class QGraphicsScene

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

Inheritance diagram of PySide6.QtWidgets.QGraphicsScene

Synopsis

Properties

Methods

Virtual methods

Slots

Signals

Note

This documentation may contain snippets that were automatically translated from C++ to Python. We always welcome contributions to the snippet translation. If you see an issue with the translation, you can also let us know by creating a ticket on https:/bugreports.qt.io/projects/PYSIDE

Detailed Description

Warning

This section contains snippets that were automatically translated from C++ to Python and may contain errors.

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:

scene = QGraphicsScene()
scene.addText("Hello, world!")
view = QGraphicsView(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. The dimensions of the items added with these functions are relative to the item’s coordinate system, and the items position is initialized to (0, 0) in the scene.

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 a 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, QCoreApplication::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 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 acceptHoverEvents() ), 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 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.

class ItemIndexMethod

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

Constant

Description

QGraphicsScene.BspTreeIndex

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

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() bspTreeDepth

class SceneLayer

(inherits enum.Flag) 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 invalidateScene() .

Constant

Description

QGraphicsScene.ItemLayer

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

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

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

All layers; this value represents a combination of all three layers.

See also

invalidate() invalidateScene()

Note

Properties can be used directly when from __feature__ import true_property is used or via accessor functions otherwise.

property backgroundBrushᅟ: QBrush

Warning

This section contains snippets that were automatically translated from C++ to Python and may contain errors.

This property holds the background brush of the scene..

Set this property to changes the scene’s background to a different color, gradient or texture. The default background brush is Qt::NoBrush. The background is drawn before (behind) the items.

Example:

scene = QGraphicsScene()
view = QGraphicsView(scene)
view.show()
# a blue background
scene.setBackgroundBrush(Qt.blue)
# a gradient background
gradient = QRadialGradient(0, 0, 10)
gradient.setSpread(QGradient.RepeatSpread)
scene.setBackgroundBrush(gradient)

render() calls drawBackground() to draw the scene background. For more detailed control over how the background is drawn, you can reimplement drawBackground() in a subclass of QGraphicsScene .

Access functions:
property bspTreeDepthᅟ: int

Warning

This section contains snippets that were automatically translated from C++ to Python and may contain errors.

This property holds the depth of QGraphicsScene ‘s BSP index tree.

This property has no effect when NoIndex is used.

This value determines the depth of QGraphicsScene ‘s BSP tree. The depth directly affects QGraphicsScene ‘s performance and memory usage; the latter growing exponentially with the depth of the tree. With an optimal tree depth, QGraphicsScene can instantly determine the locality of items, even for scenes with thousands or millions of items. This also greatly improves rendering performance.

By default, the value is 0, in which case Qt will guess a reasonable default depth based on the size, location and number of items in the scene. If these parameters change frequently, however, you may experience slowdowns as QGraphicsScene retunes the depth internally. You can avoid potential slowdowns by fixating the tree depth through setting this property.

The depth of the tree and the size of the scene rectangle decide the granularity of the scene’s partitioning. The size of each scene segment is determined by the following algorithm:

segmentSize = sceneRect().size() / pow(2, depth - 1)

The BSP tree has an optimal size when each segment contains between 0 and 10 items.

See also

itemIndexMethod

Access functions:
property focusOnTouchᅟ: bool

This property holds whether items gain focus when receiving a touch begin event..

The usual behavior is to transfer focus only when an item is clicked. Often a tap on a touchpad is interpreted as equivalent to a mouse click by the operating system, generating a synthesized click event in response. However, at least on macOS you can configure this behavior.

By default, QGraphicsScene also transfers focus when you touch on a trackpad or similar. If the operating system is configured to not generate a synthetic mouse click on tapping the trackpad, this is surprising. If the operating system does generate synthetic mouse clicks on tapping the trackpad, the focus transfer on starting a touch gesture is unnecessary.

With focusOnTouch switched off, QGraphicsScene behaves as one would expect on macOS.

The default value is true, ensuring that the default behavior is just as in Qt versions prior to 5.12. Set to false to prevent touch events from triggering focus changes.

Access functions:
property fontᅟ: QFont

This property holds the scene’s default font.

This property provides the scene’s font. The scene font defaults to, and resolves all its entries from, font .

