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// Copyright 2015 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
import 'dart:developer';
import 'dart:ui' as ui show PictureRecorder;
import 'package:flutter/animation.dart';
import 'package:flutter/foundation.dart';
import 'package:flutter/gestures.dart';
import 'package:flutter/painting.dart';
import 'package:flutter/scheduler.dart';
import 'package:flutter/semantics.dart';
import 'package:vector_math/vector_math_64.dart';
import 'binding.dart';
import 'debug.dart';
import 'layer.dart';
export 'package:flutter/foundation.dart' show FlutterError, InformationCollector, DiagnosticsNode, DiagnosticsProperty, StringProperty, DoubleProperty, EnumProperty, FlagProperty, IntProperty, DiagnosticPropertiesBuilder;
export 'package:flutter/gestures.dart' show HitTestEntry, HitTestResult;
export 'package:flutter/painting.dart';
/// Base class for data associated with a [RenderObject] by its parent.
///
/// Some render objects wish to store data on their children, such as their
/// input parameters to the parent's layout algorithm or their position relative
/// to other children.
class ParentData {
/// Called when the RenderObject is removed from the tree.
@protected
@mustCallSuper
void detach() { }
@override
String toString() => '<none>';
}
/// Signature for painting into a [PaintingContext].
///
/// The `offset` argument is the offset from the origin of the coordinate system
/// of the [PaintingContext.canvas] to the coordinate system of the callee.
///
/// Used by many of the methods of [PaintingContext].
typedef void PaintingContextCallback(PaintingContext context, Offset offset);
/// A place to paint.
///
/// Rather than holding a canvas directly, [RenderObject]s paint using a painting
/// context. The painting context has a [Canvas], which receives the
/// individual draw operations, and also has functions for painting child
/// render objects.
///
/// When painting a child render object, the canvas held by the painting context
/// can change because the draw operations issued before and after painting the
/// child might be recorded in separate compositing layers. For this reason, do
/// not hold a reference to the canvas across operations that might paint
/// child render objects.
///
/// New [PaintingContext] objects are created automatically when using
/// [PaintingContext.repaintCompositedChild] and [pushLayer].
class PaintingContext {
PaintingContext._(this._containerLayer, this.estimatedBounds)
: assert(_containerLayer != null),
assert(estimatedBounds != null);
final ContainerLayer _containerLayer;
/// An estimate of the bounds within which the painting context's [canvas]
/// will record painting commands. This can be useful for debugging.
///
/// The canvas will allow painting outside these bounds.
///
/// The [estimatedBounds] rectangle is in the [canvas] coordinate system.
final Rect estimatedBounds;
/// Repaint the given render object.
///
/// The render object must be attached to a [PipelineOwner], must have a
/// composited layer, and must be in need of painting. The render object's
/// layer, if any, is re-used, along with any layers in the subtree that don't
/// need to be repainted.
///
/// See also:
///
/// * [RenderObject.isRepaintBoundary], which determines if a [RenderObject]
/// has a composited layer.
static void repaintCompositedChild(RenderObject child, { bool debugAlsoPaintedParent = false }) {
assert(child.isRepaintBoundary);
assert(child._needsPaint);
assert(() {
// register the call for RepaintBoundary metrics
child.debugRegisterRepaintBoundaryPaint(
includedParent: debugAlsoPaintedParent,
includedChild: true,
);
return true;
}());
if (child._layer == null) {
assert(debugAlsoPaintedParent);
child._layer = new OffsetLayer();
} else {
assert(debugAlsoPaintedParent || child._layer.attached);
child._layer.removeAllChildren();
}
assert(() {
child._layer.debugCreator = child.debugCreator ?? child.runtimeType;
return true;
}());
final PaintingContext childContext = new PaintingContext._(child._layer, child.paintBounds);
child._paintWithContext(childContext, Offset.zero);
childContext._stopRecordingIfNeeded();
}
/// Paint a child [RenderObject].
///
/// If the child has its own composited layer, the child will be composited
/// into the layer subtree associated with this painting context. Otherwise,
/// the child will be painted into the current PictureLayer for this context.
void paintChild(RenderObject child, Offset offset) {
assert(() {
if (debugProfilePaintsEnabled)
Timeline.startSync('${child.runtimeType}', arguments: timelineWhitelistArguments);
return true;
}());
if (child.isRepaintBoundary) {
_stopRecordingIfNeeded();
_compositeChild(child, offset);
} else {
child._paintWithContext(this, offset);
}
assert(() {
if (debugProfilePaintsEnabled)
Timeline.finishSync();
return true;
}());
}
void _compositeChild(RenderObject child, Offset offset) {
assert(!_isRecording);
assert(child.isRepaintBoundary);
assert(_canvas == null || _canvas.getSaveCount() == 1);
// Create a layer for our child, and paint the child into it.
if (child._needsPaint) {
repaintCompositedChild(child, debugAlsoPaintedParent: true);
} else {
assert(child._layer != null);
assert(() {
// register the call for RepaintBoundary metrics
child.debugRegisterRepaintBoundaryPaint(
includedParent: true,
includedChild: false,
);
child._layer.debugCreator = child.debugCreator ?? child;
return true;
}());
}
child._layer.offset = offset;
_appendLayer(child._layer);
}
void _appendLayer(Layer layer) {
assert(!_isRecording);
layer.remove();
_containerLayer.append(layer);
}
bool get _isRecording {
final bool hasCanvas = _canvas != null;
assert(() {
if (hasCanvas) {
assert(_currentLayer != null);
assert(_recorder != null);
assert(_canvas != null);
} else {
assert(_currentLayer == null);
assert(_recorder == null);
assert(_canvas == null);
}
return true;
}());
return hasCanvas;
}
// Recording state
PictureLayer _currentLayer;
ui.PictureRecorder _recorder;
Canvas _canvas;
/// The canvas on which to paint.
///
/// The current canvas can change whenever you paint a child using this
/// context, which means it's fragile to hold a reference to the canvas
/// returned by this getter.
Canvas get canvas {
if (_canvas == null)
_startRecording();
return _canvas;
}
void _startRecording() {
assert(!_isRecording);
_currentLayer = new PictureLayer(estimatedBounds);
_recorder = new ui.PictureRecorder();
_canvas = new Canvas(_recorder);
_containerLayer.append(_currentLayer);
}
void _stopRecordingIfNeeded() {
if (!_isRecording)
return;
assert(() {
if (debugRepaintRainbowEnabled) {
final Paint paint = new Paint()
..style = PaintingStyle.stroke
..strokeWidth = 6.0
..color = debugCurrentRepaintColor.toColor();
canvas.drawRect(estimatedBounds.deflate(3.0), paint);
}
if (debugPaintLayerBordersEnabled) {
final Paint paint = new Paint()
..style = PaintingStyle.stroke
..strokeWidth = 1.0
..color = const Color(0xFFFF9800);
canvas.drawRect(estimatedBounds, paint);
}
return true;
}());
_currentLayer.picture = _recorder.endRecording();
_currentLayer = null;
_recorder = null;
_canvas = null;
}
static final Paint _defaultPaint = new Paint();
/// Hints that the painting in the current layer is complex and would benefit
/// from caching.
///
/// If this hint is not set, the compositor will apply its own heuristics to
/// decide whether the current layer is complex enough to benefit from
/// caching.
void setIsComplexHint() {
_currentLayer?.isComplexHint = true;
}
/// Hints that the painting in the current layer is likely to change next frame.
///
/// This hint tells the compositor not to cache the current layer because the
/// cache will not be used in the future. If this hint is not set, the
/// compositor will apply its own heuristics to decide whether the current
/// layer is likely to be reused in the future.
void setWillChangeHint() {
_currentLayer?.willChangeHint = true;
}
/// Adds a composited leaf layer to the recording.
///
/// After calling this function, the [canvas] property will change to refer to
/// a new [Canvas] that draws on top of the given layer.
///
/// A [RenderObject] that uses this function is very likely to require its
/// [RenderObject.alwaysNeedsCompositing] property to return true. That informs
/// ancestor render objects that this render object will include a composited
/// layer, which, for example, causes them to use composited clips.
///
/// See also:
///
/// * [pushLayer], for adding a layer and using its canvas to paint with that
/// layer.
void addLayer(Layer layer) {
_stopRecordingIfNeeded();
_appendLayer(layer);
}
/// Appends the given layer to the recording, and calls the `painter` callback
/// with that layer, providing the `childPaintBounds` as the estimated paint
/// bounds of the child. The `childPaintBounds` can be used for debugging but
/// have no effect on painting.
///
/// The given layer must be an unattached orphan. (Providing a newly created
/// object, rather than reusing an existing layer, satisfies that
/// requirement.)
///
/// The `offset` is the offset to pass to the `painter`.
///
/// If the `childPaintBounds` are not specified then the current layer's paint
/// bounds are used. This is appropriate if the child layer does not apply any
/// transformation or clipping to its contents. The `childPaintBounds`, if
/// specified, must be in the coordinate system of the new layer, and should
/// not go outside the current layer's paint bounds.
///
/// See also:
///
/// * [addLayer], for pushing a leaf layer whose canvas is not used.
void pushLayer(Layer childLayer, PaintingContextCallback painter, Offset offset, { Rect childPaintBounds }) {
assert(!childLayer.attached);
assert(childLayer.parent == null);
assert(painter != null);
_stopRecordingIfNeeded();
_appendLayer(childLayer);
final PaintingContext childContext = new PaintingContext._(childLayer, childPaintBounds ?? estimatedBounds);
painter(childContext, offset);
childContext._stopRecordingIfNeeded();
}
/// Clip further painting using a rectangle.
///
/// * `needsCompositing` is whether the child needs compositing. Typically
/// matches the value of [RenderObject.needsCompositing] for the caller.
/// * `offset` is the offset from the origin of the canvas' coordinate system
/// to the origin of the caller's coordinate system.
/// * `clipRect` is rectangle (in the caller's coordinate system) to use to
/// clip the painting done by [painter].
/// * `painter` is a callback that will paint with the [clipRect] applied. This
/// function calls the [painter] synchronously.
void pushClipRect(bool needsCompositing, Offset offset, Rect clipRect, PaintingContextCallback painter) {
final Rect offsetClipRect = clipRect.shift(offset);
if (needsCompositing) {
pushLayer(new ClipRectLayer(clipRect: offsetClipRect), painter, offset, childPaintBounds: offsetClipRect);
} else {
canvas
..save()
..clipRect(offsetClipRect);
painter(this, offset);
canvas
..restore();
}
}
/// Clip further painting using a rounded rectangle.
///
/// * `needsCompositing` is whether the child needs compositing. Typically
/// matches the value of [RenderObject.needsCompositing] for the caller.
/// * `offset` is the offset from the origin of the canvas' coordinate system
/// to the origin of the caller's coordinate system.
/// * `bounds` is the region of the canvas (in the caller's coordinate system)
/// into which `painter` will paint in.
/// * `clipRRect` is the rounded-rectangle (in the caller's coordinate system)
/// to use to clip the painting done by `painter`.
/// * `painter` is a callback that will paint with the `clipRRect` applied. This
/// function calls the `painter` synchronously.
void pushClipRRect(bool needsCompositing, Offset offset, Rect bounds, RRect clipRRect, PaintingContextCallback painter) {
final Rect offsetBounds = bounds.shift(offset);
final RRect offsetClipRRect = clipRRect.shift(offset);
if (needsCompositing) {
pushLayer(new ClipRRectLayer(clipRRect: offsetClipRRect), painter, offset, childPaintBounds: offsetBounds);
} else {
canvas
..save()
..clipRRect(offsetClipRRect)
..saveLayer(offsetBounds, _defaultPaint);
painter(this, offset);
canvas
..restore()
..restore();
}
}
/// Clip further painting using a path.
///
/// * `needsCompositing` is whether the child needs compositing. Typically
/// matches the value of [RenderObject.needsCompositing] for the caller.
/// * `offset` is the offset from the origin of the canvas' coordinate system
/// to the origin of the caller's coordinate system.
/// * `bounds` is the region of the canvas (in the caller's coordinate system)
/// into which `painter` will paint in.
/// * `clipPath` is the path (in the coordinate system of the caller) to use to
/// clip the painting done by `painter`.
/// * `painter` is a callback that will paint with the `clipPath` applied. This
/// function calls the `painter` synchronously.
void pushClipPath(bool needsCompositing, Offset offset, Rect bounds, Path clipPath, PaintingContextCallback painter) {
final Rect offsetBounds = bounds.shift(offset);
final Path offsetClipPath = clipPath.shift(offset);
if (needsCompositing) {
pushLayer(new ClipPathLayer(clipPath: offsetClipPath), painter, offset, childPaintBounds: offsetBounds);
} else {
canvas
..save()
..clipPath(clipPath.shift(offset))
..saveLayer(bounds.shift(offset), _defaultPaint);
painter(this, offset);
canvas
..restore()
..restore();
}
}
/// Transform further painting using a matrix.
///
/// * `needsCompositing` is whether the child needs compositing. Typically
/// matches the value of [RenderObject.needsCompositing] for the caller.
/// * `offset` is the offset from the origin of the canvas' coordinate system
/// to the origin of the caller's coordinate system.
/// * `transform` is the matrix to apply to the painting done by `painter`.
/// * `painter` is a callback that will paint with the `transform` applied. This
/// function calls the `painter` synchronously.
void pushTransform(bool needsCompositing, Offset offset, Matrix4 transform, PaintingContextCallback painter) {
final Matrix4 effectiveTransform = new Matrix4.translationValues(offset.dx, offset.dy, 0.0)
..multiply(transform)..translate(-offset.dx, -offset.dy);
if (needsCompositing) {
pushLayer(
new TransformLayer(transform: effectiveTransform),
painter,
offset,
childPaintBounds: MatrixUtils.inverseTransformRect(effectiveTransform, estimatedBounds),
);
} else {
canvas
..save()
..transform(effectiveTransform.storage);
painter(this, offset);
canvas
..restore();
}
}
/// Blend further painting with an alpha value.
///
/// * `offset` is the offset from the origin of the canvas' coordinate system
/// to the origin of the caller's coordinate system.
/// * `alpha` is the alpha value to use when blending the painting done by
/// `painter`. An alpha value of 0 means the painting is fully transparent
/// and an alpha value of 255 means the painting is fully opaque.
/// * `painter` is a callback that will paint with the `alpha` applied. This
/// function calls the `painter` synchronously.
