FollowerLayer class

A composited layer that applies a transformation matrix to its children such that they are positioned to match a LeaderLayer.

If any of the ancestors of this layer have a degenerate matrix (e.g. scaling by zero), then the FollowerLayer will not be able to transform its child to the coordinate space of the LeaderLayer.

A linkedOffset property can be provided to further offset the child layer from the leader layer, for example if the child is to follow the linked layer at a distance rather than directly overlapping it.

Inheritance

Constructors

FollowerLayer({required LayerLink link, bool? showWhenUnlinked = true, Offset? unlinkedOffset = Offset.zero, Offset? linkedOffset = Offset.zero})
Creates a follower layer.

Properties

alwaysNeedsAddToScene bool
This disables retained rendering.
no setteroverride
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
The link to the LeaderLayer.
getter/setter pair
linkedOffset Offset?
Offset from the origin of the leader layer to the origin of the child layers, used when the layer is linked to a LeaderLayer.
getter/setter pair
nextSibling Layer?
This layer's next sibling in the parent layer's child list.
no setterinherited
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
showWhenUnlinked bool?
Whether to show the layer's contents when the link does not point to a LeaderLayer.
getter/setter pair
subtreeHasCompositionCallbacks bool
Whether the subtree rooted at this layer has any composition callback observers.
no setterinherited
unlinkedOffset Offset?
Offset from parent in the parent's coordinate system, used when the layer is not linked to a LeaderLayer.
getter/setter pair

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
getLastTransform() Matrix4?
The transform that was used during the last composition phase.
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 Scene.toImage or 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
toString({DiagnosticLevel minLevel = DiagnosticLevel.info}) String
A string representation of this object.
inherited
toStringDeep({String prefixLineOne = '', String? prefixOtherLines, DiagnosticLevel minLevel = DiagnosticLevel.debug}) 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