

Processes the event event, and dispatches it to the respective event handlers.

In addition to calling the convenience event handlers, this function is responsible for converting mouse move events to hover events for when there is no mouse grabber item. Hover events are delivered directly to items; there is no convenience function for them.

Reimplemented from QObject.

See also contextMenuEvent(), keyPressEvent(), keyReleaseEvent(), mousePressEvent(), mouseMoveEvent(), mouseReleaseEvent(), mouseDoubleClickEvent(), focusInEvent(), and focusOutEvent().

### QGraphicsScene.focusInEvent (self, QFocusEvent event)

This event handler, for event focusEvent, can be reimplemented in a subclass to receive focus in events.

The default implementation sets focus on the scene, and then on the last focus item.

See also QGraphicsItem.focusOutEvent().

### QGraphicsItem QGraphicsScene.focusItem (self)

Returns the scene's current focus item, or 0 if no item currently has focus.

The focus item receives keyboard input when the scene receives a key event.

See also setFocusItem() and QGraphicsItem.hasFocus().

### QGraphicsScene.focusOutEvent (self, QFocusEvent event)

This event handler, for event focusEvent, can be reimplemented in a subclass to receive focus out events.

The default implementation removes focus from any focus item, then removes focus from the scene.

See also QGraphicsItem.focusInEvent().

### QBrush QGraphicsScene.foregroundBrush (self)

### bool QGraphicsScene.hasFocus (self)

Returns true if the scene has focus; otherwise returns false. If the scene has focus, it will will forward key events from QKeyEvent to any item that has focus.

See also setFocus() and setFocusItem().

### float QGraphicsScene.height (self)

This convenience function is equivalent to calling `sceneRect().height()`.

See also width().

### QGraphicsScene.helpEvent (self, QGraphicsSceneHelpEvent event)

This event handler, for event helpEvent, can be reimplemented in a subclass to receive help events. The events are of type QEvent.ToolTip, which are created when a tooltip is requested.

The default implementation shows the tooltip of the topmost item, i.e., the item with the highest z-value, at the mouse cursor position. If no item has a tooltip set, this function does nothing.

See also QGraphicsItem.toolTip() and QGraphicsSceneHelpEvent.

### QGraphicsScene.inputMethodEvent (self, QInputMethodEvent event)

This event handler, for event event, can be reimplemented in a subclass to receive input method events for the scene.

The default implementation forwards the event to the focusItem(). If no item currently has focus, this function does nothing.

See also QGraphicsItem.inputMethodEvent().

### QVariant QGraphicsScene.inputMethodQuery (self, Qt.InputMethodQuery query)

This method is used by input methods to query a set of properties of the scene to be able to support complex input method operations as support for surrounding text and reconversions.

The query parameter specifies which property is queried.

See also QWidget.inputMethodQuery().

### QGraphicsScene.invalidate (self, QRectF rect = QRectF(), SceneLayers layers = QGraphicsScene.AllLayers)

This method is also a Qt slot with the C++ signature `void invalidate(const QRectF& = QRectF(),QGraphicsScene::SceneLayers = QGraphicsScene.AllLayers)`.

This convenience function is equivalent to calling invalidate(QRectF(x, y, w, h), layers);

This function was introduced in Qt 4.3.

### QGraphicsScene.invalidate (self, float x, float y, float w, float h, SceneLayers layers = QGraphicsScene.AllLayers)

This is an overloaded member function, provided for convenience.

Invalidates and schedules a redraw of the layers in rect on the scene. Any cached content in layers is unconditionally invalidated and redrawn.

You can use this function overload to notify QGraphicsScene of changes to the background or the foreground of the scene. This function is commonly used for scenes with tile-based backgrounds to notify changes when QGraphicsView has enabled CacheBackground.

Example:

     QRectF TileScene.rectForTile(int x, int y) const
     {
         // Return the rectangle for the tile at position (x, y).
         return QRectF(x * tileWidth, y * tileHeight, tileWidth, tileHeight);
     }

     void TileScene.setTile(int x, int y, const QPixmap &pixmap)
     {
         // Sets or replaces the tile at position (x, y) with pixmap.
         if (x >= 0 && x < numTilesH && y >= 0 && y < numTilesV) {
             tiles[y][x] = pixmap;
             invalidate(rectForTile(x, y), BackgroundLayer);
         }
     }

     void TileScene.drawBackground(QPainter *painter, const QRectF &exposed)
     {
         // Draws all tiles that intersect the exposed area.
         for (int y = 0; y < numTilesV; ++y) {
             for (int x = 0; x < numTilesH; ++x) {
                 QRectF rect = rectForTile(x, y);
                 if (exposed.intersects(rect))
                     painter->drawPixmap(rect.topLeft(), tiles[y][x]);
             }
         }
     }

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

See also QGraphicsView.resetCachedContent().

