CopperSpice API  1.7.2
QGraphicsScene Class Reference

Provides a surface for managing a large number of 2D graphical items. More...

Inheritance diagram for QGraphicsScene:
QObject

Public Typedefs

using SceneLayers = QFlags< SceneLayer >
 

Public Types

enum  ItemIndexMethod
 
enum  SceneLayer
 

Public Signals

void changed (const QList< QRectF > &region)
 
void focusItemChanged (QGraphicsItem *newFocus, QGraphicsItem *oldFocus, Qt::FocusReason reason)
 
void sceneRectChanged (const QRectF &rect)
 
void selectionChanged ()
 
- Public Signals inherited from QObject
void destroyed (QObject *obj=nullptr)
 
void objectNameChanged (const QString &objectName)
 

Public Slots

void advance ()
 
void clear ()
 
void clearSelection ()
 
void invalidate (const QRectF &rect=QRectF (), SceneLayers layers=AllLayers)
 
void update (const QRectF &rect=QRectF ())
 
- Public Slots inherited from QObject
void deleteLater ()
 

Public Methods

 QGraphicsScene (const QRectF &sceneRect, QObject *parent=nullptr)
 
 QGraphicsScene (QObject *parent=nullptr)
 
 QGraphicsScene (qreal x, qreal y, qreal width, qreal height, QObject *parent=nullptr)
 
virtual ~QGraphicsScene ()
 
QGraphicsItemactivePanel () const
 
QGraphicsWidgetactiveWindow () const
 
QGraphicsEllipseItemaddEllipse (const QRectF &rect, const QPen &pen=QPen (), const QBrush &brush=QBrush ())
 
QGraphicsEllipseItemaddEllipse (qreal x, qreal y, qreal w, qreal h, const QPen &pen=QPen (), const QBrush &brush=QBrush ())
 
void addItem (QGraphicsItem *item)
 
QGraphicsLineItemaddLine (const QLineF &line, const QPen &pen=QPen ())
 
QGraphicsLineItemaddLine (qreal x1, qreal y1, qreal x2, qreal y2, const QPen &pen=QPen ())
 
QGraphicsPathItemaddPath (const QPainterPath &path, const QPen &pen=QPen (), const QBrush &brush=QBrush ())
 
QGraphicsPixmapItemaddPixmap (const QPixmap &pixmap)
 
QGraphicsPolygonItemaddPolygon (const QPolygonF &polygon, const QPen &pen=QPen (), const QBrush &brush=QBrush ())
 
QGraphicsRectItemaddRect (const QRectF &rect, const QPen &pen=QPen (), const QBrush &brush=QBrush ())
 
QGraphicsRectItemaddRect (qreal x, qreal y, qreal w, qreal h, const QPen &pen=QPen (), const QBrush &brush=QBrush ())
 
QGraphicsSimpleTextItemaddSimpleText (const QString &text, const QFont &font=QFont ())
 
QGraphicsTextItemaddText (const QString &text, const QFont &font=QFont ())
 
QGraphicsProxyWidgetaddWidget (QWidget *widget, Qt::WindowFlags flags=Qt::EmptyFlag)
 
QBrush backgroundBrush () const
 
int bspTreeDepth () const
 
void clearFocus ()
 
QList< QGraphicsItem * > collidingItems (const QGraphicsItem *item, Qt::ItemSelectionMode mode=Qt::IntersectsItemShape) const
 
QGraphicsItemGroupcreateItemGroup (const QList< QGraphicsItem * > &items)
 
void destroyItemGroup (QGraphicsItemGroup *group)
 
QGraphicsItemfocusItem () const
 
QFont font () const
 
QBrush foregroundBrush () const
 
bool hasFocus () const
 
qreal height () const
 
virtual QVariant inputMethodQuery (Qt::InputMethodQuery query) const
 
void invalidate (qreal x, qreal y, qreal w, qreal h, SceneLayers layers=AllLayers)
 
bool isActive () const
 
bool isSortCacheEnabled () const
 
QGraphicsItemitemAt (const QPointF &pos, const QTransform &deviceTransform) const
 
QGraphicsItemitemAt (qreal x, qreal y, const QTransform &deviceTransform) const
 
ItemIndexMethod itemIndexMethod () const
 
QList< QGraphicsItem * > items (const QPainterPath &path, Qt::ItemSelectionMode mode=Qt::IntersectsItemShape, Qt::SortOrder order=Qt::DescendingOrder, const QTransform &deviceTransform=QTransform ()) const
 
QList< QGraphicsItem * > items (const QPointF &pos, Qt::ItemSelectionMode mode=Qt::IntersectsItemShape, Qt::SortOrder order=Qt::DescendingOrder, const QTransform &deviceTransform=QTransform ()) const
 
QList< QGraphicsItem * > items (const QPolygonF &polygon, Qt::ItemSelectionMode mode=Qt::IntersectsItemShape, Qt::SortOrder order=Qt::DescendingOrder, const QTransform &deviceTransform=QTransform ()) const
 
QList< QGraphicsItem * > items (const QRectF &rect, Qt::ItemSelectionMode mode=Qt::IntersectsItemShape, Qt::SortOrder order=Qt::DescendingOrder, const QTransform &deviceTransform=QTransform ()) const
 
QList< QGraphicsItem * > items (qreal x, qreal y, qreal w, qreal h, Qt::ItemSelectionMode mode, Qt::SortOrder order, const QTransform &deviceTransform=QTransform ()) const
 