///
/// A [RenderObject] that uses this function is very likely to require its
/// [RenderObject.alwaysNeedsCompositing] property to return true. That informs
/// ancestor render objects that this render object will include a composited
/// layer, which, for example, causes them to use composited clips.
void pushOpacity(Offset offset, int alpha, PaintingContextCallback painter) {
pushLayer(new OpacityLayer(alpha: alpha), painter, offset);
}
@override
String toString() => '$runtimeType#$hashCode(layer: $_containerLayer, canvas bounds: $estimatedBounds)';
}
/// An abstract set of layout constraints.
///
/// Concrete layout models (such as box) will create concrete subclasses to
/// communicate layout constraints between parents and children.
///
/// ## Writing a Constraints subclass
///
/// When creating a new [RenderObject] subclass with a new layout protocol, one
/// will usually need to create a new [Constraints] subclass to express the
/// input to the layout algorithms.
///
/// A [Constraints] subclass should be immutable (all fields final). There are
/// several members to implement, in addition to whatever fields, constructors,
/// and helper methods one may find useful for a particular layout protocol:
///
/// * The [isTight] getter, which should return true if the object represents a
/// case where the [RenderObject] class has no choice for how to lay itself
/// out. For example, [BoxConstraints] returns true for [isTight] when both
/// the minimum and maximum widths and the minimum and maximum heights are
/// equal.
///
/// * The [isNormalized] getter, which should return true if the object
/// represents its data in its canonical form. Sometimes, it is possible for
/// fields to be redundant with each other, such that several different
/// representations have the same implications. For example, a
/// [BoxConstraints] instance with its minimum width greater than its maximum
/// width is equivalent to one where the maximum width is set to that minimum
/// width (`2<w<1` is equivalent to `2<w<2`, since minimum constraints have
/// priority). This getter is used by the default implementation of
/// [debugAssertIsValid].
///
/// * The [debugAssertIsValid] method, which should assert if there's anything
/// wrong with the constraints object. (We use this approach rather than
/// asserting in constructors so that our constructors can be `const` and so
/// that it is possible to create invalid constraints temporarily while
/// building valid ones.) See the implementation of
/// [BoxConstraints.debugAssertIsValid] for an example of the detailed checks
/// that can be made.
///
/// * The [==] operator and the [hashCode] getter, so that constraints can be
/// compared for equality. If a render object is given constraints that are
/// equal, then the rendering library will avoid laying the object out again
/// if it is not dirty.
///
/// * The [toString] method, which should describe the constraints so that they
/// appear in a usefully readable form in the output of [debugDumpRenderTree].
@immutable
abstract class Constraints {
/// Abstract const constructor. This constructor enables subclasses to provide
/// const constructors so that they can be used in const expressions.
const Constraints();
/// Whether there is exactly one size possible given these constraints
bool get isTight;
/// Whether the constraint is expressed in a consistent manner.
bool get isNormalized;
/// Asserts that the constraints are valid.
///
/// This might involve checks more detailed than [isNormalized].
///
/// For example, the [BoxConstraints] subclass verifies that the constraints
/// are not [double.nan].
///
/// If the `isAppliedConstraint` argument is true, then even stricter rules
/// are enforced. This argument is set to true when checking constraints that
/// are about to be applied to a [RenderObject] during layout, as opposed to
/// constraints that may be further affected by other constraints. For
/// example, the asserts for verifying the validity of
/// [RenderConstrainedBox.additionalConstraints] do not set this argument, but
/// the asserts for verifying the argument passed to the [RenderObject.layout]
/// method do.
///
/// The `informationCollector` argument takes an optional callback which is
/// called when an exception is to be thrown. The collected information is
/// then included in the message after the error line.
///
/// Returns the same as [isNormalized] if asserts are disabled.
bool debugAssertIsValid({
bool isAppliedConstraint = false,
InformationCollector informationCollector
}) {
assert(isNormalized);
return isNormalized;
}
}
/// Signature for a function that is called for each [RenderObject].
///
/// Used by [RenderObject.visitChildren] and [RenderObject.visitChildrenForSemantics].
typedef void RenderObjectVisitor(RenderObject child);
/// Signature for a function that is called during layout.
///
/// Used by [RenderObject.invokeLayoutCallback].
typedef void LayoutCallback<T extends Constraints>(T constraints);
/// A reference to the semantics tree.
///
/// The framework maintains the semantics tree (used for accessibility and
/// indexing) only when there is at least one client holding an open
/// [SemanticsHandle].
///
/// The framework notifies the client that it has updated the semantics tree by
/// calling the [listener] callback. When the client no longer needs the
/// semantics tree, the client can call [dispose] on the [SemanticsHandle],
/// which stops these callbacks and closes the [SemanticsHandle]. When all the
/// outstanding [SemanticsHandle] objects are closed, the framework stops
/// updating the semantics tree.
///
/// To obtain a [SemanticsHandle], call [PipelineOwner.ensureSemantics] on the
/// [PipelineOwner] for the render tree from which you wish to read semantics.
/// You can obtain the [PipelineOwner] using the [RenderObject.owner] property.
class SemanticsHandle {
SemanticsHandle._(this._owner, this.listener)
: assert(_owner != null) {
if (listener != null)
_owner.semanticsOwner.addListener(listener);
}
PipelineOwner _owner;
/// The callback that will be notified when the semantics tree updates.
final VoidCallback listener;
/// Closes the semantics handle and stops calling [listener] when the
/// semantics updates.
///
/// When all the outstanding [SemanticsHandle] objects for a given
/// [PipelineOwner] are closed, the [PipelineOwner] will stop updating the
/// semantics tree.
@mustCallSuper
void dispose() {
assert(() {
if (_owner == null) {
throw new FlutterError(
'SemanticsHandle has already been disposed.\n'
'Each SemanticsHandle should be disposed exactly once.'
);
}
return true;
}());
if (_owner != null) {
if (listener != null)
_owner.semanticsOwner.removeListener(listener);
_owner._didDisposeSemanticsHandle();
_owner = null;
}
}
}
/// The pipeline owner manages the rendering pipeline.
///
/// The pipeline owner provides an interface for driving the rendering pipeline
/// and stores the state about which render objects have requested to be visited
/// in each stage of the pipeline. To flush the pipeline, call the following
/// functions in order:
///
/// 1. [flushLayout] updates any render objects that need to compute their
/// layout. During this phase, the size and position of each render
/// object is calculated. Render objects might dirty their painting or
/// compositing state during this phase.
/// 2. [flushCompositingBits] updates any render objects that have dirty
/// compositing bits. During this phase, each render object learns whether
/// any of its children require compositing. This information is used during
/// the painting phase when selecting how to implement visual effects such as
/// clipping. If a render object has a composited child, its needs to use a
/// [Layer] to create the clip in order for the clip to apply to the
/// composited child (which will be painted into its own [Layer]).
/// 3. [flushPaint] visits any render objects that need to paint. During this
/// phase, render objects get a chance to record painting commands into
/// [PictureLayer]s and construct other composited [Layer]s.
/// 4. Finally, if semantics are enabled, [flushSemantics] will compile the
/// semantics for the render objects. This semantic information is used by
/// assistive technology to improve the accessibility of the render tree.
///
/// The [RendererBinding] holds the pipeline owner for the render objects that
/// are visible on screen. You can create other pipeline owners to manage
/// off-screen objects, which can flush their pipelines independently of the
/// on-screen render objects.
class PipelineOwner {
/// Creates a pipeline owner.
///
/// Typically created by the binding (e.g., [RendererBinding]), but can be
/// created separately from the binding to drive off-screen render objects
/// through the rendering pipeline.
PipelineOwner({
this.onNeedVisualUpdate,
this.onSemanticsOwnerCreated,
this.onSemanticsOwnerDisposed,
});
/// Called when a render object associated with this pipeline owner wishes to
/// update its visual appearance.
///
/// Typical implementations of this function will schedule a task to flush the
/// various stages of the pipeline. This function might be called multiple
/// times in quick succession. Implementations should take care to discard
/// duplicate calls quickly.
final VoidCallback onNeedVisualUpdate;
/// Called whenever this pipeline owner creates a semantics object.
///
/// Typical implementations will schedule the creation of the initial
/// semantics tree.
final VoidCallback onSemanticsOwnerCreated;
/// Called whenever this pipeline owner disposes its semantics owner.
///
/// Typical implementations will tear down the semantics tree.
final VoidCallback onSemanticsOwnerDisposed;
/// Calls [onNeedVisualUpdate] if [onNeedVisualUpdate] is not null.
///
/// Used to notify the pipeline owner that an associated render object wishes
/// to update its visual appearance.
void requestVisualUpdate() {
if (onNeedVisualUpdate != null)
onNeedVisualUpdate();
}
/// The unique object managed by this pipeline that has no parent.
///
/// This object does not have to be a [RenderObject].
AbstractNode get rootNode => _rootNode;
AbstractNode _rootNode;
set rootNode(AbstractNode value) {
if (_rootNode == value)
return;
_rootNode?.detach();
_rootNode = value;
_rootNode?.attach(this);
}
List<RenderObject> _nodesNeedingLayout = <RenderObject>[];
/// Whether this pipeline is currently in the layout phase.
///
/// Specifically, whether [flushLayout] is currently running.
///
/// Only valid when asserts are enabled.
bool get debugDoingLayout => _debugDoingLayout;
bool _debugDoingLayout = false;
/// Update the layout information for all dirty render objects.
///
/// This function is one of the core stages of the rendering pipeline. Layout
/// information is cleaned prior to painting so that render objects will
/// appear on screen in their up-to-date locations.
///
/// See [RendererBinding] for an example of how this function is used.
void flushLayout() {
profile(() {
Timeline.startSync('Layout', arguments: timelineWhitelistArguments);
});
assert(() {
_debugDoingLayout = true;
return true;
}());
try {
// TODO(ianh): assert that we're not allowing previously dirty nodes to redirty themselves
while (_nodesNeedingLayout.isNotEmpty) {
final List<RenderObject> dirtyNodes = _nodesNeedingLayout;
_nodesNeedingLayout = <RenderObject>[];
for (RenderObject node in dirtyNodes..sort((RenderObject a, RenderObject b) => a.depth - b.depth)) {
if (node._needsLayout && node.owner == this)
node._layoutWithoutResize();
}
}
} finally {
assert(() {
_debugDoingLayout = false;
return true;
}());
profile(() {
Timeline.finishSync();
});
}
}
// This flag is used to allow the kinds of mutations performed by GlobalKey
// reparenting while a LayoutBuilder is being rebuilt and in so doing tries to
// move a node from another LayoutBuilder subtree that hasn't been updated
// yet. To set this, call [_enableMutationsToDirtySubtrees], which is called
// by [RenderObject.invokeLayoutCallback].
bool _debugAllowMutationsToDirtySubtrees = false;
// See [RenderObject.invokeLayoutCallback].
void _enableMutationsToDirtySubtrees(VoidCallback callback) {
assert(_debugDoingLayout);
bool oldState;
assert(() {
oldState = _debugAllowMutationsToDirtySubtrees;
_debugAllowMutationsToDirtySubtrees = true;
return true;
}());
try {
callback();
} finally {
assert(() {
_debugAllowMutationsToDirtySubtrees = oldState;
return true;
}());
}
}
final List<RenderObject> _nodesNeedingCompositingBitsUpdate = <RenderObject>[];
/// Updates the [RenderObject.needsCompositing] bits.
///
/// Called as part of the rendering pipeline after [flushLayout] and before
/// [flushPaint].
void flushCompositingBits() {
profile(() { Timeline.startSync('Compositing bits'); });
_nodesNeedingCompositingBitsUpdate.sort((RenderObject a, RenderObject b) => a.depth - b.depth);
for (RenderObject node in _nodesNeedingCompositingBitsUpdate) {
if (node._needsCompositingBitsUpdate && node.owner == this)
node._updateCompositingBits();
}
_nodesNeedingCompositingBitsUpdate.clear();
profile(() { Timeline.finishSync(); });
}
List<RenderObject> _nodesNeedingPaint = <RenderObject>[];
/// Whether this pipeline is currently in the paint phase.
///
/// Specifically, whether [flushPaint] is currently running.
///
/// Only valid when asserts are enabled.
bool get debugDoingPaint => _debugDoingPaint;
bool _debugDoingPaint = false;
/// Update the display lists for all render objects.
///
/// This function is one of the core stages of the rendering pipeline.
/// Painting occurs after layout and before the scene is recomposited so that
/// scene is composited with up-to-date display lists for every render object.
///
/// See [RendererBinding] for an example of how this function is used.
void flushPaint() {
profile(() { Timeline.startSync('Paint', arguments: timelineWhitelistArguments); });
assert(() {
_debugDoingPaint = true;
return true;
}());
try {
final List<RenderObject> dirtyNodes = _nodesNeedingPaint;
_nodesNeedingPaint = <RenderObject>[];
// Sort the dirty nodes in reverse order (deepest first).
for (RenderObject node in dirtyNodes..sort((RenderObject a, RenderObject b) => b.depth - a.depth)) {
assert(node._layer != null);
if (node._needsPaint && node.owner == this) {
if (node._layer.attached) {
PaintingContext.repaintCompositedChild(node);
} else {
node._skippedPaintingOnLayer();
}
}
}
assert(_nodesNeedingPaint.isEmpty);
} finally {
assert(() {
_debugDoingPaint = false;
return true;
}());
profile(() { Timeline.finishSync(); });
}
}
/// The object that is managing semantics for this pipeline owner, if any.
///
/// An owner is created by [ensureSemantics]. The owner is valid for as long
/// there are [SemanticsHandle]s returned by [ensureSemantics] that have not
/// yet been disposed. Once the last handle has been disposed, the
/// [semanticsOwner] field will revert to null, and the previous owner will be
/// disposed.
///
/// When [semanticsOwner] is null, the [PipelineOwner] skips all steps
/// relating to semantics.
SemanticsOwner get semanticsOwner => _semanticsOwner;
SemanticsOwner _semanticsOwner;
/// The number of clients registered to listen for semantics.
///
/// The number is increased whenever [ensureSemantics] is called and decreased
/// when [SemanticsHandle.dispose] is called.
int get debugOutstandingSemanticsHandles => _outstandingSemanticsHandles;
int _outstandingSemanticsHandles = 0;
/// Opens a [SemanticsHandle] and calls [listener] whenever the semantics tree
/// updates.
