class QGraphicsItem#

The QGraphicsItem class is the base class for all graphical items in a QGraphicsScene . More

Inheritance diagram of PySide6.QtWidgets.QGraphicsItem

Inherited by: QGraphicsPixmapItem, QGraphicsLineItem, QGraphicsItemGroup, QAbstractGraphicsShapeItem, QGraphicsSimpleTextItem, QGraphicsRectItem, QGraphicsPolygonItem, QGraphicsPathItem, QGraphicsEllipseItem, QGraphicsObject, QGraphicsWidget, QGraphicsProxyWidget, QGraphicsTextItem, QGraphicsSvgItem, QGraphicsVideoItem, QLegend, QChart, QPolarChart

Synopsis#

Methods#

Virtual methods#

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.

It provides a light-weight foundation for writing your own custom items. This includes defining the item’s geometry, collision detection, its painting implementation and item interaction through its event handlers. QGraphicsItem is part of the Graphics View Framework

../../_images/graphicsview-items.png

For convenience, Qt provides a set of standard graphics items for the most common shapes. These are:

All of an item’s geometric information is based on its local coordinate system. The item’s position, pos() , is the only function that does not operate in local coordinates, as it returns a position in parent coordinates. The Graphics View Coordinate System describes the coordinate system in detail.

You can set whether an item should be visible (i.e., drawn, and accepting events), by calling setVisible() . Hiding an item will also hide its children. Similarly, you can enable or disable an item by calling setEnabled() . If you disable an item, all its children will also be disabled. By default, items are both visible and enabled. To toggle whether an item is selected or not, first enable selection by setting the ItemIsSelectable flag, and then call setSelected() . Normally, selection is toggled by the scene, as a result of user interaction.

To write your own graphics item, you first create a subclass of QGraphicsItem , and then start by implementing its two pure virtual public functions: boundingRect() , which returns an estimate of the area painted by the item, and paint() , which implements the actual painting. For example:

class SimpleItem(QGraphicsItem):

# public
    QRectF boundingRect() override

        penWidth = 1
        return QRectF(-10 - penWidth / 2, -10 - penWidth / 2,
                      20 + penWidth, 20 + penWidth)

    def paint(painter, option,):
               QWidget widget) override

        painter.drawRoundedRect(-10, -10, 20, 20, 5, 5)

The boundingRect() function has many different purposes. QGraphicsScene bases its item index on boundingRect() , and QGraphicsView uses it both for culling invisible items, and for determining the area that needs to be recomposed when drawing overlapping items. In addition, QGraphicsItem ‘s collision detection mechanisms use boundingRect() to provide an efficient cut-off. The fine grained collision algorithm in collidesWithItem() is based on calling shape() , which returns an accurate outline of the item’s shape as a QPainterPath.

QGraphicsScene expects all items boundingRect() and shape() to remain unchanged unless it is notified. If you want to change an item’s geometry in any way, you must first call prepareGeometryChange() to allow QGraphicsScene to update its bookkeeping.

Collision detection can be done in two ways:

  1. Reimplement shape() to return an accurate shape for your item, and rely on the default implementation of collidesWithItem() to do shape-shape intersection. This can be rather expensive if the shapes are complex.

  2. Reimplement collidesWithItem() to provide your own custom item and shape collision algorithm.

The contains() function can be called to determine whether the item contains a point or not. This function can also be reimplemented by the item. The default behavior of contains() is based on calling shape() .

Items can contain other items, and also be contained by other items. All items can have a parent item and a list of children. Unless the item has no parent, its position is in parent coordinates (i.e., the parent’s local coordinates). Parent items propagate both their position and their transformation to all children.

../../_images/graphicsview-parentchild.png

Transformations#

QGraphicsItem supports projective transformations in addition to its base position, pos() . There are several ways to change an item’s transformation. For simple transformations, you can call either of the convenience functions setRotation() or setScale() , or you can pass any transformation matrix to setTransform() . For advanced transformation control you also have the option of setting several combined transformations by calling setTransformations() .

Item transformations accumulate from parent to child, so if both a parent and child item are rotated 90 degrees, the child’s total transformation will be 180 degrees. Similarly, if the item’s parent is scaled to 2x its original size, its children will also be twice as large. An item’s transformation does not affect its own local geometry; all geometry functions (e.g., contains() , update() , and all the mapping functions) still operate in local coordinates. For convenience, QGraphicsItem provides the functions sceneTransform() , which returns the item’s total transformation matrix (including its position and all parents’ positions and transformations), and scenePos() , which returns its position in scene coordinates. To reset an item’s matrix, call resetTransform() .

Certain transformation operations produce a different outcome depending on the order in which they are applied. For example, if you scale an transform, and then rotate it, you may get a different result than if the transform was rotated first. However, the order you set the transformation properties on QGraphicsItem does not affect the resulting transformation; QGraphicsItem always applies the properties in a fixed, defined order:

Painting#

The paint() function is called by QGraphicsView to paint the item’s contents. The item has no background or default fill of its own; whatever is behind the item will shine through all areas that are not explicitly painted in this function. You can call update() to schedule a repaint, optionally passing the rectangle that needs a repaint. Depending on whether or not the item is visible in a view, the item may or may not be repainted; there is no equivalent to repaint() in QGraphicsItem .

Items are painted by the view, starting with the parent items and then drawing children, in ascending stacking order. You can set an item’s stacking order by calling setZValue() , and test it by calling zValue() , where items with low z-values are painted before items with high z-values. Stacking order applies to sibling items; parents are always drawn before their children.

Sorting#

All items are drawn in a defined, stable order, and this same order decides which items will receive mouse input first when you click on the scene. Normally you don’t have to worry about sorting, as the items follow a “natural order”, following the logical structure of the scene.

An item’s children are stacked on top of the parent, and sibling items are stacked by insertion order (i.e., in the same order that they were either added to the scene, or added to the same parent). If you add item A, and then B, then B will be on top of A. If you then add C, the items’ stacking order will be A, then B, then C.

../../_images/graphicsview-zorder.png

This example shows the stacking order of all limbs of the robot from the Drag and Drop Robot example. The torso is the root item (all other items are children or descendants of the torso), so it is drawn first. Next, the head is drawn, as it is the first item in the torso’s list of children. Then the upper left arm is drawn. As the lower arm is a child of the upper arm, the lower arm is then drawn, followed by the upper arm’s next sibling, which is the upper right arm, and so on.

For advanced users, there are ways to alter how your items are sorted:

  • You can call setZValue() on an item to explicitly stack it on top of, or under, other sibling items. The default Z value for an item is 0. Items with the same Z value are stacked by insertion order.

  • You can call stackBefore() to reorder the list of children. This will directly modify the insertion order.

  • You can set the ItemStacksBehindParent flag to stack a child item behind its parent.

The stacking order of two sibling items also counts for each item’s children and descendant items. So if one item is on top of another, then all its children will also be on top of all the other item’s children as well.

Events#

QGraphicsItem receives events from QGraphicsScene through the virtual function sceneEvent() . This function distributes the most common events to a set of convenience event handlers:

You can filter events for any other item by installing event filters. This functionality is separate from Qt’s regular event filters (see QObject::installEventFilter()), which only work on subclasses of QObject. After installing your item as an event filter for another item by calling installSceneEventFilter() , the filtered events will be received by the virtual function sceneEventFilter() . You can remove item event filters by calling removeSceneEventFilter() .

Custom Data#

Sometimes it’s useful to register custom data with an item, be it a custom item, or a standard item. You can call setData() on any item to store data in it using a key-value pair (the key being an integer, and the value is a QVariant). To get custom data from an item, call data() . This functionality is completely untouched by Qt itself; it is provided for the user’s convenience.

class GraphicsItemFlag#

(inherits enum.Flag) This enum describes different flags that you can set on an item to toggle different features in the item’s behavior.

All flags are disabled by default.

Constant

Description

QGraphicsItem.ItemIsMovable

The item supports interactive movement using the mouse. By clicking on the item and then dragging, the item will move together with the mouse cursor. If the item has children, all children are also moved. If the item is part of a selection, all selected items are also moved. This feature is provided as a convenience through the base implementation of QGraphicsItem ‘s mouse event handlers.

QGraphicsItem.ItemIsSelectable

The item supports selection. Enabling this feature will enable setSelected() to toggle selection for the item. It will also let the item be selected automatically as a result of calling setSelectionArea() , by clicking on an item, or by using rubber band selection in QGraphicsView .

QGraphicsItem.ItemIsFocusable

The item supports keyboard input focus (i.e., it is an input item). Enabling this flag will allow the item to accept focus, which again allows the delivery of key events to keyPressEvent() and keyReleaseEvent() .

QGraphicsItem.ItemClipsToShape

The item clips to its own shape. The item cannot draw or receive mouse, tablet, drag and drop or hover events outside its shape. It is disabled by default. This behavior is enforced by QGraphicsView::drawItems() or QGraphicsScene::drawItems(). This flag was introduced in Qt 4.3.

QGraphicsItem.ItemClipsChildrenToShape

The item clips the painting of all its descendants to its own shape. Items that are either direct or indirect children of this item cannot draw outside this item’s shape. By default, this flag is disabled; children can draw anywhere. This behavior is enforced by QGraphicsView::drawItems() or QGraphicsScene::drawItems(). This flag was introduced in Qt 4.3.

Note

This flag is similar to ItemContainsChildrenInShape but in addition enforces the containment by clipping the children.

Constant

Description

QGraphicsItem.ItemIgnoresTransformations

The item ignores inherited transformations (i.e., its position is still anchored to its parent, but the parent or view rotation, zoom or shear transformations are ignored). This flag is useful for keeping text label items horizontal and unscaled, so they will still be readable if the view is transformed. When set, the item’s view geometry and scene geometry will be maintained separately. You must call deviceTransform() to map coordinates and detect collisions in the view. By default, this flag is disabled. This flag was introduced in Qt 4.3.

