QGraphicsView Class | Qt Widgets 5.15.18 (original) (raw)

The QGraphicsView class provides a widget for displaying the contents of a QGraphicsScene. More...

This class was introduced in Qt 4.2.

Property Documentation

alignment : Qt::Alignment

This property holds the alignment of the scene in the view when the whole scene is visible.

If the whole scene is visible in the view, (i.e., there are no visible scroll bars,) the view's alignment will decide where the scene will be rendered in the view. For example, if the alignment is Qt::AlignCenter, which is default, the scene will be centered in the view, and if the alignment is (Qt::AlignLeft | Qt::AlignTop), the scene will be rendered in the top-left corner of the view.

Access functions:

backgroundBrush : QBrush

This property holds the background brush of the scene.

This property sets the background brush for the scene in this view. It is used to override the scene's own background, and defines the behavior of drawBackground(). To provide custom background drawing for this view, you can reimplement drawBackground() instead.

By default, this property contains a brush with the Qt::NoBrush pattern.

Access functions:

See also QGraphicsScene::backgroundBrush and foregroundBrush.

cacheMode : CacheMode

This property holds which parts of the view are cached

QGraphicsView can cache pre-rendered content in a QPixmap, which is then drawn onto the viewport. The purpose of such caching is to speed up the total rendering time for areas that are slow to render. Texture, gradient and alpha blended backgrounds, for example, can be notibly slow to render; especially with a transformed view. The CacheBackground flag enables caching of the view's background. For example:

The cache is invalidated every time the view is transformed. However, when scrolling, only partial invalidation is required.

By default, nothing is cached.

Access functions:

See also resetCachedContent() and QPixmapCache.

dragMode : DragMode

This property holds the behavior for dragging the mouse over the scene while the left mouse button is pressed.

This property defines what should happen when the user clicks on the scene background and drags the mouse (e.g., scrolling the viewport contents using a pointing hand cursor, or selecting multiple items with a rubber band). The default value, NoDrag, does nothing.

This behavior only affects mouse clicks that are not handled by any item. You can define a custom behavior by creating a subclass of QGraphicsView and reimplementing mouseMoveEvent().

Access functions:

foregroundBrush : QBrush

This property holds the foreground brush of the scene.

This property sets the foreground brush for the scene in this view. It is used to override the scene's own foreground, and defines the behavior of drawForeground(). To provide custom foreground drawing for this view, you can reimplement drawForeground() instead.

By default, this property contains a brush with the Qt::NoBrush pattern.

Access functions:

See also QGraphicsScene::foregroundBrush and backgroundBrush.

interactive : bool

This property holds whether the view allows scene interaction.

If enabled, this view is set to allow scene interaction. Otherwise, this view will not allow interaction, and any mouse or key events are ignored (i.e., it will act as a read-only view).

By default, this property is true.

Access functions:

optimizationFlags : OptimizationFlags

flags that can be used to tune QGraphicsView's performance.

QGraphicsView uses clipping, extra bounding rect adjustments, and certain other aids to improve rendering quality and performance for the common case graphics scene. However, depending on the target platform, the scene, and the viewport in use, some of these operations can degrade performance.

The effect varies from flag to flag; see the OptimizationFlags documentation for details.

By default, no optimization flags are enabled.

This property was introduced in Qt 4.3.

Access functions:

See also setOptimizationFlag().

renderHints : QPainter::RenderHints

This property holds the default render hints for the view

These hints are used to initialize QPainter before each visible item is drawn. QPainter uses render hints to toggle rendering features such as antialiasing and smooth pixmap transformation.

QPainter::TextAntialiasing is enabled by default.

Example:

Access functions:

resizeAnchor : ViewportAnchor

how the view should position the scene when the view is resized.

QGraphicsView uses this property to decide how to position the scene in the viewport when the viewport widget's size changes. The default behavior, NoAnchor, leaves the scene's position unchanged during a resize; the top-left corner of the view will appear to be anchored while resizing.