///
/// The [PipelineOwner] updates the semantics tree only when there are clients
/// that wish to use the semantics tree. These clients express their interest
/// by holding [SemanticsHandle] objects that notify them whenever the
/// semantics tree updates.
///
/// Clients can close their [SemanticsHandle] by calling
/// [SemanticsHandle.dispose]. Once all the outstanding [SemanticsHandle]
/// objects for a given [PipelineOwner] are closed, the [PipelineOwner] stops
/// maintaining the semantics tree.
SemanticsHandle ensureSemantics({ VoidCallback listener }) {
_outstandingSemanticsHandles += 1;
if (_outstandingSemanticsHandles == 1) {
assert(_semanticsOwner == null);
_semanticsOwner = new SemanticsOwner();
if (onSemanticsOwnerCreated != null)
onSemanticsOwnerCreated();
}
return new SemanticsHandle._(this, listener);
}
void _didDisposeSemanticsHandle() {
assert(_semanticsOwner != null);
_outstandingSemanticsHandles -= 1;
if (_outstandingSemanticsHandles == 0) {
_semanticsOwner.dispose();
_semanticsOwner = null;
if (onSemanticsOwnerDisposed != null)
onSemanticsOwnerDisposed();
}
}
bool _debugDoingSemantics = false;
final Set<RenderObject> _nodesNeedingSemantics = new Set<RenderObject>();
/// Update the semantics for render objects marked as needing a semantics
/// update.
///
/// Initially, only the root node, as scheduled by
/// [RenderObject.scheduleInitialSemantics], needs a semantics update.
///
/// This function is one of the core stages of the rendering pipeline. The
/// semantics are compiled after painting and only after
/// [RenderObject.scheduleInitialSemantics] has been called.
///
/// See [RendererBinding] for an example of how this function is used.
void flushSemantics() {
if (_semanticsOwner == null)
return;
profile(() { Timeline.startSync('Semantics'); });
assert(_semanticsOwner != null);
assert(() { _debugDoingSemantics = true; return true; }());
try {
final List<RenderObject> nodesToProcess = _nodesNeedingSemantics.toList()
..sort((RenderObject a, RenderObject b) => a.depth - b.depth);
_nodesNeedingSemantics.clear();
for (RenderObject node in nodesToProcess) {
if (node._needsSemanticsUpdate && node.owner == this)
node._updateSemantics();
}
_semanticsOwner.sendSemanticsUpdate();
} finally {
assert(_nodesNeedingSemantics.isEmpty);
assert(() { _debugDoingSemantics = false; return true; }());
profile(() { Timeline.finishSync(); });
}
}
}
/// An object in the render tree.
///
/// The [RenderObject] class hierarchy is the core of the rendering
/// library's reason for being.
///
/// [RenderObject]s have a [parent], and have a slot called [parentData] in
/// which the parent [RenderObject] can store child-specific data, for example,
/// the child position. The [RenderObject] class also implements the basic
/// layout and paint protocols.
///
/// The [RenderObject] class, however, does not define a child model (e.g.
/// whether a node has zero, one, or more children). It also doesn't define a
/// coordinate system (e.g. whether children are positioned in Cartesian
/// coordinates, in polar coordinates, etc) or a specific layout protocol (e.g.
/// whether the layout is width-in-height-out, or constraint-in-size-out, or
/// whether the parent sets the size and position of the child before or after
/// the child lays out, etc; or indeed whether the children are allowed to read
/// their parent's [parentData] slot).
///
/// The [RenderBox] subclass introduces the opinion that the layout
/// system uses Cartesian coordinates.
///
/// ## Writing a RenderObject subclass
///
/// In most cases, subclassing [RenderObject] itself is overkill, and
/// [RenderBox] would be a better starting point. However, if a render object
/// doesn't want to use a Cartesian coordinate system, then it should indeed
/// inherit from [RenderObject] directly. This allows it to define its own
/// layout protocol by using a new subclass of [Constraints] rather than using
/// [BoxConstraints], and by potentially using an entirely new set of objects
/// and values to represent the result of the output rather than just a [Size].
/// This increased flexibility comes at the cost of not being able to rely on
/// the features of [RenderBox]. For example, [RenderBox] implements an
/// intrinsic sizing protocol that allows you to measure a child without fully
/// laying it out, in such a way that if that child changes size, the parent
/// will be laid out again (to take into account the new dimensions of the
/// child). This is a subtle and bug-prone feature to get right.
///
/// Most aspects of writing a [RenderBox] apply to writing a [RenderObject] as
/// well, and therefore the discussion at [RenderBox] is recommended background
/// reading. The main differences are around layout and hit testing, since those
/// are the aspects that [RenderBox] primarily specializes.
///
/// ### Layout
///
/// A layout protocol begins with a subclass of [Constraints]. See the
/// discussion at [Constraints] for more information on how to write a
/// [Constraints] subclass.
///
/// The [performLayout] method should take the [constraints], and apply them.
/// The output of the layout algorithm is fields set on the object that describe
/// the geometry of the object for the purposes of the parent's layout. For
/// example, with [RenderBox] the output is the [RenderBox.size] field. This
/// output should only be read by the parent if the parent specified
/// `parentUsesSize` as true when calling [layout] on the child.
///
/// Anytime anything changes on a render object that would affect the layout of
/// that object, it should call [markNeedsLayout].
///
/// ### Hit Testing
///
/// Hit testing is even more open-ended than layout. There is no method to
/// override, you are expected to provide one.
///
/// The general behavior of your hit-testing method should be similar to the
/// behavior described for [RenderBox]. The main difference is that the input
/// need not be an [Offset]. You are also allowed to use a different subclass of
/// [HitTestEntry] when adding entries to the [HitTestResult]. When the
/// [handleEvent] method is called, the same object that was added to the
/// [HitTestResult] will be passed in, so it can be used to track information
/// like the precise coordinate of the hit, in whatever coordinate system is
/// used by the new layout protocol.
///
/// ### Adapting from one protocol to another
///
/// In general, the root of a Flutter render object tree is a [RenderView]. This
/// object has a single child, which must be a [RenderBox]. Thus, if you want to
/// have a custom [RenderObject] subclass in the render tree, you have two
/// choices: you either need to replace the [RenderView] itself, or you need to
/// have a [RenderBox] that has your class as its child. (The latter is the much
/// more common case.)
///
/// This [RenderBox] subclass converts from the box protocol to the protocol of
/// your class.
///
/// In particular, this means that for hit testing it overrides
/// [RenderBox.hitTest], and calls whatever method you have in your class for
/// hit testing.
///
/// Similarly, it overrides [performLayout] to create a [Constraints] object
/// appropriate for your class and passes that to the child's [layout] method.
///
/// ### Layout interactions between render objects
///
/// In general, the layout of a render object should only depend on the output of
/// its child's layout, and then only if `parentUsesSize` is set to true in the
/// [layout] call. Furthermore, if it is set to true, the parent must call the
/// child's [layout] if the child is to be rendered, because otherwise the
/// parent will not be notified when the child changes its layout outputs.
///
/// It is possible to set up render object protocols that transfer additional
/// information. For example, in the [RenderBox] protocol you can query your
/// children's intrinsic dimensions and baseline geometry. However, if this is
/// done then it is imperative that the child call [markNeedsLayout] on the
/// parent any time that additional information changes, if the parent used it
/// in the last layout phase. For an example of how to implement this, see the
/// [RenderBox.markNeedsLayout] method. It overrides
/// [RenderObject.markNeedsLayout] so that if a parent has queried the intrinsic
/// or baseline information, it gets marked dirty whenever the child's geometry
/// changes.
abstract class RenderObject extends AbstractNode with DiagnosticableTreeMixin implements HitTestTarget {
/// Initializes internal fields for subclasses.
RenderObject() {
_needsCompositing = isRepaintBoundary || alwaysNeedsCompositing;
}
/// 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.
///
/// This is called by the [RendererBinding] in response to the
/// `ext.flutter.reassemble` hook, which is used by development tools when the
/// application code has changed, to cause the widget tree to pick up any
/// changed implementations.
///
/// This is expensive and should not be called except during development.
///
/// See also:
///
/// * [BindingBase.reassembleApplication].
void reassemble() {
markNeedsLayout();
markNeedsCompositingBitsUpdate();
markNeedsPaint();
markNeedsSemanticsUpdate();
visitChildren((RenderObject child) {
child.reassemble();
});
}
// LAYOUT
/// Data for use by the parent render object.
///
/// The parent data is used by the render object that lays out this object
/// (typically this object's parent in the render tree) to store information
/// relevant to itself and to any other nodes who happen to know exactly what
/// the data means. The parent data is opaque to the child.
///
/// * The parent data field must not be directly set, except by calling
/// [setupParentData] on the parent node.
/// * The parent data can be set before the child is added to the parent, by
/// calling [setupParentData] on the future parent node.
/// * The conventions for using the parent data depend on the layout protocol
/// used between the parent and child. For example, in box layout, the
/// parent data is completely opaque but in sector layout the child is
/// permitted to read some fields of the parent data.
ParentData parentData;
/// Override to setup parent data correctly for your children.
///
/// You can call this function to set up the parent data for child before the
/// child is added to the parent's child list.
void setupParentData(covariant RenderObject child) {
assert(_debugCanPerformMutations);
if (child.parentData is! ParentData)
child.parentData = new ParentData();
}
/// Called by subclasses when they decide a render object is a child.
///
/// Only for use by subclasses when changing their child lists. Calling this
/// in other cases will lead to an inconsistent tree and probably cause crashes.
@override
void adoptChild(RenderObject child) {
assert(_debugCanPerformMutations);
assert(child != null);
setupParentData(child);
super.adoptChild(child);
markNeedsLayout();
markNeedsCompositingBitsUpdate();
markNeedsSemanticsUpdate();
}
/// Called by subclasses when they decide a render object is no longer a child.
///
/// Only for use by subclasses when changing their child lists. Calling this
/// in other cases will lead to an inconsistent tree and probably cause crashes.
@override
void dropChild(RenderObject child) {
assert(_debugCanPerformMutations);
assert(child != null);
assert(child.parentData != null);
child._cleanRelayoutBoundary();
child.parentData.detach();
child.parentData = null;
super.dropChild(child);
markNeedsLayout();
markNeedsCompositingBitsUpdate();
markNeedsSemanticsUpdate();
}
/// Calls visitor for each immediate child of this render object.
///
/// Override in subclasses with children and call the visitor for each child.
void visitChildren(RenderObjectVisitor visitor) { }
/// The object responsible for creating this render object.
///
/// Used in debug messages.
dynamic debugCreator;
void _debugReportException(String method, dynamic exception, StackTrace stack) {
FlutterError.reportError(new FlutterErrorDetailsForRendering(
exception: exception,
stack: stack,
library: 'rendering library',
context: 'during $method()',
renderObject: this,
informationCollector: (StringBuffer information) {
information.writeln('The following RenderObject was being processed when the exception was fired:');
information.writeln(' ${toStringShallow(joiner: '\n ')}');
final List<String> descendants = <String>[];
const int maxDepth = 5;
int depth = 0;
const int maxLines = 25;
int lines = 0;
void visitor(RenderObject child) {
if (lines < maxLines) {
depth += 1;
descendants.add('${" " * depth}$child');
if (depth < maxDepth)
child.visitChildren(visitor);
depth -= 1;
} else if (lines == maxLines) {
descendants.add(' ...(descendants list truncated after $lines lines)');
}
lines += 1;
}
visitChildren(visitor);
if (lines > 1) {
information.writeln('This RenderObject had the following descendants (showing up to depth $maxDepth):');
} else if (descendants.length == 1) {
information.writeln('This RenderObject had the following child:');
} else {
information.writeln('This RenderObject has no descendants.');
}
information.writeAll(descendants, '\n');
}
));
}
/// Whether [performResize] for this render object is currently running.
///
/// Only valid when asserts are enabled. In release builds, always returns
/// false.
bool get debugDoingThisResize => _debugDoingThisResize;
bool _debugDoingThisResize = false;
/// Whether [performLayout] for this render object is currently running.
///
/// Only valid when asserts are enabled. In release builds, always returns
/// false.
bool get debugDoingThisLayout => _debugDoingThisLayout;
bool _debugDoingThisLayout = false;
/// The render object that is actively computing layout.
///
/// Only valid when asserts are enabled. In release builds, always returns
/// null.
static RenderObject get debugActiveLayout => _debugActiveLayout;
static RenderObject _debugActiveLayout;
/// Whether the parent render object is permitted to use this render object's
/// size.
///
/// Determined by the `parentUsesSize` parameter to [layout].
///
/// Only valid when asserts are enabled. In release builds, always returns
/// null.
bool get debugCanParentUseSize => _debugCanParentUseSize;
bool _debugCanParentUseSize;
bool _debugMutationsLocked = false;
/// Whether tree mutations are currently permitted.
///
/// Only valid when asserts are enabled. In release builds, always returns
/// null.
bool get _debugCanPerformMutations {
bool result;
assert(() {
RenderObject node = this;
while (true) {
if (node._doingThisLayoutWithCallback) {
result = true;
break;
}
if (owner != null && owner._debugAllowMutationsToDirtySubtrees && node._needsLayout) {
result = true;
break;
}
if (node._debugMutationsLocked) {
result = false;
break;
}
if (node.parent is! RenderObject) {
result = true;
break;
}
node = node.parent;
}
return true;
}());
return result;
}
@override
PipelineOwner get owner => super.owner;
@override
void attach(PipelineOwner owner) {
super.attach(owner);
// If the node was dirtied in some way while unattached, make sure to add
// it to the appropriate dirty list now that an owner is available
if (_needsLayout && _relayoutBoundary != null) {
// Don't enter this block if we've never laid out at all;
// scheduleInitialLayout() will handle it
_needsLayout = false;
markNeedsLayout();
}
if (_needsCompositingBitsUpdate) {
_needsCompositingBitsUpdate = false;
markNeedsCompositingBitsUpdate();
}
if (_needsPaint && _layer != null) {
// Don't enter this block if we've never painted at all;
// scheduleInitialPaint() will handle it
_needsPaint = false;
markNeedsPaint();
}
if (_needsSemanticsUpdate && _semanticsConfiguration.isSemanticBoundary) {
// Don't enter this block if we've never updated semantics at all;
// scheduleInitialSemantics() will handle it
_needsSemanticsUpdate = false;
markNeedsSemanticsUpdate();
}
}
/// Whether this render object's layout information is dirty.