If the scene’s font changes, either directly through setFont() or indirectly when the application font changes, QGraphicsScene first sends itself a FontChange event, and it then sends FontChange events to all top-level widget items in the scene. These items respond by resolving their own fonts to the scene, and they then notify their children, who again notify their children, and so on, until all widget items have updated their fonts.

Changing the scene font, (directly or indirectly through setFont() ,) automatically schedules a redraw the entire scene.

Access functions:
property foregroundBrushᅟ: QBrush

Warning

This section contains snippets that were automatically translated from C++ to Python and may contain errors.

This property holds the foreground brush of the scene..

Change this property to set the scene’s foreground to a different color, gradient or texture.

The foreground is drawn after (on top of) the items. The default foreground brush is Qt::NoBrush ( i.e. the foreground is not drawn).

Example:

scene = QGraphicsScene()
view = QGraphicsView(scene)
view.show()
# a white semi-transparent foreground
scene.setForegroundBrush(QColor(255, 255, 255, 127))
# a grid foreground
scene.setForegroundBrush(QBrush(Qt.lightGray, Qt.CrossPattern))

render() calls drawForeground() to draw the scene foreground. For more detailed control over how the foreground is drawn, you can reimplement the drawForeground() function in a QGraphicsScene subclass.

Access functions:
property itemIndexMethodᅟ: QGraphicsScene.ItemIndexMethod

This property holds the item indexing method..

QGraphicsScene applies an indexing algorithm to the scene, to speed up item discovery functions like items() and itemAt() . Indexing is most efficient for static scenes (i.e., where items don’t move around). For dynamic scenes, or scenes with many animated items, the index bookkeeping can outweigh the fast lookup speeds.

For the common case, the default index method BspTreeIndex works fine. If your scene uses many animations and you are experiencing slowness, you can disable indexing by calling setItemIndexMethod(NoIndex).

See also

bspTreeDepth

Access functions:
property minimumRenderSizeᅟ: float

This property holds the minimal view-transformed size an item must have to be drawn.

When the scene is rendered, any item whose width or height, transformed to the target view, is smaller that minimumRenderSize(), will not be rendered. If an item is not rendered and it clips its children items they will also not be rendered. Set this value to speed up rendering of scenes with many objects rendered on a zoomed out view.

The default value is 0. If unset, or if set to 0 or a negative value, all items will always be rendered.

For example, setting this property can be especially useful if a scene is rendered by multiple views, one of which serves as an overview which always displays all items. In scenes with many items, such a view will use a high scaling factor so that all items can be shown. Due to the scaling, smaller items will only make an insignificant contribution to the final rendered scene. To avoid drawing these items and reduce the time necessary to render the scene, you can call setMinimumRenderSize() with a non-negative value.

Note

Items that are not drawn as a result of being too small, are still returned by methods such as items() and itemAt() , and participate in collision detection and interactions. It is recommended that you set minimumRenderSize() to a value less than or equal to 1 in order to avoid large unrendered items that are interactive.

See also

levelOfDetailFromTransform()

Access functions:
property paletteᅟ: QPalette

This property holds the scene’s default palette.

This property provides the scene’s palette. The scene palette defaults to, and resolves all its entries from, palette .

If the scene’s palette changes, either directly through setPalette() or indirectly when the application palette changes, QGraphicsScene first sends itself a PaletteChange event, and it then sends PaletteChange events to all top-level widget items in the scene. These items respond by resolving their own palettes to the scene, and they then notify their children, who again notify their children, and so on, until all widget items have updated their palettes.

Changing the scene palette, (directly or indirectly through setPalette() ,) automatically schedules a redraw the entire scene.

Access functions:
property sceneRectᅟ: QRectF

This property holds the scene rectangle; the bounding rectangle of the scene.

The scene rectangle defines the extent of the scene. It is primarily used by QGraphicsView to determine the view’s default scrollable area, and by QGraphicsScene to manage item indexing.

If unset, or if set to a null QRectF, sceneRect() will return the largest bounding rect of all items on the scene since the scene was created (i.e., a rectangle that grows when items are added to or moved in the scene, but never shrinks).

Access functions:
property stickyFocusᅟ: bool

This property holds whether clicking into the scene background will clear focus.

In a QGraphicsScene with stickyFocus set to true, focus will remain unchanged when the user clicks into the scene background or on an item that does not accept focus. Otherwise, focus will be cleared.

By default, this property is false.