Note that the effect of this property is noticeable when only a part of the scene is visible (i.e., when there are scroll bars). Otherwise, if the whole scene fits in the view, QGraphicsScene uses the view alignment to position the scene in the view.

Access functions:

See also alignment and transformationAnchor.

rubberBandSelectionMode : Qt::ItemSelectionMode

This property holds the behavior for selecting items with a rubber band selection rectangle.

This property defines how items are selected when using the RubberBandDrag drag mode.

The default value is Qt::IntersectsItemShape; all items whose shape intersects with or is contained by the rubber band are selected.

This property was introduced in Qt 4.3.

Access functions:

See also dragMode, items(), and rubberBandRect().

sceneRect : QRectF

This property holds the area of the scene visualized by this view.

The scene rectangle defines the extent of the scene, and in the view's case, this means the area of the scene that you can navigate using the scroll bars.

If unset, or if a null QRectF is set, this property has the same value as QGraphicsScene::sceneRect, and it changes with QGraphicsScene::sceneRect. Otherwise, the view's scene rect is unaffected by the scene.

Note that, although the scene supports a virtually unlimited size, the range of the scroll bars will never exceed the range of an integer (INT_MIN, INT_MAX). When the scene is larger than the scroll bars' values, you can choose to use translate() to navigate the scene instead.

By default, this property contains a rectangle at the origin with zero width and height.

Access functions:

See also QGraphicsScene::sceneRect.

transformationAnchor : ViewportAnchor

how the view should position the scene during transformations.

QGraphicsView uses this property to decide how to position the scene in the viewport when the transformation matrix changes, and the coordinate system of the view is transformed. The default behavior, AnchorViewCenter, ensures that the scene point at the center of the view remains unchanged during transformations (e.g., when rotating, the scene will appear to rotate around the center of the view).

Note that the effect of this property is noticeable when only a part of the scene is visible (i.e., when there are scroll bars). Otherwise, if the whole scene fits in the view, QGraphicsScene uses the view alignment to position the scene in the view.

Access functions:

See also alignment and resizeAnchor.

viewportUpdateMode : ViewportUpdateMode

how the viewport should update its contents.

QGraphicsView uses this property to decide how to update areas of the scene that have been reexposed or changed. Usually you do not need to modify this property, but there are some cases where doing so can improve rendering performance. See the ViewportUpdateMode documentation for specific details.

The default value is MinimalViewportUpdate, where QGraphicsView will update as small an area of the viewport as possible when the contents change.

This property was introduced in Qt 4.3.

Access functions:

See also ViewportUpdateMode and cacheMode.

Member Function Documentation

QGraphicsView::QGraphicsView(QGraphicsScene *scene, QWidget *parent = nullptr)

Constructs a QGraphicsView and sets the visualized scene to scene. parent is passed to QWidget's constructor.

QGraphicsView::QGraphicsView(QWidget *parent = nullptr)

Constructs a QGraphicsView. parent is passed to QWidget's constructor.

[slot] void QGraphicsView::invalidateScene(const QRectF &rect = QRectF(), QGraphicsScene::SceneLayers layers = QGraphicsScene::AllLayers)

Invalidates and schedules a redraw of layers inside rect. rect is in scene coordinates. Any cached content for layers inside rect is unconditionally invalidated and redrawn.

You can call this function to notify QGraphicsView of changes to the background or the foreground of the scene. It is commonly used for scenes with tile-based backgrounds to notify changes when QGraphicsView has enabled background caching.

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

See also QGraphicsScene::invalidate() and update().

[signal] void QGraphicsView::rubberBandChanged(QRect rubberBandRect, QPointF fromScenePoint, QPointF toScenePoint)

This signal is emitted when the rubber band rect is changed. The viewport Rect is specified by rubberBandRect. The drag start position and drag end position are provided in scene points with fromScenePoint and toScenePoint.

When rubberband selection ends this signal will be emitted with null vales.

This function was introduced in Qt 5.1.

See also rubberBandRect().