QList< QGraphicsItem * > items (Qt::SortOrder order=Qt::DescendingOrder) const
 
QRectF itemsBoundingRect () const
 
qreal minimumRenderSize () const
 
QGraphicsItemmouseGrabberItem () const
 
QPalette palette () const
 
void removeItem (QGraphicsItem *item)
 
void render (QPainter *painter, const QRectF &target=QRectF (), const QRectF &source=QRectF (), Qt::AspectRatioMode aspectRatioMode=Qt::KeepAspectRatio)
 
QRectF sceneRect () const
 
QList< QGraphicsItem * > selectedItems () const
 
QPainterPath selectionArea () const
 
bool sendEvent (QGraphicsItem *item, QEvent *event)
 
void setActivePanel (QGraphicsItem *item)
 
void setActiveWindow (QGraphicsWidget *widget)
 
void setBackgroundBrush (const QBrush &brush)
 
void setBspTreeDepth (int depth)
 
void setFocus (Qt::FocusReason focusReason=Qt::OtherFocusReason)
 
void setFocusItem (QGraphicsItem *item, Qt::FocusReason focusReason=Qt::OtherFocusReason)
 
void setFont (const QFont &font)
 
void setForegroundBrush (const QBrush &brush)
 
void setItemIndexMethod (ItemIndexMethod method)
 
void setMinimumRenderSize (qreal minSize)
 
void setPalette (const QPalette &palette)
 
void setSceneRect (const QRectF &rect)
 
void setSceneRect (qreal x, qreal y, qreal w, qreal h)
 
void setSelectionArea (const QPainterPath &path, const QTransform &deviceTransform)
 
void setSelectionArea (const QPainterPath &path, Qt::ItemSelectionOperation selectionOperation=Qt::ReplaceSelection, Qt::ItemSelectionMode mode=Qt::IntersectsItemShape, const QTransform &deviceTransform=QTransform ())
 
void setSortCacheEnabled (bool enabled)
 
void setStickyFocus (bool enabled)
 
void setStyle (QStyle *style)
 
bool stickyFocus () const
 
QStylestyle () const
 
void update (qreal x, qreal y, qreal w, qreal h)
 
QList< QGraphicsView * > views () const
 
qreal width () const
 
- Public Methods inherited from QObject
 QObject (QObject *parent=nullptr)
 
 ~QObject ()
 
bool blockSignals (bool block)
 
const QList< QObject * > & children () const
 
bool connect (const QObject *sender, const QString &signalMethod, const QString &location, const QString &slotMethod, Qt::ConnectionType type=Qt::AutoConnection)
 
bool connect (const QObject *sender, const QString &signalMethod, const QString &slotMethod, Qt::ConnectionType type=Qt::AutoConnection)
 
bool disconnect (const QObject *receiver, const QString &slotMethod=QString ()) const
 
bool disconnect (const QString &signalMethod, const QString &location, const QObject *receiver=nullptr, const QString &slotMethod=QString ()) const
 
bool disconnect (const QString &signalMethod=QString (), const QObject *receiver=nullptr, const QString &slotMethod=QString ()) const
 
void dumpObjectInfo ()
 
void dumpObjectTree ()
 
QList< QStringdynamicPropertyNames () const
 
template<typename T >
findChild (const QString &childName=QString ()) const
 
template<class T >
QList< T > findChildren (const QRegularExpression &regExp, Qt::FindChildOptions options=Qt::FindChildrenRecursively) const
 
template<class T >
QList< T > findChildren (const QString &objName=QString (), Qt::FindChildOptions options=Qt::FindChildrenRecursively) const
 
bool inherits (const QString &className) const
 
void installEventFilter (QObject *filterObj)
 
bool isWidgetType () const
 
bool isWindowType () const
 
void killTimer (int id)
 
const QMetaObjectmetaObject () const
 
void moveToThread (QThread *targetThread)
 
QString objectName () const
 
QObject * parent () const
 
template<class T = QVariant>
property (const QString &name) const
 
void removeEventFilter (QObject *obj)
 
void setObjectName (const QString &name)
 
void setParent (QObject *parent)
 
bool setProperty (const QString &name, const QVariant &value)
 
bool signalsBlocked () const
 
int startTimer (int interval, Qt::TimerType timerType=Qt::CoarseTimer)
 
QThreadthread () const
 

Protected Slots

bool focusNextPrevChild (bool next)
 

Protected Methods

virtual void contextMenuEvent (QGraphicsSceneContextMenuEvent *event)
 
virtual void dragEnterEvent (QGraphicsSceneDragDropEvent *event)
 
virtual void dragLeaveEvent (QGraphicsSceneDragDropEvent *event)
 
virtual void dragMoveEvent (QGraphicsSceneDragDropEvent *event)
 
virtual void drawBackground (QPainter *painter, const QRectF &rect)
 
virtual void drawForeground (QPainter *painter, const QRectF &rect)
 
virtual void drawItems (QPainter *painter, int numItems, QGraphicsItem *items[], const QStyleOptionGraphicsItem options[], QWidget *widget=nullptr)
 
virtual void dropEvent (QGraphicsSceneDragDropEvent *event)
 
bool event (QEvent *event) override
 
bool eventFilter (QObject *watched, QEvent *event) override
 
virtual void focusInEvent (QFocusEvent *event)
 
virtual void focusOutEvent (QFocusEvent *event)
 
virtual void helpEvent (QGraphicsSceneHelpEvent *event)
 
virtual void inputMethodEvent (QInputMethodEvent *event)
 
virtual void keyPressEvent (QKeyEvent *event)
 
virtual void keyReleaseEvent (QKeyEvent *event)
 
virtual void mouseDoubleClickEvent (QGraphicsSceneMouseEvent *event)
 
virtual void mouseMoveEvent (QGraphicsSceneMouseEvent *event)
 
virtual void mousePressEvent (QGraphicsSceneMouseEvent *event)
 
virtual void mouseReleaseEvent (QGraphicsSceneMouseEvent *event)
 
virtual void wheelEvent (QGraphicsSceneWheelEvent *event)
 
