RenderBox class - rendering library (original) (raw)

A render object in a 2D Cartesian coordinate system.

The size of each box is expressed as a width and a height. Each box has its own coordinate system in which its upper left corner is placed at (0, 0). The lower right corner of the box is therefore at (width, height). The box contains all the points including the upper left corner and extending to, but not including, the lower right corner.

Box layout is performed by passing a BoxConstraints object down the tree. The box constraints establish a min and max value for the child's width and height. In determining its size, the child must respect the constraints given to it by its parent.

This protocol is sufficient for expressing a number of common box layout data flows. For example, to implement a width-in-height-out data flow, call your child's layout function with a set of box constraints with a tight width value (and pass true for parentUsesSize). After the child determines its height, use the child's height to determine your size.

Writing a RenderBox subclass

One would implement a new RenderBox subclass to describe a new layout model, new paint model, new hit-testing model, or new semantics model, while remaining in the Cartesian space defined by the RenderBox protocol.

To create a new protocol, consider subclassing RenderObject instead.

Constructors and properties of a new RenderBox subclass

The constructor will typically take a named argument for each property of the class. The value is then passed to a private field of the class and the constructor asserts its correctness (e.g. if it should not be null, it asserts it's not null).

Properties have the form of a getter/setter/field group like the following:

AxisDirection get axis => _axis;
AxisDirection _axis = AxisDirection.down; // or initialized in constructor
set axis(AxisDirection value) {
  if (value == _axis) {
    return;
  }
  _axis = value;
  markNeedsLayout();
}

The setter will typically finish with either a call to markNeedsLayout, if the layout uses this property, or markNeedsPaint, if only the painter function does. (No need to call both, markNeedsLayout impliesmarkNeedsPaint.)

Consider layout and paint to be expensive; be conservative about callingmarkNeedsLayout or markNeedsPaint. They should only be called if the layout (or paint, respectively) has actually changed.

Children

If a render object is a leaf, that is, it cannot have any children, then ignore this section. (Examples of leaf render objects are RenderImage andRenderParagraph.)

For render objects with children, there are four possible scenarios:

• A single RenderBox child. In this scenario, consider inheriting fromRenderProxyBox (if the render object sizes itself to match the child) orRenderShiftedBox (if the child will be smaller than the box and the box will align the child inside itself).
• A single child, but it isn't a RenderBox. Use theRenderObjectWithChildMixin mixin.
• A single list of children. Use the ContainerRenderObjectMixin mixin.
• A more complicated child model.

Using RenderProxyBox

By default, a RenderProxyBox render object sizes itself to fit its child, or to be as small as possible if there is no child; it passes all hit testing and painting on to the child, and intrinsic dimensions and baseline measurements similarly are proxied to the child.

A subclass of RenderProxyBox just needs to override the parts of theRenderBox protocol that matter. For example, RenderOpacity just overrides the paint method (and alwaysNeedsCompositing to reflect what the paint method does, and the visitChildrenForSemantics method so that the child is hidden from accessibility tools when it's invisible), and adds anRenderOpacity.opacity field.

RenderProxyBox assumes that the child is the size of the parent and positioned at 0,0. If this is not true, then use RenderShiftedBox instead.

Seeproxy_box.dartfor examples of inheriting from RenderProxyBox.

Using RenderShiftedBox

By default, a RenderShiftedBox acts much like a RenderProxyBox but without assuming that the child is positioned at 0,0 (the actual position recorded in the child's parentData field is used), and without providing a default layout algorithm.

Seeshifted_box.dartfor examples of inheriting from RenderShiftedBox.

Kinds of children and child-specific data

A RenderBox doesn't have to have RenderBox children. One can use another subclass of RenderObject for a RenderBox's children. See the discussion at RenderObject.

Children can have additional data owned by the parent but stored on the child using the parentData field. The class used for that data must inherit from ParentData. The setupParentData method is used to initialize the parentData field of a child when the child is attached.