[override virtual protected slot] void QGraphicsView::setupViewport(QWidget *widget)

Reimplements: QAbstractScrollArea::setupViewport(QWidget *viewport).

This slot is called by QAbstractScrollArea after setViewport() has been called. Reimplement this function in a subclass of QGraphicsView to initialize the new viewport widget before it is used.

See also setViewport().

[slot] void QGraphicsView::updateScene(const QList<QRectF> &rects)

Schedules an update of the scene rectangles rects.

See also QGraphicsScene::changed().

[slot] void QGraphicsView::updateSceneRect(const QRectF &rect)

Notifies QGraphicsView that the scene's scene rect has changed. rect is the new scene rect. If the view already has an explicitly set scene rect, this function does nothing.

See also sceneRect and QGraphicsScene::sceneRectChanged().

[virtual] QGraphicsView::~QGraphicsView()

Destructs the QGraphicsView object.

void QGraphicsView::centerOn(const QPointF &pos)

Scrolls the contents of the viewport to ensure that the scene coordinate pos, is centered in the view.

Because pos is a floating point coordinate, and the scroll bars operate on integer coordinates, the centering is only an approximation.

Note: If the item is close to or outside the border, it will be visible in the view, but not centered.

See also ensureVisible().

void QGraphicsView::centerOn(qreal x, qreal y)

This is an overloaded function.

This function is provided for convenience. It's equivalent to calling centerOn(QPointF(x, y)).

void QGraphicsView::centerOn(const QGraphicsItem *item)

This is an overloaded function.

Scrolls the contents of the viewport to ensure that item is centered in the view.

See also ensureVisible().

[override virtual protected] void QGraphicsView::contextMenuEvent(QContextMenuEvent *event)

Reimplements: QAbstractScrollArea::contextMenuEvent(QContextMenuEvent *e).

[override virtual protected] void QGraphicsView::dragEnterEvent(QDragEnterEvent *event)

Reimplements: QAbstractScrollArea::dragEnterEvent(QDragEnterEvent *event).

[override virtual protected] void QGraphicsView::dragLeaveEvent(QDragLeaveEvent *event)

Reimplements: QAbstractScrollArea::dragLeaveEvent(QDragLeaveEvent *event).

[override virtual protected] void QGraphicsView::dragMoveEvent(QDragMoveEvent *event)

Reimplements: QAbstractScrollArea::dragMoveEvent(QDragMoveEvent *event).

[virtual protected] void QGraphicsView::drawBackground(QPainter *painter, const QRectF &rect)

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

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

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

The default implementation fills rect using the view's backgroundBrush. If no such brush is defined (the default), the scene's drawBackground() function is called instead.

See also drawForeground() and QGraphicsScene::drawBackground().

[virtual protected] void QGraphicsView::drawForeground(QPainter *painter, const QRectF &rect)

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

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

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

The default implementation fills rect using the view's foregroundBrush. If no such brush is defined (the default), the scene's drawForeground() function is called instead.

See also drawBackground() and QGraphicsScene::drawForeground().

[override virtual protected] void QGraphicsView::dropEvent(QDropEvent *event)

Reimplements: QAbstractScrollArea::dropEvent(QDropEvent *event).

void QGraphicsView::ensureVisible(const QRectF &rect, int xmargin = 50, int ymargin = 50)

Scrolls the contents of the viewport so that the scene rectangle rect is visible, with margins specified in pixels by xmargin and ymargin. If the specified rect cannot be reached, the contents are scrolled to the nearest valid position. The default value for both margins is 50 pixels.

See also centerOn().

void QGraphicsView::ensureVisible(qreal x, qreal y, qreal w, qreal h, int xmargin = 50, int ymargin = 50)

This is an overloaded function.

This function is provided for convenience. It's equivalent to calling ensureVisible(QRectF(x, y, w, h), xmargin, ymargin).

void QGraphicsView::ensureVisible(const QGraphicsItem *item, int xmargin = 50, int ymargin = 50)

This is an overloaded function.