- Protected Methods inherited from QObject
virtual void childEvent (QChildEvent *event)
 
virtual void connectNotify (const QMetaMethod &signalMethod) const
 
virtual void customEvent (QEvent *event)
 
virtual void disconnectNotify (const QMetaMethod &signalMethod) const
 
bool isSignalConnected (const QMetaMethod &signalMethod) const
 
int receivers (const QString &signal) const
 
QObject * sender () const
 
int senderSignalIndex () const
 
virtual void timerEvent (QTimerEvent *event)
 

Properties

 backgroundBrush
 
 bspTreeDepth
 
 font
 
 foregroundBrush
 
 itemIndexMethod
 
 minimumRenderSize
 
 palette
 
 sceneRect
 
 stickyFocus
 
- Properties inherited from QObject
 objectName
 

Friends

class QGesture
 
class QGraphicsEffect
 
class QGraphicsItem
 
class QGraphicsObject
 
class QGraphicsView
 
class QGraphicsWidget
 

Additional Inherited Members

- Static Public Methods inherited from QObject
static bool connect (const QObject *sender, const QMetaMethod &signalMethod, const QObject *receiver, const QMetaMethod &slotMethod, Qt::ConnectionType type=Qt::AutoConnection)
 
static bool connect (const QObject *sender, const QString &signalMethod, const QObject *receiver, const QString &slotMethod, Qt::ConnectionType type=Qt::AutoConnection, const QString &location=QString ())
 
static bool connect (const QObject *sender, const QString &signalMethod, const QString &location, const QObject *receiver, const QString &slotMethod, Qt::ConnectionType type=Qt::AutoConnection)
 
template<class Sender , class SignalClass , class... SignalArgs, class Receiver , class SlotClass , class... SlotArgs, class SlotReturn >
static bool connect (const Sender *sender, void (SignalClass::*signalMethod)(SignalArgs...), const Receiver *receiver, SlotReturn (SlotClass::*slotMethod)(SlotArgs...), Qt::ConnectionType type=Qt::AutoConnection)
 
template<class Sender , class SignalClass , class... SignalArgs, class Receiver , class T >
static bool connect (const Sender *sender, void (SignalClass::*signalMethod)(SignalArgs...), const Receiver *receiver, T slotLambda, Qt::ConnectionType type=Qt::AutoConnection)
 
static bool disconnect (const QObject *sender, const QMetaMethod &signalMethod, const QObject *receiver, const QMetaMethod &slotMethod)
 
static bool disconnect (const QObject *sender, const QString &signalMethod, const QObject *receiver, const QString &slotMethod)
 
static bool disconnect (const QObject *sender, const QString &signalMethod, const QString &location, const QObject *receiver, const QString &slotMethod)
 
template<class Sender , class SignalClass , class... SignalArgs, class Receiver , class SlotClass , class... SlotArgs, class SlotReturn >
static bool disconnect (const Sender *sender, void (SignalClass::*signalMethod)(SignalArgs...), const Receiver *receiver, SlotReturn (SlotClass::*slotMethod)(SlotArgs...))
 
template<class Sender , class SignalClass , class... SignalArgs, class Receiver >
static bool disconnect (const Sender *sender, void (SignalClass::*signalMethod)(SignalArgs...), const Receiver *receiver, std::nullptr_t slotMethod=nullptr)
 
template<class Sender , class SignalClass , class... SignalArgs, class Receiver , class T >
static bool disconnect (const Sender *sender, void (SignalClass::*signalMethod)(SignalArgs...), const Receiver *receiver, T slotMethod)
 
static QMetaObjectstaticMetaObject ()
 
static QString tr (const char *text, const char *comment=nullptr, std::optional< int > numArg=std::optional< int >())
 

Detailed Description

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

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

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

scene.addText("Hello world");
QGraphicsView view(&scene);
view.show();

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

To add items to a scene, you start off by constructing a QGraphicsScene object. Then, you have two options: either add your existing QGraphicsItem objects by calling addItem(), or you can call one of the convenience functions addEllipse(), addLine(), addPath(), addPixmap(), addPolygon(), addRect(), or addText(), which all return a pointer to the newly added item. The dimensions of the items added with these functions are relative to the item's coordinate system, and the items position is initialized to (0, 0) in the scene.

You can then visualize the scene using QGraphicsView. When the scene changes, (e.g., when an item moves or is transformed) QGraphicsScene emits the changed() signal. To remove an item, call removeItem().

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

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

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

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

Event Handling and Propagation

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

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

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

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

See also
QGraphicsItem, QGraphicsView

Member Typedef Documentation

Member Enumeration Documentation

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

ConstantValueDescription
QGraphicsScene::BspTreeIndex0 A Binary Space Partitioning tree is applied. All QGraphicsScene's item location algorithms are of an order close to logarithmic complexity, by making use of binary search. Adding, moving and removing items is logarithmic. This approach is best for static scenes (i.e., scenes where most items do not move).
QGraphicsScene::NoIndex-1No index is applied. Item location is of linear complexity, as all items on the scene are searched. Adding, moving and removing items, however, is done in constant time. This approach is ideal for dynamic scenes, where many items are added, moved or removed continuously.
See also
setItemIndexMethod(), bspTreeDepth

This enum describes the rendering layers in a QGraphicsScene. When QGraphicsScene draws the scene contents, it renders each of these layers separately, in order. Each layer represents a flag that can be OR'ed together when calling functions such as invalidate() or QGraphicsView::invalidateScene().