Note

With this flag set you can still scale the item itself, and that scale transformation will influence the item’s children.

Constant

Description

QGraphicsItem.ItemIgnoresParentOpacity

The item ignores its parent’s opacity. The item’s effective opacity is the same as its own; it does not combine with the parent’s opacity. This flags allows your item to keep its absolute opacity even if the parent is semitransparent. This flag was introduced in Qt 4.5.

QGraphicsItem.ItemDoesntPropagateOpacityToChildren

The item doesn’t propagate its opacity to its children. This flag allows you to create a semitransparent item that does not affect the opacity of its children. This flag was introduced in Qt 4.5.

QGraphicsItem.ItemStacksBehindParent

The item is stacked behind its parent. By default, child items are stacked on top of the parent item. But setting this flag, the child will be stacked behind it. This flag is useful for drop shadow effects and for decoration objects that follow the parent item’s geometry without drawing on top of it. This flag was introduced in Qt 4.5.

QGraphicsItem.ItemUsesExtendedStyleOption

The item makes use of either exposedRect in QStyleOptionGraphicsItem . By default, the exposedRect is initialized to the item’s boundingRect() . You can enable this flag for the style options to be set up with more fine-grained values. Use levelOfDetailFromTransform() if you need a higher value. This flag was introduced in Qt 4.6.

QGraphicsItem.ItemHasNoContents

The item does not paint anything (i.e., calling paint() on the item has no effect). You should set this flag on items that do not need to be painted to ensure that Graphics View avoids unnecessary painting preparations. This flag was introduced in Qt 4.6.

QGraphicsItem.ItemSendsGeometryChanges

The item enables itemChange() notifications for ItemPositionChange , ItemPositionHasChanged , ItemTransformChange , ItemTransformHasChanged , ItemRotationChange , ItemRotationHasChanged , ItemScaleChange , ItemScaleHasChanged , ItemTransformOriginPointChange , and ItemTransformOriginPointHasChanged . For performance reasons, these notifications are disabled by default. You must enable this flag to receive notifications for position and transform changes. This flag was introduced in Qt 4.6.

QGraphicsItem.ItemAcceptsInputMethod

The item supports input methods typically used for Asian languages. This flag was introduced in Qt 4.6.

QGraphicsItem.ItemNegativeZStacksBehindParent

The item automatically stacks behind it’s parent if it’s z-value is negative. This flag enables setZValue() to toggle ItemStacksBehindParent. This flag was introduced in Qt 4.6.

QGraphicsItem.ItemIsPanel

The item is a panel. A panel provides activation and contained focus handling. Only one panel can be active at a time (see isActive() ). When no panel is active, QGraphicsScene activates all non-panel items. Window items (i.e., isWindow() returns true) are panels. This flag was introduced in Qt 4.6.

QGraphicsItem.ItemSendsScenePositionChanges

The item enables itemChange() notifications for ItemScenePositionHasChanged . For performance reasons, these notifications are disabled by default. You must enable this flag to receive notifications for scene position changes. This flag was introduced in Qt 4.6.

QGraphicsItem.ItemContainsChildrenInShape

This flag indicates that all of the item’s direct or indirect children only draw within the item’s shape. Unlike ItemClipsChildrenToShape, this restriction is not enforced. Set ItemContainsChildrenInShape when you manually assure that drawing is bound to the item’s shape and want to avoid the cost associated with enforcing the clip. Setting this flag enables more efficient drawing and collision detection. The flag is disabled by default.

Note

If both this flag and ItemClipsChildrenToShape are set, the clip will be enforced. This is equivalent to just setting ItemClipsChildrenToShape.

This flag was introduced in Qt 5.4.

class GraphicsItemChange#

This enum describes the state changes that are notified by itemChange() . The notifications are sent as the state changes, and in some cases, adjustments can be made (see the documentation for each change for details).

Note: Be careful with calling functions on the QGraphicsItem itself inside itemChange() , as certain function calls can lead to unwanted recursion. For example, you cannot call setPos() in itemChange() on an ItemPositionChange notification, as the setPos() function will again call itemChange (ItemPositionChange). Instead, you can return the new, adjusted position from itemChange() .

Constant

Description

QGraphicsItem.ItemEnabledChange

The item’s enabled state changes. If the item is presently enabled, it will become disabled, and vice verca. The value argument is the new enabled state (i.e., true or false). Do not call setEnabled() in itemChange() as this notification is delivered. Instead, you can return the new state from itemChange() .

QGraphicsItem.ItemEnabledHasChanged

The item’s enabled state has changed. The value argument is the new enabled state (i.e., true or false). Do not call setEnabled() in itemChange() as this notification is delivered. The return value is ignored.

QGraphicsItem.ItemPositionChange

The item’s position changes. This notification is sent if the ItemSendsGeometryChanges flag is enabled, and when the item’s local position changes, relative to its parent (i.e., as a result of calling setPos() or moveBy() ). The value argument is the new position (i.e., a QPointF). You can call pos() to get the original position. Do not call setPos() or moveBy() in itemChange() as this notification is delivered; instead, you can return the new, adjusted position from itemChange() . After this notification, QGraphicsItem immediately sends the ItemPositionHasChanged notification if the position changed.

QGraphicsItem.ItemPositionHasChanged

The item’s position has changed. This notification is sent if the ItemSendsGeometryChanges flag is enabled, and after the item’s local position, relative to its parent, has changed. The value argument is the new position (the same as pos() ), and QGraphicsItem ignores the return value for this notification (i.e., a read-only notification).

QGraphicsItem.ItemTransformChange

The item’s transformation matrix changes. This notification is sent if the ItemSendsGeometryChanges flag is enabled, and when the item’s local transformation matrix changes (i.e., as a result of calling setTransform() . The value argument is the new matrix (i.e., a QTransform); to get the old matrix, call transform() . Do not call setTransform() or set any of the transformation properties in itemChange() as this notification is delivered; instead, you can return the new matrix from itemChange() . This notification is not sent if you change the transformation properties.

QGraphicsItem.ItemTransformHasChanged

The item’s transformation matrix has changed either because setTransform is called, or one of the transformation properties is changed. This notification is sent if the ItemSendsGeometryChanges flag is enabled, and after the item’s local transformation matrix has changed. The value argument is the new matrix (same as transform() ), and QGraphicsItem ignores the return value for this notification (i.e., a read-only notification).

QGraphicsItem.ItemRotationChange

The item’s rotation property changes. This notification is sent if the ItemSendsGeometryChanges flag is enabled, and when the item’s rotation property changes (i.e., as a result of calling setRotation() ). The value argument is the new rotation (i.e., a double); to get the old rotation, call rotation() . Do not call setRotation() in itemChange() as this notification is delivered; instead, you can return the new rotation from itemChange() .

QGraphicsItem.ItemRotationHasChanged

The item’s rotation property has changed. This notification is sent if the ItemSendsGeometryChanges flag is enabled, and after the item’s rotation property has changed. The value argument is the new rotation (i.e., a double), and QGraphicsItem ignores the return value for this notification (i.e., a read-only notification). Do not call setRotation() in itemChange() as this notification is delivered.

QGraphicsItem.ItemScaleChange

The item’s scale property changes. This notification is sent if the ItemSendsGeometryChanges flag is enabled, and when the item’s scale property changes (i.e., as a result of calling setScale() ). The value argument is the new scale (i.e., a double); to get the old scale, call scale() . Do not call setScale() in itemChange() as this notification is delivered; instead, you can return the new scale from itemChange() .

QGraphicsItem.ItemScaleHasChanged

The item’s scale property has changed. This notification is sent if the ItemSendsGeometryChanges flag is enabled, and after the item’s scale property has changed. The value argument is the new scale (i.e., a double), and QGraphicsItem ignores the return value for this notification (i.e., a read-only notification). Do not call setScale() in itemChange() as this notification is delivered.

QGraphicsItem.ItemTransformOriginPointChange

The item’s transform origin point property changes. This notification is sent if the ItemSendsGeometryChanges flag is enabled, and when the item’s transform origin point property changes (i.e., as a result of calling setTransformOriginPoint() ). The value argument is the new origin point (i.e., a QPointF); to get the old origin point, call transformOriginPoint() . Do not call setTransformOriginPoint() in itemChange() as this notification is delivered; instead, you can return the new transform origin point from itemChange() .

QGraphicsItem.ItemTransformOriginPointHasChanged

The item’s transform origin point property has changed. This notification is sent if the ItemSendsGeometryChanges flag is enabled, and after the item’s transform origin point property has changed. The value argument is the new origin point (i.e., a QPointF), and QGraphicsItem ignores the return value for this notification (i.e., a read-only notification). Do not call setTransformOriginPoint() in itemChange() as this notification is delivered.

QGraphicsItem.ItemSelectedChange

The item’s selected state changes. If the item is presently selected, it will become unselected, and vice verca. The value argument is the new selected state (i.e., true or false). Do not call setSelected() in itemChange() as this notification is delivered; instead, you can return the new selected state from itemChange() .

QGraphicsItem.ItemSelectedHasChanged

The item’s selected state has changed. The value argument is the new selected state (i.e., true or false). Do not call setSelected() in itemChange() as this notification is delivered. The return value is ignored.

QGraphicsItem.ItemVisibleChange

The item’s visible state changes. If the item is presently visible, it will become invisible, and vice verca. The value argument is the new visible state (i.e., true or false). Do not call setVisible() in itemChange() as this notification is delivered; instead, you can return the new visible state from itemChange() .

QGraphicsItem.ItemVisibleHasChanged

The item’s visible state has changed. The value argument is the new visible state (i.e., true or false). Do not call setVisible() in itemChange() as this notification is delivered. The return value is ignored.