Scrolls the contents of the viewport so that the center of item item is visible, with margins specified in pixels by xmargin and ymargin. If the specified point cannot be reached, the contents are scrolled to the nearest valid position. The default value for both margins is 50 pixels.

See also centerOn().

[override virtual protected] bool QGraphicsView::event(QEvent *event)

Reimplements: QAbstractScrollArea::event(QEvent *event).

void QGraphicsView::fitInView(const QRectF &rect, Qt::AspectRatioMode aspectRatioMode = Qt::IgnoreAspectRatio)

Scales the view matrix and scrolls the scroll bars to ensure that the scene rectangle rect fits inside the viewport. rect must be inside the scene rect; otherwise, fitInView() cannot guarantee that the whole rect is visible.

This function keeps the view's rotation, translation, or shear. The view is scaled according to aspectRatioMode. rect will be centered in the view if it does not fit tightly.

It's common to call fitInView() from inside a reimplementation of resizeEvent(), to ensure that the whole scene, or parts of the scene, scales automatically to fit the new size of the viewport as the view is resized. Note though, that calling fitInView() from inside resizeEvent() can lead to unwanted resize recursion, if the new transformation toggles the automatic state of the scrollbars. You can toggle the scrollbar policies to always on or always off to prevent this (see horizontalScrollBarPolicy() and verticalScrollBarPolicy()).

If rect is empty, or if the viewport is too small, this function will do nothing.

See also setTransform(), ensureVisible(), and centerOn().

void QGraphicsView::fitInView(qreal x, qreal y, qreal w, qreal h, Qt::AspectRatioMode aspectRatioMode = Qt::IgnoreAspectRatio)

This is an overloaded function.

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

See also ensureVisible() and centerOn().

void QGraphicsView::fitInView(const QGraphicsItem *item, Qt::AspectRatioMode aspectRatioMode = Qt::IgnoreAspectRatio)

This is an overloaded function.

Ensures that item fits tightly inside the view, scaling the view according to aspectRatioMode.

See also ensureVisible() and centerOn().

[override virtual protected] void QGraphicsView::focusInEvent(QFocusEvent *event)

Reimplements: QWidget::focusInEvent(QFocusEvent *event).

[override virtual protected] bool QGraphicsView::focusNextPrevChild(bool next)

Reimplements: QWidget::focusNextPrevChild(bool next).

[override virtual protected] void QGraphicsView::focusOutEvent(QFocusEvent *event)

Reimplements: QWidget::focusOutEvent(QFocusEvent *event).

[override virtual protected] void QGraphicsView::inputMethodEvent(QInputMethodEvent *event)

Reimplements: QWidget::inputMethodEvent(QInputMethodEvent *event).

[override virtual] QVariant QGraphicsView::inputMethodQuery(Qt::InputMethodQuery query) const

Reimplements: QWidget::inputMethodQuery(Qt::InputMethodQuery query) const.

bool QGraphicsView::isTransformed() const

Returns true if the view is transformed (i.e., a non-identity transform has been assigned, or the scrollbars are adjusted).

This function was introduced in Qt 4.6.

See also setTransform(), horizontalScrollBar(), and verticalScrollBar().

QGraphicsItem *QGraphicsView::itemAt(const QPoint &pos) const

Returns the item at position pos, which is in viewport coordinates. If there are several items at this position, this function returns the topmost item.

Example:

void CustomView::mousePressEvent(QMouseEvent *event) { if (QGraphicsItem *item = itemAt(event->pos())) { qDebug() << "You clicked on item" << item; } else { qDebug("You didn't click on an item."); } }

See also items() and Sorting.

QGraphicsItem *QGraphicsView::itemAt(int x, int y) const

This is an overloaded function.

This function is provided for convenience. It's equivalent to calling itemAt(QPoint(x, y)).

QList<QGraphicsItem *> QGraphicsView::items() const

Returns a list of all the items in the associated scene, in descending stacking order (i.e., the first item in the returned list is the uppermost item).