///
/// This is only set in debug mode. In general, render objects should not need
/// to condition their runtime behavior on whether they are dirty or not,
/// since they should only be marked dirty immediately prior to being laid
/// out and painted.
///
/// It is intended to be used by tests and asserts.
bool get debugNeedsLayout {
bool result;
assert(() {
result = _needsLayout;
return true;
}());
return result;
}
bool _needsLayout = true;
RenderObject _relayoutBoundary;
bool _doingThisLayoutWithCallback = false;
/// The layout constraints most recently supplied by the parent.
@protected
Constraints get constraints => _constraints;
Constraints _constraints;
/// 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
void debugAssertDoesMeetConstraints();
/// When true, debugAssertDoesMeetConstraints() is currently
/// executing asserts for verifying the consistent behavior of
/// intrinsic dimensions methods.
///
/// This should only be set by debugAssertDoesMeetConstraints()
/// implementations. It is used by tests to selectively ignore
/// custom layout callbacks. It should not be set outside of
/// debugAssertDoesMeetConstraints(), and should not be checked in
/// release mode (where it will always be false).
static bool debugCheckingIntrinsics = false;
bool _debugSubtreeRelayoutRootAlreadyMarkedNeedsLayout() {
if (_relayoutBoundary == null)
return true; // we haven't yet done layout even once, so there's nothing for us to do
RenderObject node = this;
while (node != _relayoutBoundary) {
assert(node._relayoutBoundary == _relayoutBoundary);
assert(node.parent != null);
node = node.parent;
if ((!node._needsLayout) && (!node._debugDoingThisLayout))
return false;
}
assert(node._relayoutBoundary == node);
return true;
}
/// 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.
///
/// ## Background
///
/// Rather than eagerly updating layout information in response to writes into
/// a render object, we instead mark the layout information as dirty, which
/// schedules a visual update. As part of the visual update, the rendering
/// pipeline updates the render object's layout information.
///
/// This mechanism batches the layout work so that multiple sequential writes
/// are coalesced, removing redundant computation.
///
/// If a render object's parent indicates that it uses the size of one of its
/// render object children when computing its layout information, this
/// function, when called for the child, will also mark the parent as needing
/// layout. In that case, since both the parent and the child need to have
/// their layout recomputed, the pipeline owner is only notified about the
/// parent; when the parent is laid out, it will call the child's [layout]
/// method and thus the child will be laid out as well.
///
/// Once [markNeedsLayout] has been called on a render object,
/// [debugNeedsLayout] returns true for that render object until just after
/// the pipeline owner has called [layout] on the render object.
///
/// ## Special cases
///
/// Some subclasses of [RenderObject], notably [RenderBox], have other
/// situations in which the parent needs to be notified if the child is
/// dirtied. Such subclasses override markNeedsLayout and either call
/// `super.markNeedsLayout()`, in the normal case, or call
/// [markParentNeedsLayout], in the case where the parent needs to be laid out
/// as well as the child.
///
/// If [sizedByParent] has changed, called
/// [markNeedsLayoutForSizedByParentChange] instead of [markNeedsLayout].
void markNeedsLayout() {
assert(_debugCanPerformMutations);
if (_needsLayout) {
assert(_debugSubtreeRelayoutRootAlreadyMarkedNeedsLayout());
return;
}
assert(_relayoutBoundary != null);
if (_relayoutBoundary != this) {
markParentNeedsLayout();
} else {
_needsLayout = true;
if (owner != null) {
assert(() {
if (debugPrintMarkNeedsLayoutStacks)
debugPrintStack(label: 'markNeedsLayout() called for $this');
return true;
}());
owner._nodesNeedingLayout.add(this);
owner.requestVisualUpdate();
}
}
}
/// Mark this render object's layout information as dirty, and then defer to
/// the parent.
///
/// This function should only be called from [markNeedsLayout] or
/// [markNeedsLayoutForSizedByParentChange] implementations of subclasses that
/// introduce more reasons for deferring the handling of dirty layout to the
/// parent. See [markNeedsLayout] for details.
///
/// Only call this if [parent] is not null.
@protected
void markParentNeedsLayout() {
_needsLayout = true;
final RenderObject parent = this.parent;
if (!_doingThisLayoutWithCallback) {
parent.markNeedsLayout();
} else {
assert(parent._debugDoingThisLayout);
}
assert(parent == this.parent);
}
/// 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.
///
/// This should be called whenever [sizedByParent] might have changed.
///
/// Only call this if [parent] is not null.
void markNeedsLayoutForSizedByParentChange() {
markNeedsLayout();
markParentNeedsLayout();
}
void _cleanRelayoutBoundary() {
if (_relayoutBoundary != this) {
_relayoutBoundary = null;
_needsLayout = true;
visitChildren((RenderObject child) {
child._cleanRelayoutBoundary();
});
}
}
/// Bootstrap the rendering pipeline by scheduling the very first layout.
///
/// Requires this render object to be attached and that this render object
/// is the root of the render tree.
///
/// See [RenderView] for an example of how this function is used.
void scheduleInitialLayout() {
assert(attached);
assert(parent is! RenderObject);
assert(!owner._debugDoingLayout);
assert(_relayoutBoundary == null);
_relayoutBoundary = this;
assert(() {
_debugCanParentUseSize = false;
return true;
}());
owner._nodesNeedingLayout.add(this);
}
void _layoutWithoutResize() {
assert(_relayoutBoundary == this);
RenderObject debugPreviousActiveLayout;
assert(!_debugMutationsLocked);
assert(!_doingThisLayoutWithCallback);
assert(_debugCanParentUseSize != null);
assert(() {
_debugMutationsLocked = true;
_debugDoingThisLayout = true;
debugPreviousActiveLayout = _debugActiveLayout;
_debugActiveLayout = this;
if (debugPrintLayouts)
debugPrint('Laying out (without resize) $this');
return true;
}());
try {
performLayout();
markNeedsSemanticsUpdate();
} catch (e, stack) {
_debugReportException('performLayout', e, stack);
}
assert(() {
_debugActiveLayout = debugPreviousActiveLayout;
_debugDoingThisLayout = false;
_debugMutationsLocked = false;
return true;
}());
_needsLayout = false;
markNeedsPaint();
}
/// Compute the layout for this render object.
///
/// This method is the main entry point for parents to ask their children to
/// update their layout information. The parent passes a constraints object,
/// which informs the child as which layouts are permissible. The child is
/// required to obey the given constraints.
///
/// If the parent reads information computed during the child's layout, the
/// parent must pass true for parentUsesSize. In that case, the parent will be
/// marked as needing layout whenever the child is marked as needing layout
/// because the parent's layout information depends on the child's layout
/// information. If the parent uses the default value (false) for
/// parentUsesSize, the child can change its layout information (subject to
/// the given constraints) without informing the parent.
///
/// Subclasses should not override [layout] directly. Instead, they should
/// override [performResize] and/or [performLayout]. The [layout] method
/// delegates the actual work to [performResize] and [performLayout].
///
/// The parent's performLayout method should call the [layout] of all its
/// children unconditionally. It is the [layout] method's responsibility (as
/// implemented here) to return early if the child does not need to do any
/// work to update its layout information.
void layout(Constraints constraints, { bool parentUsesSize = false }) {
assert(constraints != null);
assert(constraints.debugAssertIsValid(
isAppliedConstraint: true,
informationCollector: (StringBuffer information) {
final List<String> stack = StackTrace.current.toString().split('\n');
int targetFrame;
final Pattern layoutFramePattern = new RegExp(r'^#[0-9]+ +RenderObject.layout \(');
for (int i = 0; i < stack.length; i += 1) {
if (layoutFramePattern.matchAsPrefix(stack[i]) != null) {
targetFrame = i + 1;
break;
}
}
if (targetFrame != null && targetFrame < stack.length) {
information.writeln(
'These invalid constraints were provided to $runtimeType\'s layout() '
'function by the following function, which probably computed the '
'invalid constraints in question:'
);
final Pattern targetFramePattern = new RegExp(r'^#[0-9]+ +(.+)$');
final Match targetFrameMatch = targetFramePattern.matchAsPrefix(stack[targetFrame]);
if (targetFrameMatch != null && targetFrameMatch.groupCount > 0) {
information.writeln(' ${targetFrameMatch.group(1)}');
} else {
information.writeln(stack[targetFrame]);
}
}
}
));
assert(!_debugDoingThisResize);
assert(!_debugDoingThisLayout);
RenderObject relayoutBoundary;
if (!parentUsesSize || sizedByParent || constraints.isTight || parent is! RenderObject) {
relayoutBoundary = this;
} else {
final RenderObject parent = this.parent;
relayoutBoundary = parent._relayoutBoundary;
}
assert(() {
_debugCanParentUseSize = parentUsesSize;
return true;
}());
if (!_needsLayout && constraints == _constraints && relayoutBoundary == _relayoutBoundary) {
assert(() {
// in case parentUsesSize changed since the last invocation, set size
// to itself, so it has the right internal debug values.
_debugDoingThisResize = sizedByParent;
_debugDoingThisLayout = !sizedByParent;
final RenderObject debugPreviousActiveLayout = _debugActiveLayout;
_debugActiveLayout = this;
debugResetSize();
_debugActiveLayout = debugPreviousActiveLayout;
_debugDoingThisLayout = false;
_debugDoingThisResize = false;
return true;
}());
return;
}
_constraints = constraints;
_relayoutBoundary = relayoutBoundary;
assert(!_debugMutationsLocked);
assert(!_doingThisLayoutWithCallback);
assert(() {
_debugMutationsLocked = true;
if (debugPrintLayouts)
debugPrint('Laying out (${sizedByParent ? "with separate resize" : "with resize allowed"}) $this');
return true;
}());
if (sizedByParent) {
assert(() { _debugDoingThisResize = true; return true; }());
try {
performResize();
assert(() { debugAssertDoesMeetConstraints(); return true; }());
} catch (e, stack) {
_debugReportException('performResize', e, stack);
}
assert(() { _debugDoingThisResize = false; return true; }());
}
RenderObject debugPreviousActiveLayout;
assert(() {
_debugDoingThisLayout = true;
debugPreviousActiveLayout = _debugActiveLayout;
_debugActiveLayout = this;
return true;
}());
try {
performLayout();
markNeedsSemanticsUpdate();
assert(() { debugAssertDoesMeetConstraints(); return true; }());
} catch (e, stack) {
_debugReportException('performLayout', e, stack);
}
assert(() {
_debugActiveLayout = debugPreviousActiveLayout;
_debugDoingThisLayout = false;
_debugMutationsLocked = false;
return true;
}());
_needsLayout = false;
markNeedsPaint();
}
/// 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 checked 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
void debugResetSize() { }
/// Whether the constraints are the only input to the sizing algorithm (in
/// particular, child nodes have no impact).
///
/// Returning false is always correct, but returning true can be more
/// efficient when computing the size of this render object because we don't
/// need to recompute the size if the constraints don't change.
///
/// Typically, subclasses will always return the same value. If the value can
/// change, then, when it does change, the subclass should make sure to call
/// [markNeedsLayoutForSizedByParentChange].
@protected
bool get sizedByParent => false;
/// Updates the render objects size using only the constraints.
///
/// Do not call this function directly: call [layout] instead. This function
/// is called by [layout] when there is actually work to be done by this
/// render object during layout. The layout constraints provided by your
/// parent are available via the [constraints] getter.
///
/// Subclasses that set [sizedByParent] to true should override this method
/// to compute their size.
///
/// This function is called only if [sizedByParent] is true.
@protected
void performResize();
/// Do the work of computing the layout for this render object.
///
/// Do not call this function directly: call [layout] instead. This function
/// is called by [layout] when there is actually work to be done by this
/// render object during layout. The layout constraints provided by your
/// parent are available via the [constraints] getter.
///
/// If [sizedByParent] is true, then this function should not actually change
/// the dimensions of this render object. Instead, that work should be done by
/// [performResize]. If [sizedByParent] is false, then this function should
/// both change the dimensions of this render object and instruct its children
/// to layout.
///
/// In implementing this function, you must call [layout] on each of your
/// children, passing true for parentUsesSize if your layout information is
/// dependent on your child's layout information. Passing true for
/// parentUsesSize ensures that this render object will undergo layout if the
/// child undergoes layout. Otherwise, the child can changes its layout
/// information without informing this render object.
@protected
void performLayout();
/// 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.
///
/// This exists to allow child lists to be built on-demand during layout (e.g.
/// based on the object's size), and to enable nodes to be moved around the
/// tree as this happens (e.g. to handle [GlobalKey] reparenting), while still
/// ensuring that any particular node is only laid out once per frame.
///
/// Calling this function disables a number of assertions that are intended to
/// catch likely bugs. As such, using this function is generally discouraged.
///
/// This function can only be called during layout.
@protected
void invokeLayoutCallback<T extends Constraints>(LayoutCallback<T> callback) {
assert(_debugMutationsLocked);
assert(_debugDoingThisLayout);
assert(!_doingThisLayoutWithCallback);
_doingThisLayoutWithCallback = true;
try {
owner._enableMutationsToDirtySubtrees(() { callback(constraints); });
} finally {
_doingThisLayoutWithCallback = false;
}
}
/// Rotate this render object (not yet implemented).
void rotate({
int oldAngle, // 0..3
int newAngle, // 0..3
Duration time
}) { }
// when the parent has rotated (e.g. when the screen has been turned
// 90 degrees), immediately prior to layout() being called for the
// new dimensions, rotate() is called with the old and new angles.
// The next time paint() is called, the coordinate space will have
// been rotated N quarter-turns clockwise, where:
// N = newAngle-oldAngle
// ...but the rendering is expected to remain the same, pixel for
// pixel, on the output device. Then, the layout() method or
// equivalent will be called.
// PAINTING
/// Whether [paint] for this render object is currently running.
///
/// Only valid when asserts are enabled. In release builds, always returns
/// false.
bool get debugDoingThisPaint => _debugDoingThisPaint;
bool _debugDoingThisPaint = false;
/// The render object that is actively painting.
///
/// Only valid when asserts are enabled. In release builds, always returns
/// null.
static RenderObject get debugActivePaint => _debugActivePaint;
static RenderObject _debugActivePaint;
/// Whether this render object repaints separately from its parent.
///
/// Override this in subclasses to indicate that instances of your class ought
/// to repaint independently. For example, render objects that repaint
/// frequently might want to repaint themselves without requiring their parent
/// to repaint.