QGraphicsItem.ItemParentChange

The item’s parent changes. The value argument is the new parent item (i.e., a QGraphicsItem pointer). Do not call setParentItem() in itemChange() as this notification is delivered; instead, you can return the new parent from itemChange() .

QGraphicsItem.ItemParentHasChanged

The item’s parent has changed. The value argument is the new parent (i.e., a pointer to a QGraphicsItem ). Do not call setParentItem() in itemChange() as this notification is delivered. The return value is ignored.

QGraphicsItem.ItemChildAddedChange

A child is added to this item. The value argument is the new child item (i.e., a QGraphicsItem pointer). Do not pass this item to any item’s setParentItem() function as this notification is delivered. The return value is unused; you cannot adjust anything in this notification. Note that the new child might not be fully constructed when this notification is sent; calling pure virtual functions on the child can lead to a crash.

QGraphicsItem.ItemChildRemovedChange

A child is removed from this item. The value argument is the child item that is about to be removed (i.e., a QGraphicsItem pointer). The return value is unused; you cannot adjust anything in this notification.

QGraphicsItem.ItemSceneChange

The item is moved to a new scene. This notification is also sent when the item is added to its initial scene, and when it is removed. The item’s scene() is the old scene, or None if the item has not been added to a scene yet. The value argument is the new scene (i.e., a QGraphicsScene pointer), or None if the item is removed from a scene. Do not override this change by passing this item to addItem() as this notification is delivered; instead, you can return the new scene from itemChange() . Use this feature with caution; objecting to a scene change can quickly lead to unwanted recursion.

QGraphicsItem.ItemSceneHasChanged

The item’s scene has changed. The item’s scene() is the new scene. This notification is also sent when the item is added to its initial scene, and when it is removed.The value argument is the new scene (i.e., a pointer to a QGraphicsScene ). Do not call setScene() in itemChange() as this notification is delivered. The return value is ignored.

QGraphicsItem.ItemCursorChange

The item’s cursor changes. The value argument is the new cursor (i.e., a QCursor). Do not call setCursor() in itemChange() as this notification is delivered. Instead, you can return a new cursor from itemChange() .

QGraphicsItem.ItemCursorHasChanged

The item’s cursor has changed. The value argument is the new cursor (i.e., a QCursor). Do not call setCursor() as this notification is delivered. The return value is ignored.

QGraphicsItem.ItemToolTipChange

The item’s tooltip changes. The value argument is the new tooltip (i.e., a QToolTip ). Do not call setToolTip() in itemChange() as this notification is delivered. Instead, you can return a new tooltip from itemChange() .

QGraphicsItem.ItemToolTipHasChanged

The item’s tooltip has changed. The value argument is the new tooltip (i.e., a QToolTip ). Do not call setToolTip() as this notification is delivered. The return value is ignored.

QGraphicsItem.ItemFlagsChange

The item’s flags change. The value argument is the new flags (i.e., a quint32). Do not call setFlags() in itemChange() as this notification is delivered. Instead, you can return the new flags from itemChange() .

QGraphicsItem.ItemFlagsHaveChanged

The item’s flags have changed. The value argument is the new flags (i.e., a quint32). Do not call setFlags() in itemChange() as this notification is delivered. The return value is ignored.

QGraphicsItem.ItemZValueChange

The item’s Z-value changes. The value argument is the new Z-value (i.e., a double). Do not call setZValue() in itemChange() as this notification is delivered. Instead, you can return a new Z-value from itemChange() .

QGraphicsItem.ItemZValueHasChanged

The item’s Z-value has changed. The value argument is the new Z-value (i.e., a double). Do not call setZValue() as this notification is delivered. The return value is ignored.

QGraphicsItem.ItemOpacityChange

The item’s opacity changes. The value argument is the new opacity (i.e., a double). Do not call setOpacity() in itemChange() as this notification is delivered. Instead, you can return a new opacity from itemChange() .

QGraphicsItem.ItemOpacityHasChanged

The item’s opacity has changed. The value argument is the new opacity (i.e., a double). Do not call setOpacity() as this notification is delivered. The return value is ignored.

QGraphicsItem.ItemScenePositionHasChanged

The item’s scene position has changed. This notification is sent if the ItemSendsScenePositionChanges flag is enabled, and after the item’s scene position has changed (i.e., the position or transformation of the item itself or the position or transformation of any ancestor has changed). The value argument is the new scene position (the same as scenePos() ), and QGraphicsItem ignores the return value for this notification (i.e., a read-only notification).

class CacheMode#

This enum describes QGraphicsItem ‘s cache modes. Caching is used to speed up rendering by allocating and rendering to an off-screen pixel buffer, which can be reused when the item requires redrawing. For some paint devices, the cache is stored directly in graphics memory, which makes rendering very quick.

Constant

Description

QGraphicsItem.NoCache

The default; all item caching is disabled. paint() is called every time the item needs redrawing.

QGraphicsItem.ItemCoordinateCache

Caching is enabled for the item’s logical (local) coordinate system. QGraphicsItem creates an off-screen pixel buffer with a configurable size / resolution that you can pass to setCacheMode() . Rendering quality will typically degrade, depending on the resolution of the cache and the item transformation. The first time the item is redrawn, it will render itself into the cache, and the cache is then reused for every subsequent expose. The cache is also reused as the item is transformed. To adjust the resolution of the cache, you can call setCacheMode() again.

QGraphicsItem.DeviceCoordinateCache

Caching is enabled at the paint device level, in device coordinates. This mode is for items that can move, but are not rotated, scaled or sheared. If the item is transformed directly or indirectly, the cache will be regenerated automatically. Unlike ItemCoordinateCacheMode, DeviceCoordinateCache always renders at maximum quality.

See also

setCacheMode()

class PanelModality#

This enum specifies the behavior of a modal panel. A modal panel is one that blocks input to other panels. Note that items that are children of a modal panel are not blocked.

The values are:

Constant

Description

QGraphicsItem.NonModal

The panel is not modal and does not block input to other panels. This is the default value for panels.

QGraphicsItem.PanelModal

The panel is modal to a single item hierarchy and blocks input to its parent pane, all grandparent panels, and all siblings of its parent and grandparent panels.

QGraphicsItem.SceneModal

The window is modal to the entire scene and blocks input to all panels.

New in version 4.6.

class Extension#
__init__([parent=None])#
Parameters:

parentQGraphicsItem

Constructs a QGraphicsItem with the given parent item. It does not modify the parent object returned by QObject::parent().

If parent is None, you can add the item to a scene by calling addItem() . The item will then become a top-level item.

acceptDrops()#
Return type:

bool

Returns true if this item can accept drag and drop events; otherwise, returns false. By default, items do not accept drag and drop events; items are transparent to drag and drop.

See also

setAcceptDrops()

acceptHoverEvents()#
Return type:

bool

Returns true if an item accepts hover events ( QGraphicsSceneHoverEvent ); otherwise, returns false. By default, items do not accept hover events.

acceptTouchEvents()#
Return type:

bool

Returns true if an item accepts touch events; otherwise, returns false. By default, items do not accept touch events.

acceptedMouseButtons()#
Return type:

Combination of MouseButton

Returns the mouse buttons that this item accepts mouse events for. By default, all mouse buttons are accepted.

If an item accepts a mouse button, it will become the mouse grabber item when a mouse press event is delivered for that mouse button. However, if the item does not accept the button, QGraphicsScene will forward the mouse events to the first item beneath it that does.

addToIndex()#
advance(phase)#
Parameters:

phase – int

This virtual function is called twice for all items by the advance() slot. In the first phase, all items are called with phase == 0, indicating that items on the scene are about to advance, and then all items are called with phase == 1. Reimplement this function to update your item if you need simple scene-controlled animation.

The default implementation does nothing.

This function is intended for animations. An alternative is to multiple-inherit from QObject and QGraphicsItem and use the Animation Framework.

See also

advance() QTimeLine

abstract boundingRect()#
Return type:

QRectF

Warning

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

This pure virtual function defines the outer bounds of the item as a rectangle; all painting must be restricted to inside an item’s bounding rect. QGraphicsView uses this to determine whether the item requires redrawing.

Although the item’s shape can be arbitrary, the bounding rect is always rectangular, and it is unaffected by the items’ transformation.

If you want to change the item’s bounding rectangle, you must first call prepareGeometryChange() . This notifies the scene of the imminent change, so that it can update its item geometry index; otherwise, the scene will be unaware of the item’s new geometry, and the results are undefined (typically, rendering artifacts are left within the view).

Reimplement this function to let QGraphicsView determine what parts of the widget, if any, need to be redrawn.

Note: For shapes that paint an outline / stroke, it is important to include half the pen width in the bounding rect. It is not necessary to compensate for antialiasing, though.

Example:

def boundingRect(self):

    penWidth = 1
    return QRectF(-radius - penWidth / 2, -radius - penWidth / 2,
                  diameter + penWidth, diameter + penWidth)
boundingRegion(itemToDeviceTransform)#
Parameters:

itemToDeviceTransformQTransform

Return type:

QRegion

Returns the bounding region for this item. The coordinate space of the returned region depends on itemToDeviceTransform. If you pass an identity QTransform as a parameter, this function will return a local coordinate region.

The bounding region describes a coarse outline of the item’s visual contents. Although it’s expensive to calculate, it’s also more precise than boundingRect() , and it can help to avoid unnecessary repainting when an item is updated. This is particularly efficient for thin items (e.g., lines or simple polygons). You can tune the granularity for the bounding region by calling setBoundingRegionGranularity() . The default granularity is 0; in which the item’s bounding region is the same as its bounding rect.

itemToDeviceTransform is the transformation from item coordinates to device coordinates. If you want this function to return a QRegion in scene coordinates, you can pass sceneTransform() as an argument.

boundingRegionGranularity()#
Return type:

float

Returns the item’s bounding region granularity; a value between and including 0 and 1. The default value is 0 (i.e., the lowest granularity, where the bounding region corresponds to the item’s bounding rectangle).

cacheMode()#
Return type:

CacheMode

Returns the cache mode for this item. The default mode is NoCache (i.e., cache is disabled and all painting is immediate).