See also QGraphicsScene::items() and Sorting.

QList<QGraphicsItem *> QGraphicsView::items(const QPoint &pos) const

Returns a list of all the items at the position pos in the view. The items are listed in descending stacking order (i.e., the first item in the list is the uppermost item, and the last item is the lowermost item). pos is in viewport coordinates.

This function is most commonly called from within mouse event handlers in a subclass in QGraphicsView. pos is in untransformed viewport coordinates, just like QMouseEvent::pos().

void CustomView::mousePressEvent(QMouseEvent *event) { qDebug() << "There are" << items(event->pos()).size() << "items at position" << mapToScene(event->pos()); }

See also QGraphicsScene::items() and Sorting.

QList<QGraphicsItem *> QGraphicsView::items(int x, int y) const

This function is provided for convenience. It's equivalent to calling items(QPoint(x, y)).

QList<QGraphicsItem *> QGraphicsView::items(const QRect &rect, Qt::ItemSelectionMode mode = Qt::IntersectsItemShape) const

This is an overloaded function.

Returns a list of all the items that, depending on mode, are either contained by or intersect with rect. rect is in viewport coordinates.

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

The items are sorted in descending stacking order (i.e., the first item in the returned list is the uppermost item).

See also itemAt(), items(), mapToScene(), and Sorting.

QList<QGraphicsItem *> QGraphicsView::items(int x, int y, int w, int h, Qt::ItemSelectionMode mode = Qt::IntersectsItemShape) const

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

This function was introduced in Qt 4.3.

QList<QGraphicsItem *> QGraphicsView::items(const QPolygon &polygon, Qt::ItemSelectionMode mode = Qt::IntersectsItemShape) const

This is an overloaded function.

Returns a list of all the items that, depending on mode, are either contained by or intersect with polygon. polygon is in viewport coordinates.

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

The items are sorted by descending stacking order (i.e., the first item in the returned list is the uppermost item).

See also itemAt(), items(), mapToScene(), and Sorting.

QList<QGraphicsItem *> QGraphicsView::items(const QPainterPath &path, Qt::ItemSelectionMode mode = Qt::IntersectsItemShape) const

This is an overloaded function.

Returns a list of all the items that, depending on mode, are either contained by or intersect with path. path is in viewport coordinates.

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

See also itemAt(), items(), mapToScene(), and Sorting.

[override virtual protected] void QGraphicsView::keyPressEvent(QKeyEvent *event)

Reimplements: QAbstractScrollArea::keyPressEvent(QKeyEvent *e).

[override virtual protected] void QGraphicsView::keyReleaseEvent(QKeyEvent *event)

Reimplements: QWidget::keyReleaseEvent(QKeyEvent *event).

QPoint QGraphicsView::mapFromScene(const QPointF &point) const

Returns the scene coordinate point to viewport coordinates.

See also mapToScene().

QPolygon QGraphicsView::mapFromScene(const QRectF &rect) const

Returns the scene rectangle rect to a viewport coordinate polygon.

See also mapToScene().

QPolygon QGraphicsView::mapFromScene(const QPolygonF &polygon) const

Returns the scene coordinate polygon polygon to a viewport coordinate polygon.

See also mapToScene().

QPainterPath QGraphicsView::mapFromScene(const QPainterPath &path) const

Returns the scene coordinate painter path path to a viewport coordinate painter path.

See also mapToScene().

QPoint QGraphicsView::mapFromScene(qreal x, qreal y) const

This function is provided for convenience. It's equivalent to calling mapFromScene(QPointF(x, y)).

QPolygon QGraphicsView::mapFromScene(qreal x, qreal y, qreal w, qreal h) const

This function is provided for convenience. It's equivalent to calling mapFromScene(QRectF(x, y, w, h)).

QPointF QGraphicsView::mapToScene(const QPoint &point) const

Returns the viewport coordinate point mapped to scene coordinates.

Note: It can be useful to map the whole rectangle covered by the pixel at point instead of the point itself. To do this, you can call mapToScene(QRect(point, QSize(2, 2))).