By convention, RenderBox objects that have RenderBox children use theBoxParentData class, which has a BoxParentData.offset field to store the position of the child relative to the parent. (RenderProxyBox does not need this offset and therefore is an exception to this rule.)

Using RenderObjectWithChildMixin

If a render object has a single child but it isn't a RenderBox, then theRenderObjectWithChildMixin class, which is a mixin that will handle the boilerplate of managing a child, will be useful.

It's a generic class with one type argument, the type of the child. For example, if you are building a RenderFoo class which takes a singleRenderBar child, you would use the mixin as follows:

class RenderFoo extends RenderBox
  with RenderObjectWithChildMixin<RenderBar> {
  // ...
}

Since the RenderFoo class itself is still a RenderBox in this case, you still have to implement the RenderBox layout algorithm, as well as features like intrinsics and baselines, painting, and hit testing.

Using ContainerRenderObjectMixin

If a render box can have multiple children, then theContainerRenderObjectMixin mixin can be used to handle the boilerplate. It uses a linked list to model the children in a manner that is easy to mutate dynamically and that can be walked efficiently. Random access is not efficient in this model; if you need random access to the children consider the next section on more complicated child models.

The ContainerRenderObjectMixin class has two type arguments. The first is the type of the child objects. The second is the type for theirparentData. The class used for parentData must itself have theContainerParentDataMixin class mixed into it; this is whereContainerRenderObjectMixin stores the linked list. A ParentData class can extend ContainerBoxParentData; this is essentiallyBoxParentData mixed with ContainerParentDataMixin. For example, if aRenderFoo class wanted to have a linked list of RenderBox children, one might create a FooParentData class as follows:

class FooParentData extends ContainerBoxParentData<RenderBox> {
  // (any fields you might need for these children)
}

When using ContainerRenderObjectMixin in a RenderBox, consider mixing inRenderBoxContainerDefaultsMixin, which provides a collection of utility methods that implement common parts of the RenderBox protocol (such as painting the children).

The declaration of the RenderFoo class itself would thus look like this:

// continuing from previous example...
class RenderFoo extends RenderBox with
  ContainerRenderObjectMixin<RenderBox, FooParentData>,
  RenderBoxContainerDefaultsMixin<RenderBox, FooParentData> {
  // ...
}

When walking the children (e.g. during layout), the following pattern is commonly used (in this case assuming that the children are all RenderBoxobjects and that this render object uses FooParentData objects for its children's parentData fields):

// continuing from previous example...
RenderBox? child = firstChild;
while (child != null) {
  final FooParentData childParentData = child.parentData! as FooParentData;
  // ...operate on child and childParentData...
  assert(child.parentData == childParentData);
  child = childParentData.nextSibling;
}

More complicated child models

Render objects can have more complicated models, for example a map of children keyed on an enum, or a 2D grid of efficiently randomly-accessible children, or multiple lists of children, etc. If a render object has a model that can't be handled by the mixins above, it must implement theRenderObject child protocol, as follows:

• Any time a child is removed, call dropChild with the child.
• Any time a child is added, call adoptChild with the child.
• Implement the attach method such that it calls attach on each child.
• Implement the detach method such that it calls detach on each child.
• Implement the redepthChildren method such that it calls redepthChildon each child.
• Implement the visitChildren method such that it calls its argument for each child, typically in paint order (back-most to front-most).
• Implement debugDescribeChildren such that it outputs a DiagnosticsNodefor each child.

Implementing these seven bullet points is essentially all that the two aforementioned mixins do.

Layout

RenderBox classes implement a layout algorithm. They have a set of constraints provided to them, and they size themselves based on those constraints and whatever other inputs they may have (for example, their children or properties).

When implementing a RenderBox subclass, one must make a choice. Does it size itself exclusively based on the constraints, or does it use any other information in sizing itself? An example of sizing purely based on the constraints would be growing to fit the parent.

Sizing purely based on the constraints allows the system to make some significant optimizations. Classes that use this approach should overridesizedByParent to return true, and then override computeDryLayout to compute the Size using nothing but the constraints, e.g.:

@override
bool get sizedByParent => true;

@override
Size computeDryLayout(BoxConstraints constraints) {
  return constraints.smallest;
}

Otherwise, the size is set in the performLayout function.