ConstantValueDescription
QGraphicsScene::ItemLayer0x1 The item layer. QGraphicsScene renders all items are in this layer by calling the virtual function drawItems(). The item layer is drawn after the background layer, but before the foreground layer.
QGraphicsScene::BackgroundLayer0x2 The background layer. QGraphicsScene renders the scene's background in this layer by calling the virtual function drawBackground(). The background layer is drawn first of all layers.
QGraphicsScene::ForegroundLayer0x4 The foreground layer. QGraphicsScene renders the scene's foreground in this layer by calling the virtual function drawForeground(). The foreground layer is drawn last of all layers.
QGraphicsScene::AllLayers0xffff All layers, this value represents a combination of all three layers.
See also
invalidate(), QGraphicsView::invalidateScene()

Constructor & Destructor Documentation

QGraphicsScene::QGraphicsScene ( QObject parent = nullptr)

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

QGraphicsScene::QGraphicsScene ( const QRectF sceneRect,
QObject parent = nullptr 
)

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

See also
sceneRect
QGraphicsScene::QGraphicsScene ( qreal  x,
qreal  y,
qreal  width,
qreal  height,
QObject parent = nullptr 
)

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

See also
sceneRect
QGraphicsScene::~QGraphicsScene ( )
virtual

Removes and deletes all items from the scene object before destroying the scene object. The scene object is removed from the application's global scene list, and it is removed from all associated views.

Method Documentation

QGraphicsItem * QGraphicsScene::activePanel ( ) const

Returns the current active panel, or 0 if no panel is currently active.

See also
QGraphicsScene::setActivePanel()
QGraphicsWidget * QGraphicsScene::activeWindow ( ) const

Returns the current active window or nullptr if no window is currently active.

See also
QGraphicsScene::setActiveWindow()
QGraphicsEllipseItem * QGraphicsScene::addEllipse ( const QRectF rect,
const QPen pen = QPen(),
const QBrush brush = QBrush() 
)

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

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

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

See also
addLine(), addPath(), addPixmap(), addRect(), addText(), addItem(), addWidget()
QGraphicsEllipseItem * QGraphicsScene::addEllipse ( qreal  x,
qreal  y,
qreal  w,
qreal  h,
const QPen pen = QPen(),
const QBrush brush = QBrush() 
)
inline

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

void QGraphicsScene::addItem ( QGraphicsItem item)

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

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

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

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

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

See also
removeItem(), addEllipse(), addLine(), addPath(), addPixmap(), addRect(), addText(), addWidget(), Sorting
QGraphicsLineItem * QGraphicsScene::addLine ( const QLineF line,
const QPen pen = QPen() 
)

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

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

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

See also
addEllipse(), addPath(), addPixmap(), addRect(), addText(), addItem(), addWidget()
QGraphicsLineItem * QGraphicsScene::addLine ( qreal  x1,
qreal  y1,
qreal  x2,
qreal  y2,
const QPen pen = QPen() 
)
inline

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

QGraphicsPathItem * QGraphicsScene::addPath ( const QPainterPath path,
const QPen pen = QPen(),
const QBrush brush = QBrush() 
)

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

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

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

See also
addEllipse(), addLine(), addPixmap(), addRect(), addText(), addItem(), addWidget()
QGraphicsPixmapItem * QGraphicsScene::addPixmap ( const QPixmap pixmap)

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

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

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

See also
addEllipse(), addLine(), addPath(), addRect(), addText(), addItem(), addWidget()
QGraphicsPolygonItem * QGraphicsScene::addPolygon ( const QPolygonF polygon,
const QPen pen = QPen(),
const QBrush brush = QBrush() 
)

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

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

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

See also
addEllipse(), addLine(), addPath(), addRect(), addText(), addItem(), addWidget()
QGraphicsRectItem * QGraphicsScene::addRect ( const QRectF rect,
const QPen pen = QPen(),
const QBrush brush = QBrush() 
)

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

Note that the item's geometry is provided in item coordinates, and its position is initialized to (0, 0). For example, if a QRect(50, 50, 100, 100) is added, its top-left corner will be at (50, 50) relative to the origin in the items coordinate system.

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

See also
addEllipse(), addLine(), addPixmap(), addPixmap(), addText(), addItem(), addWidget()
QGraphicsRectItem * QGraphicsScene::addRect ( qreal  x,
qreal  y,
qreal  w,
qreal  h,
const QPen pen = QPen(),
const QBrush brush = QBrush() 
)
inline

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

QGraphicsSimpleTextItem * QGraphicsScene::addSimpleText ( const QString text,
const QFont font = QFont() 
)

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

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

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

See also
addEllipse(), addLine(), addPixmap(), addPixmap(), addRect(), addItem(), addWidget()
QGraphicsTextItem * QGraphicsScene::addText ( const QString text,
const QFont font = QFont() 
)

Creates and adds a text item to the scene, and returns the item pointer. The text string is initialized to text, and its font is initialized to font. The item's position is initialized to (0, 0).

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

See also
addEllipse(), addLine(), addPixmap(), addPixmap(), addRect(), addItem(), addWidget()
QGraphicsProxyWidget * QGraphicsScene::addWidget ( QWidget widget,
Qt::WindowFlags  flags = Qt::EmptyFlag 
)

Creates a new QGraphicsProxyWidget for widget, adds it to the scene, and then returns a pointer to the proxy. The value for flags sets the default window flags for the embedding proxy widget. The item's position is initialized to (0, 0).