///
/// If this getter returns true, the [paintBounds] are applied to this object
/// and all descendants.
///
/// Warning: This getter must not change value over the lifetime of this object.
bool get isRepaintBoundary => false;
/// Called, in checked mode, if [isRepaintBoundary] is true, when either the
/// this render object or its parent attempt to paint.
///
/// This can be used to record metrics about whether the node should actually
/// be a repaint boundary.
void debugRegisterRepaintBoundaryPaint({ bool includedParent = true, bool includedChild = false }) { }
/// Whether this render object always needs compositing.
///
/// Override this in subclasses to indicate that your paint function always
/// creates at least one composited layer. For example, videos should return
/// true if they use hardware decoders.
///
/// You must call [markNeedsCompositingBitsUpdate] if the value of this getter
/// changes. (This is implied when [adoptChild] or [dropChild] are called.)
@protected
bool get alwaysNeedsCompositing => false;
OffsetLayer _layer;
/// The compositing layer that this render object uses to repaint.
///
/// Call only when [isRepaintBoundary] is true and the render object has
/// already painted.
///
/// To access the layer in debug code, even when it might be inappropriate to
/// access it (e.g. because it is dirty), consider [debugLayer].
OffsetLayer get layer {
assert(isRepaintBoundary, 'You can only access RenderObject.layer for render objects that are repaint boundaries.');
assert(!_needsPaint);
return _layer;
}
/// In debug mode, the compositing layer that this render object uses to repaint.
///
/// This getter is intended for debugging purposes only. In release builds, it
/// always returns null. In debug builds, it returns the layer even if the layer
/// is dirty.
///
/// For production code, consider [layer].
OffsetLayer get debugLayer {
OffsetLayer result;
assert(() {
result = _layer;
return true;
}());
return result;
}
bool _needsCompositingBitsUpdate = false; // set to true when a child is added
/// Mark the compositing state for this render object as dirty.
///
/// When the subtree is mutated, we need to recompute our
/// [needsCompositing] bit, and some of our ancestors need to do the
/// same (in case ours changed in a way that will change theirs). To
/// this end, [adoptChild] and [dropChild] call this method, and, as
/// necessary, this method calls the parent's, etc, walking up the
/// tree to mark all the nodes that need updating.
///
/// This method does not schedule a rendering frame, because since
/// it cannot be the case that _only_ the compositing bits changed,
/// something else will have scheduled a frame for us.
void markNeedsCompositingBitsUpdate() {
if (_needsCompositingBitsUpdate)
return;
_needsCompositingBitsUpdate = true;
if (parent is RenderObject) {
final RenderObject parent = this.parent;
if (parent._needsCompositingBitsUpdate)
return;
if (!isRepaintBoundary && !parent.isRepaintBoundary) {
parent.markNeedsCompositingBitsUpdate();
return;
}
}
assert(() {
final AbstractNode parent = this.parent;
if (parent is RenderObject)
return parent._needsCompositing;
return true;
}());
// parent is fine (or there isn't one), but we are dirty
if (owner != null)
owner._nodesNeedingCompositingBitsUpdate.add(this);
}
bool _needsCompositing; // initialised in the constructor
/// Whether we or one of our descendants has a compositing layer.
///
/// Only legal to call after [PipelineOwner.flushLayout] and
/// [PipelineOwner.flushCompositingBits] have been called.
bool get needsCompositing {
assert(!_needsCompositingBitsUpdate); // make sure we don't use this bit when it is dirty
return _needsCompositing;
}
void _updateCompositingBits() {
if (!_needsCompositingBitsUpdate)
return;
final bool oldNeedsCompositing = _needsCompositing;
_needsCompositing = false;
visitChildren((RenderObject child) {
child._updateCompositingBits();
if (child.needsCompositing)
_needsCompositing = true;
});
if (isRepaintBoundary || alwaysNeedsCompositing)
_needsCompositing = true;
if (oldNeedsCompositing != _needsCompositing)
markNeedsPaint();
_needsCompositingBitsUpdate = false;
}
/// Whether this render object's paint information is dirty.
///
/// This is only set in debug mode. In general, render objects should not need
/// to condition their runtime behavior on whether they are dirty or not,
/// since they should only be marked dirty immediately prior to being laid
/// out and painted.
///
/// It is intended to be used by tests and asserts.
///
/// It is possible (and indeed, quite common) for [debugNeedsPaint] to be
/// false and [debugNeedsLayout] to be true. The render object will still be
/// repainted in the next frame when this is the case, because the
/// [markNeedsPaint] method is implicitly called by the framework after a
/// render object is laid out, prior to the paint phase.
bool get debugNeedsPaint {
bool result;
assert(() {
result = _needsPaint;
return true;
}());
return result;
}
bool _needsPaint = true;
/// Mark this render object as having changed its visual appearance.
///
/// Rather than eagerly updating this render object's display list
/// in response to writes, we instead mark the render object as needing to
/// paint, which schedules a visual update. As part of the visual update, the
/// rendering pipeline will give this render object an opportunity to update
/// its display list.
///
/// This mechanism batches the painting work so that multiple sequential
/// writes are coalesced, removing redundant computation.
///
/// Once [markNeedsPaint] has been called on a render object,
/// [debugNeedsPaint] returns true for that render object until just after
/// the pipeline owner has called [paint] on the render object.
///
/// See also:
///
/// * [RepaintBoundary], to scope a subtree of render objects to their own
/// layer, thus limiting the number of nodes that [markNeedsPaint] must mark
/// dirty.
void markNeedsPaint() {
assert(owner == null || !owner.debugDoingPaint);
if (_needsPaint)
return;
_needsPaint = true;
if (isRepaintBoundary) {
assert(() {
if (debugPrintMarkNeedsPaintStacks)
debugPrintStack(label: 'markNeedsPaint() called for $this');
return true;
}());
// If we always have our own layer, then we can just repaint
// ourselves without involving any other nodes.
assert(_layer != null);
if (owner != null) {
owner._nodesNeedingPaint.add(this);
owner.requestVisualUpdate();
}
} else if (parent is RenderObject) {
// We don't have our own layer; one of our ancestors will take
// care of updating the layer we're in and when they do that
// we'll get our paint() method called.
assert(_layer == null);
final RenderObject parent = this.parent;
parent.markNeedsPaint();
assert(parent == this.parent);
} else {
assert(() {
if (debugPrintMarkNeedsPaintStacks)
debugPrintStack(label: 'markNeedsPaint() called for $this (root of render tree)');
return true;
}());
// If we're the root of the render tree (probably a RenderView),
// then we have to paint ourselves, since nobody else can paint
// us. We don't add ourselves to _nodesNeedingPaint in this
// case, because the root is always told to paint regardless.
if (owner != null)
owner.requestVisualUpdate();
}
}
// Called when flushPaint() tries to make us paint but our layer is detached.
// To make sure that our subtree is repainted when it's finally reattached,
// even in the case where some ancestor layer is itself never marked dirty, we
// have to mark our entire detached subtree as dirty and needing to be
// repainted. That way, we'll eventually be repainted.
void _skippedPaintingOnLayer() {
assert(attached);
assert(isRepaintBoundary);
assert(_needsPaint);
assert(_layer != null);
assert(!_layer.attached);
AbstractNode ancestor = parent;
while (ancestor is RenderObject) {
final RenderObject node = ancestor;
if (node.isRepaintBoundary) {
if (node._layer == null)
break; // looks like the subtree here has never been painted. let it handle itself.
if (node._layer.attached)
break; // it's the one that detached us, so it's the one that will decide to repaint us.
node._needsPaint = true;
}
ancestor = node.parent;
}
}
/// Bootstrap the rendering pipeline by scheduling the very first paint.
///
/// Requires that this render object is attached, is the root of the render
/// tree, and has a composited layer.
///
/// See [RenderView] for an example of how this function is used.
void scheduleInitialPaint(ContainerLayer rootLayer) {
assert(rootLayer.attached);
assert(attached);
assert(parent is! RenderObject);
assert(!owner._debugDoingPaint);
assert(isRepaintBoundary);
assert(_layer == null);
_layer = rootLayer;
assert(_needsPaint);
owner._nodesNeedingPaint.add(this);
}
/// Replace the layer. This is only valid for the root of a render
/// object subtree (whatever object [scheduleInitialPaint] was
/// called on).
///
/// This might be called if, e.g., the device pixel ratio changed.
void replaceRootLayer(OffsetLayer rootLayer) {
assert(rootLayer.attached);
assert(attached);
assert(parent is! RenderObject);
assert(!owner._debugDoingPaint);
assert(isRepaintBoundary);
assert(_layer != null); // use scheduleInitialPaint the first time
_layer.detach();
_layer = rootLayer;
markNeedsPaint();
}
void _paintWithContext(PaintingContext context, Offset offset) {
assert(() {
if (_debugDoingThisPaint) {
throw new FlutterError(
'Tried to paint a RenderObject reentrantly.\n'
'The following RenderObject was already being painted when it was '
'painted again:\n'
' ${toStringShallow(joiner: "\n ")}\n'
'Since this typically indicates an infinite recursion, it is '
'disallowed.'
);
}
return true;
}());
// If we still need layout, then that means that we were skipped in the
// layout phase and therefore don't need painting. We might not know that
// yet (that is, our layer might not have been detached yet), because the
// same node that skipped us in layout is above us in the tree (obviously)
// and therefore may not have had a chance to paint yet (since the tree
// paints in reverse order). In particular this will happen if they have
// a different layer, because there's a repaint boundary between us.
if (_needsLayout)
return;
assert(() {
if (_needsCompositingBitsUpdate) {
throw new FlutterError(
'Tried to paint a RenderObject before its compositing bits were '
'updated.\n'
'The following RenderObject was marked as having dirty compositing '
'bits at the time that it was painted:\n'
' ${toStringShallow(joiner: "\n ")}\n'
'A RenderObject that still has dirty compositing bits cannot be '
'painted because this indicates that the tree has not yet been '
'properly configured for creating the layer tree.\n'
'This usually indicates an error in the Flutter framework itself.'
);
}
return true;
}());
RenderObject debugLastActivePaint;
assert(() {
_debugDoingThisPaint = true;
debugLastActivePaint = _debugActivePaint;
_debugActivePaint = this;
assert(!isRepaintBoundary || _layer != null);
return true;
}());
_needsPaint = false;
try {
paint(context, offset);
assert(!_needsLayout); // check that the paint() method didn't mark us dirty again
assert(!_needsPaint); // check that the paint() method didn't mark us dirty again
} catch (e, stack) {
_debugReportException('paint', e, stack);
}
assert(() {
debugPaint(context, offset);
_debugActivePaint = debugLastActivePaint;
_debugDoingThisPaint = false;
return true;
}());
}
/// An estimate of the bounds within which this render object will paint.
/// Useful for debugging flags such as [debugPaintLayerBordersEnabled].
///
/// These are also the bounds used by [showOnScreen] to make a [RenderObject]
/// visible on screen.
Rect get paintBounds;
/// Override this method to paint debugging information.
@protected
void debugPaint(PaintingContext context, Offset offset) { }
/// Paint this render object into the given context at the given offset.
///
/// Subclasses should override this method to provide a visual appearance
/// for themselves. The render object's local coordinate system is
/// axis-aligned with the coordinate system of the context's canvas and the
/// render object's local origin (i.e, x=0 and y=0) is placed at the given
/// offset in the context's canvas.
///
/// Do not call this function directly. If you wish to paint yourself, call
/// [markNeedsPaint] instead to schedule a call to this function. If you wish
/// to paint one of your children, call [PaintingContext.paintChild] on the
/// given `context`.
///
/// When painting one of your children (via a paint child function on the
/// given context), the current canvas held by the context might change
/// because draw operations before and after painting children might need to
/// be recorded on separate compositing layers.
void paint(PaintingContext context, Offset offset) { }
/// Applies the transform that would be applied when painting the given child
/// to the given matrix.
///
/// Used by coordinate conversion functions to translate coordinates local to
/// one render object into coordinates local to another render object.
void applyPaintTransform(covariant RenderObject child, Matrix4 transform) {
assert(child.parent == this);
}
/// Applies the paint transform up the tree to `ancestor`.
///
/// Returns a matrix that maps the local paint coordinate system to the
/// coordinate system of `ancestor`.
///
/// If `ancestor` is null, this method returns a matrix that maps from the
/// local paint coordinate system to the coordinate system of the
/// [PipelineOwner.rootNode]. For the render tree owner by the
/// [RendererBinding] (i.e. for the main render tree displayed on the device)
/// this means that this method maps to the global coordinate system in
/// logical pixels. To get physical pixels, use [applyPaintTransform] from the
/// [RenderView] to further transform the coordinate.
Matrix4 getTransformTo(RenderObject ancestor) {
assert(attached);
if (ancestor == null) {
final AbstractNode rootNode = owner.rootNode;
if (rootNode is RenderObject)
ancestor = rootNode;
}
final List<RenderObject> renderers = <RenderObject>[];
for (RenderObject renderer = this; renderer != ancestor; renderer = renderer.parent) {
assert(renderer != null); // Failed to find ancestor in parent chain.
renderers.add(renderer);
}
final Matrix4 transform = new Matrix4.identity();
for (int index = renderers.length - 1; index > 0; index -= 1)
renderers[index].applyPaintTransform(renderers[index - 1], transform);
return transform;
}
/// 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.
///
/// Returns null if the child would not be clipped.
///
/// This is used in the semantics phase to avoid including children
/// that are not physically visible.
Rect describeApproximatePaintClip(covariant RenderObject child) => null;
/// Returns a rect in this object's coordinate system that describes
/// which [SemanticsNode]s produced by the `child` should be included in the
/// semantics tree. [SemanticsNode]s from the `child` that are positioned
/// outside of this rect will be dropped. Child [SemanticsNode]s that are
/// positioned inside this rect, but outside of [describeApproximatePaintClip]
/// will be included in the tree marked as hidden. Child [SemanticsNode]s
/// that are inside of both rect will be included in the tree as regular
/// nodes.
///
/// This method only returns a non-null value if the semantics clip rect
/// is different from the rect returned by [describeApproximatePaintClip].
/// If the semantics clip rect and the paint clip rect are the same, this
/// method returns null.
///
/// A viewport would typically implement this method to include semantic nodes
/// in the semantics tree that are currently hidden just before the leading
/// or just after the trailing edge. These nodes have to be included in the
/// semantics tree to implement implicit accessibility scrolling on iOS where
/// the viewport scrolls implicitly when moving the accessibility focus from
/// a the last visible node in the viewport to the first hidden one.