Focus changes in response to a mouse press. You can reimplement mousePressEvent() in a subclass of QGraphicsScene to toggle this property based on where the user has clicked.

Access functions:
__init__([parent=None])
Parameters:

parent – QObject

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

__init__(sceneRect[, parent=None])
Parameters:

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

See also

sceneRect

__init__(x, y, width, height[, parent=None])
Parameters:

  • x – float

  • y – float

  • width – float

  • height – float

  • parent – QObject

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

activePanel()
Return type:

QGraphicsItem

Returns the current active panel, or None if no panel is currently active.

See also

setActivePanel()

activeWindow()
Return type:

QGraphicsWidget

Returns the current active window, or None if no window is currently active.

addEllipse(rect[, pen=QPen()[, brush=QBrush()]])
Parameters:
Return type:

QGraphicsEllipseItem

Creates and adds an ellipse item to the scene, and returns the item pointer. The geometry of the ellipse is defined by rect, and its 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., isVisible() returns true), QGraphicsScene will emit changed() once control goes back to the event loop.

addEllipse(x, y, w, h[, pen=QPen()[, brush=QBrush()]])
Parameters:

  • x – float

  • y – float

  • w – float

  • h – float

  • pen – QPen

  • brush – QBrush

Return type:

QGraphicsEllipseItem

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

addItem(item)
Parameters:

item – QGraphicsItem

Adds or moves the item and all its children to this scene. This scene takes ownership of the item.

If the item is visible (i.e., 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.

QGraphicsScene will send ItemSceneChange notifications to item while it is added to the scene. If item does not currently belong to a scene, only one notification is sent. If it does belong to scene already (i.e., it is moved to this scene), QGraphicsScene will send an addition notification as the item is removed from its previous scene.

If the item is a panel, the scene is active, and there is no active panel in the scene, then the item will be activated.

addLine(line[, pen=QPen()])
Parameters:
Return type:

QGraphicsLineItem

Creates and adds a line item to the scene, and returns the item pointer. The geometry of the line is defined by line, and its 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., isVisible() returns true), QGraphicsScene will emit changed() once control goes back to the event loop.

addLine(x1, y1, x2, y2[, pen=QPen()])
Parameters:

  • x1 – float

  • y1 – float

  • x2 – float

  • y2 – float

  • pen – QPen

Return type:

QGraphicsLineItem

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

addPath(path[, pen=QPen()[, brush=QBrush()]])
Parameters:
Return type:

QGraphicsPathItem

Creates and adds a path item to the scene, and returns the item pointer. The geometry of the path is defined by path, and its 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., isVisible() returns true), QGraphicsScene will emit changed() once control goes back to the event loop.

addPixmap(pixmap)
Parameters:

pixmap – QPixmap

Return type:

QGraphicsPixmapItem

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., isVisible() returns true), QGraphicsScene will emit changed() once control goes back to the event loop.

addPolygon(polygon[, pen=QPen()[, brush=QBrush()]])
Parameters:
Return type:

QGraphicsPolygonItem

Creates and adds a polygon item to the scene, and returns the item pointer. The polygon is defined by polygon, and its 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., isVisible() returns true), QGraphicsScene will emit changed() once control goes back to the event loop.

addRect(rect[, pen=QPen()[, brush=QBrush()]])
Parameters:
Return type:

QGraphicsRectItem

Creates and adds a rectangle item to the scene, and returns the item pointer. The geometry of the rectangle is defined by rect, and its 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). For example, if a QRect(50, 50, 100, 100) is added, its top-left corner will be at (50, 50) relative to the origin in the item’s coordinate system.

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

addRect(x, y, w, h[, pen=QPen()[, brush=QBrush()]])
Parameters:

  • x – float

  • y – float

  • w – float

  • h – float

  • pen – QPen

  • brush – QBrush

Return type:

QGraphicsRectItem

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

addSimpleText(text[, font=QFont()])
Parameters:

  • text – str

  • font – QFont

Return type:

QGraphicsSimpleTextItem

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

The item’s position is initialized to (0, 0).

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

addText(text[, font=QFont()])
Parameters:

  • text – str

  • font – QFont

Return type:

QGraphicsTextItem

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

The item’s position is initialized to (0, 0).

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

addWidget(widget[, wFlags=Qt.WindowFlags()])
Parameters:
Return type:

QGraphicsProxyWidget

Creates a new QGraphicsProxyWidget for widget, adds it to the scene, and returns a pointer to the proxy. wFlags set the default window flags for the embedding proxy widget.