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

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

See also
addEllipse(), addLine(), addPixmap(), addPixmap(), addRect(), addText(), addSimpleText(), addItem()
void QGraphicsScene::advance ( )
slot

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

See also
QGraphicsItem::advance(), QGraphicsItemAnimation, QTimeLine
QBrush QGraphicsScene::backgroundBrush ( ) const

Property documentation pending.

int QGraphicsScene::bspTreeDepth ( ) const

Property documentation pending.

void QGraphicsScene::changed ( const QList< QRectF > &  region)
signal

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

See also
QGraphicsView::updateScene()
void QGraphicsScene::clear ( )
slot

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

See also
addItem()
void QGraphicsScene::clearFocus ( )

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

A scene that does not have focus ignores key events.

See also
hasFocus(), setFocus(), setFocusItem()
void QGraphicsScene::clearSelection ( )
slot

Clears the current selection.

See also
setSelectionArea(), selectedItems()
QList< QGraphicsItem * > QGraphicsScene::collidingItems ( const QGraphicsItem item,
Qt::ItemSelectionMode  mode = Qt::IntersectsItemShape 
) const

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

The items are returned in descending stacking order. This means the first item in the list is the uppermost item, and the last item is the lowermost item.

See also
items(), itemAt(), QGraphicsItem::collidesWithItem(), Sorting
void QGraphicsScene::contextMenuEvent ( QGraphicsSceneContextMenuEvent event)
protectedvirtual

This event handler, for event event, can be reimplemented in a subclass to receive context menu events. The default implementation forwards the event to the topmost item that accepts context menu events at the position of the event. If no items accept context menu events at this position, the event is ignored.

See also
QGraphicsItem::contextMenuEvent()
QGraphicsItemGroup * QGraphicsScene::createItemGroup ( const QList< QGraphicsItem * > &  items)

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

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

See also
destroyItemGroup(), QGraphicsItemGroup::addToGroup()
void QGraphicsScene::destroyItemGroup ( QGraphicsItemGroup group)

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

See also
createItemGroup(), QGraphicsItemGroup::removeFromGroup()
void QGraphicsScene::dragEnterEvent ( QGraphicsSceneDragDropEvent event)
protectedvirtual

This event handler, for event event, can be reimplemented in a subclass to receive drag enter events for the scene. The default implementation accepts the event and prepares the scene to accept drag move events.

See also
QGraphicsItem::dragEnterEvent(), dragMoveEvent(), dragLeaveEvent(), dropEvent()
void QGraphicsScene::dragLeaveEvent ( QGraphicsSceneDragDropEvent event)
protectedvirtual

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

See also
QGraphicsItem::dragLeaveEvent(), dragEnterEvent(), dragMoveEvent(), dropEvent()
void QGraphicsScene::dragMoveEvent ( QGraphicsSceneDragDropEvent event)
protectedvirtual

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

See also
QGraphicsItem::dragMoveEvent(), dragEnterEvent(), dragLeaveEvent(), dropEvent()
void QGraphicsScene::drawBackground ( QPainter painter,
const QRectF rect 
)
protectedvirtual

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

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

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

See also
drawForeground(), drawItems()
void QGraphicsScene::drawForeground ( QPainter painter,
const QRectF rect 
)
protectedvirtual

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

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

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

See also
drawBackground(), drawItems()
void QGraphicsScene::drawItems ( QPainter painter,
int  numItems,
QGraphicsItem items[],
const QStyleOptionGraphicsItem  options[],
QWidget widget = nullptr 
)
deprecatedprotectedvirtual
Deprecated:
Paints the given items using the provided painter, after the background has been drawn, and before the foreground has been drawn. All painting is done in scene coordinates. Before drawing each item, the painter must be transformed using QGraphicsItem::sceneTransform().

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

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

Example:

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

This function is not called unless the QGraphicsView::IndirectPainting flag is given as an Optimization flag.

See also
drawBackground(), drawForeground()
void QGraphicsScene::dropEvent ( QGraphicsSceneDragDropEvent event)
protectedvirtual

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

See also
QGraphicsItem::dropEvent(), dragEnterEvent(), dragMoveEvent(), dragLeaveEvent()
bool QGraphicsScene::event ( QEvent event)
overrideprotectedvirtual

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

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

Unlike QWidget, QGraphicsScene does not have the convenience functions enterEvent() and leaveEvent(). Use this function to obtain those events instead.

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

Reimplemented from QObject.

bool QGraphicsScene::eventFilter ( QObject watched,
QEvent event 
)
overrideprotectedvirtual

QGraphicsScene filters QApplication's events to detect palette and font changes.

Reimplemented from QObject.

void QGraphicsScene::focusInEvent ( QFocusEvent event)
protectedvirtual

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

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

See also
QGraphicsItem::focusOutEvent()
QGraphicsItem * QGraphicsScene::focusItem ( ) const

When the scene is active, this functions returns the scene's current focus item, or 0 if no item currently has focus. When the scene is inactive, this functions returns the item that will gain input focus when the scene becomes active.

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

See also
setFocusItem(), QGraphicsItem::hasFocus(), isActive()
void QGraphicsScene::focusItemChanged ( QGraphicsItem newFocus,
QGraphicsItem oldFocus,
Qt::FocusReason  reason 
)
signal

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

The value for oldFocus is a pointer to the item which previously had focus or nullptr if no item had focus before the signal was emitted. The newFocus is a pointer to the item which has gained input focus, or nullptr if focus was lost. The value for reason is the reason for the focus change. For example, if the scene was deactivated while an input field had focus, oldFocus would point to the input field item, newFocus would be nullptr, and reason would be Qt::ActiveWindowFocusReason.

bool QGraphicsScene::focusNextPrevChild ( bool  next)
protectedslot

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

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

void QGraphicsScene::focusOutEvent ( QFocusEvent event)
protectedvirtual

This event handler, for event event can be reimplemented in a subclass to receive focus out events. The default implementation removes focus from any focus item, then removes focus from the scene.