Rect describeSemanticsClip(covariant RenderObject child) => null;
// SEMANTICS
/// Bootstrap the semantics reporting mechanism by marking this node
/// as needing a semantics update.
///
/// Requires that this render object is attached, and is the root of
/// the render tree.
///
/// See [RendererBinding] for an example of how this function is used.
void scheduleInitialSemantics() {
assert(attached);
assert(parent is! RenderObject);
assert(!owner._debugDoingSemantics);
assert(_semantics == null);
assert(_needsSemanticsUpdate);
assert(owner._semanticsOwner != null);
owner._nodesNeedingSemantics.add(this);
owner.requestVisualUpdate();
}
/// Report the semantics of this node, for example for accessibility purposes.
///
/// This method should be overridden by subclasses that have interesting
/// semantic information.
///
/// The given [SemanticsConfiguration] object is mutable and should be
/// annotated in a manner that describes the current state. No reference
/// should be kept to that object; mutating it outside of the context of the
/// [describeSemanticsConfiguration] call (for example as a result of
/// asynchronous computation) will at best have no useful effect and at worse
/// will cause crashes as the data will be in an inconsistent state.
///
/// ## Sample code
///
/// The following snippet will describe the node as a button that responds to
/// tap actions.
///
/// ```dart
/// abstract class SemanticButtonRenderObject extends RenderObject {
/// @override
/// void describeSemanticsConfiguration(SemanticsConfiguration config) {
/// super.describeSemanticsConfiguration(config);
/// config
/// ..onTap = _handleTap
/// ..label = 'I am a button'
/// ..isButton = true;
/// }
///
/// void _handleTap() {
/// // Do something.
/// }
/// }
/// ```
@protected
void describeSemanticsConfiguration(SemanticsConfiguration config) {
// Nothing to do by default.
}
/// Sends a [SemanticsEvent] associated with this render object's [SemanticsNode].
///
/// If this render object has no semantics information, the first parent
/// render object with a non-null semantic node is used.
///
/// If semantics are disabled, no events are dispatched.
///
/// See [SemanticsNode.sendEvent] for a full description of the behavior.
void sendSemanticsEvent(SemanticsEvent semanticsEvent) {
if (owner.semanticsOwner == null)
return;
if (_semantics != null) {
_semantics.sendEvent(semanticsEvent);
} else if (parent != null) {
final RenderObject renderParent = parent;
renderParent.sendSemanticsEvent(semanticsEvent);
}
}
// Use [_semanticsConfiguration] to access.
SemanticsConfiguration _cachedSemanticsConfiguration;
SemanticsConfiguration get _semanticsConfiguration {
if (_cachedSemanticsConfiguration == null) {
_cachedSemanticsConfiguration = new SemanticsConfiguration();
describeSemanticsConfiguration(_cachedSemanticsConfiguration);
}
return _cachedSemanticsConfiguration;
}
/// The bounding box, in the local coordinate system, of this
/// object, for accessibility purposes.
Rect get semanticBounds;
bool _needsSemanticsUpdate = true;
SemanticsNode _semantics;
/// The semantics of this render object.
///
/// Exposed only for testing and debugging. To learn about the semantics of
/// render objects in production, obtain a [SemanticsHandle] from
/// [PipelineOwner.ensureSemantics].
///
/// Only valid when asserts are enabled. In release builds, always returns
/// null.
SemanticsNode get debugSemantics {
SemanticsNode result;
assert(() {
result = _semantics;
return true;
}());
return result;
}
/// Removes all semantics from this render object and its descendants.
///
/// Should only be called on objects whose [parent] is not a [RenderObject].
///
/// Override this method if you instantiate new [SemanticsNode]s in an
/// overridden [assembleSemanticsNode] method, to dispose of those nodes.
@mustCallSuper
void clearSemantics() {
_needsSemanticsUpdate = true;
_semantics = null;
visitChildren((RenderObject child) {
child.clearSemantics();
});
}
/// Mark this node as needing an update to its semantics description.
///
/// This must be called whenever the semantics configuration of this
/// [RenderObject] as annotated by [describeSemanticsConfiguration] changes in
/// any way to update the semantics tree.
void markNeedsSemanticsUpdate() {
assert(!attached || !owner._debugDoingSemantics);
if (!attached || owner._semanticsOwner == null) {
_cachedSemanticsConfiguration = null;
return;
}
// Dirty the semantics tree starting at `this` until we have reached a
// RenderObject that is a semantics boundary. All semantics past this
// RenderObject are still up-to date. Therefore, we will later only rebuild
// the semantics subtree starting at the identified semantics boundary.
final bool wasSemanticsBoundary = _semantics != null && _cachedSemanticsConfiguration?.isSemanticBoundary == true;
_cachedSemanticsConfiguration = null;
bool isEffectiveSemanticsBoundary = _semanticsConfiguration.isSemanticBoundary && wasSemanticsBoundary;
RenderObject node = this;
while (!isEffectiveSemanticsBoundary && node.parent is RenderObject) {
if (node != this && node._needsSemanticsUpdate)
break;
node._needsSemanticsUpdate = true;
node = node.parent;
isEffectiveSemanticsBoundary = node._semanticsConfiguration.isSemanticBoundary;
if (isEffectiveSemanticsBoundary && node._semantics == null) {
// We have reached a semantics boundary that doesn't own a semantics node.
// That means the semantics of this branch are currently blocked and will
// not appear in the semantics tree. We can abort the walk here.
return;
}
}
if (node != this && _semantics != null && _needsSemanticsUpdate) {
// If `this` node has already been added to [owner._nodesNeedingSemantics]
// remove it as it is no longer guaranteed that its semantics
// node will continue to be in the tree. If it still is in the tree, the
// ancestor `node` added to [owner._nodesNeedingSemantics] at the end of
// this block will ensure that the semantics of `this` node actually gets
// updated.
// (See semantics_10_test.dart for an example why this is required).
owner._nodesNeedingSemantics.remove(this);
}
if (!node._needsSemanticsUpdate) {
node._needsSemanticsUpdate = true;
if (owner != null) {
assert(node._semanticsConfiguration.isSemanticBoundary || node.parent is! RenderObject);
owner._nodesNeedingSemantics.add(node);
owner.requestVisualUpdate();
}
}
}
/// Updates the semantic information of the render object.
void _updateSemantics() {
assert(_semanticsConfiguration.isSemanticBoundary || parent is! RenderObject);
final _SemanticsFragment fragment = _getSemanticsForParent(
mergeIntoParent: _semantics?.parent?.isPartOfNodeMerging ?? false,
);
assert(fragment is _InterestingSemanticsFragment);
final _InterestingSemanticsFragment interestingFragment = fragment;
final SemanticsNode node = interestingFragment.compileChildren(
parentSemanticsClipRect: _semantics?.parentSemanticsClipRect,
parentPaintClipRect: _semantics?.parentPaintClipRect,
).single;
// Fragment only wants to add this node's SemanticsNode to the parent.
assert(interestingFragment.config == null && node == _semantics);
}
/// Returns the semantics that this node would like to add to its parent.
_SemanticsFragment _getSemanticsForParent({
@required bool mergeIntoParent,
}) {
assert(mergeIntoParent != null);
final SemanticsConfiguration config = _semanticsConfiguration;
bool dropSemanticsOfPreviousSiblings = config.isBlockingSemanticsOfPreviouslyPaintedNodes;
final bool producesForkingFragment = !config.hasBeenAnnotated && !config.isSemanticBoundary;
final List<_InterestingSemanticsFragment> fragments = <_InterestingSemanticsFragment>[];
final Set<_InterestingSemanticsFragment> toBeMarkedExplicit = new Set<_InterestingSemanticsFragment>();
final bool childrenMergeIntoParent = mergeIntoParent || config.isMergingSemanticsOfDescendants;
visitChildrenForSemantics((RenderObject renderChild) {
final _SemanticsFragment fragment = renderChild._getSemanticsForParent(
mergeIntoParent: childrenMergeIntoParent,
);
if (fragment.dropsSemanticsOfPreviousSiblings) {
fragments.clear();
toBeMarkedExplicit.clear();
if (!config.isSemanticBoundary)
dropSemanticsOfPreviousSiblings = true;
}
// Figure out which child fragments are to be made explicit.
for (_InterestingSemanticsFragment fragment in fragment.interestingFragments) {
fragments.add(fragment);
fragment.addAncestor(this);
fragment.addTags(config.tagsForChildren);
if (config.explicitChildNodes || parent is! RenderObject) {
fragment.markAsExplicit();
continue;
}
if (!fragment.hasConfigForParent || producesForkingFragment)
continue;
if (!config.isCompatibleWith(fragment.config))
toBeMarkedExplicit.add(fragment);
for (_InterestingSemanticsFragment siblingFragment in fragments.sublist(0, fragments.length - 1)) {
if (!fragment.config.isCompatibleWith(siblingFragment.config)) {
toBeMarkedExplicit.add(fragment);
toBeMarkedExplicit.add(siblingFragment);
}
}
}
});
for (_InterestingSemanticsFragment fragment in toBeMarkedExplicit)
fragment.markAsExplicit();
_needsSemanticsUpdate = false;
_SemanticsFragment result;
if (parent is! RenderObject) {
assert(!config.hasBeenAnnotated);
assert(!mergeIntoParent);
result = new _RootSemanticsFragment(
owner: this,
dropsSemanticsOfPreviousSiblings: dropSemanticsOfPreviousSiblings,
);
} else if (producesForkingFragment) {
result = new _ContainerSemanticsFragment(
dropsSemanticsOfPreviousSiblings: dropSemanticsOfPreviousSiblings,
);
} else {
result = new _SwitchableSemanticsFragment(
config: config,
mergeIntoParent: mergeIntoParent,
owner: this,
dropsSemanticsOfPreviousSiblings: dropSemanticsOfPreviousSiblings,
);
if (config.isSemanticBoundary) {
final _SwitchableSemanticsFragment fragment = result;
fragment.markAsExplicit();
}
}
result.addAll(fragments);
return result;
}
/// Called when collecting the semantics of this node.
///
/// The implementation has to return the children in paint order skipping all
/// children that are not semantically relevant (e.g. because they are
/// invisible).
///
/// The default implementation mirrors the behavior of
/// [visitChildren()] (which is supposed to walk all the children).
void visitChildrenForSemantics(RenderObjectVisitor visitor) {
visitChildren(visitor);
}
/// Assemble the [SemanticsNode] for this [RenderObject].
///
/// If [isSemanticBoundary] is true, this method is called with the `node`
/// created for this [RenderObject], the `config` to be applied to that node
/// and the `children` [SemanticNode]s that descendants of this RenderObject
/// have generated.
///
/// By default, the method will annotate `node` with `config` and add the
/// `children` to it.
///
/// Subclasses can override this method to add additional [SemanticsNode]s
/// to the tree. If new [SemanticsNode]s are instantiated in this method
/// they must be disposed in [clearSemantics].
void assembleSemanticsNode(
SemanticsNode node,
SemanticsConfiguration config,
Iterable<SemanticsNode> children,
) {
assert(node == _semantics);
node.updateWith(config: config, childrenInInversePaintOrder: children);
}
// EVENTS
/// Override this method to handle pointer events that hit this render object.
@override
void handleEvent(PointerEvent event, covariant HitTestEntry entry) { }
// HIT TESTING
// RenderObject subclasses are expected to have a method like the following
// (with the signature being whatever passes for coordinates for this
// particular class):
//
// bool hitTest(HitTestResult result, { Offset position }) {
// // If the given position is not inside this node, then return false.
// // Otherwise:
// // For each child that intersects the position, in z-order starting from
// // the top, call hitTest() for that child, passing it /result/, and the
// // coordinates converted to the child's coordinate origin, and stop at
// // the first child that returns true.
// // Then, add yourself to /result/, and return true.
// }
//
// If you add yourself to /result/ and still return false, then that means you
// will see events but so will objects below you.
/// Returns a human understandable name.
@override
String toStringShort() {
String header = describeIdentity(this);
if (_relayoutBoundary != null && _relayoutBoundary != this) {
int count = 1;
RenderObject target = parent;
while (target != null && target != _relayoutBoundary) {
target = target.parent;
count += 1;
}
header += ' relayoutBoundary=up$count';
}
if (_needsLayout)
header += ' NEEDS-LAYOUT';
if (_needsPaint)
header += ' NEEDS-PAINT';
if (!attached)
header += ' DETACHED';
return header;
}
@override
String toString({ DiagnosticLevel minLevel }) => toStringShort();
/// 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.
@override
String toStringDeep({
String prefixLineOne = '',
String prefixOtherLines = '',
DiagnosticLevel minLevel = DiagnosticLevel.debug,
}) {
RenderObject debugPreviousActiveLayout;
assert(() {
debugPreviousActiveLayout = _debugActiveLayout;
_debugActiveLayout = null;
return true;
}());
final String result = super.toStringDeep(
prefixLineOne: prefixLineOne,
prefixOtherLines: prefixOtherLines,
minLevel: minLevel,
);
assert(() {
_debugActiveLayout = debugPreviousActiveLayout;
return true;
}());
return result;
}
/// Returns a one-line detailed description of the render object.
/// This description is often somewhat long.
///
/// This includes the same information for this RenderObject as given by
/// [toStringDeep], but does not recurse to any children.
@override
String toStringShallow({
String joiner = '; ',
DiagnosticLevel minLevel = DiagnosticLevel.debug,
}) {
RenderObject debugPreviousActiveLayout;
assert(() {
debugPreviousActiveLayout = _debugActiveLayout;
_debugActiveLayout = null;
return true;
}());
final String result = super.toStringShallow(joiner: joiner, minLevel: minLevel);
assert(() {
_debugActiveLayout = debugPreviousActiveLayout;
return true;
}());
return result;
}
@protected
@override
void debugFillProperties(DiagnosticPropertiesBuilder properties) {
properties.add(new DiagnosticsProperty<dynamic>('creator', debugCreator, defaultValue: null, level: DiagnosticLevel.debug));
properties.add(new DiagnosticsProperty<ParentData>('parentData', parentData, tooltip: _debugCanParentUseSize == true ? 'can use size' : null, missingIfNull: true));
properties.add(new DiagnosticsProperty<Constraints>('constraints', constraints, missingIfNull: true));
// don't access it via the "layer" getter since that's only valid when we don't need paint
properties.add(new DiagnosticsProperty<OffsetLayer>('layer', _layer, defaultValue: null));
properties.add(new DiagnosticsProperty<SemanticsNode>('semantics node', _semantics, defaultValue: null));
properties.add(new FlagProperty(
'isBlockingSemanticsOfPreviouslyPaintedNodes',
value: _semanticsConfiguration.isBlockingSemanticsOfPreviouslyPaintedNodes,
ifTrue: 'blocks semantics of earlier render objects below the common boundary',
));
properties.add(new FlagProperty('isSemanticBoundary', value: _semanticsConfiguration.isSemanticBoundary, ifTrue: 'semantic boundary'));
}
@override
List<DiagnosticsNode> debugDescribeChildren() => <DiagnosticsNode>[];
/// Attempt to make (a portion of) this or a descendant [RenderObject] visible
/// on screen.