The item’s position is initialized to (0, 0).

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

Note that widgets with the Qt::WA_PaintOnScreen widget attribute set and widgets that wrap an external application or controller are not supported. Examples are QOpenGLWidget and QAxWidget.

advance()

This slot advances the scene by one step, by calling 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, advance() is called passing a value of 0 as an argument, and 1 is passed in the second phase.

Note that you can also use the Animation Framework for animations.

See also

advance() QTimeLine

backgroundBrush()
Return type:

QBrush

See also

setBackgroundBrush()

Getter of property backgroundBrushᅟ .

bspTreeDepth()
Return type:

int

See also

setBspTreeDepth()

Getter of property bspTreeDepthᅟ .

changed(region)
Parameters:

region – .list of 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

updateScene()

clear()

Removes and deletes all items from the scene, but otherwise leaves the state of the scene unchanged.

See also

addItem()

clearFocus()

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.

clearSelection()

Clears the current selection.

collidingItems(item[, mode=Qt.IntersectsItemShape])
Parameters:
Return type:

.list of QGraphicsItem

Returns a list of all items that collide with item. Collisions are determined by calling 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 stacking order (i.e., the first item in the list is the uppermost item, and the last item is the lowermost item).

contextMenuEvent(event)
Parameters:

event – QGraphicsSceneContextMenuEvent

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 topmost visible item that accepts context menu events at the position of the event. If no items accept context menu events at this position, the event is ignored.

Note: See items() for a definition of which items are considered visible by this function.

createItemGroup(items)
Parameters:

items – .list of QGraphicsItem

Return type:

QGraphicsItemGroup

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() .

destroyItemGroup(group)
Parameters:

group – QGraphicsItemGroup

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.

dragEnterEvent(event)
Parameters:

event – QGraphicsSceneDragDropEvent

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.

dragLeaveEvent(event)
Parameters:

event – QGraphicsSceneDragDropEvent

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

dragMoveEvent(event)
Parameters:

event – QGraphicsSceneDragDropEvent

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

Note: See items() for a definition of which items are considered visible by this function.

drawBackground(painter, rect)
Parameters:

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.

If all you want is to define a color, texture, or gradient for the background, you can call setBackgroundBrush() instead.

See also

drawForeground() drawItems()

drawForeground(painter, rect)
Parameters:

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.

If all you want is to define a color, texture or gradient for the foreground, you can call setForegroundBrush() instead.

See also

drawBackground() drawItems()

dropEvent(event)
Parameters:

event – QGraphicsSceneDragDropEvent

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

focusInEvent(event)
Parameters:

event – QFocusEvent

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

focusOutEvent()

focusItem()
Return type:

QGraphicsItem

When the scene is active, this functions returns the scene’s current focus item, or None if no item currently has focus. When the scene is inactive, this functions returns the item that will gain input focus when the scene becomes active.

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

focusItemChanged(newFocus, oldFocus, reason)
Parameters:

This signal is emitted by QGraphicsScene whenever focus changes in the scene (i.e., when an item gains or loses input focus, or when focus passes from one item to another). You can connect to this signal if you need to keep track of when other items gain input focus. It is particularly useful for implementing virtual keyboards, input methods, and cursor items.

oldFocusItem is a pointer to the item that previously had focus, or 0 if no item had focus before the signal was emitted. newFocusItem is a pointer to the item that gained input focus, or None if focus was lost. reason is the reason for the focus change (e.g., if the scene was deactivated while an input field had focus, oldFocusItem would point to the input field item, newFocusItem would be None, and reason would be Qt::ActiveWindowFocusReason.

focusNextPrevChild(next)
Parameters:

next – bool

Return type:

bool

Finds a new widget to give the keyboard focus to, as appropriate for Tab and Shift+Tab, and returns true if it can find a new widget, or false if it cannot. If next is true, this function searches forward; if next is false, it searches backward.

You can reimplement this function in a subclass of QGraphicsScene to provide fine-grained control over how tab focus passes inside your scene. The default implementation is based on the tab focus chain defined by setTabOrder() .

focusOnTouch()
Return type:

bool

See also

setFocusOnTouch()

Getter of property focusOnTouchᅟ .

focusOutEvent(event)
Parameters:

event – QFocusEvent

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

focusInEvent()

font()
Return type:

QFont

See also

setFont()

Getter of property fontᅟ .

foregroundBrush()
Return type:

QBrush

See also

setForegroundBrush()

Getter of property foregroundBrushᅟ .

hasFocus()
Return type:

bool

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

height()
Return type:

float

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

See also

width()

helpEvent(event)
Parameters:

event – QGraphicsSceneHelpEvent

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 visible 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.

