DebugOverflowIndicatorMixin mixin Null safety

An mixin indicator that is drawn when a RenderObject overflows its container.

This is used by some RenderObjects that are containers to show where, and by how much, their children overflow their containers. These indicators are typically only shown in a debug build (where the call to paintOverflowIndicator is surrounded by an assert).

This class will also print a debug message to the console when the container overflows. It will print on the first occurrence, and once after each time that reassemble is called.

link 
class MyRenderObject extends RenderAligningShiftedBox with DebugOverflowIndicatorMixin {
  MyRenderObject({
    super.alignment = Alignment.center,
    required super.textDirection,
    super.child,
  });

  late Rect _containerRect;
  late Rect _childRect;

  @override
  void performLayout() {
    // ...
    final BoxParentData childParentData = child!.parentData! as BoxParentData;
    _containerRect = Offset.zero & size;
    _childRect = childParentData.offset & child!.size;
  }

  @override
  void paint(PaintingContext context, Offset offset) {
    // Do normal painting here...
    // ...

    assert(() {
      paintOverflowIndicator(context, offset, _containerRect, _childRect);
      return true;
    }());
  }
}

See also:

Superclass Constraints
Mixin Applications

Properties

parentData ↔ ParentData?
Data for use by the parent render object.
read / writeinherited
debugCreator ↔ Object?
The object responsible for creating this render object.
read / writeinherited
debugDisposed → bool?
Whether this has been disposed.
read-onlyinherited
debugDoingThisResize → bool
Whether performResize for this render object is currently running.
read-onlyinherited
debugDoingThisLayout → bool
Whether performLayout for this render object is currently running.
read-onlyinherited
debugCanParentUseSize → bool
Whether the parent render object is permitted to use this render object's size.
read-onlyinherited
owner → PipelineOwner?
The owner for this node (null if unattached).
read-onlyinherited
debugNeedsLayout → bool
Whether this render object's layout information is dirty.
read-onlyinherited
debugDoingThisLayoutWithCallback → bool
Whether invokeLayoutCallback for this render object is currently running.
read-onlyinherited
constraints → Constraints
The layout constraints most recently supplied by the parent.
protected">@protectedread-onlyinherited
sizedByParent → bool
Whether the constraints are the only input to the sizing algorithm (in particular, child nodes have no impact).
protected">@protectedread-onlyinherited
debugDoingThisPaint → bool
Whether paint for this render object is currently running.
read-onlyinherited
isRepaintBoundary → bool
Whether this render object repaints separately from its parent.
read-onlyinherited
alwaysNeedsCompositing → bool
Whether this render object always needs compositing.
protected">@protectedread-onlyinherited
layer ↔ ContainerLayer?
The compositing layer that this render object uses to repaint.
protected">@protectedprotected">@protectedread / writeinherited
debugLayer → ContainerLayer?
In debug mode, the compositing layer that this render object uses to repaint.
read-onlyinherited
needsCompositing → bool
Whether we or one of our descendants has a compositing layer.
read-onlyinherited
debugNeedsPaint → bool
Whether this render object's paint information is dirty.
read-onlyinherited
debugNeedsCompositedLayerUpdate → bool
Whether this render object's layer information is dirty.
read-onlyinherited
paintBounds → Rect
An estimate of the bounds within which this render object will paint. Useful for debugging flags such as debugPaintLayerBordersEnabled.
read-onlyinherited
semanticBounds → Rect
The bounding box, in the local coordinate system, of this object, for accessibility purposes.
read-onlyinherited
debugSemantics → SemanticsNode?
The semantics of this render object.
read-onlyinherited
depth → int
The depth of this node in the tree.
read-onlyinherited
attached → bool
Whether this node is in a tree whose root is attached to something.
read-onlyinherited
parent → AbstractNode?
The parent of this node in the tree.
read-onlyinherited
hashCode → int
The hash code for this object.
read-onlyinherited
runtimeType → Type
A representation of the runtime type of the object.
read-onlyinherited

