SignalPainterWidget class

A high-performance, leaf render-object widget driven by a double progress signal.

SignalPainterWidget bypasses the entire widget build and layout phases, subscribing directly to a progress signal and rendering on the canvas. When progress updates, only the GPU paint phase is run.

Example

final progress = signal(0.0);

@override
Widget build(BuildContext context) {
  return SignalPainterWidget(
    progress: progress,
    painter: (canvas, size, value) {
      final paint = Paint()
        ..color = Colors.blue
        ..style = PaintingStyle.stroke
        ..strokeWidth = 4.0;
      canvas.drawCircle(
        Offset(size.width / 2, size.height / 2),
        value * 50.0,
        paint,
      );
    },
  );
}

Inheritance

Constructors

SignalPainterWidget({Key? key, required ReadonlySignal<double> progress, required void painter(Canvas canvas, Size size, double value)}): Creates a new SignalPainterWidget.
const

Properties

hashCode → int: The hash code for this object.
no setterinherited
key → Key?: Controls how one widget replaces another widget in the tree.
finalinherited
painter → void Function(Canvas canvas, Size size, double value): The custom painting callback function.
final
progress → ReadonlySignal<double>: The progress signal whose value will be passed to painter.
final
runtimeType → Type: A representation of the runtime type of the object.
no setterinherited

Methods

createElement() → LeafRenderObjectElement: RenderObjectWidgets always inflate to a RenderObjectElement subclass.
inherited
createRenderObject(BuildContext context) → RenderSignalBox: Creates an instance of the RenderObject class that this RenderObjectWidget represents, using the configuration described by this RenderObjectWidget.
override
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.
inherited
didUnmountRenderObject(covariant RenderObject renderObject) → void: This method is called when a RenderObject that was previously associated with this widget is removed from the render tree. The provided RenderObject will be of the same type as the one created by this widget's createRenderObject method.
inherited
noSuchMethod(Invocation invocation) → dynamic: Invoked when a nonexistent method or property is accessed.
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, 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 short, textual description of this widget.
inherited
updateRenderObject(BuildContext context, covariant RenderSignalBox renderObject) → void: Copies the configuration described by this RenderObjectWidget to the given RenderObject, which will be of the same type as returned by this object's createRenderObject.
override

Operators

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