// Copyright 2014 The Flutter 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:ui' as ui; import 'package:flutter/foundation.dart'; import 'package:flutter/gestures.dart'; import 'package:flutter/painting.dart'; import 'package:vector_math/vector_math_64.dart'; import 'debug.dart'; /// Information collected for an annotation that is found in the layer tree. /// /// See also: /// /// * [Layer.findAnnotations], which create and use objects of this class. @immutable class AnnotationEntry<T> { /// Create an entry of found annotation by providing the object and related /// information. const AnnotationEntry({ required this.annotation, required this.localPosition, }) : assert(localPosition != null); /// The annotation object that is found. final T annotation; /// The target location described by the local coordinate space of the /// annotation object. final Offset localPosition; @override String toString() { return '${objectRuntimeType(this, 'AnnotationEntry')}(annotation: $annotation, localPosition: $localPosition)'; } } /// Information collected about a list of annotations that are found in the /// layer tree. /// /// See also: /// /// * [AnnotationEntry], which are members of this class. /// * [Layer.findAllAnnotations], and [Layer.findAnnotations], which create and /// use an object of this class. class AnnotationResult<T> { final List<AnnotationEntry<T>> _entries = <AnnotationEntry<T>>[]; /// Add a new entry to the end of the result. /// /// Usually, entries should be added in order from most specific to least /// specific, typically during an upward walk of the tree. void add(AnnotationEntry<T> entry) => _entries.add(entry); /// An unmodifiable list of [AnnotationEntry] objects recorded. /// /// The first entry is the most specific, typically the one at the leaf of /// tree. Iterable<AnnotationEntry<T>> get entries => _entries; /// An unmodifiable list of annotations recorded. /// /// The first entry is the most specific, typically the one at the leaf of /// tree. /// /// It is similar to [entries] but does not contain other information. Iterable<T> get annotations sync* { for (final AnnotationEntry<T> entry in _entries) yield entry.annotation; } } /// A composited layer. /// /// During painting, the render tree generates a tree of composited layers that /// are uploaded into the engine and displayed by the compositor. This class is /// the base class for all composited layers. /// /// Most layers can have their properties mutated, and layers can be moved to /// different parents. The scene must be explicitly recomposited after such /// changes are made; the layer tree does not maintain its own dirty state. /// /// To composite the tree, create a [SceneBuilder] object, pass it to the /// root [Layer] object's [addToScene] method, and then call /// [SceneBuilder.build] to obtain a [Scene]. A [Scene] can then be painted /// using [dart:ui.FlutterView.render]. /// /// See also: /// /// * [RenderView.compositeFrame], which implements this recomposition protocol /// for painting [RenderObject] trees on the display. abstract class Layer extends AbstractNode with DiagnosticableTreeMixin { /// This layer's parent in the layer tree. /// /// The [parent] of the root node in the layer tree is null. /// /// Only subclasses of [ContainerLayer] can have children in the layer tree. /// All other layer classes are used for leaves in the layer tree. @override ContainerLayer? get parent => super.parent as ContainerLayer?; // Whether this layer has any changes since its last call to [addToScene]. // // Initialized to true as a new layer has never called [addToScene], and is // set to false after calling [addToScene]. The value can become true again // if [markNeedsAddToScene] is called, or when [updateSubtreeNeedsAddToScene] // is called on this layer or on an ancestor layer. // // The values of [_needsAddToScene] in a tree of layers are said to be // _consistent_ if every layer in the tree satisfies the following: // // - If [alwaysNeedsAddToScene] is true, then [_needsAddToScene] is also true. // - If [_needsAddToScene] is true and [parent] is not null, then // `parent._needsAddToScene` is true. // // Typically, this value is set during the paint phase and during compositing. // During the paint phase render objects create new layers and call // [markNeedsAddToScene] on existing layers, causing this value to become // true. After the paint phase the tree may be in an inconsistent state. // During compositing [ContainerLayer.buildScene] first calls // [updateSubtreeNeedsAddToScene] to bring this tree to a consistent state, // then it calls [addToScene], and finally sets this field to false. bool _needsAddToScene = true; /// Mark that this layer has changed and [addToScene] needs to be called. @protected @visibleForTesting void markNeedsAddToScene() { assert( !alwaysNeedsAddToScene, '$runtimeType with alwaysNeedsAddToScene set called markNeedsAddToScene.