### QGraphicsItem QGraphicsScene.itemAt (self, QPointF pos)

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

See also items() and collidingItems().

### QGraphicsItem QGraphicsScene.itemAt (self, float x, float y)

This is an overloaded member function, provided for convenience.

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

This convenience function is equivalent to calling `itemAt(QPointF(x, y))`.

### ItemIndexMethod QGraphicsScene.itemIndexMethod (self)

### QGraphicsItem-list QGraphicsScene.items (self)

Returns a list of all items on the scene, in no particular order.

See also addItem() and removeItem().

### QGraphicsItem-list QGraphicsScene.items (self, QPointF pos)

This is an overloaded member function, provided for convenience.

Returns all visible items at position pos in the scene. The items are listed in descending Z order (i.e., the first item in the list is the top-most item, and the last item is the bottom-most item).

See also itemAt().

### QGraphicsItem-list QGraphicsScene.items (self, QRectF rect, Qt.ItemSelectionMode mode = Qt.IntersectsItemShape)

This is an overloaded member function, provided for convenience.

This convenience function is equivalent to calling items(QRectF(x, y, w, h), mode).

This function was introduced in Qt 4.3.

### QGraphicsItem-list QGraphicsScene.items (self, QPolygonF polygon, Qt.ItemSelectionMode mode = Qt.IntersectsItemShape)

This is an overloaded member function, provided for convenience.

Returns all visible items that, depending on mode, are either inside or intersect with the specified rectangle.

The default value for mode is Qt.IntersectsItemShape; all items whose exact shape intersects with or is contained by rectangle are returned.

See also itemAt().

### QGraphicsItem-list QGraphicsScene.items (self, QPainterPath path, Qt.ItemSelectionMode mode = Qt.IntersectsItemShape)

This is an overloaded member function, provided for convenience.

Returns all visible items that, depending on mode, are either inside or intersect with the polygon polygon.

The default value for mode is Qt.IntersectsItemShape; all items whose exact shape intersects with or is contained by polygon are returned.

See also itemAt().

### QGraphicsItem-list QGraphicsScene.items (self, float x, float y, float w, float h, Qt.ItemSelectionMode mode = Qt.IntersectsItemShape)

This is an overloaded member function, provided for convenience.

Returns all visible items that, depending on path, are either inside or intersect with the path path.

The default value for mode is Qt.IntersectsItemShape; all items whose exact shape intersects with or is contained by path are returned.

See also itemAt().

### QRectF QGraphicsScene.itemsBoundingRect (self)

Calculates and returns the bounding rect of all items on the scene. This function works by iterating over all items, and because if this, it can be slow for large scenes.

See also sceneRect().

### QGraphicsScene.keyPressEvent (self, QKeyEvent event)

This event handler, for event keyEvent, can be reimplemented in a subclass to receive keypress events. The default implementation forwards the event to current focus item.

See also QGraphicsItem.keyPressEvent() and focusItem().

### QGraphicsScene.keyReleaseEvent (self, QKeyEvent event)

This event handler, for event keyEvent, can be reimplemented in a subclass to receive key release events. The default implementation forwards the event to current focus item.

See also QGraphicsItem.keyReleaseEvent() and focusItem().

### QGraphicsScene.mouseDoubleClickEvent (self, QGraphicsSceneMouseEvent event)

This event handler, for event mouseEvent, can be reimplemented in a subclass to receive mouse doubleclick events for the scene.

If someone doubleclicks on the scene, the scene will first receive a mouse press event, followed by a release event (i.e., a click), then a doubleclick event, and finally a release event. If the doubleclick event is delivered to a different item than the one that received the first press and release, it will be delivered as a press event. However, tripleclick events are not delivered as doubleclick events in this case.

The default implementation is similar to mousePressEvent().