The performLayout function is where render boxes decide, if they are notsizedByParent, what size they should be, and also where they decide where their children should be.

Layout of RenderBox children

The performLayout function should call the layout function of each (box) child, passing it a BoxConstraints object describing the constraints within which the child can render. Passing tight constraints (seeBoxConstraints.isTight) to the child will allow the rendering library to apply some optimizations, as it knows that if the constraints are tight, the child's dimensions cannot change even if the layout of the child itself changes.

If the performLayout function will use the child's size to affect other aspects of the layout, for example if the render box sizes itself around the child, or positions several children based on the size of those children, then it must specify the parentUsesSize argument to the child's layoutfunction, setting it to true.

This flag turns off some optimizations; algorithms that do not rely on the children's sizes will be more efficient. (In particular, relying on the child's size means that if the child is marked dirty for layout, the parent will probably also be marked dirty for layout, unless theconstraints given by the parent to the child were tight constraints.)

For RenderBox classes that do not inherit from RenderProxyBox, once they have laid out their children, they should also position them, by setting theBoxParentData.offset field of each child's parentData object.

Layout of non-RenderBox children

The children of a RenderBox do not have to be RenderBoxes themselves. If they use another protocol (as discussed at RenderObject), then instead ofBoxConstraints, the parent would pass in the appropriate Constraintssubclass, and instead of reading the child's size, the parent would read whatever the output of layout is for that layout protocol. TheparentUsesSize flag is still used to indicate whether the parent is going to read that output, and optimizations still kick in if the child has tight constraints (as defined by Constraints.isTight).

Painting

To describe how a render box paints, implement the paint method. It is given a PaintingContext object and an Offset. The painting context provides methods to affect the layer tree as well as aPaintingContext.canvas which can be used to add drawing commands. The canvas object should not be cached across calls to the PaintingContext's methods; every time a method on PaintingContext is called, there is a chance that the canvas will change identity. The offset specifies the position of the top left corner of the box in the coordinate system of thePaintingContext.canvas.

To draw text on a canvas, use a TextPainter.

To draw an image to a canvas, use the paintImage method.

A RenderBox that uses methods on PaintingContext that introduce new layers should override the alwaysNeedsCompositing getter and set it to true. If the object sometimes does and sometimes does not, it can have that getter return true in some cases and false in others. In that case, whenever the return value would change, call markNeedsCompositingBitsUpdate. (This is done automatically when a child is added or removed, so you don't have to call it explicitly if the alwaysNeedsCompositing getter only changes value based on the presence or absence of children.)

Anytime anything changes on the object that would cause the paint method to paint something different (but would not cause the layout to change), the object should call markNeedsPaint.

Painting children

The paint method's context argument has a PaintingContext.paintChildmethod, which should be called for each child that is to be painted. It should be given a reference to the child, and an Offset giving the position of the child relative to the parent.

If the paint method applies a transform to the painting context before painting children (or generally applies an additional offset beyond the offset it was itself given as an argument), then the applyPaintTransformmethod should also be overridden. That method must adjust the matrix that it is given in the same manner as it transformed the painting context and offset before painting the given child. This is used by the globalToLocaland localToGlobal methods.

Hit Tests

Hit testing for render boxes is implemented by the hitTest method. The default implementation of this method defers to hitTestSelf andhitTestChildren. When implementing hit testing, you can either override these latter two methods, or ignore them and just override hitTest.

The hitTest method itself is given an Offset, and must return true if the object or one of its children has absorbed the hit (preventing objects below this one from being hit), or false if the hit can continue to other objects below this one.

For each child RenderBox, the hitTest method on the child should be called with the same HitTestResult argument and with the point transformed into the child's coordinate space (in the same manner that theapplyPaintTransform method would). The default implementation defers tohitTestChildren to call the children. RenderBoxContainerDefaultsMixinprovides a RenderBoxContainerDefaultsMixin.defaultHitTestChildren method that does this assuming that the children are axis-aligned, not transformed, and positioned according to the BoxParentData.offset field of theparentData; more elaborate boxes can override hitTestChildrenaccordingly.