See also

setCacheMode()

childItems()#
Return type:

.list of QGraphicsItem

Returns a list of this item’s children.

The items are sorted by stacking order. This takes into account both the items’ insertion order and their Z-values.

See also

setParentItem() zValue() Sorting

childrenBoundingRect()#
Return type:

QRectF

Returns the bounding rect of this item’s descendants (i.e., its children, their children, etc.) in local coordinates. The rectangle will contain all descendants after they have been mapped to local coordinates. If the item has no children, this function returns an empty QRectF.

This does not include this item’s own bounding rect; it only returns its descendants’ accumulated bounding rect. If you need to include this item’s bounding rect, you can add boundingRect() to childrenBoundingRect() using QRectF::operator|().

This function is linear in complexity; it determines the size of the returned bounding rect by iterating through all descendants.

clearFocus()#

Takes keyboard input focus from the item.

If it has focus, a focus out event is sent to this item to tell it that it is about to lose the focus.

Only items that set the ItemIsFocusable flag, or widgets that set an appropriate focus policy, can accept keyboard focus.

clipPath()#
Return type:

QPainterPath

Returns this item’s clip path, or an empty QPainterPath if this item is not clipped. The clip path constrains the item’s appearance and interaction (i.e., restricts the area the item can draw within and receive events for).

You can enable clipping by setting the ItemClipsToShape or ItemClipsChildrenToShape flags. The item’s clip path is calculated by intersecting all clipping ancestors’ shapes. If the item sets ItemClipsToShape , the final clip is intersected with the item’s own shape.

Note

Clipping introduces a performance penalty for all items involved; you should generally avoid using clipping if you can (e.g., if your items always draw inside boundingRect() or shape() boundaries, clipping is not necessary).

collidesWithItem(other[, mode=Qt.IntersectsItemShape])#
Parameters:
Return type:

bool

Returns true if this item collides with other; otherwise returns false.

The mode is applied to other, and the resulting shape or bounding rectangle is then compared to this item’s shape. The default value for mode is Qt::IntersectsItemShape; other collides with this item if it either intersects, contains, or is contained by this item’s shape (see Qt::ItemSelectionMode for details).

The default implementation is based on shape intersection, and it calls shape() on both items. Because the complexity of arbitrary shape-shape intersection grows with an order of magnitude when the shapes are complex, this operation can be noticeably time-consuming. You have the option of reimplementing this function in a subclass of QGraphicsItem to provide a custom algorithm. This allows you to make use of natural constraints in the shapes of your own items, in order to improve the performance of the collision detection. For instance, two untransformed perfectly circular items’ collision can be determined very efficiently by comparing their positions and radii.

Keep in mind that when reimplementing this function and calling shape() or boundingRect() on other, the returned coordinates must be mapped to this item’s coordinate system before any intersection can take place.

See also

contains() shape()

collidesWithPath(path[, mode=Qt.IntersectsItemShape])#
Parameters:
Return type:

bool

Returns true if this item collides with path.

The collision is determined by mode. The default value for mode is Qt::IntersectsItemShape; path collides with this item if it either intersects, contains, or is contained by this item’s shape.

Note that this function checks whether the item’s shape or bounding rectangle (depending on mode) is contained within path, and not whether path is contained within the items shape or bounding rectangle.

collidingItems([mode=Qt.IntersectsItemShape])#
Parameters:

modeItemSelectionMode

Return type:

.list of QGraphicsItem

Returns a list of all items that collide with this item.

The way collisions are detected is determined by applying mode to items that are compared to this item, i.e., each item’s shape or bounding rectangle is checked against this item’s shape. The default value for mode is Qt::IntersectsItemShape.

commonAncestorItem(other)#
Parameters:

otherQGraphicsItem

Return type:

QGraphicsItem

Returns the closest common ancestor item of this item and other, or None if either other is None, or there is no common ancestor.

See also

isAncestorOf()

contains(point)#
Parameters:

pointQPointF

Return type:

bool

Returns true if this item contains point, which is in local coordinates; otherwise, false is returned. It is most often called from QGraphicsView to determine what item is under the cursor, and for that reason, the implementation of this function should be as light-weight as possible.

By default, this function calls shape() , but you can reimplement it in a subclass to provide a (perhaps more efficient) implementation.

contextMenuEvent(event)#
Parameters:

eventQGraphicsSceneContextMenuEvent

Warning

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

This event handler can be reimplemented in a subclass to process context menu events. The event parameter contains details about the event to be handled.

If you ignore the event (i.e., by calling QEvent::ignore()), event will propagate to any item beneath this item. If no items accept the event, it will be ignored by the scene and propagate to the view.

It’s common to open a QMenu in response to receiving a context menu event. Example:

def contextMenuEvent(self, event):

    menu = QMenu()
    removeAction = menu.addAction("Remove")
    markAction = menu.addAction("Mark")
    selectedAction = menu.exec(event.screenPos())
    # ...

The default implementation ignores the event.

See also

sceneEvent()

cursor()#
Return type:

QCursor

Warning

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

Returns the current cursor shape for the item. The mouse cursor will assume this shape when it’s over this item. See the list of predefined cursor objects for a range of useful shapes.

An editor item might want to use an I-beam cursor:

item.setCursor(Qt.IBeamCursor)

If no cursor has been set, the cursor of the item beneath is used.

data(key)#
Parameters:

key – int

Return type:

object

Warning

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

Returns this item’s custom data for the key key as a QVariant.

Custom item data is useful for storing arbitrary properties in any item. Example:

ObjectName = 0
item = scene.itemAt(100, 50)
if item.data(ObjectName).toString().isEmpty():
    if ButtonItem(item):
        item.setData(ObjectName, "Button")

Qt does not use this feature for storing data; it is provided solely for the convenience of the user.

See also

setData()

deviceTransform(viewportTransform)#
Parameters:

viewportTransformQTransform

Return type:

QTransform

Warning

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

Returns this item’s device transformation matrix, using viewportTransform to map from scene to device coordinates. This matrix can be used to map coordinates and geometrical shapes from this item’s local coordinate system to the viewport’s (or any device’s) coordinate system. To map coordinates from the viewport, you must first invert the returned matrix.

Example:

rect = QGraphicsRectItem()
rect.setPos(100, 100)
rect.deviceTransform(view.viewportTransform()).map(QPointF(0, 0))
# returns the item's (0, 0) point in view's viewport coordinates
rect.deviceTransform(view.viewportTransform()).inverted().map(QPointF(100, 100))
# returns view's viewport's (100, 100) coordinate in item coordinates

This function is the same as combining this item’s scene transform with the view’s viewport transform, but it also understands the ItemIgnoresTransformations flag. The device transform can be used to do accurate coordinate mapping (and collision detection) for untransformable items.

dragEnterEvent(event)#
Parameters:

eventQGraphicsSceneDragDropEvent

Warning

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

This event handler, for event event, can be reimplemented to receive drag enter events for this item. Drag enter events are generated as the cursor enters the item’s area.

By accepting the event (i.e., by calling QEvent::accept()), the item will accept drop events, in addition to receiving drag move and drag leave. Otherwise, the event will be ignored and propagate to the item beneath. If the event is accepted, the item will receive a drag move event before control goes back to the event loop.

A common implementation of dragEnterEvent accepts or ignores event depending on the associated mime data in event. Example:

def __init__(self):

    setAcceptDrops(True)
    ...

def dragEnterEvent(self, event):

    event.setAccepted(event.mimeData().hasFormat("text/plain"))

Items do not receive drag and drop events by default; to enable this feature, call setAcceptDrops(true).

The default implementation does nothing.

dragLeaveEvent(event)#
Parameters:

eventQGraphicsSceneDragDropEvent

This event handler, for event event, can be reimplemented to receive drag leave events for this item. Drag leave events are generated as the cursor leaves the item’s area. Most often you will not need to reimplement this function, but it can be useful for resetting state in your item (e.g., highlighting).

Calling QEvent::ignore() or QEvent::accept() on event has no effect.

Items do not receive drag and drop events by default; to enable this feature, call setAcceptDrops(true).

The default implementation does nothing.

dragMoveEvent(event)#
Parameters:

eventQGraphicsSceneDragDropEvent

This event handler, for event event, can be reimplemented to receive drag move events for this item. Drag move events are generated as the cursor moves around inside the item’s area. Most often you will not need to reimplement this function; it is used to indicate that only parts of the item can accept drops.

Calling QEvent::ignore() or QEvent::accept() on event toggles whether or not the item will accept drops at the position from the event. By default, event is accepted, indicating that the item allows drops at the specified position.

Items do not receive drag and drop events by default; to enable this feature, call setAcceptDrops(true).

The default implementation does nothing.

dropEvent(event)#
Parameters:

eventQGraphicsSceneDragDropEvent

This event handler, for event event, can be reimplemented to receive drop events for this item. Items can only receive drop events if the last drag move event was accepted.

Calling QEvent::ignore() or QEvent::accept() on event has no effect.

Items do not receive drag and drop events by default; to enable this feature, call setAcceptDrops(true).

The default implementation does nothing.

effectiveOpacity()#
Return type:

float

Returns this item’s effective opacity, which is between 0.0 (transparent) and 1.0 (opaque). This value is a combination of this item’s local opacity, and its parent and ancestors’ opacities. The effective opacity decides how the item is rendered.

ensureVisible(x, y, w, h[, xmargin=50[, ymargin=50]])#
Parameters:
  • x – float

  • y – float

  • w – float

  • h – float

  • xmargin – int

  • ymargin – int

This convenience function is equivalent to calling ensureVisible (QRectF(x, y, w, h), xmargin, ymargin).

ensureVisible([rect=QRectF()[, xmargin=50[, ymargin=50]]])
Parameters:
  • rectQRectF

  • xmargin – int

  • ymargin – int

If this item is part of a scene that is viewed by a QGraphicsView , this convenience function will attempt to scroll the view to ensure that rect is visible inside the view’s viewport. If rect is a null rect (the default), QGraphicsItem will default to the item’s bounding rect. xmargin and ymargin are the number of pixels the view should use for margins.