///
/// If `descendant` is provided, that [RenderObject] is made visible. If
/// `descendant` is omitted, this [RenderObject] is made visible.
///
/// The optional `rect` parameter describes which area of that [RenderObject]
/// should be shown on screen. If `rect` is null, the entire
/// [RenderObject] (as defined by its [paintBounds]) will be revealed. The
/// `rect` parameter is interpreted relative to the coordinate system of
/// `descendant` if that argument is provided and relative to this
/// [RenderObject] otherwise.
///
/// The `duration` parameter can be set to a non-zero value to bring the
/// target object on screen in an animation defined by `curve`.
void showOnScreen({
RenderObject descendant,
Rect rect,
Duration duration = Duration.zero,
Curve curve = Curves.ease,
}) {
if (parent is RenderObject) {
final RenderObject renderParent = parent;
renderParent.showOnScreen(
descendant: descendant ?? this,
rect: rect,
duration: duration,
curve: curve,
);
}
}
}
/// Generic mixin for render objects with one child.
///
/// Provides a child model for a render object subclass that has a unique child.
abstract class RenderObjectWithChildMixin<ChildType extends RenderObject> extends RenderObject {
// This class is intended to be used as a mixin, and should not be
// extended directly.
factory RenderObjectWithChildMixin._() => null;
/// Checks whether the given render object has the correct [runtimeType] to be
/// a child of this render object.
///
/// Does nothing if assertions are disabled.
///
/// Always returns true.
bool debugValidateChild(RenderObject child) {
assert(() {
if (child is! ChildType) {
throw new FlutterError(
'A $runtimeType expected a child of type $ChildType but received a '
'child of type ${child.runtimeType}.\n'
'RenderObjects expect specific types of children because they '
'coordinate with their children during layout and paint. For '
'example, a RenderSliver cannot be the child of a RenderBox because '
'a RenderSliver does not understand the RenderBox layout protocol.\n'
'\n'
'The $runtimeType that expected a $ChildType child was created by:\n'
' $debugCreator\n'
'\n'
'The ${child.runtimeType} that did not match the expected child type '
'was created by:\n'
' ${child.debugCreator}\n'
);
}
return true;
}());
return true;
}
ChildType _child;
/// The render object's unique child
ChildType get child => _child;
set child(ChildType value) {
if (_child != null)
dropChild(_child);
_child = value;
if (_child != null)
adoptChild(_child);
}
@override
void attach(PipelineOwner owner) {
super.attach(owner);
if (_child != null)
_child.attach(owner);
}
@override
void detach() {
super.detach();
if (_child != null)
_child.detach();
}
@override
void redepthChildren() {
if (_child != null)
redepthChild(_child);
}
@override
void visitChildren(RenderObjectVisitor visitor) {
if (_child != null)
visitor(_child);
}
@override
List<DiagnosticsNode> debugDescribeChildren() {
return child != null ? <DiagnosticsNode>[child.toDiagnosticsNode(name: 'child')] : <DiagnosticsNode>[];
}
}
/// Parent data to support a doubly-linked list of children.
abstract class ContainerParentDataMixin<ChildType extends RenderObject> extends ParentData {
// This class is intended to be used as a mixin, and should not be
// extended directly.
factory ContainerParentDataMixin._() => null;
/// The previous sibling in the parent's child list.
ChildType previousSibling;
/// The next sibling in the parent's child list.
ChildType nextSibling;
/// Clear the sibling pointers.
@override
void detach() {
super.detach();
if (previousSibling != null) {
final ContainerParentDataMixin<ChildType> previousSiblingParentData = previousSibling.parentData;
assert(previousSibling != this);
assert(previousSiblingParentData.nextSibling == this);
previousSiblingParentData.nextSibling = nextSibling;
}
if (nextSibling != null) {
final ContainerParentDataMixin<ChildType> nextSiblingParentData = nextSibling.parentData;
assert(nextSibling != this);
assert(nextSiblingParentData.previousSibling == this);
nextSiblingParentData.previousSibling = previousSibling;
}
previousSibling = null;
nextSibling = null;
}
}
/// Generic mixin for render objects with a list of children.
///
/// Provides a child model for a render object subclass that has a doubly-linked
/// list of children.
abstract class ContainerRenderObjectMixin<ChildType extends RenderObject, ParentDataType extends ContainerParentDataMixin<ChildType>> extends RenderObject {
// This class is intended to be used as a mixin, and should not be
// extended directly.
factory ContainerRenderObjectMixin._() => null;
bool _debugUltimatePreviousSiblingOf(ChildType child, { ChildType equals }) {
ParentDataType childParentData = child.parentData;
while (childParentData.previousSibling != null) {
assert(childParentData.previousSibling != child);
child = childParentData.previousSibling;
childParentData = child.parentData;
}
return child == equals;
}
bool _debugUltimateNextSiblingOf(ChildType child, { ChildType equals }) {
ParentDataType childParentData = child.parentData;
while (childParentData.nextSibling != null) {
assert(childParentData.nextSibling != child);
child = childParentData.nextSibling;
childParentData = child.parentData;
}
return child == equals;
}
int _childCount = 0;
/// The number of children.
int get childCount => _childCount;
/// Checks whether the given render object has the correct [runtimeType] to be
/// a child of this render object.
///
/// Does nothing if assertions are disabled.
///
/// Always returns true.
bool debugValidateChild(RenderObject child) {
assert(() {
if (child is! ChildType) {
throw new FlutterError(
'A $runtimeType expected a child of type $ChildType but received a '
'child of type ${child.runtimeType}.\n'
'RenderObjects expect specific types of children because they '
'coordinate with their children during layout and paint. For '
'example, a RenderSliver cannot be the child of a RenderBox because '
'a RenderSliver does not understand the RenderBox layout protocol.\n'
'\n'
'The $runtimeType that expected a $ChildType child was created by:\n'
' $debugCreator\n'
'\n'
'The ${child.runtimeType} that did not match the expected child type '
'was created by:\n'
' ${child.debugCreator}\n'
);
}
return true;
}());
return true;
}
ChildType _firstChild;
ChildType _lastChild;
void _insertIntoChildList(ChildType child, { ChildType after }) {
final ParentDataType childParentData = child.parentData;
assert(childParentData.nextSibling == null);
assert(childParentData.previousSibling == null);
_childCount += 1;
assert(_childCount > 0);
if (after == null) {
// insert at the start (_firstChild)
childParentData.nextSibling = _firstChild;
if (_firstChild != null) {
final ParentDataType _firstChildParentData = _firstChild.parentData;
_firstChildParentData.previousSibling = child;
}
_firstChild = child;
_lastChild ??= child;
} else {
assert(_firstChild != null);
assert(_lastChild != null);
assert(_debugUltimatePreviousSiblingOf(after, equals: _firstChild));
assert(_debugUltimateNextSiblingOf(after, equals: _lastChild));
final ParentDataType afterParentData = after.parentData;
if (afterParentData.nextSibling == null) {
// insert at the end (_lastChild); we'll end up with two or more children
assert(after == _lastChild);
childParentData.previousSibling = after;
afterParentData.nextSibling = child;
_lastChild = child;
} else {
// insert in the middle; we'll end up with three or more children
// set up links from child to siblings
childParentData.nextSibling = afterParentData.nextSibling;
childParentData.previousSibling = after;
// set up links from siblings to child
final ParentDataType childPreviousSiblingParentData = childParentData.previousSibling.parentData;
final ParentDataType childNextSiblingParentData = childParentData.nextSibling.parentData;
childPreviousSiblingParentData.nextSibling = child;
childNextSiblingParentData.previousSibling = child;
assert(afterParentData.nextSibling == child);
}
}
}
/// Insert child into this render object's child list after the given child.
///
/// If `after` is null, then this inserts the child at the start of the list,
/// and the child becomes the new [firstChild].
void insert(ChildType child, { ChildType after }) {
assert(child != this, 'A RenderObject cannot be inserted into itself.');
assert(after != this, 'A RenderObject cannot simultaneously be both the parent and the sibling of another RenderObject.');
assert(child != after, 'A RenderObject cannot be inserted after itself.');
assert(child != _firstChild);
assert(child != _lastChild);
adoptChild(child);
_insertIntoChildList(child, after: after);
}
/// Append child to the end of this render object's child list.
void add(ChildType child) {
insert(child, after: _lastChild);
}
/// Add all the children to the end of this render object's child list.
void addAll(List<ChildType> children) {
children?.forEach(add);
}
void _removeFromChildList(ChildType child) {
final ParentDataType childParentData = child.parentData;
assert(_debugUltimatePreviousSiblingOf(child, equals: _firstChild));
assert(_debugUltimateNextSiblingOf(child, equals: _lastChild));
assert(_childCount >= 0);
if (childParentData.previousSibling == null) {
assert(_firstChild == child);
_firstChild = childParentData.nextSibling;
} else {
final ParentDataType childPreviousSiblingParentData = childParentData.previousSibling.parentData;
childPreviousSiblingParentData.nextSibling = childParentData.nextSibling;
}
if (childParentData.nextSibling == null) {
assert(_lastChild == child);
_lastChild = childParentData.previousSibling;
} else {
final ParentDataType childNextSiblingParentData = childParentData.nextSibling.parentData;
childNextSiblingParentData.previousSibling = childParentData.previousSibling;
}
childParentData.previousSibling = null;
childParentData.nextSibling = null;
_childCount -= 1;
}
/// Remove this child from the child list.
///
/// Requires the child to be present in the child list.
void remove(ChildType child) {
_removeFromChildList(child);
dropChild(child);
}
/// Remove all their children from this render object's child list.
///
/// More efficient than removing them individually.
void removeAll() {
ChildType child = _firstChild;
while (child != null) {
final ParentDataType childParentData = child.parentData;
final ChildType next = childParentData.nextSibling;
childParentData.previousSibling = null;
childParentData.nextSibling = null;
dropChild(child);
child = next;
}
_firstChild = null;
_lastChild = null;
_childCount = 0;
}
/// Move this child in the child list to be before the given child.
///
/// More efficient than removing and re-adding the child. Requires the child
/// to already be in the child list at some position. Pass null for before to
/// move the child to the end of the child list.
void move(ChildType child, { ChildType after }) {
assert(child != this);
assert(after != this);
assert(child != after);
assert(child.parent == this);
final ParentDataType childParentData = child.parentData;
if (childParentData.previousSibling == after)
return;
_removeFromChildList(child);
_insertIntoChildList(child, after: after);
markNeedsLayout();
}
@override
void attach(PipelineOwner owner) {
super.attach(owner);
ChildType child = _firstChild;
while (child != null) {
child.attach(owner);
final ParentDataType childParentData = child.parentData;
child = childParentData.nextSibling;
}
}
@override
void detach() {
super.detach();
ChildType child = _firstChild;
while (child != null) {
child.detach();
final ParentDataType childParentData = child.parentData;
child = childParentData.nextSibling;
}
}
@override
void redepthChildren() {
ChildType child = _firstChild;
while (child != null) {
redepthChild(child);
final ParentDataType childParentData = child.parentData;
child = childParentData.nextSibling;
}
}
@override
void visitChildren(RenderObjectVisitor visitor) {
ChildType child = _firstChild;
while (child != null) {
visitor(child);
final ParentDataType childParentData = child.parentData;
child = childParentData.nextSibling;
}
}
/// The first child in the child list.
ChildType get firstChild => _firstChild;
/// The last child in the child list.
ChildType get lastChild => _lastChild;
/// The previous child before the given child in the child list.
ChildType childBefore(ChildType child) {
assert(child != null);
assert(child.parent == this);
final ParentDataType childParentData = child.parentData;
return childParentData.previousSibling;
}
/// The next child after the given child in the child list.
ChildType childAfter(ChildType child) {
assert(child != null);
assert(child.parent == this);
final ParentDataType childParentData = child.parentData;
return childParentData.nextSibling;
}
@override
List<DiagnosticsNode> debugDescribeChildren() {
final List<DiagnosticsNode> children = <DiagnosticsNode>[];
if (firstChild != null) {
ChildType child = firstChild;
int count = 1;
while (true) {
children.add(child.toDiagnosticsNode(name: 'child $count'));
if (child == lastChild)
break;
count += 1;
final ParentDataType childParentData = child.parentData;
child = childParentData.nextSibling;
}
}
return children;
}
}
/// Variant of [FlutterErrorDetails] with extra fields for the rendering
/// library.
class FlutterErrorDetailsForRendering extends FlutterErrorDetails {
/// Creates a [FlutterErrorDetailsForRendering] object with the given
/// arguments setting the object's properties.
///
/// The rendering library calls this constructor when catching an exception
/// that will subsequently be reported using [FlutterError.onError].
const FlutterErrorDetailsForRendering({
dynamic exception,
StackTrace stack,
String library,
String context,
this.renderObject,
InformationCollector informationCollector,
bool silent = false
}) : super(
exception: exception,
stack: stack,
library: library,
context: context,
informationCollector: informationCollector,
silent: silent
);
/// The RenderObject that was being processed when the exception was caught.
final RenderObject renderObject;
}
/// Describes the semantics information a [RenderObject] wants to add to its
/// parent.
///
/// It has two notable subclasses:
/// * [_InterestingSemanticsFragment] describing actual semantic information to
/// be added to the parent.
