OffsetLayer class

A layer that is displayed at an offset from its parent layer.

Offset layers are key to efficient repainting because they are created by repaint boundaries in the RenderObject tree (see RenderObject.isRepaintBoundary). When a render object that is a repaint boundary is asked to paint at given offset in a PaintingContext, the render object first checks whether it needs to repaint itself. If not, it reuses its existing OffsetLayer (and its entire subtree) by mutating its offset property, cutting off the paint walk.

Inheritance
Implementers

Constructors

OffsetLayer({Offset offset = Offset.zero})
Creates an offset layer.

Properties

alwaysNeedsAddToScene → bool
Subclasses may override this to true to disable retained rendering.
no setterinherited
attached → bool
Whether the layer tree containing this layer is attached to an owner.
no setterinherited
debugCreator ↔ Object?
The object responsible for creating this layer.
getter/setter pairinherited
debugDisposed → bool
If asserts are enabled, returns whether dispose has been called since the last time any retained resources were created.
no setterinherited
debugHandleCount → int
Returns the number of objects holding a LayerHandle to this layer.
no setterinherited
debugSubtreeNeedsAddToScene → bool?
Whether this or any descendant layer in the subtree needs addToScene.
no setterinherited
depth → int
The depth of this layer in the layer tree.
no setterinherited
engineLayer ↔ EngineLayer?
Stores the engine layer created for this layer in order to reuse engine resources across frames for better app performance.
getter/setter pairinherited
firstChild → Layer?
The first composited layer in this layer's child list.
no setterinherited
hasChildren → bool
Returns whether this layer has at least one child layer.
no setterinherited
hashCode → int
The hash code for this object.
no setterinherited
lastChild → Layer?
The last composited layer in this layer's child list.
no setterinherited
nextSibling → Layer?
This layer's next sibling in the parent layer's child list.
no setterinherited
offset ↔ Offset
Offset from parent in the parent's coordinate system.
getter/setter pair
owner → Object?
The owner for this layer (null if unattached).
no setterinherited
parent → ContainerLayer?
This layer's parent in the layer tree.
no setterinherited
previousSibling → Layer?
This layer's previous sibling in the parent layer's child list.
no setterinherited
runtimeType → Type
A representation of the runtime type of the object.
no setterinherited
subtreeHasCompositionCallbacks → bool
Whether the subtree rooted at this layer has any composition callback observers.
no setterinherited

Methods

addChildrenToScene(SceneBuilder builder) → void
Uploads all of this layer's children to the engine.
inherited
addCompositionCallback(CompositionCallback callback) → VoidCallback
Adds a callback for when the layer tree that this layer is part of gets composited, or when it is detached and will not be rendered again.
inherited
addToScene(SceneBuilder builder) → void
Override this method to upload this layer to the engine.
override
append(Layer child) → void
Adds the given layer to the end of this layer's child list.
inherited
applyTransform(Layer? child, Matrix4 transform) → void
Applies the transform that would be applied when compositing the given child to the given matrix.
override
attach(covariant Object owner) → void
Mark this layer as attached to the given owner.
inherited
buildScene(SceneBuilder builder) → Scene
Consider this layer as the root and build a scene (a tree of layers) in the engine.
inherited
debugDescribeChildren() → List<DiagnosticsNode>
Returns a list of DiagnosticsNode objects describing this node's children.
inherited
debugFillProperties(DiagnosticPropertiesBuilder properties) → void
Add additional properties associated with the node.
override
debugMarkClean() → void
Mark that this layer is in sync with engine.
inherited
depthFirstIterateChildren() → List<Layer>
Returns the descendants of this layer in depth first order.
inherited
describeClipBounds() → Rect?
Describes the clip that would be applied to contents of this layer, if any.
inherited
detach() → void
Mark this layer as detached from its owner.
inherited
dispose() → void
Clears any retained resources that this layer holds.
inherited
find<S extends Object>(Offset localPosition) → S?
Search this layer and its subtree for the first annotation of type S under the point described by localPosition.
inherited
findAllAnnotations<S extends Object>(Offset localPosition) → AnnotationResult<S>
Search this layer and its subtree for all annotations of type S under the point described by localPosition.
inherited
findAnnotations<S extends Object>(AnnotationResult<S> result, Offset localPosition, {required bool onlyFirst}) → bool
Search this layer and its subtree for annotations of type S at the location described by localPosition.
override
markNeedsAddToScene() → void
Mark that this layer has changed and addToScene needs to be called.
inherited
noSuchMethod(Invocation invocation) → dynamic
Invoked when a nonexistent method or property is accessed.
inherited
redepthChild(Layer child) → void
Adjust the depth of the given child to be greater than this node's own depth.
inherited
redepthChildren() → void
Adjust the depth of this node's children, if any.
inherited
remove() → void
Removes this layer from its parent layer's child list.
inherited
removeAllChildren() → void
Removes all of this layer's children from its child list.
inherited
supportsRasterization() → bool
Whether or not this layer, or any child layers, can be rasterized with ui.Scene.toImage or ui.Scene.toImageSync.
inherited
toDiagnosticsNode({String? name, DiagnosticsTreeStyle? style}) → DiagnosticsNode
Returns a debug representation of the object that is used by debugging tools and by DiagnosticsNode.toStringDeep.
inherited
toImage(Rect bounds, {double pixelRatio = 1.0}) → Future<Image>
Capture an image of the current state of this layer and its children.
toImageSync(Rect bounds, {double pixelRatio = 1.0}) → Image
Capture an image of the current state of this layer and its children.
toString({DiagnosticLevel minLevel = DiagnosticLevel.info}) → String
A string representation of this object.
inherited
toStringDeep({String prefixLineOne = '', String? prefixOtherLines, DiagnosticLevel minLevel = DiagnosticLevel.debug, int wrapWidth = 65}) → String
Returns a string representation of this node and its descendants.
inherited
toStringShallow({String joiner = ', ', DiagnosticLevel minLevel = DiagnosticLevel.debug}) → String
Returns a one-line detailed description of the object.
inherited
toStringShort() → String
A brief description of this object, usually just the runtimeType and the hashCode.
inherited
updateSubtreeNeedsAddToScene() → void
Traverses the layer subtree starting from this layer and determines whether it needs addToScene.
inherited

Operators

operator ==(Object other) → bool
The equality operator.
inherited