See also mapFromScene().

QPolygonF QGraphicsView::mapToScene(const QRect &rect) const

Returns the viewport rectangle rect mapped to a scene coordinate polygon.

See also mapFromScene().

QPolygonF QGraphicsView::mapToScene(const QPolygon &polygon) const

Returns the viewport polygon polygon mapped to a scene coordinate polygon.

See also mapFromScene().

QPainterPath QGraphicsView::mapToScene(const QPainterPath &path) const

Returns the viewport painter path path mapped to a scene coordinate painter path.

See also mapFromScene().

QPointF QGraphicsView::mapToScene(int x, int y) const

This function is provided for convenience. It's equivalent to calling mapToScene(QPoint(x, y)).

QPolygonF QGraphicsView::mapToScene(int x, int y, int w, int h) const

This function is provided for convenience. It's equivalent to calling mapToScene(QRect(x, y, w, h)).

[override virtual protected] void QGraphicsView::mouseDoubleClickEvent(QMouseEvent *event)

Reimplements: QAbstractScrollArea::mouseDoubleClickEvent(QMouseEvent *e).

[override virtual protected] void QGraphicsView::mouseMoveEvent(QMouseEvent *event)

Reimplements: QAbstractScrollArea::mouseMoveEvent(QMouseEvent *e).

[override virtual protected] void QGraphicsView::mousePressEvent(QMouseEvent *event)

Reimplements: QAbstractScrollArea::mousePressEvent(QMouseEvent *e).

[override virtual protected] void QGraphicsView::mouseReleaseEvent(QMouseEvent *event)

Reimplements: QAbstractScrollArea::mouseReleaseEvent(QMouseEvent *e).

[override virtual protected] void QGraphicsView::paintEvent(QPaintEvent *event)

Reimplements: QAbstractScrollArea::paintEvent(QPaintEvent *event).

void QGraphicsView::render(QPainter *painter, const QRectF &target = QRectF(), const QRect &source = QRect(), Qt::AspectRatioMode aspectRatioMode = Qt::KeepAspectRatio)

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

QGraphicsScene scene; scene.addItem(... ...

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

QPrinter printer(QPrinter::HighResolution); printer.setPageSize(QPrinter::A4); QPainter painter(&printer);

// print, fitting the viewport contents into a full page view.render(&painter);

// print the upper half of the viewport into the lower. // half of the page. QRect viewport = view.viewport()->rect(); view.render(&painter, QRectF(0, printer.height() / 2, printer.width(), printer.height() / 2), viewport.adjusted(0, 0, 0, -viewport.height() / 2));

If source is a null rect, this function will use viewport()->rect() to determine what to draw. If target is a null rect, the full dimensions of painter's paint device (e.g., for a QPrinter, the page size) will be used.

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

See also QGraphicsScene::render().

void QGraphicsView::resetCachedContent()

Resets any cached content. Calling this function will clear QGraphicsView's cache. If the current cache mode is CacheNone, this function does nothing.

This function is called automatically for you when the backgroundBrush or QGraphicsScene::backgroundBrush properties change; you only need to call this function if you have reimplemented QGraphicsScene::drawBackground() or QGraphicsView::drawBackground() to draw a custom background, and need to trigger a full redraw.

See also cacheMode().

void QGraphicsView::resetTransform()

Resets the view transformation to the identity matrix.

See also transform() and setTransform().

[override virtual protected] void QGraphicsView::resizeEvent(QResizeEvent *event)

Reimplements: QAbstractScrollArea::resizeEvent(QResizeEvent *event).

void QGraphicsView::rotate(qreal angle)

Rotates the current view transformation angle degrees clockwise.

See also setTransform(), transform(), scale(), shear(), and translate().

QRect QGraphicsView::rubberBandRect() const

This functions returns the current rubber band area (in viewport coordinates) if the user is currently doing an itemselection with rubber band. When the user is not using the rubber band this functions returns (a null) QRectF().