See also QGraphicsItem.mousePressEvent(), QGraphicsItem.mouseMoveEvent(), QGraphicsItem.mouseReleaseEvent(), and QGraphicsItem.setAcceptedMouseButtons().

### QGraphicsItem QGraphicsScene.mouseGrabberItem (self)

Returns the current mouse grabber item, or 0 if no item is currently grabbing the mouse. The mouse grabber item is the item that receives all mouse events sent to the scene.

An item becomes a mouse grabber when it receives and accepts a mouse press event, and it stays the mouse grabber until either of the following events occur:

- If the item receives a mouse release event when there are no other buttons pressed, it loses the mouse grab.
- If the item becomes invisible (i.e., someone calls `item->setVisible(false))`, or if it becomes disabled (i.e., someone calls `item->setEnabled(false))`, it loses the mouse grab.
- If the item is removed from the scene, it loses the mouse grab.

If the item loses its mouse grab, the scene will ignore all mouse events until a new item grabs the mouse (i.e., until a new item receives a mouse press event).

### QGraphicsScene.mouseMoveEvent (self, QGraphicsSceneMouseEvent event)

This event handler, for event mouseEvent, can be reimplemented in a subclass to receive mouse move events for the scene.

The default implementation depends on the mouse grabber state. If there is a mouse grabber item, the event is sent to the mouse grabber; otherwise, the event is ignored.

See also QGraphicsItem.mousePressEvent(), QGraphicsItem.mouseReleaseEvent(), QGraphicsItem.mouseDoubleClickEvent(), and QGraphicsItem.setAcceptedMouseButtons().

### QGraphicsScene.mousePressEvent (self, QGraphicsSceneMouseEvent event)

This event handler, for event mouseEvent, can be reimplemented in a subclass to receive mouse press events for the scene.

The default implementation depends on the state of the scene. If there is a mouse grabber item, then the event is sent to the mouse grabber. Otherwise, it is forwarded to the topmost item that accepts mouse events at the scene position from the event, and that item promptly becomes the mouse grabber item.

If there is no item at the given position on the scene, the selection area is reset, any focus item loses its input focus, and the event is then ignored.

See also QGraphicsItem.mousePressEvent() and QGraphicsItem.setAcceptedMouseButtons().

### QGraphicsScene.mouseReleaseEvent (self, QGraphicsSceneMouseEvent event)

This event handler, for event mouseEvent, can be reimplemented in a subclass to receive mouse release events for the scene.

The default implementation depends on the mouse grabber state. If there is no mouse grabber, the event is ignored. Otherwise, if there is a mouse grabber item, the event is sent to the mouse grabber. If this mouse release represents the last pressed button on the mouse, the mouse grabber item then loses the mouse grab.

See also QGraphicsItem.mousePressEvent(), QGraphicsItem.mouseMoveEvent(), QGraphicsItem.mouseDoubleClickEvent(), and QGraphicsItem.setAcceptedMouseButtons().

### QGraphicsScene.removeItem (self, QGraphicsItem item)

The item argument

Removes the item item and all its children from the scene. The ownership of item is passed on to the caller (i.e., QGraphicsScene will no longer delete item when destroyed).

See also addItem().

### QGraphicsScene.render (self, QPainter painter, QRectF target = QRectF(), QRectF source = QRectF(), Qt.AspectRatioMode aspectRatioMode = Qt.KeepAspectRatio)

Renders the source rect from scene into target, using painter. This function is useful for capturing the contents of the scene onto a paint device, such as a QImage (e.g., to take a screenshot), or for printing with QPrinter. For example:

     QGraphicsScene scene;
     scene.addItem(...
     ...
     QPrinter printer(QPrinter.HighResolution);
     printer.setPageSize(QPrinter.A4);

     QPainter painter(&printer);
     scene.render(&painter);

If source is a null rect, this function will use sceneRect() to determine what to render. If target is a null rect, the dimensions of painter's paint device will be used.

The source rect contents will be transformed according to aspectRatioMode to fit into the target rect. By default, the aspect ratio is kept, and source is scaled to fit in target.

See also QGraphicsView.render().

### QRectF QGraphicsScene.sceneRect (self)

### QGraphicsItem-list QGraphicsScene.selectedItems (self)

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

See also setSelectionArea().