Note: See items() for a definition of which items are considered visible by this function.

inputMethodEvent(event)
Parameters:

event – QInputMethodEvent

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 or the current focus item does not accept input methods, this function does nothing.

inputMethodQuery(query)
Parameters:

query – InputMethodQuery

Return type:

object

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.

invalidate([rect=QRectF()[, layers=QGraphicsScene.SceneLayer.AllLayers]])
Parameters:

Warning

This section contains snippets that were automatically translated from C++ to Python and may contain errors.

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:

def rectForTile(self, int x, int y):

    # Return the rectangle for the tile at position (x, y).
    return QRectF(x * tileWidth, y * tileHeight, tileWidth, tileHeight)

def setTile(self, x, y, pixmap):

    # Sets or replaces the tile at position (x, y) with pixmap.
    if x >= 0 and x < numTilesH and y >= 0 and y < numTilesV:
        tiles[y][x] = pixmap
        invalidate(rectForTile(x, y), BackgroundLayer)


def drawBackground(self, painter, exposed):

    # Draws all tiles that intersect the exposed area.
    for y in range(0, numTilesV):
        for x in range(0, numTilesH):
            rect = rectForTile(x, y)
            if exposed.intersects(rect):
                painter.drawPixmap(rect.topLeft(), tiles[y][x])

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

invalidate(x, y, w, h[, layers=QGraphicsScene.SceneLayer.AllLayers])
Parameters:

  • x – float

  • y – float

  • w – float

  • h – float

  • layers – Combination of SceneLayer

This is an overloaded function.

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

isActive()
Return type:

bool

Returns true if the scene is active (e.g., it’s viewed by at least one QGraphicsView that is active); otherwise returns false.

itemAt(pos, deviceTransform)
Parameters:
Return type:

QGraphicsItem

Returns the topmost visible item at the specified position, or None if there are no items at this position.

deviceTransform is the transformation that applies to the view, and needs to be provided if the scene contains items that ignore transformations.

Note: See items() for a definition of which items are considered visible by this function.

See also

items() collidingItems() Sorting

itemAt(x, y, deviceTransform)
Parameters:

  • x – float

  • y – float

  • deviceTransform – QTransform

Return type:

QGraphicsItem

This is an overloaded function.

Returns the topmost visible item at the position specified by (x, y), or None if there are no items at this position.

deviceTransform is the transformation that applies to the view, and needs to be provided if the scene contains items that ignore transformations.

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

Note: See items() for a definition of which items are considered visible by this function.

itemIndexMethod()
Return type:

ItemIndexMethod

See also

setItemIndexMethod()

Getter of property itemIndexMethodᅟ .

items([order=Qt.DescendingOrder])
Parameters:

order – SortOrder

Return type:

.list of QGraphicsItem

Returns an ordered list of all items on the scene. order decides the stacking order.

See also

addItem() removeItem() Sorting

items(path[, mode=Qt.IntersectsItemShape[, order=Qt.DescendingOrder[, deviceTransform=QTransform()]]])
Parameters:
Return type:

.list of QGraphicsItem

This is an overloaded function.

Returns all visible items that, depending on mode, are either inside or intersect with the specified path, in a list sorted using order. In this case, “visible” defines items for which: isVisible() returns true, effectiveOpacity() returns a value greater than 0.0 (which is fully transparent) and the parent item does not clip it.

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

deviceTransform is the transformation that applies to the view, and needs to be provided if the scene contains items that ignore transformations.

See also

itemAt() Sorting

items(pos[, mode=Qt.IntersectsItemShape[, order=Qt.DescendingOrder[, deviceTransform=QTransform()]]])
Parameters:
Return type:

.list of QGraphicsItem

Returns all visible items that, depending on mode, are at the specified pos in a list sorted using order. In this case, “visible” defines items for which: isVisible() returns true, effectiveOpacity() returns a value greater than 0.0 (which is fully transparent) and the parent item does not clip it.