If the object is hit, then it should also add itself to the HitTestResultobject that is given as an argument to the hitTest method, usingHitTestResult.add. The default implementation defers to hitTestSelf to determine if the box is hit. If the object adds itself before the children can add themselves, then it will be as if the object was above the children. If it adds itself after the children, then it will be as if it was below the children. Entries added to the HitTestResult object should use theBoxHitTestEntry class. The entries are subsequently walked by the system in the order they were added, and for each entry, the target's handleEventmethod is called, passing in the HitTestEntry object.

Hit testing cannot rely on painting having happened.

Semantics

For a render box to be accessible, implement thedescribeApproximatePaintClip, visitChildrenForSemantics, anddescribeSemanticsConfiguration methods. The default implementations are sufficient for objects that only affect layout, but nodes that represent interactive components or information (diagrams, text, images, etc) should provide more complete implementations. For more information, see the documentation for these members.

Intrinsics and Baselines

The layout, painting, hit testing, and semantics protocols are common to all render objects. RenderBox objects must implement two additional protocols: intrinsic sizing and baseline measurements.

There are four methods to implement for intrinsic sizing, to compute the minimum and maximum intrinsic width and height of the box. The documentation for these methods discusses the protocol in detail:computeMinIntrinsicWidth, computeMaxIntrinsicWidth,computeMinIntrinsicHeight, computeMaxIntrinsicHeight.

Be sure to set debugCheckIntrinsicSizes to true in your unit tests if you do override any of these methods, which will add additional checks to help validate your implementation.

In addition, if the box has any children, it must implementcomputeDistanceToActualBaseline. RenderProxyBox provides a simple implementation that forwards to the child; RenderShiftedBox provides an implementation that offsets the child's baseline information by the position of the child relative to the parent. If you do not inherited from either of these classes, however, you must implement the algorithm yourself.

Inheritance

• Object
• RenderObject
• RenderBox

Implementers

• PlatformViewRenderBox
• RenderCustomMultiChildLayoutBox
• RenderDarwinPlatformView
• RenderEditable
• RenderErrorBox
• RenderFlex
• RenderFlow
• RenderImage
• RenderInlineChildrenContainerDefaults
• RenderListBody
• RenderListWheelViewport
• RenderParagraph
• RenderPerformanceOverlay
• RenderProxyBox
• RenderProxyBoxMixin
• RenderRotatedBox
• RenderShiftedBox
• RenderStack
• RenderTable
• RenderTwoDimensionalViewport
• RenderViewportBase
• RenderWrap
• TextureBox

Constructors

RenderBox()

Properties

alwaysNeedsCompositing → bool

Whether this render object always needs compositing.

no setterinherited

attached → bool

Whether the render tree this render object belongs to is attached to a PipelineOwner.

no setterinherited

constraints → BoxConstraints

The box constraints most recently received from the parent.

no setteroverride

debugCanParentUseSize → bool

Whether the parent render object is permitted to use this render object's size.

no setterinherited

debugCreator ↔ Object?

The object responsible for creating this render object.

getter/setter pairinherited

debugDisposed → bool?

Whether this has been disposed.

no setterinherited

debugDoingThisLayout → bool

Whether performLayout for this render object is currently running.

no setterinherited

debugDoingThisLayoutWithCallback → bool

Whether invokeLayoutCallback for this render object is currently running.

no setterinherited

debugDoingThisPaint → bool

Whether paint for this render object is currently running.

no setterinherited

debugDoingThisResize → bool

Whether performResize for this render object is currently running.

no setterinherited

debugLayer → ContainerLayer?

In debug mode, the compositing layer that this render object uses to repaint.

no setterinherited

debugLayoutParent → RenderObject?