If the specified rect cannot be reached, the contents are scrolled to the nearest valid position.

If this item is not viewed by a QGraphicsView , this function does nothing.

See also

ensureVisible()

extension(variant)#
Parameters:

variant – object

Return type:

object

filtersChildEvents()#
Return type:

bool

Returns true if this item filters child events (i.e., all events intended for any of its children are instead sent to this item); otherwise, false is returned.

The default value is false; child events are not filtered.

flags()#
Return type:

Combination of GraphicsItemFlag

Returns this item’s flags. The flags describe what configurable features of the item are enabled and not. For example, if the flags include ItemIsFocusable , the item can accept input focus.

By default, no flags are enabled.

focusInEvent(event)#
Parameters:

eventQFocusEvent

This event handler, for event event, can be reimplemented to receive focus in events for this item. The default implementation calls ensureVisible() .

focusItem()#
Return type:

QGraphicsItem

If this item, a child or descendant of this item currently has input focus, this function will return a pointer to that item. If no descendant has input focus, None is returned.

focusOutEvent(event)#
Parameters:

eventQFocusEvent

This event handler, for event event, can be reimplemented to receive focus out events for this item. The default implementation does nothing.

focusProxy()#
Return type:

QGraphicsItem

Returns this item’s focus proxy, or None if this item has no focus proxy.

focusScopeItem()#
Return type:

QGraphicsItem

grabKeyboard()#

Grabs the keyboard input.

The item will receive all keyboard input to the scene until one of the following events occur:

  • The item becomes invisible

  • The item is removed from the scene

  • The item is deleted

  • The item calls ungrabKeyboard()

  • Another item calls grabKeyboard(); the item will regain the keyboard grab when the other item calls ungrabKeyboard() .

When an item gains the keyboard grab, it receives a QEvent::GrabKeyboard event. When it loses the keyboard grab, it receives a QEvent::UngrabKeyboard event. These events can be used to detect when your item gains or loses the keyboard grab through other means than gaining input focus.

It is almost never necessary to explicitly grab the keyboard in Qt, as Qt grabs and releases it sensibly. In particular, Qt grabs the keyboard when your item gains input focus, and releases it when your item loses input focus, or when the item is hidden.

Note that only visible items can grab keyboard input. Calling grabKeyboard() on an invisible item has no effect.

Keyboard events are not affected.

grabMouse()#

Grabs the mouse input.

This item will receive all mouse events for the scene until any of the following events occurs:

  • The item becomes invisible

  • The item is removed from the scene

  • The item is deleted

  • The item call ungrabMouse()

  • Another item calls grabMouse(); the item will regain the mouse grab when the other item calls ungrabMouse() .

When an item gains the mouse grab, it receives a QEvent::GrabMouse event. When it loses the mouse grab, it receives a QEvent::UngrabMouse event. These events can be used to detect when your item gains or loses the mouse grab through other means than receiving mouse button events.

It is almost never necessary to explicitly grab the mouse in Qt, as Qt grabs and releases it sensibly. In particular, Qt grabs the mouse when you press a mouse button, and keeps the mouse grabbed until you release the last mouse button. Also, Qt::Popup widgets implicitly call grabMouse() when shown, and ungrabMouse() when hidden.

Note that only visible items can grab mouse input. Calling grabMouse() on an invisible item has no effect.

Keyboard events are not affected.

graphicsEffect()#
Return type:

QGraphicsEffect

Returns a pointer to this item’s effect if it has one; otherwise None.

group()#
Return type:

QGraphicsItemGroup

Returns a pointer to this item’s item group, or None if this item is not member of a group.

handlesChildEvents()#
Return type:

bool

Returns true if this item handles child events (i.e., all events intended for any of its children are instead sent to this item); otherwise, false is returned.

This property is useful for item groups; it allows one item to handle events on behalf of its children, as opposed to its children handling their events individually.

The default is to return false; children handle their own events. The exception for this is if the item is a QGraphicsItemGroup , then it defaults to return true.

hasCursor()#
Return type:

bool

Returns true if this item has a cursor set; otherwise, false is returned.

By default, items don’t have any cursor set. cursor() will return a standard pointing arrow cursor.

See also

unsetCursor()

hasFocus()#
Return type:

bool

Returns true if this item is active, and it or its focus proxy has keyboard input focus; otherwise, returns false.

hide()#

Hides the item (items are visible by default).

This convenience function is equivalent to calling setVisible(false).

See also

show() setVisible()

hoverEnterEvent(event)#
Parameters:

eventQGraphicsSceneHoverEvent

This event handler, for event event, can be reimplemented to receive hover enter events for this item. The default implementation calls update() ; otherwise it does nothing.

Calling QEvent::ignore() or QEvent::accept() on event has no effect.

hoverLeaveEvent(event)#
Parameters:

eventQGraphicsSceneHoverEvent

This event handler, for event event, can be reimplemented to receive hover leave events for this item. The default implementation calls update() ; otherwise it does nothing.

Calling QEvent::ignore() or QEvent::accept() on event has no effect.

hoverMoveEvent(event)#
Parameters:

eventQGraphicsSceneHoverEvent

This event handler, for event event, can be reimplemented to receive hover move events for this item. The default implementation does nothing.

Calling QEvent::ignore() or QEvent::accept() on event has no effect.

inputMethodEvent(event)#
Parameters:

eventQInputMethodEvent

This event handler, for event event, can be reimplemented to receive input method events for this item. The default implementation ignores the event.

inputMethodHints()#
Return type:

Combination of InputMethodHint

Returns the current input method hints of this item.

Input method hints are only relevant for input items. The hints are used by the input method to indicate how it should operate. For example, if the Qt::ImhNumbersOnly flag is set, the input method may change its visual components to reflect that only numbers can be entered.

The effect may vary between input method implementations.

inputMethodQuery(query)#
Parameters:

queryInputMethodQuery

Return type:

object

This method is only relevant for input items. It is used by the input method to query a set of properties of the item to be able to support complex input method operations, such as support for surrounding text and reconversions. query specifies which property is queried.

installSceneEventFilter(filterItem)#
Parameters:

filterItemQGraphicsItem

Warning

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

Installs an event filter for this item on filterItem, causing all events for this item to first pass through filterItem's sceneEventFilter() function.

To filter another item’s events, install this item as an event filter for the other item. Example:

scene = QGraphicsScene()
ellipse = scene.addEllipse(QRectF(-10, -10, 20, 20))
line = scene.addLine(QLineF(-10, -10, 20, 20))
line.installSceneEventFilter(ellipse)
# line's events are filtered by ellipse's sceneEventFilter() function.
ellipse.installSceneEventFilter(line)
# ellipse's events are filtered by line's sceneEventFilter() function.

An item can only filter events for other items in the same scene. Also, an item cannot filter its own events; instead, you can reimplement sceneEvent() directly.

Items must belong to a scene for scene event filters to be installed and used.

isActive()#
Return type:

bool

Returns true if this item is active; otherwise returns false.

An item can only be active if the scene is active. An item is active if it is, or is a descendent of, an active panel. Items in non-active panels are not active.

Items that are not part of a panel follow scene activation when the scene has no active panel.

Only active items can gain input focus.

isAncestorOf(child)#
Parameters:

childQGraphicsItem

Return type:

bool

Returns true if this item is an ancestor of child (i.e., if this item is child's parent, or one of child's parent’s ancestors).

See also

parentItem()

isBlockedByModalPanel()#
Return type:

(retval, blockingPanel)

Returns true if this item is blocked by a modal panel, false otherwise. If blockingPanel is non-zero, blockingPanel will be set to the modal panel that is blocking this item. If this item is not blocked, blockingPanel will not be set by this function.

This function always returns false for items not in a scene.

isClipped()#
Return type:

bool

Returns true if this item is clipped. An item is clipped if it has either set the ItemClipsToShape flag, or if it or any of its ancestors has set the ItemClipsChildrenToShape flag.

Clipping affects the item’s appearance (i.e., painting), as well as mouse and hover event delivery.

isEnabled()#
Return type:

bool

Returns true if the item is enabled; otherwise, false is returned.

See also

setEnabled()

isObscured([rect=QRectF()])#
Parameters:

rectQRectF

Return type:

bool

This is an overloaded function.

Returns true if rect is completely obscured by the opaque shape of any of colliding items above it (i.e., with a higher Z value than this item).

See also

opaqueArea()

isObscured(x, y, w, h)
Parameters:
  • x – float

  • y – float

  • w – float

  • h – float

Return type:

bool

This is an overloaded function.

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

isObscuredBy(item)#
Parameters:

itemQGraphicsItem

Return type:

bool

Returns true if this item’s bounding rect is completely obscured by the opaque shape of item.

The base implementation maps item's opaqueArea() to this item’s coordinate system, and then checks if this item’s boundingRect() is fully contained within the mapped shape.

You can reimplement this function to provide a custom algorithm for determining whether this item is obscured by item.

isPanel()#
Return type:

bool

Returns true if the item is a panel; otherwise returns false.

See also

panel() ItemIsPanel

isSelected()#
Return type:

bool

Returns true if this item is selected; otherwise, false is returned.

Items that are in a group inherit the group’s selected state.

Items are not selected by default.

isUnderMouse()#
Return type:

bool

Returns true if this item is currently under the mouse cursor in one of the views; otherwise, false is returned.