The default value for mode is Qt::IntersectsItemShape; all items whose exact shape intersects with pos are returned.

deviceTransform is the transformation that applies to the view, and needs to be provided if the scene contains items that ignore transformations.

See also

itemAt() Sorting

items(polygon[, mode=Qt.IntersectsItemShape[, order=Qt.DescendingOrder[, deviceTransform=QTransform()]]])
Parameters:
Return type:

.list of QGraphicsItem

This is an overloaded function.

Returns all visible items that, depending on mode, are either inside or intersect with the specified polygon, in a list sorted using order. In this case, “visible” defines items for which: isVisible() returns true, effectiveOpacity() returns a value greater than 0.0 (which is fully transparent) and the parent item does not clip it.

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

deviceTransform is the transformation that applies to the view, and needs to be provided if the scene contains items that ignore transformations.

See also

itemAt() Sorting

items(rect[, mode=Qt.IntersectsItemShape[, order=Qt.DescendingOrder[, deviceTransform=QTransform()]]])
Parameters:
Return type:

.list of QGraphicsItem

This is an overloaded function.

Returns all visible items that, depending on mode, are either inside or intersect with the specified rect, in a list sorted using order. In this case, “visible” defines items for which: isVisible() returns true, effectiveOpacity() returns a value greater than 0.0 (which is fully transparent) and the parent item does not clip it.

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

deviceTransform is the transformation that applies to the view, and needs to be provided if the scene contains items that ignore transformations.

See also

itemAt() Sorting

items(x, y, w, h, mode, order[, deviceTransform=QTransform()])
Parameters:
Return type:

.list of QGraphicsItem

This is an overloaded function.

Returns all visible items that, depending on mode, are either inside or intersect with the rectangle defined by x, y, w and h, in a list sorted using order. In this case, “visible” defines items for which: isVisible() returns true, effectiveOpacity() returns a value greater than 0.0 (which is fully transparent) and the parent item does not clip it.

deviceTransform is the transformation that applies to the view, and needs to be provided if the scene contains items that ignore transformations.

itemsBoundingRect()
Return type:

QRectF

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

See also

sceneRect()

keyPressEvent(event)
Parameters:

event – QKeyEvent

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.

keyReleaseEvent(event)
Parameters:

event – QKeyEvent

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.

minimumRenderSize()
Return type:

float

See also

setMinimumRenderSize()

Getter of property minimumRenderSizeᅟ .

mouseDoubleClickEvent(event)
Parameters:

event – QGraphicsSceneMouseEvent

This event handler, for event mouseEvent, can be reimplemented in a subclass to receive mouse double-click 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 double-click event, and finally a release event. If the double-click 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 double-click events in this case.

The default implementation is similar to mousePressEvent() .

Note: See items() for a definition of which items are considered visible by this function.

mouseGrabberItem()
Return type:

QGraphicsItem

Returns the current mouse grabber item, or None 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).

mouseMoveEvent(event)
Parameters:

event – QGraphicsSceneMouseEvent

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. If there are any items that accept hover events at the current position, the event is translated into a hover event and accepted; otherwise it’s ignored.

mousePressEvent(event)
Parameters:

event – QGraphicsSceneMouseEvent

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 visible 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.

Note: See items() for a definition of which items are considered visible by this function.

mouseReleaseEvent(event)
Parameters:

event – QGraphicsSceneMouseEvent

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.

palette()
Return type:

QPalette

See also

setPalette()

Getter of property paletteᅟ .

removeItem(item)
Parameters:

item – QGraphicsItem

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()

render(painter[, target=QRectF()[, source=QRectF()[, aspectRatioMode=Qt.KeepAspectRatio]]])
Parameters:

Warning

This section contains snippets that were automatically translated from C++ to Python and may contain errors.

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:

scene = QGraphicsScene()
scene.addItem(...
...
printer = QPrinter(QPrinter.HighResolution)
printer.setPaperSize(QPrinter.A4)
painter = QPainter(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

render()

sceneRect()
Return type:

QRectF

See also

setSceneRect()

Getter of property sceneRectᅟ .

sceneRectChanged(rect)
Parameters:

rect – QRectF

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

selectedItems()
Return type:

.list of QGraphicsItem

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

selectionArea()
Return type:

QPainterPath

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

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).

sendEvent(item, event)
Parameters:
Return type:

bool

Sends event event to item item through possible event filters.

The event is sent only if the item is enabled.