Methods

adoptChild(covariant RenderObject child) → void
Called by subclasses when they decide a render object is a child.
inherited
applyPaintTransform(covariant RenderObject child, Matrix4 transform) → void
Applies the transform that would be applied when painting the given child to the given matrix.
inherited
assembleSemanticsNode(SemanticsNode node, SemanticsConfiguration config, Iterable<SemanticsNode> children) → void
Assemble the SemanticsNode for this RenderObject.
inherited
attach(covariant PipelineOwner owner) → void
Mark this node as attached to the given owner.
inherited
clearSemantics() → void
Removes all semantics from this render object and its descendants.
mustCallSuper">@mustCallSuperinherited
debugAssertDoesMeetConstraints() → void
Verify that the object's constraints are being met. Override this function in a subclass to verify that your state matches the constraints object. This function is only called in checked mode and only when needsLayout is false. If the constraints are not met, it should assert or throw an exception.
protected">@protectedinherited
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.
protected">@protectedinherited
debugPaint(PaintingContext context, Offset offset) → void
Override this method to paint debugging information.
inherited
debugRegisterRepaintBoundaryPaint({bool includedParent = true, bool includedChild = false}) → void
Called, in debug mode, if isRepaintBoundary is true, when either the this render object or its parent attempt to paint.
inherited
debugResetSize() → void
If a subclass has a "size" (the state controlled by parentUsesSize, whatever it is in the subclass, e.g. the actual size property of RenderBox), and the subclass verifies that in debug mode this "size" property isn't used when debugCanParentUseSize isn't set, then that subclass should override debugResetSize to reapply the current values of debugCanParentUseSize to that state.
protected">@protectedinherited
describeApproximatePaintClip(covariant RenderObject child) → Rect?
Returns a rect in this object's coordinate system that describes the approximate bounding box of the clip rect that would be applied to the given child during the paint phase, if any.
inherited
describeForError(String name, {DiagnosticsTreeStyle style = DiagnosticsTreeStyle.shallow}) → DiagnosticsNode
Adds a debug representation of a RenderObject optimized for including in error messages.
inherited
describeSemanticsClip(covariant RenderObject? child) → Rect?
Returns a rect in this object's coordinate system that describes which SemanticsNodes produced by the child should be included in the semantics tree. SemanticsNodes from the child that are positioned outside of this rect will be dropped. Child SemanticsNodes that are positioned inside this rect, but outside of describeApproximatePaintClip will be included in the tree marked as hidden. Child SemanticsNodes that are inside of both rect will be included in the tree as regular nodes.
inherited
describeSemanticsConfiguration(SemanticsConfiguration config) → void
Report the semantics of this node, for example for accessibility purposes.
protected">@protectedinherited
detach() → void
Mark this node as detached.
mustCallSuper">@mustCallSuperinherited
dispose() → void
Release any resources held by this render object.
mustCallSuper">@mustCallSuperinherited
dropChild(covariant RenderObject child) → void
Called by subclasses when they decide a render object is no longer a child.
inherited
getTransformTo(RenderObject? ancestor) → Matrix4
Applies the paint transform up the tree to ancestor.
inherited
handleEvent(PointerEvent event, covariant HitTestEntry<HitTestTarget> entry) → void
Override this method to handle pointer events that hit this render object.
inherited
invokeLayoutCallback<T extends Constraints>(LayoutCallback<T> callback) → void
Allows mutations to be made to this object's child list (and any descendants) as well as to any other dirty nodes in the render tree owned by the same PipelineOwner as this object. The callback argument is invoked synchronously, and the mutations are allowed only during that callback's execution.
protected">@protectedinherited
layout(Constraints constraints, {bool parentUsesSize = false}) → void
Compute the layout for this render object.
inherited
markNeedsCompositedLayerUpdate() → void
Mark this render object as having changed a property on its composited layer.
inherited
markNeedsCompositingBitsUpdate() → void
Mark the compositing state for this render object as dirty.
inherited
markNeedsLayout() → void
Mark this render object's layout information as dirty, and either register this object with its PipelineOwner, or defer to the parent, depending on whether this object is a relayout boundary or not respectively.
inherited
markNeedsLayoutForSizedByParentChange() → void
Mark this render object's layout information as dirty (like markNeedsLayout), and additionally also handle any necessary work to handle the case where sizedByParent has changed value.
inherited
markNeedsPaint() → void
Mark this render object as having changed its visual appearance.
inherited
markNeedsSemanticsUpdate() → void
Mark this node as needing an update to its semantics description.
inherited
markParentNeedsLayout() → void
Mark this render object's layout information as dirty, and then defer to the parent.
protected">@protectedinherited
noSuchMethod(Invocation invocation) → dynamic
Invoked when a non-existent method or property is accessed.
inherited
paint(PaintingContext context, Offset offset) → void
Paint this render object into the given context at the given offset.
inherited
paintOverflowIndicator(PaintingContext context, Offset offset, Rect containerRect, Rect childRect, {List<DiagnosticsNode>? overflowHints}) → void
To be called when the overflow indicators should be painted.
paintsChild(covariant RenderObject child) → bool
Whether the given child would be painted if paint were called.
inherited
performLayout() → void
Do the work of computing the layout for this render object.
protected">@protectedinherited
performResize() → void
Updates the render objects size using only the constraints.
protected">@protectedinherited
reassemble() → void
Cause the entire subtree rooted at the given RenderObject to be marked dirty for layout, paint, etc, so that the effects of a hot reload can be seen, or so that the effect of changing a global debug flag (such as debugPaintSizeEnabled) can be applied.
override
redepthChild(AbstractNode child) → void
Adjust the depth of the given child to be greater than this node's own depth.
protected">@protectedinherited
redepthChildren() → void
Adjust the depth of this node's children, if any.
inherited
replaceRootLayer(OffsetLayer rootLayer) → void
Replace the layer. This is only valid for the root of a render object subtree (whatever object scheduleInitialPaint was called on).
inherited
scheduleInitialLayout() → void
Bootstrap the rendering pipeline by scheduling the very first layout.
inherited
scheduleInitialPaint(ContainerLayer rootLayer) → void
Bootstrap the rendering pipeline by scheduling the very first paint.
inherited
scheduleInitialSemantics() → void
Bootstrap the semantics reporting mechanism by marking this node as needing a semantics update.
inherited
sendSemanticsEvent(SemanticsEvent semanticsEvent) → void
Sends a SemanticsEvent associated with this render object's SemanticsNode.
inherited
setupParentData(covariant RenderObject child) → void
Override to setup parent data correctly for your children.
inherited
showOnScreen({RenderObject? descendant, Rect? rect, Duration duration = Duration.zero, Curve curve = Curves.ease}) → void
Attempt to make (a portion of) this or a descendant RenderObject visible on screen.
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 description of the tree rooted at this node. If the prefix argument is provided, then every line in the output will be prefixed by that string.
inherited
toStringShallow({String joiner = ', ', DiagnosticLevel minLevel = DiagnosticLevel.debug}) → String
Returns a one-line detailed description of the render object. This description is often somewhat long.
inherited
toStringShort() → String
Returns a human understandable name.
inherited
updateCompositedLayer({required covariant OffsetLayer? oldLayer}) → OffsetLayer
Update the composited layer owned by this render object.
inherited
visitChildren(RenderObjectVisitor visitor) → void
Calls visitor for each immediate child of this render object.
inherited
visitChildrenForSemantics(RenderObjectVisitor visitor) → void
Called when collecting the semantics of this node.
inherited

Operators

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