\n' "The layer's alwaysNeedsAddToScene is set to true, and therefore it should not call markNeedsAddToScene.", ); // Already marked. Short-circuit. if (_needsAddToScene) { return; } _needsAddToScene = true; } /// Mark that this layer is in sync with engine. /// /// This is for debugging and testing purposes only. In release builds /// this method has no effect. @visibleForTesting void debugMarkClean() { assert(() { _needsAddToScene = false; return true; }()); } /// Subclasses may override this to true to disable retained rendering. @protected bool get alwaysNeedsAddToScene => false; /// Whether this or any descendant layer in the subtree needs [addToScene]. /// /// This is for debug and test purpose only. It only becomes valid after /// calling [updateSubtreeNeedsAddToScene]. @visibleForTesting bool? get debugSubtreeNeedsAddToScene { bool? result; assert(() { result = _needsAddToScene; return true; }()); return result; } /// Stores the engine layer created for this layer in order to reuse engine /// resources across frames for better app performance. /// /// This value may be passed to [ui.SceneBuilder.addRetained] to communicate /// to the engine that nothing in this layer or any of its descendants /// changed. The native engine could, for example, reuse the texture rendered /// in a previous frame. The web engine could, for example, reuse the HTML /// DOM nodes created for a previous frame. /// /// This value may be passed as `oldLayer` argument to a "push" method to /// communicate to the engine that a layer is updating a previously rendered /// layer. The web engine could, for example, update the properties of /// previously rendered HTML DOM nodes rather than creating new nodes. @protected ui.EngineLayer? get engineLayer => _engineLayer; /// Sets the engine layer used to render this layer. /// /// Typically this field is set to the value returned by [addToScene], which /// in turn returns the engine layer produced by one of [ui.SceneBuilder]'s /// "push" methods, such as [ui.SceneBuilder.pushOpacity]. @protected set engineLayer(ui.EngineLayer? value) { _engineLayer = value; if (!alwaysNeedsAddToScene) { // The parent must construct a new engine layer to add this layer to, and // so we mark it as needing [addToScene]. // // This is designed to handle two situations: // // 1. When rendering the complete layer tree as normal. In this case we // call child `addToScene` methods first, then we call `set engineLayer` // for the parent. The children will call `markNeedsAddToScene` on the // parent to signal that they produced new engine layers and therefore // the parent needs to update. In this case, the parent is already adding // itself to the scene via [addToScene], and so after it's done, its // `set engineLayer` is called and it clears the `_needsAddToScene` flag. // // 2. When rendering an interior layer (e.g. `OffsetLayer.toImage`). In // this case we call `addToScene` for one of the children but not the // parent, i.e. we produce new engine layers for children but not for the // parent. Here the children will mark the parent as needing // `addToScene`, but the parent does not clear the flag until some future // frame decides to render it, at which point the parent knows that it // cannot retain its engine layer and will call `addToScene` again. if (parent != null && !parent!.alwaysNeedsAddToScene) { parent!.markNeedsAddToScene(); } } } ui.EngineLayer? _engineLayer; /// Traverses the layer subtree starting from this layer and determines whether it needs [addToScene]. /// /// A layer needs [addToScene] if any of the following is true: /// /// - [alwaysNeedsAddToScene] is true. /// - [markNeedsAddToScene] has been called. /// - Any of its descendants need [addToScene]. /// /// [ContainerLayer] overrides this method to recursively call it on its children. @protected @visibleForTesting void updateSubtreeNeedsAddToScene() { _needsAddToScene = _needsAddToScene || alwaysNeedsAddToScene; } /// This layer's next sibling in the parent layer's child list. Layer? get nextSibling => _nextSibling; Layer? _nextSibling; /// This layer's previous sibling in the parent layer's child list. Layer? get previousSibling => _previousSibling; Layer? _previousSibling; @override void dropChild(AbstractNode child) { if (!alwaysNeedsAddToScene) { markNeedsAddToScene(); } super.dropChild(child); } @override void adoptChild(AbstractNode child) { if (!alwaysNeedsAddToScene) { markNeedsAddToScene(); } super.adoptChild(child); } /// Removes this layer from its parent layer's child list. /// /// This has no effect if the layer's parent is already null. @mustCallSuper void remove() { parent?._removeChild(this); } /// Search this layer and its subtree for annotations of type `S` at the /// location described by `localPosition`. /// /// This method is called by the default implementation of [find] and /// [findAllAnnotations]. Override this method to customize how the layer /// should search for annotations, or if the layer has its own annotations to /// add. /// /// The default implementation simply returns `false`, which means neither /// the layer nor its children has annotations, and the annotation search /// is not absorbed either (see below for explanation). /// /// ## About layer annotations /// /// {@template flutter.rendering.Layer.findAnnotations.aboutAnnotations} /// An annotation is an optional object of any type that can be carried with a /// layer. An annotation can be found at a location as long as the owner layer /// contains the location and is walked