Returns false if the event was filtered or if the item is disabled. Otherwise returns the value that was returned from the event handler.

setActivePanel(item)
Parameters:

item – QGraphicsItem

Activates item, which must be an item in this scene. You can also pass 0 for item, in which case QGraphicsScene will deactivate any currently active panel.

If the scene is currently inactive, item remains inactive until the scene becomes active (or, ir item is None, no item will be activated).

setActiveWindow(widget)
Parameters:

widget – QGraphicsWidget

Activates widget, which must be a widget in this scene. You can also pass 0 for widget, in which case QGraphicsScene will deactivate any currently active window.

setBackgroundBrush(brush)
Parameters:

brush – QBrush

See also

backgroundBrush()

Setter of property backgroundBrushᅟ .

setBspTreeDepth(depth)
Parameters:

depth – int

See also

bspTreeDepth()

Setter of property bspTreeDepthᅟ .

setFocus([focusReason=Qt.OtherFocusReason])
Parameters:

focusReason – FocusReason

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.

setFocusItem(item[, focusReason=Qt.OtherFocusReason])
Parameters:

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 None, or if it either does not accept focus (i.e., it does not have the ItemIsFocusable flag enabled), or is not visible or not enabled, this function only removes focus from any previous focusitem.

If item is not None, and the scene does not currently have focus (i.e., hasFocus() returns false), this function will call setFocus() automatically.

setFocusOnTouch(enabled)
Parameters:

enabled – bool

See also

focusOnTouch()

Setter of property focusOnTouchᅟ .

setFont(font)
Parameters:

font – QFont

See also

font()

Setter of property fontᅟ .

setForegroundBrush(brush)
Parameters:

brush – QBrush

See also

foregroundBrush()

Setter of property foregroundBrushᅟ .

setItemIndexMethod(method)
Parameters:

method – ItemIndexMethod

See also

itemIndexMethod()

Setter of property itemIndexMethodᅟ .

setMinimumRenderSize(minSize)
Parameters:

minSize – float

See also

minimumRenderSize()

Setter of property minimumRenderSizeᅟ .

setPalette(palette)
Parameters:

palette – QPalette

See also

palette()

Setter of property paletteᅟ .

setSceneRect(rect)
Parameters:

rect – QRectF

See also

sceneRect()

Setter of property sceneRectᅟ .

setSceneRect(x, y, w, h)
Parameters:

  • x – float

  • y – float

  • w – float

  • h – float

setSelectionArea(path, deviceTransform)
Parameters:

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() .

deviceTransform is the transformation that applies to the view, and needs to be provided if the scene contains items that ignore transformations.

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

setSelectionArea(path[, selectionOperation=Qt.ReplaceSelection[, mode=Qt.IntersectsItemShape[, deviceTransform=QTransform()]]])
Parameters:

This is an overloaded function.

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

deviceTransform is the transformation that applies to the view, and needs to be provided if the scene contains items that ignore transformations.

selectionOperation determines what to do with the currently selected items.

setStickyFocus(enabled)
Parameters:

enabled – bool

See also

stickyFocus()

Setter of property stickyFocusᅟ .

setStyle(style)
Parameters:

style – QStyle

Sets or replaces the style of the scene to style, and reparents the style to this scene. Any previously assigned style is deleted. The scene’s style defaults to style() , and serves as the default for all QGraphicsWidget items in the scene.

Changing the style, either directly by calling this function, or indirectly by calling setStyle() , will automatically update the style for all widgets in the scene that do not have a style explicitly assigned to them.

If style is None, QGraphicsScene will revert to style() .

See also

style()

stickyFocus()
Return type:

bool

See also

setStickyFocus()

Getter of property stickyFocusᅟ .

style()
Return type:

QStyle

Returns the scene’s style, or the same as style() if the scene has not been explicitly assigned a style.

See also

setStyle()

update([rect=QRectF()])
Parameters:

rect – QRectF

Schedules a redraw of the area rect on the scene.

update(x, y, w, h)
Parameters:

  • x – float

  • y – float

  • w – float

  • h – float

This is an overloaded function.

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

views()
Return type:

.list of QGraphicsView

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

See also

scene()

wheelEvent(event)
Parameters:

event – QGraphicsSceneWheelEvent

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.

Note: See items() for a definition of which items are considered visible by this function.

See also

wheelEvent()

width()
Return type:

float

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

See also

height()