Notice that part of this QRect can be outise the visual viewport. It can e.g contain negative values.

This function was introduced in Qt 5.1.

See also rubberBandSelectionMode and rubberBandChanged().

void QGraphicsView::scale(qreal sx, qreal sy)

Scales the current view transformation by (sx, sy).

See also setTransform(), transform(), rotate(), shear(), and translate().

QGraphicsScene *QGraphicsView::scene() const

Returns a pointer to the scene that is currently visualized in the view. If no scene is currently visualized, nullptr is returned.

See also setScene().

[override virtual protected] void QGraphicsView::scrollContentsBy(int dx, int dy)

Reimplements: QAbstractScrollArea::scrollContentsBy(int dx, int dy).

void QGraphicsView::setOptimizationFlag(QGraphicsView::OptimizationFlag flag, bool enabled = true)

Enables flag if enabled is true; otherwise disables flag.

See also optimizationFlags.

void QGraphicsView::setRenderHint(QPainter::RenderHint hint, bool enabled = true)

If enabled is true, the render hint hint is enabled; otherwise it is disabled.

See also renderHints.

void QGraphicsView::setScene(QGraphicsScene *scene)

Sets the current scene to scene. If scene is already being viewed, this function does nothing.

When a scene is set on a view, the QGraphicsScene::changed() signal is automatically connected to this view's updateScene() slot, and the view's scroll bars are adjusted to fit the size of the scene.

The view does not take ownership of scene.

See also scene().

void QGraphicsView::setTransform(const QTransform &matrix, bool combine = false)

Sets the view's current transformation matrix to matrix.

If combine is true, then matrix is combined with the current matrix; otherwise, matrix replaces the current matrix. combine is false by default.

The transformation matrix transforms the scene into view coordinates. Using the default transformation, provided by the identity matrix, one pixel in the view represents one unit in the scene (e.g., a 10x10 rectangular item is drawn using 10x10 pixels in the view). If a 2x2 scaling matrix is applied, the scene will be drawn in 1:2 (e.g., a 10x10 rectangular item is then drawn using 20x20 pixels in the view).

Example:

QGraphicsScene scene; scene.addText("GraphicsView rotated clockwise");

QGraphicsView view(&scene); view.rotate(90); // the text is rendered with a 90 degree clockwise rotation view.show();

To simplify interation with items using a transformed view, QGraphicsView provides mapTo... and mapFrom... functions that can translate between scene and view coordinates. For example, you can call mapToScene() to map a view coordinate to a floating point scene coordinate, or mapFromScene() to map from floating point scene coordinates to view coordinates.

See also transform(), rotate(), scale(), shear(), and translate().

void QGraphicsView::shear(qreal sh, qreal sv)

Shears the current view transformation by (sh, sv).

See also setTransform(), transform(), rotate(), scale(), and translate().

[override virtual protected] void QGraphicsView::showEvent(QShowEvent *event)

Reimplements: QWidget::showEvent(QShowEvent *event).

[override virtual] QSize QGraphicsView::sizeHint() const

Reimplements: QAbstractScrollArea::sizeHint() const.

QTransform QGraphicsView::transform() const

Returns the current transformation matrix for the view. If no current transformation is set, the identity matrix is returned.

See also setTransform(), rotate(), scale(), shear(), and translate().

void QGraphicsView::translate(qreal dx, qreal dy)

Translates the current view transformation by (dx, dy).

See also setTransform(), transform(), rotate(), and shear().

[override virtual protected] bool QGraphicsView::viewportEvent(QEvent *event)

Reimplements: QAbstractScrollArea::viewportEvent(QEvent *event).

QTransform QGraphicsView::viewportTransform() const

Returns a matrix that maps scene coordinates to viewport coordinates.

See also mapToScene() and mapFromScene().

[override virtual protected] void QGraphicsView::wheelEvent(QWheelEvent *event)

Reimplements: QAbstractScrollArea::wheelEvent(QWheelEvent *e).