See also
QGraphicsItem::focusInEvent()
QFont QGraphicsScene::font ( ) const

Property documentation pending.

QBrush QGraphicsScene::foregroundBrush ( ) const

Property documentation pending.

bool QGraphicsScene::hasFocus ( ) const

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

See also
setFocus(), setFocusItem()
qreal QGraphicsScene::height ( ) const
inline

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

See also
width()
void QGraphicsScene::helpEvent ( QGraphicsSceneHelpEvent event)
protectedvirtual

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

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

See also
QGraphicsItem::toolTip(), QGraphicsSceneHelpEvent
void QGraphicsScene::inputMethodEvent ( QInputMethodEvent event)
protectedvirtual

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

The default implementation forwards the event to the focusItem(). If no item currently has focus or the current focus item does not accept input methods, this function does nothing.

See also
QGraphicsItem::inputMethodEvent()
QVariant QGraphicsScene::inputMethodQuery ( Qt::InputMethodQuery  query) const
virtual

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

The query parameter specifies which property is queried.

See also
QWidget::inputMethodQuery()
void QGraphicsScene::invalidate ( const QRectF rect = QRectF(),
SceneLayers  layers = AllLayers 
)
slot

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

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

QRectF TileScene::rectForTile(int x, int y) const
{
// Return the rectangle for the tile at position (x, y).
return QRectF(x * tileWidth, y * tileHeight, tileWidth, tileHeight);
}
void TileScene::setTile(int x, int y, const QPixmap &pixmap)
{
// Sets or replaces the tile at position (x, y) with pixmap.
if (x >= 0 && x < numTilesH && y >= 0 && y < numTilesV) {
tiles[y][x] = pixmap;
invalidate(rectForTile(x, y), BackgroundLayer);
}
}
void TileScene::drawBackground(QPainter *painter, const QRectF &exposed)
{
// Draws all tiles that intersect the exposed area.
for (int y = 0; y < numTilesV; ++y) {
for (int x = 0; x < numTilesH; ++x) {
QRectF rect = rectForTile(x, y);
if (exposed.intersects(rect))
painter->drawPixmap(rect.topLeft(), tiles[y][x]);
}
}
}

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

See also
QGraphicsView::resetCachedContent()
void QGraphicsScene::invalidate ( qreal  x,
qreal  y,
qreal  w,
qreal  h,
SceneLayers  layers = AllLayers 
)
inline

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

bool QGraphicsScene::isActive ( ) const

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

See also
QGraphicsItem::isActive(), QWidget::isActiveWindow()
bool QGraphicsScene::isSortCacheEnabled ( ) const

Property documentation pending.

QGraphicsItem * QGraphicsScene::itemAt ( const QPointF pos,
const QTransform deviceTransform 
) const

Returns the topmost visible item at the specified pos nullptr if there are no items at this position. The deviceTransform is the transformation that applies to the view and needs to be provided if the scene contains items that ignore transformations.

See also
items(), collidingItems(), Sorting
QGraphicsItem * QGraphicsScene::itemAt ( qreal  x,
qreal  y,
const QTransform deviceTransform 
) const
inline

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

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

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

ItemIndexMethod QGraphicsScene::itemIndexMethod ( ) const

Property documentation pending.

QList< QGraphicsItem * > QGraphicsScene::items ( const QPainterPath path,
Qt::ItemSelectionMode  mode = Qt::IntersectsItemShape,
Qt::SortOrder  order = Qt::DescendingOrder,
const QTransform deviceTransform = QTransform() 
) const

Returns all visible items that, depending on mode, are either inside or intersect with the specified path and return a list sorted using order.

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

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

See also
itemAt(), Sorting
QList< QGraphicsItem * > QGraphicsScene::items ( const QPointF pos,
Qt::ItemSelectionMode  mode = Qt::IntersectsItemShape,
Qt::SortOrder  order = Qt::DescendingOrder,
const QTransform deviceTransform = QTransform() 
) const

Returns all visible items that, depending on mode, are at the specified pos in a list sorted using order.

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

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

See also
itemAt(), Sorting
QList< QGraphicsItem * > QGraphicsScene::items ( const QPolygonF polygon,
Qt::ItemSelectionMode  mode = Qt::IntersectsItemShape,
Qt::SortOrder  order = Qt::DescendingOrder,
const QTransform deviceTransform = QTransform() 
) const

Returns all visible items that, depending on mode, are either inside or intersect with the specified polygon and return a list sorted using order.

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

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

See also
itemAt(), Sorting
QList< QGraphicsItem * > QGraphicsScene::items ( const QRectF rect,
Qt::ItemSelectionMode  mode = Qt::IntersectsItemShape,
Qt::SortOrder  order = Qt::DescendingOrder,
const QTransform deviceTransform = QTransform() 
) const

Returns all visible items that, depending on mode, are either inside or intersect with the specified rect and return a list sorted using order.

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

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

See also
itemAt(), Sorting
QList< QGraphicsItem * > QGraphicsScene::items ( qreal  x,
qreal  y,
qreal  w,
qreal  h,
Qt::ItemSelectionMode  mode,
Qt::SortOrder  order,
const QTransform deviceTransform = QTransform() 
) const
inline

Returns all visible items that, depending on mode, are either inside or intersect with the rectangle defined by x, y, w and h, in a list sorted using order.