See also

views() pos()

isVisible()#
Return type:

bool

Returns true if the item is visible; otherwise, false is returned.

Note that the item’s general visibility is unrelated to whether or not it is actually being visualized by a QGraphicsView .

See also

setVisible()

isVisibleTo(parent)#
Parameters:

parentQGraphicsItem

Return type:

bool

Returns true if the item is visible to parent; otherwise, false is returned. parent can be None, in which case this function will return whether the item is visible to the scene or not.

An item may not be visible to its ancestors even if isVisible() is true. It may also be visible to its ancestors even if isVisible() is false. If any ancestor is hidden, the item itself will be implicitly hidden, in which case this function will return false.

isWidget()#
Return type:

bool

Returns true if this item is a widget (i.e., QGraphicsWidget ); otherwise, returns false.

isWindow()#
Return type:

bool

Returns true if the item is a QGraphicsWidget window, otherwise returns false.

See also

windowFlags()

itemChange(change, value)#
Parameters:
Return type:

object

Warning

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

This virtual function is called by QGraphicsItem to notify custom items that some part of the item’s state changes. By reimplementing this function, you can react to a change, and in some cases (depending on change), adjustments can be made.

change is the parameter of the item that is changing. value is the new value; the type of the value depends on change.

Example:

def itemChange(self, GraphicsItemChange change, QVariant value):

    if change == ItemPositionChange and scene():
        # value is the new position.
        newPos = value.toPointF()
        rect = scene().sceneRect()
        if not rect.contains(newPos):
            # Keep the item inside the scene rect.
            newPos.setX(qMin(rect.right(), qMax(newPos.x(), rect.left())))
            newPos.setY(qMin(rect.bottom(), qMax(newPos.y(), rect.top())))
            return newPos


    return QGraphicsItem.itemChange(change, value)

The default implementation does nothing, and returns value.

Note: Certain QGraphicsItem functions cannot be called in a reimplementation of this function; see the GraphicsItemChange documentation for details.

itemTransform(other)#
Parameters:

otherQGraphicsItem

Return type:

(QTransform, bool ok)

Returns a QTransform that maps coordinates from this item to other. If ok is not null, and if there is no such transform, the boolean pointed to by ok will be set to false; otherwise it will be set to true.

This transform provides an alternative to the mapToItem() or mapFromItem() functions, by returning the appropriate transform so that you can map shapes and coordinates yourself. It also helps you write more efficient code when repeatedly mapping between the same two items.

Note

In rare circumstances, there is no transform that maps between two items.

keyPressEvent(event)#
Parameters:

eventQKeyEvent

This event handler, for event event, can be reimplemented to receive key press events for this item. The default implementation ignores the event. If you reimplement this handler, the event will by default be accepted.

Note that key events are only received for items that set the ItemIsFocusable flag, and that have keyboard input focus.

keyReleaseEvent(event)#
Parameters:

eventQKeyEvent

This event handler, for event event, can be reimplemented to receive key release events for this item. The default implementation ignores the event. If you reimplement this handler, the event will by default be accepted.

Note that key events are only received for items that set the ItemIsFocusable flag, and that have keyboard input focus.

mapFromItem(item, x, y, w, h)#
Parameters:
  • itemQGraphicsItem

  • x – float

  • y – float

  • w – float

  • h – float

Return type:

QPolygonF

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

mapFromItem(item, x, y)
Parameters:
Return type:

QPointF

This is an overloaded function.

This convenience function is equivalent to calling mapFromItem (item, QPointF(x, y)).

mapFromItem(item, rect)
Parameters:
Return type:

QPolygonF

Maps the rectangle rect, which is in item's coordinate system, to this item’s coordinate system, and returns the mapped rectangle as a polygon.

If item is None, this function returns the same as mapFromScene()

mapFromItem(item, point)
Parameters:
Return type:

QPointF

Maps the point point, which is in item's coordinate system, to this item’s coordinate system, and returns the mapped coordinate.

If item is None, this function returns the same as mapFromScene() .

mapFromItem(item, path)
Parameters:
Return type:

QPainterPath

Maps the path path, which is in item's coordinate system, to this item’s coordinate system, and returns the mapped path.

If item is None, this function returns the same as mapFromScene() .

mapFromItem(item, polygon)
Parameters:
Return type:

QPolygonF

Maps the polygon polygon, which is in item's coordinate system, to this item’s coordinate system, and returns the mapped polygon.

If item is None, this function returns the same as mapFromScene() .

mapFromParent(path)#
Parameters:

pathQPainterPath

Return type:

QPainterPath

Maps the path path, which is in this item’s parent’s coordinate system, to this item’s coordinate system, and returns the mapped path.

mapFromParent(point)
Parameters:

pointQPointF

Return type:

QPointF

Maps the point point, which is in this item’s parent’s coordinate system, to this item’s coordinate system, and returns the mapped coordinate.

mapFromParent(polygon)
Parameters:

polygonQPolygonF

Return type:

QPolygonF

Maps the polygon polygon, which is in this item’s parent’s coordinate system, to this item’s coordinate system, and returns the mapped polygon.

mapFromParent(rect)
Parameters:

rectQRectF

Return type:

QPolygonF

Maps the rectangle rect, which is in this item’s parent’s coordinate system, to this item’s coordinate system, and returns the mapped rectangle as a polygon.

mapFromParent(x, y)
Parameters:
  • x – float

  • y – float

Return type:

QPointF

This is an overloaded function.

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

mapFromParent(x, y, w, h)
Parameters:
  • x – float

  • y – float

  • w – float

  • h – float

Return type:

QPolygonF

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

mapFromScene(x, y)#
Parameters:
  • x – float

  • y – float

Return type:

QPointF

This is an overloaded function.

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

mapFromScene(x, y, w, h)
Parameters:
  • x – float

  • y – float

  • w – float

  • h – float

Return type:

QPolygonF

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

mapFromScene(rect)
Parameters:

rectQRectF

Return type:

QPolygonF

Maps the rectangle rect, which is in this item’s scene’s coordinate system, to this item’s coordinate system, and returns the mapped rectangle as a polygon.

mapFromScene(polygon)
Parameters:

polygonQPolygonF

Return type:

QPolygonF

Maps the polygon polygon, which is in this item’s scene’s coordinate system, to this item’s coordinate system, and returns the mapped polygon.

mapFromScene(point)
Parameters:

pointQPointF

Return type:

QPointF

Maps the point point, which is in this item’s scene’s coordinate system, to this item’s coordinate system, and returns the mapped coordinate.

mapFromScene(path)
Parameters:

pathQPainterPath

Return type:

QPainterPath

Maps the path path, which is in this item’s scene’s coordinate system, to this item’s coordinate system, and returns the mapped path.

mapRectFromItem(item, rect)#
Parameters:
Return type:

QRectF

Maps the rectangle rect, which is in item's coordinate system, to this item’s coordinate system, and returns the mapped rectangle as a new rectangle (i.e., the bounding rectangle of the resulting polygon).

If item is None, this function returns the same as mapRectFromScene() .

mapRectFromItem(item, x, y, w, h)
Parameters:
  • itemQGraphicsItem

  • x – float

  • y – float

  • w – float

  • h – float

Return type:

QRectF

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

mapRectFromParent(rect)#
Parameters:

rectQRectF

Return type:

QRectF

Maps the rectangle rect, which is in this item’s parent’s coordinate system, to this item’s coordinate system, and returns the mapped rectangle as a new rectangle (i.e., the bounding rectangle of the resulting polygon).

mapRectFromParent(x, y, w, h)
Parameters:
  • x – float

  • y – float

  • w – float

  • h – float

Return type:

QRectF

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

mapRectFromScene(rect)#
Parameters:

rectQRectF

Return type:

QRectF

Maps the rectangle rect, which is in scene coordinates, to this item’s coordinate system, and returns the mapped rectangle as a new rectangle (i.e., the bounding rectangle of the resulting polygon).

mapRectFromScene(x, y, w, h)
Parameters:
  • x – float

  • y – float

  • w – float

  • h – float

Return type:

QRectF

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

mapRectToItem(item, rect)#
Parameters:
Return type:

QRectF

Maps the rectangle rect, which is in this item’s coordinate system, to item's coordinate system, and returns the mapped rectangle as a new rectangle (i.e., the bounding rectangle of the resulting polygon).

If item is None, this function returns the same as mapRectToScene() .

mapRectToItem(item, x, y, w, h)
Parameters:
  • itemQGraphicsItem

  • x – float

  • y – float

  • w – float

  • h – float

Return type:

QRectF

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

mapRectToParent(rect)#
Parameters:

rectQRectF

Return type:

QRectF

Maps the rectangle rect, which is in this item’s coordinate system, to its parent’s coordinate system, and returns the mapped rectangle as a new rectangle (i.e., the bounding rectangle of the resulting polygon).

mapRectToParent(x, y, w, h)
Parameters:
  • x – float

  • y – float

  • w – float

  • h – float

Return type:

QRectF

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

mapRectToScene(x, y, w, h)#
Parameters:
  • x – float

  • y – float

  • w – float

  • h – float

Return type:

QRectF

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

mapRectToScene(rect)
Parameters:

rectQRectF

Return type:

QRectF

Maps the rectangle rect, which is in this item’s coordinate system, to the scene coordinate system, and returns the mapped rectangle as a new rectangle (i.e., the bounding rectangle of the resulting polygon).

mapToItem(item, path)#
Parameters:
Return type:

QPainterPath

Maps the path path, which is in this item’s coordinate system, to item's coordinate system, and returns the mapped path.

If item is None, this function returns the same as mapToScene() .

mapToItem(item, x, y, w, h)
Parameters:
  • itemQGraphicsItem

  • x – float

  • y – float

  • w – float

  • h – float

Return type:

QPolygonF

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

mapToItem(item, x, y)
Parameters:
Return type:

QPointF

This is an overloaded function.