### QPainterPath QGraphicsScene.selectionArea (self)

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

See also setSelectionArea().

### QGraphicsScene.setBackgroundBrush (self, QBrush brush)

### QGraphicsScene.setBspTreeDepth (self, int depth)

### QGraphicsScene.setFocus (self, Qt.FocusReason focusReason = Qt.OtherFocusReason)

Sets focus on the scene by sending a QFocusEvent to the scene, passing focusReason as the reason. If the scene regains focus after having previously lost it while an item had focus, the last focus item will receive focus with focusReason as the reason.

If the scene already has focus, this function does nothing.

See also hasFocus(), clearFocus(), and setFocusItem().

### QGraphicsScene.setFocusItem (self, QGraphicsItem item, Qt.FocusReason focusReason = Qt.OtherFocusReason)

Sets the scene's focus item to item, with the focus reason focusReason, after removing focus from any previous item that may have had focus.

If item is 0, or if it either does not accept focus (i.e., it does not have the QGraphicsItem.ItemIsFocusable flag enabled), or is not visible or not enabled, this function only removes focus from any previous focusitem.

If item is not 0, and the scene does not currently have focus (i.e., hasFocus() returns false), this function will call setFocus() automatically.

See also focusItem(), hasFocus(), and setFocus().

### QGraphicsScene.setForegroundBrush (self, QBrush brush)

### QGraphicsScene.setItemIndexMethod (self, ItemIndexMethod method)

### QGraphicsScene.setSceneRect (self, QRectF rect)

### QGraphicsScene.setSceneRect (self, float x, float y, float w, float h)

### QGraphicsScene.setSelectionArea (self, QPainterPath path)

Sets the selection area to 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 selectable (QGraphicsItem.ItemIsSelectable).

See also clearSelection() and selectionArea().

### QGraphicsScene.setSelectionArea (self, QPainterPath path, Qt.ItemSelectionMode)

This is an overloaded member function, provided for convenience.

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

This function was introduced in Qt 4.3.

See also clearSelection() and selectionArea().

### QGraphicsScene.update (self, QRectF rect = QRectF())

This method is also a Qt slot with the C++ signature `void update(const QRectF& = QRectF())`.

This convenience function is equivalent to calling update(QRectF(x, y, w, h));

This function was introduced in Qt 4.3.

### QGraphicsScene.update (self, float x, float y, float w, float h)

This is an overloaded member function, provided for convenience.

Schedules a redraw of the area rect on the scene.

See also sceneRect() and changed().

### QGraphicsView-list QGraphicsScene.views (self)

Returns a list of all the views that display this scene.

See also QGraphicsView.scene().

### QGraphicsScene.wheelEvent (self, QGraphicsSceneWheelEvent event)

This event handler, for event wheelEvent, can be reimplemented in a subclass to receive mouse wheel events for the scene.

By default, the event is delivered to the topmost visible item under the cursor. If ignored, the event propagates to the item beneath, and again until the event is accepted, or it reaches the scene. If no items accept the event, it is ignored.

See also QGraphicsItem.wheelEvent().

### float QGraphicsScene.width (self)

This convenience function is equivalent to calling sceneRect().width().

See also height().

## Qt Signal Documentation

### void changed (const QList<QRectF>&)

This signal is emitted by QGraphicsScene when control reaches the event loop, if the scene content changes. The region parameter contains a list of scene rectangles that indicate the area that has been changed.

See also QGraphicsView.update().

### void sceneRectChanged (const QRectF&)

This signal is emitted by QGraphicsScene whenever the scene rect changes. The rect parameter is the new scene rectangle.

See also QGraphicsView.updateSceneRect().

### void selectionChanged ()

This signal is emitted by QGraphicsScene whenever the selection changes. You can call selectedItems() to get the new list of selected items.

The selection changes whenever an item is selected or unselected, a selection area is set, cleared or otherwise changed, if a preselected item is added to the scene, or if a selected item is removed from the scene.

QGraphicsScene emits this signal only once for group selection operations. For example, if you set a selection area, select or unselect a QGraphicsItemGroup, or if you add or remove from the scene a parent item that contains several selected items, selectionChanged() is emitted only once after the operation has completed (instead of once for each item).

This function was introduced in Qt 4.3.

See also setSelectionArea(), selectedItems(), and QGraphicsItem.setSelected().