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

QList< QGraphicsItem * > QGraphicsScene::items ( Qt::SortOrder  order = Qt::DescendingOrder) const

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

See also
addItem(), removeItem(), Sorting
QRectF QGraphicsScene::itemsBoundingRect ( ) const

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

See also
sceneRect()
void QGraphicsScene::keyPressEvent ( QKeyEvent event)
protectedvirtual

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

See also
QGraphicsItem::keyPressEvent(), focusItem()
void QGraphicsScene::keyReleaseEvent ( QKeyEvent event)
protectedvirtual

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

See also
QGraphicsItem::keyReleaseEvent(), focusItem()
qreal QGraphicsScene::minimumRenderSize ( ) const

Property documentation pending.

void QGraphicsScene::mouseDoubleClickEvent ( QGraphicsSceneMouseEvent event)
protectedvirtual

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

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

The default implementation is similar to mousePressEvent().

See also
QGraphicsItem::mousePressEvent(), QGraphicsItem::mouseMoveEvent(), QGraphicsItem::mouseReleaseEvent(), QGraphicsItem::setAcceptedMouseButtons()
QGraphicsItem * QGraphicsScene::mouseGrabberItem ( ) const

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

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

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

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

void QGraphicsScene::mouseMoveEvent ( QGraphicsSceneMouseEvent event)
protectedvirtual

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

The default implementation depends on the mouse grabber state. If there is a mouse grabber item, the event is sent to the mouse grabber. If there are any items that accept hover events at the current position, the event is translated into a hover event and accepted, otherwise it's ignored.

See also
QGraphicsItem::mousePressEvent(), QGraphicsItem::mouseReleaseEvent(), QGraphicsItem::mouseDoubleClickEvent(), QGraphicsItem::setAcceptedMouseButtons()
void QGraphicsScene::mousePressEvent ( QGraphicsSceneMouseEvent event)
protectedvirtual

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

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

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

See also
QGraphicsItem::mousePressEvent(), QGraphicsItem::setAcceptedMouseButtons()
void QGraphicsScene::mouseReleaseEvent ( QGraphicsSceneMouseEvent event)
protectedvirtual

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

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

See also
QGraphicsItem::mousePressEvent(), QGraphicsItem::mouseMoveEvent(), QGraphicsItem::mouseDoubleClickEvent(), QGraphicsItem::setAcceptedMouseButtons()
QPalette QGraphicsScene::palette ( ) const

Property documentation pending.

void QGraphicsScene::removeItem ( QGraphicsItem item)

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

See also
addItem()
void QGraphicsScene::render ( QPainter painter,
const QRectF target = QRectF(),
const QRectF source = QRectF(),
Qt::AspectRatioMode  aspectRatioMode = Qt::KeepAspectRatio 
)

Renders the source rectangle from the current scene into target, using painter. This method is useful for capturing the contents of the scene onto a paint device, such as a QImage or for printing with QPrinter.

scene.addItem(...);
QPrinter printer(QPrinter::HighResolution);
printer.setPaperSize(QPrinter::A4);
QPainter painter(&printer);
scene.render(&painter);

If source is a null rectangle this methods will use sceneRect() to determine what to render. If target is a null rectangle the dimensions of the QPainter device will be used.

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

See also
QGraphicsView::render()
QRectF QGraphicsScene::sceneRect ( ) const

Property documentation pending.

void QGraphicsScene::sceneRectChanged ( const QRectF rect)
signal

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

See also
QGraphicsView::updateSceneRect()
QList< QGraphicsItem * > QGraphicsScene::selectedItems ( ) const

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

See also
setSelectionArea()
QPainterPath QGraphicsScene::selectionArea ( ) const

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

See also
setSelectionArea()
void QGraphicsScene::selectionChanged ( )
signal

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

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

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

See also
setSelectionArea(), selectedItems(), QGraphicsItem::setSelected()
bool QGraphicsScene::sendEvent ( QGraphicsItem item,
QEvent event 
)

Sends event event to item> through possible event filters. The event is sent only if the item is enabled. Returns false if the event was filtered or if the item is disabled. Otherwise returns the value that was returned from the event handler.

See also
QGraphicsItem::sceneEvent(), QGraphicsItem::sceneEventFilter()
void QGraphicsScene::setActivePanel ( QGraphicsItem item)

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

If the scene is currently inactive, item remains inactive until the scene becomes active (or, if item is 0, no item will be activated).

See also
activePanel(), isActive(), QGraphicsItem::isActive()
void QGraphicsScene::setActiveWindow ( QGraphicsWidget widget)

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

See also
activeWindow(), QGraphicsWidget::isActiveWindow()
void QGraphicsScene::setBackgroundBrush ( const QBrush brush)

Property documentation pending.

void QGraphicsScene::setBspTreeDepth ( int  depth)

Property documentation pending.

void QGraphicsScene::setFocus ( Qt::FocusReason  focusReason = Qt::OtherFocusReason)

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

If the scene already has focus this method does nothing.

See also
hasFocus(), clearFocus(), setFocusItem()
void QGraphicsScene::setFocusItem ( QGraphicsItem item,
Qt::FocusReason  focusReason = Qt::OtherFocusReason 
)

Sets the focus in the current QGraphicsScene to item, with the given focus reason focusReason.

This is done after removing focus from any previous item. If item is a nullptr, does not accept focus, or is not visible or not enabled, this method only removes focus from any previous item.

If item is not a nullptr and the scene does not currently have focus, this method will call setFocus() automatically.