This convenience function is equivalent to calling mapToItem (item, QPointF(x, y)).

mapToItem(item, polygon)
Parameters:
Return type:

QPolygonF

Maps the polygon polygon, which is in this item’s coordinate system, to item's coordinate system, and returns the mapped polygon.

If item is None, this function returns the same as mapToScene() .

mapToItem(item, rect)
Parameters:
Return type:

QPolygonF

Maps the rectangle rect, which is in this item’s coordinate system, to item's coordinate system, and returns the mapped rectangle as a polygon.

If item is None, this function returns the same as mapToScene() .

mapToItem(item, point)
Parameters:
Return type:

QPointF

Maps the point point, which is in this item’s coordinate system, to item's coordinate system, and returns the mapped coordinate.

If item is None, this function returns the same as mapToScene() .

mapToParent(path)#
Parameters:

pathQPainterPath

Return type:

QPainterPath

Maps the path path, which is in this item’s coordinate system, to its parent’s coordinate system, and returns the mapped path. If the item has no parent, path will be mapped to the scene’s coordinate system.

mapToParent(point)
Parameters:

pointQPointF

Return type:

QPointF

Maps the point point, which is in this item’s coordinate system, to its parent’s coordinate system, and returns the mapped coordinate. If the item has no parent, point will be mapped to the scene’s coordinate system.

mapToParent(polygon)
Parameters:

polygonQPolygonF

Return type:

QPolygonF

Maps the polygon polygon, which is in this item’s coordinate system, to its parent’s coordinate system, and returns the mapped polygon. If the item has no parent, polygon will be mapped to the scene’s coordinate system.

mapToParent(rect)
Parameters:

rectQRectF

Return type:

QPolygonF

Maps the rectangle rect, which is in this item’s coordinate system, to its parent’s coordinate system, and returns the mapped rectangle as a polygon. If the item has no parent, rect will be mapped to the scene’s coordinate system.

mapToParent(x, y)
Parameters:
  • x – float

  • y – float

Return type:

QPointF

This is an overloaded function.

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

mapToParent(x, y, w, h)
Parameters:
  • x – float

  • y – float

  • w – float

  • h – float

Return type:

QPolygonF

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

mapToScene(x, y)#
Parameters:
  • x – float

  • y – float

Return type:

QPointF

This is an overloaded function.

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

mapToScene(x, y, w, h)
Parameters:
  • x – float

  • y – float

  • w – float

  • h – float

Return type:

QPolygonF

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

mapToScene(rect)
Parameters:

rectQRectF

Return type:

QPolygonF

Maps the rectangle rect, which is in this item’s coordinate system, to the scene’s coordinate system, and returns the mapped rectangle as a polygon.

mapToScene(polygon)
Parameters:

polygonQPolygonF

Return type:

QPolygonF

Maps the polygon polygon, which is in this item’s coordinate system, to the scene’s coordinate system, and returns the mapped polygon.

mapToScene(point)
Parameters:

pointQPointF

Return type:

QPointF

Maps the point point, which is in this item’s coordinate system, to the scene’s coordinate system, and returns the mapped coordinate.

mapToScene(path)
Parameters:

pathQPainterPath

Return type:

QPainterPath

Maps the path path, which is in this item’s coordinate system, to the scene’s coordinate system, and returns the mapped path.

mouseDoubleClickEvent(event)#
Parameters:

eventQGraphicsSceneMouseEvent

This event handler, for event event, can be reimplemented to receive mouse double-click events for this item.

When doubleclicking an item, the item 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.

Calling QEvent::ignore() or QEvent::accept() on event has no effect.

The default implementation calls mousePressEvent() . If you want to keep the base implementation when reimplementing this function, call QGraphicsItem::mouseDoubleClickEvent() in your reimplementation.

Note that an item will not receive double click events if it is neither selectable nor movable (single mouse clicks are ignored in this case, and that stops the generation of double clicks).

mouseMoveEvent(event)#
Parameters:

eventQGraphicsSceneMouseEvent

This event handler, for event event, can be reimplemented to receive mouse move events for this item. If you do receive this event, you can be certain that this item also received a mouse press event, and that this item is the current mouse grabber.

Calling QEvent::ignore() or QEvent::accept() on event has no effect.

The default implementation handles basic item interaction, such as selection and moving. If you want to keep the base implementation when reimplementing this function, call QGraphicsItem::mouseMoveEvent() in your reimplementation.

Please note that mousePressEvent() decides which graphics item it is that receives mouse events. See the mousePressEvent() description for details.

mousePressEvent(event)#
Parameters:

eventQGraphicsSceneMouseEvent

This event handler, for event event, can be reimplemented to receive mouse press events for this item. Mouse press events are only delivered to items that accept the mouse button that is pressed. By default, an item accepts all mouse buttons, but you can change this by calling setAcceptedMouseButtons() .

The mouse press event decides which item should become the mouse grabber (see mouseGrabberItem() ). If you do not reimplement this function, the press event will propagate to any topmost item beneath this item, and no other mouse events will be delivered to this item.

If you do reimplement this function, event will by default be accepted (see QEvent::accept()), and this item is then the mouse grabber. This allows the item to receive future move, release and double-click events. If you call QEvent::ignore() on event, this item will lose the mouse grab, and event will propagate to any topmost item beneath. No further mouse events will be delivered to this item unless a new mouse press event is received.

The default implementation handles basic item interaction, such as selection and moving. If you want to keep the base implementation when reimplementing this function, call QGraphicsItem::mousePressEvent() in your reimplementation.

The event is QEvent::ignore()d for items that are neither movable nor selectable .

mouseReleaseEvent(event)#
Parameters:

eventQGraphicsSceneMouseEvent

This event handler, for event event, can be reimplemented to receive mouse release events for this item.

Calling QEvent::ignore() or QEvent::accept() on event has no effect.

The default implementation handles basic item interaction, such as selection and moving. If you want to keep the base implementation when reimplementing this function, call QGraphicsItem::mouseReleaseEvent() in your reimplementation.

Please note that mousePressEvent() decides which graphics item it is that receives mouse events. See the mousePressEvent() description for details.

moveBy(dx, dy)#
Parameters:
  • dx – float

  • dy – float

Moves the item by dx points horizontally, and dy point vertically. This function is equivalent to calling setPos ( pos() + QPointF(dx, dy)).

opacity()#
Return type:

float

Returns this item’s local opacity, which is between 0.0 (transparent) and 1.0 (opaque). This value is combined with parent and ancestor values into the effectiveOpacity() . The effective opacity decides how the item is rendered and also affects its visibility when queried by functions such as items() .

The opacity property decides the state of the painter passed to the paint() function. If the item is cached, i.e., ItemCoordinateCache or DeviceCoordinateCache , the effective property will be applied to the item’s cache as it is rendered.

The default opacity is 1.0; fully opaque.

opaqueArea()#
Return type:

QPainterPath

This virtual function returns a shape representing the area where this item is opaque. An area is opaque if it is filled using an opaque brush or color (i.e., not transparent).

This function is used by isObscuredBy() , which is called by underlying items to determine if they are obscured by this item.

The default implementation returns an empty QPainterPath, indicating that this item is completely transparent and does not obscure any other items.

abstract paint(painter, option[, widget=None])#
Parameters:

Warning

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

This function, which is usually called by QGraphicsView , paints the contents of an item in local coordinates.

Reimplement this function in a QGraphicsItem subclass to provide the item’s painting implementation, using painter. The option parameter provides style options for the item, such as its state, exposed area and its level-of-detail hints. The widget argument is optional. If provided, it points to the widget that is being painted on; otherwise, it is 0. For cached painting, widget is always 0.

def paint(self, painter,):
                          QStyleOptionGraphicsItem option,
                          QWidget widget)

    painter.drawRoundedRect(-10, -10, 20, 20, 5, 5)

The painter’s pen is 0-width by default, and its pen is initialized to the QPalette::Text brush from the paint device’s palette. The brush is initialized to QPalette::Window.

Make sure to constrain all painting inside the boundaries of boundingRect() to avoid rendering artifacts (as QGraphicsView does not clip the painter for you). In particular, when QPainter renders the outline of a shape using an assigned QPen, half of the outline will be drawn outside, and half inside, the shape you’re rendering (e.g., with a pen width of 2 units, you must draw outlines 1 unit inside boundingRect() ). QGraphicsItem does not support use of cosmetic pens with a non-zero width.

All painting is done in local coordinates.

Note

It is mandatory that an item will always redraw itself in the exact same way, unless update() was called; otherwise visual artifacts may occur. In other words, two subsequent calls to paint() must always produce the same output, unless update() was called between them.

Note

Enabling caching for an item does not guarantee that paint() will be invoked only once by the Graphics View framework, even without any explicit call to update() . See the documentation of setCacheMode() for more details.

panel()#
Return type:

QGraphicsItem

Returns the item’s panel, or None if this item does not have a panel. If the item is a panel, it will return itself. Otherwise it will return the closest ancestor that is a panel.

panelModality()#
Return type:

PanelModality

Returns the modality for this item.

parentItem()#
Return type:

QGraphicsItem

Returns a pointer to this item’s parent item. If this item does not have a parent, None is returned.

parentObject()#
Return type:

QGraphicsObject

Returns a pointer to the item’s parent, cast to a QGraphicsObject . Returns None if the parent item is not a QGraphicsObject .

parentWidget()#
Return type:

QGraphicsWidget

Returns a pointer to the item’s parent widget. The item’s parent widget is the closest parent item that is a widget.

pos()#
Return type:

QPointF

Returns the position of the item in parent coordinates. If the item has no parent, its position is given in scene coordinates.

The position of the item describes its origin (local coordinate (0, 0)) in parent coordinates; this function returns the same as mapToParent (0, 0).