The RenderObject that's expected to call layout on this RenderObjectin its performLayout implementation.

no setterinherited

debugNeedsCompositedLayerUpdate → bool

Whether this render object's layer information is dirty.

no setterinherited

debugNeedsLayout → bool

Whether this render object's layout information is dirty.

no setterinherited

debugNeedsPaint → bool

Whether this render object's paint information is dirty.

no setterinherited

debugNeedsSemanticsUpdate → bool

Whether the semantics of this render object is dirty and await the update.

no setterinherited

debugSemantics → SemanticsNode?

The semantics of this render object.

no setterinherited

depth → int

The depth of this render object in the render tree.

no setterinherited

hashCode → int

The hash code for this object.

no setterinherited

hasSize → bool

Whether this render object has undergone layout and has a size.

no setter

isRepaintBoundary → bool

Whether this render object repaints separately from its parent.

no setterinherited

layer ↔ ContainerLayer?

The compositing layer that this render object uses to repaint.

getter/setter pairinherited

needsCompositing → bool

Whether we or one of our descendants has a compositing layer.

no setterinherited

owner → PipelineOwner?

The owner for this render object (null if unattached).

no setterinherited

paintBounds → Rect

Returns a rectangle that contains all the pixels painted by this box.

no setteroverride

parent → RenderObject?

The parent of this render object in the render tree.

no setterinherited

parentData ↔ ParentData?

Data for use by the parent render object.

getter/setter pairinherited

runtimeType → Type

A representation of the runtime type of the object.

no setterinherited

semanticBounds → Rect

The bounding box, in the local coordinate system, of this object, for accessibility purposes.

no setteroverride

semanticsParent → RenderObject?

The semantics parent of this render object in the semantics tree.

no setterinherited

size ↔ Size

The size of this render box computed during layout.

getter/setter pair

sizedByParent → bool

Whether the constraints are the only input to the sizing algorithm (in particular, child nodes have no impact).

no setterinherited

Methods

adoptChild(RenderObject child)→ void

Called by subclasses when they decide a render object is a child.

inherited

applyPaintTransform(covariant RenderObject child, Matrix4 transform)→ void

Multiply the transform from the parent's coordinate system to this box's coordinate system into the given transform.

override

assembleSemanticsNode(SemanticsNode node, SemanticsConfiguration config, Iterable<SemanticsNode> children)→ void

Assemble the SemanticsNode for this RenderObject.

inherited

attach(PipelineOwner owner)→ void

Mark this render object as attached to the given owner.

inherited

clearSemantics()→ void

Removes all semantics from this render object and its descendants.

inherited

computeDistanceToActualBaseline(TextBaseline baseline)→ double?

Returns the distance from the y-coordinate of the position of the box to the y-coordinate of the first given baseline in the box's contents, if any, or null otherwise.

computeDryBaseline(covariant BoxConstraints constraints, TextBaseline baseline)→ double?

Computes the value returned by getDryBaseline.

computeDryLayout(covariant BoxConstraints constraints)→ Size

Computes the value returned by getDryLayout. Do not call this function directly, instead, call getDryLayout.

computeMaxIntrinsicHeight(double width)→ double

Computes the value returned by getMaxIntrinsicHeight. Do not call this function directly, instead, call getMaxIntrinsicHeight.

computeMaxIntrinsicWidth(double height)→ double

Computes the value returned by getMaxIntrinsicWidth. Do not call this function directly, instead, call getMaxIntrinsicWidth.

computeMinIntrinsicHeight(double width)→ double

Computes the value returned by getMinIntrinsicHeight. Do not call this function directly, instead, call getMinIntrinsicHeight.

computeMinIntrinsicWidth(double height)→ double

Computes the value returned by getMinIntrinsicWidth. Do not call this function directly, instead, call getMinIntrinsicWidth.

debugAdoptSize(Size value)→ Size

Claims ownership of the given Size.

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 when asserts are enabled (i.e. in debug mode) and only when needsLayout is false. If the constraints are not met, it should assert or throw an exception.

override

debugCannotComputeDryLayout({String? reason, FlutterError? error})→ bool

Called from computeDryLayout or computeDryBaseline within an assert if the given RenderBox subclass does not support calculating a dry layout.