See also
focusItem(), hasFocus(), setFocus()
void QGraphicsScene::setFont ( const QFont font)

Property documentation pending.

void QGraphicsScene::setForegroundBrush ( const QBrush brush)

Property documentation pending.

void QGraphicsScene::setItemIndexMethod ( ItemIndexMethod  method)

Property documentation pending.

void QGraphicsScene::setMinimumRenderSize ( qreal  minSize)

Property documentation pending.

void QGraphicsScene::setPalette ( const QPalette palette)

Property documentation pending.

void QGraphicsScene::setSceneRect ( const QRectF rect)

Property documentation pending.

void QGraphicsScene::setSceneRect ( qreal  x,
qreal  y,
qreal  w,
qreal  h 
)
inline

Property documentation pending.

void QGraphicsScene::setSelectionArea ( const QPainterPath path,
const QTransform deviceTransform 
)

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

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

For an item to be selected it must be marked as selectable using QGraphicsItem::ItemIsSelectable.

See also
clearSelection(), selectionArea()
void QGraphicsScene::setSelectionArea ( const QPainterPath path,
Qt::ItemSelectionOperation  selectionOperation = Qt::ReplaceSelection,
Qt::ItemSelectionMode  mode = Qt::IntersectsItemShape,
const QTransform deviceTransform = QTransform() 
)

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

The selectionOperation determines what to do with the currently selected items.

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

See also
clearSelection(), selectionArea()
void QGraphicsScene::setSortCacheEnabled ( bool  enabled)

Property documentation pending.

void QGraphicsScene::setStickyFocus ( bool  enabled)

Property documentation pending.

void QGraphicsScene::setStyle ( QStyle style)

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

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

If style is a nullptr QGraphicsScene will revert to QApplication::style().

See also
style()
bool QGraphicsScene::stickyFocus ( ) const

Property documentation pending.

QStyle * QGraphicsScene::style ( ) const

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

See also
setStyle()
void QGraphicsScene::update ( const QRectF rect = QRectF())
slot

Schedules a redraw of the area rect on the scene.

See also
sceneRect(), changed()
void QGraphicsScene::update ( qreal  x,
qreal  y,
qreal  w,
qreal  h 
)
inline

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

QList< QGraphicsView * > QGraphicsScene::views ( ) const

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

See also
QGraphicsView::scene()
void QGraphicsScene::wheelEvent ( QGraphicsSceneWheelEvent event)
protectedvirtual

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

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

See also
QGraphicsItem::wheelEvent()
qreal QGraphicsScene::width ( ) const
inline

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

See also
height()

Property Documentation

QGraphicsScene::backgroundBrush

This property holds the background brush of the scene.

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

QGraphicsView view(&scene);
view.show();
// a blue background
scene.setBackgroundBrush(Qt::blue);
// a gradient background
QRadialGradient gradient(0, 0, 10);
gradient.setSpread(QGradient::RepeatSpread);
scene.setBackgroundBrush(gradient);

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

PropertiesClass Methods
read backgroundBrush
write setBackgroundBrush
QGraphicsScene::bspTreeDepth

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

This property has no effect when NoIndex is used.

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

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

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

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

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

See also
itemIndexMethod
PropertiesClass Methods
read bspTreeDepth
write setBspTreeDepth
QGraphicsScene::font

This property holds the scene's default font.

The scene font defaults to, and resolves all its entries from, QApplication::font.

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

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

See also
QWidget::font, QApplication::setFont(), palette, style()
PropertiesClass Methods
read font
write setFont
QGraphicsScene::foregroundBrush

This property holds the foreground brush of the scene.

Change this property to set the scene's foreground to a different color, gradient or texture. The foreground is drawn after (on top of) the items. The default foreground brush is Qt::NoBrush ( i.e. the foreground is not drawn).

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

QGraphicsView view(&scene);
view.show();
// a white semi-transparent foreground
scene.setForegroundBrush(QColor(255, 255, 255, 127));
// a grid foreground
scene.setForegroundBrush(QBrush(Qt::lightGray, Qt::CrossPattern));
PropertiesClass Methods
read foregroundBrush
write setForegroundBrush
QGraphicsScene::itemIndexMethod

This property holds the item indexing method.

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

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

See also
bspTreeDepth
PropertiesClass Methods
read itemIndexMethod
write setItemIndexMethod
QGraphicsScene::minimumRenderSize

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

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

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

Note
Items that are not drawn as a result of being too small, are still returned by methods such as items() and itemAt(), and participate in collision detection and interactions. It is recommended that you set minimumRenderSize() to a value less than or equal to 1 in order to avoid large unrendered items that are interactive.
See also
QStyleOptionGraphicsItem::levelOfDetailFromTransform()
PropertiesClass Methods
read minimumRenderSize
write setMinimumRenderSize
QGraphicsScene::palette

This property holds the scene's default palette. This property provides the scene's palette. The scene palette defaults to, and resolves all its entries from, QApplication::palette.

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

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

See also
QWidget::palette, QApplication::setPalette(), font, style()
PropertiesClass Methods
read palette
write setPalette
QGraphicsScene::sceneRect

This property holds the scene rectangle the bounding rectangle of the scene. The scene rectangle defines the extent of the scene. It is primarily used by QGraphicsView to determine the view's default scrollable area, and by Graphicness to manage item indexing.

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

See also
width(), height(), QGraphicsView::sceneRect
PropertiesClass Methods
read sceneRect
write cs_setSceneRect
QGraphicsScene::stickyFocus

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

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

By default this property is false.

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

See also
clearFocus(), setFocusItem()
PropertiesClass Methods
read stickyFocus
write setStickyFocus