For convenience, you can also call scenePos() to determine the item’s position in scene coordinates, regardless of its parent.

prepareGeometryChange()#

Warning

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

Prepares the item for a geometry change. Call this function before changing the bounding rect of an item to keep QGraphicsScene ‘s index up to date.

prepareGeometryChange() will call update() if this is necessary.

Example:

def setRadius(self, newRadius):

    if radius != newRadius:
        prepareGeometryChange()
        radius = newRadius

See also

boundingRect()

removeFromIndex()#
removeSceneEventFilter(filterItem)#
Parameters:

filterItemQGraphicsItem

Removes an event filter on this item from filterItem.

resetTransform()#

Resets this item’s transformation matrix to the identity matrix or all the transformation properties to their default values. This is equivalent to calling setTransform(QTransform()).

rotation()#
Return type:

float

Returns the clockwise rotation, in degrees, around the Z axis. The default value is 0 (i.e., the item is not rotated).

The rotation is combined with the item’s scale() , transform() and transformations() to map the item’s coordinate system to the parent item.

See also

setRotation() transformOriginPoint() Transformations

scale()#
Return type:

float

Returns the scale factor of the item. The default scale factor is 1.0 (i.e., the item is not scaled).

The scale is combined with the item’s rotation() , transform() and transformations() to map the item’s coordinate system to the parent item.

See also

setScale() rotation() Transformations

scene()#
Return type:

QGraphicsScene

Returns the current scene for the item, or None if the item is not stored in a scene.

To add or move an item to a scene, call addItem() .

sceneBoundingRect()#
Return type:

QRectF

Returns the bounding rect of this item in scene coordinates, by combining sceneTransform() with boundingRect() .

sceneEvent(event)#
Parameters:

eventQEvent

Return type:

bool

This virtual function receives events to this item. Reimplement this function to intercept events before they are dispatched to the specialized event handlers contextMenuEvent() , focusInEvent() , focusOutEvent() , hoverEnterEvent() , hoverMoveEvent() , hoverLeaveEvent() , keyPressEvent() , keyReleaseEvent() , mousePressEvent() , mouseReleaseEvent() , mouseMoveEvent() , and mouseDoubleClickEvent() .

Returns true if the event was recognized and handled; otherwise, (e.g., if the event type was not recognized,) false is returned.

event is the intercepted event.

sceneEventFilter(watched, event)#
Parameters:
Return type:

bool

Filters events for the item watched. event is the filtered event.

Reimplementing this function in a subclass makes it possible for the item to be used as an event filter for other items, intercepting all the events sent to those items before they are able to respond.

Reimplementations must return true to prevent further processing of a given event, ensuring that it will not be delivered to the watched item, or return false to indicate that the event should be propagated further by the event system.

scenePos()#
Return type:

QPointF

Returns the item’s position in scene coordinates. This is equivalent to calling mapToScene(0, 0).

sceneTransform()#
Return type:

QTransform

Warning

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

Returns this item’s scene transformation matrix. This matrix can be used to map coordinates and geometrical shapes from this item’s local coordinate system to the scene’s coordinate system. To map coordinates from the scene, you must first invert the returned matrix.

Example:

rect = QGraphicsRectItem()
rect.setPos(100, 100)
rect.sceneTransform().map(QPointF(0, 0))
# returns QPointF(100, 100)
rect.sceneTransform().inverted().map(QPointF(100, 100))
# returns QPointF(0, 0)

Unlike transform() , which returns only an item’s local transformation, this function includes the item’s (and any parents’) position, and all the transformation properties.

setAcceptDrops(on)#
Parameters:

on – bool

If on is true, this item will accept drag and drop events; otherwise, it is transparent for drag and drop events. By default, items do not accept drag and drop events.

See also

acceptDrops()

setAcceptHoverEvents(enabled)#
Parameters:

enabled – bool

If enabled is true, this item will accept hover events; otherwise, it will ignore them. By default, items do not accept hover events.

Hover events are delivered when there is no current mouse grabber item. They are sent when the mouse cursor enters an item, when it moves around inside the item, and when the cursor leaves an item. Hover events are commonly used to highlight an item when it’s entered, and for tracking the mouse cursor as it hovers over the item (equivalent to mouseTracking ).

Parent items receive hover enter events before their children, and leave events after their children. The parent does not receive a hover leave event if the cursor enters a child, though; the parent stays “hovered” until the cursor leaves its area, including its children’s areas.

If a parent item handles child events, it will receive hover move, drag move, and drop events as the cursor passes through its children, but it does not receive hover enter and hover leave, nor drag enter and drag leave events on behalf of its children.

A QGraphicsWidget with window decorations will accept hover events regardless of the value of acceptHoverEvents() .

setAcceptTouchEvents(enabled)#
Parameters:

enabled – bool

If enabled is true, this item will accept touch events; otherwise, it will ignore them. By default, items do not accept touch events.

setAcceptedMouseButtons(buttons)#
Parameters:

buttons – Combination of MouseButton

Sets the mouse buttons that this item accepts mouse events for.

By default, all mouse buttons are accepted. If an item accepts a mouse button, it will become the mouse grabber item when a mouse press event is delivered for that button. However, if the item does not accept the mouse button, QGraphicsScene will forward the mouse events to the first item beneath it that does.

To disable mouse events for an item (i.e., make it transparent for mouse events), call setAcceptedMouseButtons(Qt::NoButton).

setActive(active)#
Parameters:

active – bool

If active is true, and the scene is active, this item’s panel will be activated. Otherwise, the panel is deactivated.

If the item is not part of an active scene, active will decide what happens to the panel when the scene becomes active or the item is added to the scene. If true, the item’s panel will be activated when the item is either added to the scene or the scene is activated. Otherwise, the item will stay inactive independent of the scene’s activated state.

setBoundingRegionGranularity(granularity)#
Parameters:

granularity – float

Sets the bounding region granularity to granularity; a value between and including 0 and 1. The default value is 0 (i.e., the lowest granularity, where the bounding region corresponds to the item’s bounding rectangle).

The granularity is used by boundingRegion() to calculate how fine the bounding region of the item should be. The highest achievable granularity is 1, where boundingRegion() will return the finest outline possible for the respective device (e.g., for a QGraphicsView viewport, this gives you a pixel-perfect bounding region). The lowest possible granularity is 0. The value of granularity describes the ratio between device resolution and the resolution of the bounding region (e.g., a value of 0.25 will provide a region where each chunk corresponds to 4x4 device units / pixels).

setCacheMode(mode[, cacheSize=QSize()])#
Parameters:

Sets the item’s cache mode to mode.

The optional logicalCacheSize argument is used only by ItemCoordinateCache mode, and describes the resolution of the cache buffer; if logicalCacheSize is (100, 100), QGraphicsItem will fit the item into 100x100 pixels in graphics memory, regardless of the logical size of the item itself. By default QGraphicsItem uses the size of boundingRect() . For all other cache modes than ItemCoordinateCache , logicalCacheSize is ignored.

Caching can speed up rendering if your item spends a significant time redrawing itself. In some cases the cache can also slow down rendering, in particular when the item spends less time redrawing than QGraphicsItem spends redrawing from the cache.

When caching is enabled, an item’s paint() function will generally draw into an offscreen pixmap cache; for any subsequent repaint requests, the Graphics View framework will redraw from the cache. This approach works particularly well with QGLWidget, which stores all the cache as OpenGL textures.

Be aware that QPixmapCache’s cache limit may need to be changed to obtain optimal performance.

You can read more about the different cache modes in the CacheMode documentation.

Note

Enabling caching does not imply that the item’s paint() function will be called only in response to an explicit update() call. For instance, under memory pressure, Qt may decide to drop some of the cache information; in such cases an item’s paint() function will be called even if there was no update() call (that is, exactly as if there were no caching enabled).

setCursor(cursor)#
Parameters:

cursorQCursor

Warning

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

Sets the current cursor shape for the item to cursor. The mouse cursor will assume this shape when it’s over this item. See the list of predefined cursor objects for a range of useful shapes.

An editor item might want to use an I-beam cursor:

item.setCursor(Qt.IBeamCursor)

If no cursor has been set, the cursor of the item beneath is used.

setData(key, value)#
Parameters:
  • key – int

  • value – object

Sets this item’s custom data for the key key to value.

Custom item data is useful for storing arbitrary properties for any item. Qt does not use this feature for storing data; it is provided solely for the convenience of the user.

See also

data()

setEnabled(enabled)#
Parameters:

enabled – bool

If enabled is true, the item is enabled; otherwise, it is disabled.

Disabled items are visible, but they do not receive any events, and cannot take focus nor be selected. Mouse events are discarded; they are not propagated unless the item is also invisible, or if it does not accept mouse events (see acceptedMouseButtons() ). A disabled item cannot become the mouse grabber, and as a result of this, an item loses the grab if it becomes disabled when grabbing the mouse, just like it loses focus if it had focus when it was disabled.

Disabled items are traditionally drawn using grayed-out colors (see QPalette::Disabled).

If you disable a parent item, all its children will also be disabled. If you enable a parent item, all children will be enabled, unless they have been explicitly disabled (i.e., if you call setEnabled(false) on a child, it will not be re-enabled if its parent is disabled, and then enabled again).

Items are enabled by default.

Note

If you install an event filter, you can still intercept events before they are delivered to items; this mechanism disregards the item’s enabled state.

See also

isEnabled()

setFiltersChildEvents(enabled)#
Parameters:

enabled – bool

If enabled is true, this item is set to filter all events for all its children (i.e., all events intended for any of its children are instead sent to this item); otherwise, if enabled is false, this item will only handle its own events. The default value is false.

setFlag(flag[, enabled=true])#
Parameters:

If enabled is true, the item flag flag is enabled; otherwise, it is disabled.

See also

flags() setFlags()

setFlags(flags)#
Parameters:

flags – Combination of GraphicsItemFlag<