/// * [_ContainerSemanticsFragment]: a container class to transport the semantic
/// information of multiple [_InterestingSemanticsFragment] to a parent.
abstract class _SemanticsFragment {
_SemanticsFragment({@required this.dropsSemanticsOfPreviousSiblings })
: assert (dropsSemanticsOfPreviousSiblings != null);
/// Incorporate the fragments of children into this fragment.
void addAll(Iterable<_InterestingSemanticsFragment> fragments);
/// Whether this fragment wants to make the semantics information of
/// previously painted [RenderObject]s unreachable for accessibility purposes.
///
/// See also:
///
/// * [SemanticsConfiguration.isBlockingSemanticsOfPreviouslyPaintedNodes]
/// describes what semantics are dropped in more detail.
final bool dropsSemanticsOfPreviousSiblings;
/// Returns [_InterestingSemanticsFragment] describing the actual semantic
/// information that this fragment wants to add to the parent.
Iterable<_InterestingSemanticsFragment> get interestingFragments;
}
/// A container used when a [RenderObject] wants to add multiple independent
/// [_InterestingSemanticsFragment] to its parent.
///
/// The [_InterestingSemanticsFragment] to be added to the parent can be
/// obtained via [interestingFragments].
class _ContainerSemanticsFragment extends _SemanticsFragment {
_ContainerSemanticsFragment({ @required bool dropsSemanticsOfPreviousSiblings })
: super(dropsSemanticsOfPreviousSiblings: dropsSemanticsOfPreviousSiblings);
@override
void addAll(Iterable<_InterestingSemanticsFragment> fragments) {
interestingFragments.addAll(fragments);
}
@override
final List<_InterestingSemanticsFragment> interestingFragments = <_InterestingSemanticsFragment>[];
}
/// A [_SemanticsFragment] that describes which concrete semantic information
/// a [RenderObject] wants to add to the [SemanticsNode] of its parent.
///
/// Specifically, it describes which children (as returned by [compileChildren])
/// should be added to the parent's [SemanticsNode] and which [config] should be
/// merged into the parent's [SemanticsNode].
abstract class _InterestingSemanticsFragment extends _SemanticsFragment {
_InterestingSemanticsFragment({
@required RenderObject owner,
@required bool dropsSemanticsOfPreviousSiblings
}) : assert(owner != null),
_ancestorChain = <RenderObject>[owner],
super(dropsSemanticsOfPreviousSiblings: dropsSemanticsOfPreviousSiblings);
/// The [RenderObject] that owns this fragment (and any new [SemanticNode]
/// introduced by it).
RenderObject get owner => _ancestorChain.first;
final List<RenderObject> _ancestorChain;
/// The children to be added to the parent.
Iterable<SemanticsNode> compileChildren({
@required Rect parentSemanticsClipRect,
@required Rect parentPaintClipRect
});
/// The [SemanticsConfiguration] the child wants to merge into the parent's
/// [SemanticsNode] or null if it doesn't want to merge anything.
SemanticsConfiguration get config;
/// Disallows this fragment to merge any configuration into its parent's
/// [SemanticsNode].
///
/// After calling this the fragment will only produce children to be added
/// to the parent and it will return null for [config].
void markAsExplicit();
/// Consume the fragments of children.
///
/// For each provided fragment it will add that fragment's children to
/// this fragment's children (as returned by [compileChildren]) and merge that
/// fragment's [config] into this fragment's [config].
///
/// If a provided fragment should not merge anything into [config] call
/// [markAsExplicit] before passing the fragment to this method.
@override
void addAll(Iterable<_InterestingSemanticsFragment> fragments);
/// Whether this fragment wants to add any semantic information to the parent
/// [SemanticsNode].
bool get hasConfigForParent => config != null;
@override
Iterable<_InterestingSemanticsFragment> get interestingFragments sync* {
yield this;
}
Set<SemanticsTag> _tagsForChildren;
/// Tag all children produced by [compileChildren] with `tags`.
void addTags(Iterable<SemanticsTag> tags) {
if (tags == null || tags.isEmpty)
return;
_tagsForChildren ??= new Set<SemanticsTag>();
_tagsForChildren.addAll(tags);
}
/// Adds the geometric information of `ancestor` to this object.
///
/// Those information are required to properly compute the value for
/// [SemanticsNode.transform], [SemanticsNode.clipRect], and
/// [SemanticsNode.rect].
///
/// Ancestors have to be added in order from [owner] up until the next
/// [RenderObject] that owns a [SemanticsNode] is reached.
void addAncestor(RenderObject ancestor) {
_ancestorChain.add(ancestor);
}
}
/// An [_InterestingSemanticsFragment] that produces the root [SemanticsNode] of
/// the semantics tree.
///
/// The root node is available as the only element in the Iterable returned by
/// [children].
class _RootSemanticsFragment extends _InterestingSemanticsFragment {
_RootSemanticsFragment({
@required RenderObject owner,
@required bool dropsSemanticsOfPreviousSiblings,
}) : super(owner: owner, dropsSemanticsOfPreviousSiblings: dropsSemanticsOfPreviousSiblings);
@override
Iterable<SemanticsNode> compileChildren({Rect parentSemanticsClipRect, Rect parentPaintClipRect}) sync* {
assert(_tagsForChildren == null || _tagsForChildren.isEmpty);
assert(parentSemanticsClipRect == null);
assert(parentPaintClipRect == null);
assert(_ancestorChain.length == 1);
owner._semantics ??= new SemanticsNode.root(
showOnScreen: owner.showOnScreen,
owner: owner.owner.semanticsOwner,
);
final SemanticsNode node = owner._semantics;
assert(MatrixUtils.matrixEquals(node.transform, new Matrix4.identity()));
assert(node.parentSemanticsClipRect == null);
assert(node.parentPaintClipRect == null);
node.rect = owner.semanticBounds;
final List<SemanticsNode> children = <SemanticsNode>[];
for (_InterestingSemanticsFragment fragment in _children) {
assert(fragment.config == null);
children.addAll(fragment.compileChildren(
parentSemanticsClipRect: parentSemanticsClipRect,
parentPaintClipRect: parentPaintClipRect,
));
}
node.updateWith(config: null, childrenInInversePaintOrder: children);
assert(!node.isInvisible);
yield node;
}
@override
SemanticsConfiguration get config => null;
final List<_InterestingSemanticsFragment> _children = <_InterestingSemanticsFragment>[];
@override
void markAsExplicit() {
// nothing to do, we are always explicit.
}
@override
void addAll(Iterable<_InterestingSemanticsFragment> fragments) {
_children.addAll(fragments);
}
}
/// An [_InterestingSemanticsFragment] that can be told to only add explicit
/// [SemanticsNode]s to the parent.
///
/// If [markAsExplicit] was not called before this fragment is added to
/// another fragment it will merge [config] into the parent's [SemanticsNode]
/// and add its [children] to it.
///
/// If [markAsExplicit] was called before adding this fragment to another
/// fragment it will create a new [SemanticsNode]. The newly created node will
/// be annotated with the [SemanticsConfiguration] that - without the call to
/// [markAsExplicit] - would have been merged into the parent's [SemanticsNode].
/// Similarly, the new node will also take over the children that otherwise
/// would have been added to the parent's [SemanticsNode].
///
/// After a call to [markAsExplicit] the only element returned by [children]
/// is the newly created node and [config] will return null as the fragment
/// no longer wants to merge any semantic information into the parent's
/// [SemanticsNode].
class _SwitchableSemanticsFragment extends _InterestingSemanticsFragment {
_SwitchableSemanticsFragment({
@required bool mergeIntoParent,
@required SemanticsConfiguration config,
@required RenderObject owner,
@required bool dropsSemanticsOfPreviousSiblings,
}) : _mergeIntoParent = mergeIntoParent,
_config = config,
assert(mergeIntoParent != null),
assert(config != null),
super(owner: owner, dropsSemanticsOfPreviousSiblings: dropsSemanticsOfPreviousSiblings);
final bool _mergeIntoParent;
SemanticsConfiguration _config;
bool _isConfigWritable = false;
final List<_InterestingSemanticsFragment> _children = <_InterestingSemanticsFragment>[];
@override
Iterable<SemanticsNode> compileChildren({Rect parentSemanticsClipRect, Rect parentPaintClipRect}) sync* {
if (!_isExplicit) {
owner._semantics = null;
for (_InterestingSemanticsFragment fragment in _children) {
assert(_ancestorChain.first == fragment._ancestorChain.last);
fragment._ancestorChain.addAll(_ancestorChain.sublist(1));
yield* fragment.compileChildren(parentSemanticsClipRect: parentSemanticsClipRect, parentPaintClipRect: parentPaintClipRect);
}
return;
}
final _SemanticsGeometry geometry = _needsGeometryUpdate
? new _SemanticsGeometry(parentSemanticsClipRect: parentSemanticsClipRect, parentPaintClipRect: parentPaintClipRect, ancestors: _ancestorChain)
: null;
if (!_mergeIntoParent && (geometry?.dropFromTree == true))
return; // Drop the node, it's not going to be visible.
owner._semantics ??= new SemanticsNode(showOnScreen: owner.showOnScreen);
final SemanticsNode node = owner._semantics
..isMergedIntoParent = _mergeIntoParent
..tags = _tagsForChildren;
if (geometry != null) {
assert(_needsGeometryUpdate);
node
..rect = geometry.rect
..transform = geometry.transform
..parentSemanticsClipRect = geometry.semanticsClipRect
..parentPaintClipRect = geometry.paintClipRect;
if (!_mergeIntoParent && geometry.markAsHidden) {
_ensureConfigIsWritable();
_config.isHidden = true;
}
}
final List<SemanticsNode> children = <SemanticsNode>[];
for (_InterestingSemanticsFragment fragment in _children)
children.addAll(fragment.compileChildren(parentSemanticsClipRect: node.parentSemanticsClipRect, parentPaintClipRect: node.parentPaintClipRect));
if (_config.isSemanticBoundary) {
owner.assembleSemanticsNode(node, _config, children);
} else {
node.updateWith(config: _config, childrenInInversePaintOrder: children);
}
yield node;
}
@override
SemanticsConfiguration get config {
return _isExplicit ? null : _config;
}
@override
void addAll(Iterable<_InterestingSemanticsFragment> fragments) {
for (_InterestingSemanticsFragment fragment in fragments) {
_children.add(fragment);
if (fragment.config == null)
continue;
_ensureConfigIsWritable();
_config.absorb(fragment.config);
}
}
void _ensureConfigIsWritable() {
if (!_isConfigWritable) {
_config = _config.copy();
_isConfigWritable = true;
}
}
bool _isExplicit = false;
@override
void markAsExplicit() {
_isExplicit = true;
}
bool get _needsGeometryUpdate => _ancestorChain.length > 1;
}
/// Helper class that keeps track of the geometry of a [SemanticsNode].
///
/// It is used to annotate a [SemanticsNode] with the current information for
/// [SemanticsNode.rect] and [SemanticsNode.transform].
class _SemanticsGeometry {
/// The `parentClippingRect` may be null if no clip is to be applied.
///
/// The `ancestors` list has to include all [RenderObject] in order that are
/// located between the [SemanticsNode] whose geometry is represented here
/// (first [RenderObject] in the list) and its closest ancestor [RenderObject]
/// that also owns its own [SemanticsNode] (last [RenderObject] in the list).
_SemanticsGeometry({
@required Rect parentSemanticsClipRect,
@required Rect parentPaintClipRect,
@required List<RenderObject> ancestors,
}) {
_computeValues(parentSemanticsClipRect, parentPaintClipRect, ancestors);
}
Rect _paintClipRect;
Rect _semanticsClipRect;
Matrix4 _transform;
Rect _rect;
/// Value for [SemanticsNode.transform].
Matrix4 get transform => _transform;
/// Value for [SemanticsNode.parentSemanticsClipRect].
Rect get semanticsClipRect => _semanticsClipRect;
/// Value for [SemanticsNode.parentPaintClipRect].
Rect get paintClipRect => _paintClipRect;
/// Value for [SemanticsNode.rect].
Rect get rect => _rect;
void _computeValues(Rect parentSemanticsClipRect, Rect parentPaintClipRect, List<RenderObject> ancestors) {
assert(ancestors.length > 1);
_transform = new Matrix4.identity();
_semanticsClipRect = parentSemanticsClipRect;
_paintClipRect = parentPaintClipRect;
for (int index = ancestors.length-1; index > 0; index -= 1) {
final RenderObject parent = ancestors[index];
final RenderObject child = ancestors[index-1];
final Rect parentSemanticsClipRect = parent.describeSemanticsClip(child);
if (parentSemanticsClipRect != null) {
_semanticsClipRect = parentSemanticsClipRect;
_paintClipRect = _intersectRects(_paintClipRect, parent.describeApproximatePaintClip(child));
} else {
_semanticsClipRect = _intersectRects(_semanticsClipRect, parent.describeApproximatePaintClip(child));
}
_semanticsClipRect = _transformRect(_semanticsClipRect, parent, child);
_paintClipRect = _transformRect(_paintClipRect, parent, child);
parent.applyPaintTransform(child, _transform);
}
final RenderObject owner = ancestors.first;
_rect = _semanticsClipRect == null ? owner.semanticBounds : _semanticsClipRect.intersect(owner.semanticBounds);
if (_paintClipRect != null) {
final Rect paintRect = _paintClipRect.intersect(_rect);
_markAsHidden = paintRect.isEmpty && !_rect.isEmpty;
if (!_markAsHidden)
_rect = paintRect;
}
}
/// From parent to child coordinate system.
static Rect _transformRect(Rect rect, RenderObject parent, RenderObject child) {
if (rect == null)
return null;
if (rect.isEmpty)
return Rect.zero;
final Matrix4 transform = new Matrix4.identity();
parent.applyPaintTransform(child, transform);
return MatrixUtils.inverseTransformRect(transform, rect);
}
static Rect _intersectRects(Rect a, Rect b) {
if (a == null)
return b;
if (b == null)
return a;
return a.intersect(b);
}
/// Whether the [SemanticsNode] annotated with the geometric information tracked
/// by this object can be dropped from the semantics tree without losing
/// semantics information.
bool get dropFromTree {
return _rect.isEmpty;
}
/// Whether the [SemanticsNode] annotated with the geometric information
/// tracked by this object should be marked as hidden because it is not
/// visible on screen.
///
/// Hidden elements should still be included in the tree to work around
/// platform limitations (e.g. accessibility scrolling on iOS).
///
/// See also:
///
/// * [SemanticsFlag.isHidden] for the purpose of marking a node as hidden.
bool get markAsHidden => _markAsHidden;
bool _markAsHidden = false;
}