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

debugHandleEvent(PointerEvent event, HitTestEntry<HitTestTarget> entry)→ bool

Implements the debugPaintPointersEnabled debugging feature.

debugPaint(PaintingContext context, Offset offset)→ void

Override this method to paint debugging information.

override

debugPaintBaselines(PaintingContext context, Offset offset)→ void

In debug mode, paints a line for each baseline.

debugPaintPointers(PaintingContext context, Offset offset)→ void

In debug mode, paints a rectangle if this render box has counted more pointer downs than pointer up events.

debugPaintSize(PaintingContext context, Offset offset)→ void

In debug mode, paints a border around this render box.

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 ofRenderBox), 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 ofdebugCanParentUseSize to that state.

override

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 describeApproximatePaintClipwill 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.

inherited

detach()→ void

Mark this render object as detached from its PipelineOwner.

inherited

dispose()→ void

Release any resources held by this render object.

inherited

dropChild(RenderObject child)→ void

Called by subclasses when they decide a render object is no longer a child.

inherited

getDistanceToActualBaseline(TextBaseline baseline)→ double?

Calls computeDistanceToActualBaseline and caches the result.

getDistanceToBaseline(TextBaseline baseline, {bool onlyReal = false})→ double?

Returns the distance from the y-coordinate of the position of the box to the y-coordinate of the first given baseline in the box's contents.

getDryBaseline(covariant BoxConstraints constraints, TextBaseline baseline)→ double?

Returns the distance from the top of the box to the first baseline of the box's contents for the given constraints, or null if this RenderBoxdoes not have any baselines.

getDryLayout(covariant BoxConstraints constraints)→ Size

Returns the Size that this RenderBox would like to be given the provided BoxConstraints.

getMaxIntrinsicHeight(double width)→ double

Returns the smallest height beyond which increasing the height never decreases the preferred width. The preferred width is the value that would be returned by getMinIntrinsicWidth for that height.

getMaxIntrinsicWidth(double height)→ double

Returns the smallest width beyond which increasing the width never decreases the preferred height. The preferred height is the value that would be returned by getMinIntrinsicHeight for that width.

getMinIntrinsicHeight(double width)→ double

Returns the minimum height that this box could be without failing to correctly paint its contents within itself, without clipping.

getMinIntrinsicWidth(double height)→ double

Returns the minimum width that this box could be without failing to correctly paint its contents within itself, without clipping.

getTransformTo(RenderObject? target)→ Matrix4

Applies the paint transform from this RenderObject to the target RenderObject.

inherited

globalToLocal(Offset point, {RenderObject? ancestor})→ Offset

Convert the given point from the global coordinate system in logical pixels to the local coordinate system for this box.

handleEvent(PointerEvent event, covariant BoxHitTestEntry entry)→ void

Override this method to handle pointer events that hit this render object.

override

hitTest(BoxHitTestResult result, {required Offset position})→ bool

Determines the set of render objects located at the given position.

hitTestChildren(BoxHitTestResult result, {required Offset position})→ bool

Override this method to check whether any children are located at the given position.

hitTestSelf(Offset position)→ bool

Override this method if this render object can be hit even if its children were not hit.

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.

inherited

layout(Constraints constraints, {bool parentUsesSize = false})→ void

Compute the layout for this render object.

inherited

localToGlobal(Offset point, {RenderObject? ancestor})→ Offset

Convert the given point from the local coordinate system for this box to the global coordinate system in logical pixels.

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.

override

markNeedsLayoutForSizedByParentChange()→ void

Mark this render object's layout information as dirty (likemarkNeedsLayout), 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.

inherited

noSuchMethod(Invocation invocation)→ dynamic

Invoked when a nonexistent 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

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.

override

performResize()→ void

Updates the render objects size using only the constraints.

override

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 asdebugPaintSizeEnabled) can be applied.

inherited

redepthChild(RenderObject child)→ void

Adjust the depth of the given child to be greater than this node's owndepth.

inherited

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.

override

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, int wrapWidth = 65})→ 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