to. /// /// The annotations are searched by first visiting each child recursively, /// then this layer, resulting in an order from visually front to back. /// Annotations must meet the given restrictions, such as type and position. /// /// The common way for a value to be found here is by pushing an /// [AnnotatedRegionLayer] into the layer tree, or by adding the desired /// annotation by overriding [findAnnotations]. /// {@endtemplate} /// /// ## Parameters and return value /// /// The [result] parameter is where the method outputs the resulting /// annotations. New annotations found during the walk are added to the tail. /// /// The [onlyFirst] parameter indicates that, if true, the search will stop /// when it finds the first qualified annotation; otherwise, it will walk the /// entire subtree. /// /// The return value indicates the opacity of this layer and its subtree at /// this position. If it returns true, then this layer's parent should skip /// the children behind this layer. In other words, it is opaque to this type /// of annotation and has absorbed the search so that its siblings behind it /// are not aware of the search. If the return value is false, then the parent /// might continue with other siblings. /// /// The return value does not affect whether the parent adds its own /// annotations; in other words, if a layer is supposed to add an annotation, /// it will always add it even if its children are opaque to this type of /// annotation. However, the opacity that the parents return might be affected /// by their children, hence making all of its ancestors opaque to this type /// of annotation. @protected bool findAnnotations<S extends Object>( AnnotationResult<S> result, Offset localPosition, { required bool onlyFirst, }) { return false; } /// Search this layer and its subtree for the first annotation of type `S` /// under the point described by `localPosition`. /// /// Returns null if no matching annotations are found. /// /// By default this method simply calls [findAnnotations] with `onlyFirst: /// true` and returns the annotation of the first result. Prefer overriding /// [findAnnotations] instead of this method, because during an annotation /// search, only [findAnnotations] is recursively called, while custom /// behavior in this method is ignored. /// /// ## About layer annotations /// /// {@macro flutter.rendering.Layer.findAnnotations.aboutAnnotations} /// /// See also: /// /// * [findAllAnnotations], which is similar but returns all annotations found /// at the given position. /// * [AnnotatedRegionLayer], for placing values in the layer tree. S? find<S extends Object>(Offset localPosition) { final AnnotationResult<S> result = AnnotationResult<S>(); findAnnotations<S>(result, localPosition, onlyFirst: true); return result.entries.isEmpty ? null : result.entries.first.annotation; } /// Search this layer and its subtree for all annotations of type `S` under /// the point described by `localPosition`. /// /// Returns a result with empty entries if no matching annotations are found. /// /// By default this method simply calls [findAnnotations] with `onlyFirst: /// false` and returns the annotations of its result. Prefer overriding /// [findAnnotations] instead of this method, because during an annotation /// search, only [findAnnotations] is recursively called, while custom /// behavior in this method is ignored. /// /// ## About layer annotations /// /// {@macro flutter.rendering.Layer.findAnnotations.aboutAnnotations} /// /// See also: /// /// * [find], which is similar but returns the first annotation found at the /// given position. /// * [findAllAnnotations], which is similar but returns an /// [AnnotationResult], which contains more information, such as the local /// position of the event related to each annotation, and is equally fast, /// hence is preferred over [findAll]. /// * [AnnotatedRegionLayer], for placing values in the layer tree. @Deprecated( 'Use findAllAnnotations(...).annotations instead. ' 'This feature was deprecated after v1.10.14.' ) Iterable<S> findAll<S extends Object>(Offset localPosition) { final AnnotationResult<S> result = findAllAnnotations(localPosition); return result.entries.map((AnnotationEntry<S> entry) => entry.annotation); } /// Search this layer and its subtree for all annotations of type `S` under /// the point described by `localPosition`. /// /// Returns a result with empty entries if no matching annotations are found. /// /// By default this method simply calls [findAnnotations] with `onlyFirst: /// false` and returns the annotations of its result. Prefer overriding /// [findAnnotations] instead of this method, because during an annotation /// search, only [findAnnotations] is recursively called, while custom /// behavior in this method is ignored. /// /// ## About layer annotations /// /// {@macro flutter.rendering.Layer.findAnnotations.aboutAnnotations} /// /// See also: /// /// * [find], which is similar but returns the first annotation found at the /// given position. /// * [AnnotatedRegionLayer], for placing values in the layer tree. AnnotationResult<S> findAllAnnotations<S extends Object>(Offset localPosition) { final AnnotationResult<S> result = AnnotationResult<S>(); findAnnotations<S>(result, localPosition, onlyFirst: false); return result; } /// Override this method to upload this layer to the engine. /// /// Return the engine layer for retained rendering. When there's no /// corresponding engine layer, null is returned. @protected void addToScene(ui.SceneBuilder builder, [ Offset layerOffset = Offset.zero ]); void _addToSceneWithRetainedRendering(ui.SceneBuilder builder) { // There can't be a loop by adding a retained layer subtree whose // _needsAddToScene is false. // // Proof by contradiction: // // If we introduce a loop, this retained layer must be appended to one of // its descendant layers, say A. That means the child structure of A has // changed so A's _needsAddToScene is true. This contradicts // _needsAddToScene being false. if (!_needsAddToScene && _engineLayer != null) { builder.addRetained(_engineLayer!); return; } addToScene(builder); // Clearing the flag _after_ calling `addToScene`, not _before_. This is // because `addToScene` calls children's `addToScene` methods, which may // mark this layer as dirty. _needsAddToScene = false; } /// The object responsible for creating this layer. /// /// Defaults to the value of [RenderObject.debugCreator] for the render object /// that created this layer. Used in debug messages. dynamic debugCreator; @override String toStringShort() => '${super.toStringShort()}${ owner == null ? " DETACHED" : ""}'; @override void debugFillProperties(DiagnosticPropertiesBuilder properties) { super.debugFillProperties(properties); properties.add(DiagnosticsProperty<Object>('owner', owner, level: parent != null ? DiagnosticLevel.hidden : DiagnosticLevel.info, defaultValue: null)); properties.add(DiagnosticsProperty<dynamic>('creator', debugCreator, defaultValue: null, level: DiagnosticLevel.debug)); properties.add(DiagnosticsProperty<String>('engine layer', describeIdentity(_engineLayer))); } } /// A composited layer containing a [Picture]. /// /// Picture layers are always leaves in the layer tree. class PictureLayer extends Layer { /// Creates a leaf layer for the layer tree. PictureLayer(this.canvasBounds); /// The bounds that were used for the canvas that drew this layer's [picture]. /// /// This is purely advisory. It is included in the information dumped with /// [debugDumpLayerTree] (which can be triggered by pressing "L" when using /// "flutter run" at the console), which can help debug why certain drawing /// commands are being culled. final Rect canvasBounds; /// The picture recorded for this layer. /// /// The picture's coordinate system matches this layer's coordinate system. /// /// The scene must be explicitly recomposited after this property is changed /// (as described at [Layer]). ui.Picture? get picture => _picture; ui.Picture? _picture; set picture(ui.Picture? picture) { markNeedsAddToScene(); _picture = picture; } /// Hints that the painting in this 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 this layer is complex enough to benefit from caching. /// /// The scene must be explicitly recomposited after this property is changed /// (as described at [Layer]). bool get isComplexHint => _isComplexHint; bool _isComplexHint = false; set isComplexHint(bool value) { if (value != _isComplexHint) { _isComplexHint = value; markNeedsAddToScene(); } } /// Hints that the painting in this layer is likely to change next frame. /// /// This hint tells the compositor not to cache this 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 this layer is likely to be /// reused in the future. /// /// The scene must be explicitly recomposited after this property is changed /// (as described at [Layer]). bool get willChangeHint => _willChangeHint; bool _willChangeHint = false; set willChangeHint(bool value) { if (value != _willChangeHint) { _willChangeHint = value; markNeedsAddToScene(); } } @override void addToScene(ui.SceneBuilder builder, [ Offset layerOffset = Offset.zero ]) { assert(picture != null); builder.addPicture(layerOffset, picture!, isComplexHint: isComplexHint, willChangeHint: willChangeHint); } @override void debugFillProperties(DiagnosticPropertiesBuilder properties) { super.debugFillProperties(properties); properties.add(DiagnosticsProperty<Rect>('paint bounds', canvasBounds)); properties.add(DiagnosticsProperty<String>('picture', describeIdentity(_picture))); properties.add(DiagnosticsProperty<String>( 'raster cache hints', 'isComplex = $isComplexHint, willChange = $willChangeHint'), ); } @override bool findAnnotations<S extends Object>(AnnotationResult<S> result, Offset localPosition, { required bool onlyFirst }) { return false; } } /// A composited layer that maps a backend texture to a rectangle. /// /// Backend textures are images that can be applied (mapped) to an area of the /// Flutter view. They are created, managed, and updated using a /// platform-specific texture registry. This is typically done by a plugin /// that integrates with host platform video player, camera, or OpenGL APIs, /// or similar image sources. /// /// A texture layer refers to its backend texture using an integer ID. Texture /// IDs are obtained from the texture registry and are scoped to the Flutter /// view. Texture IDs may be reused after deregistration, at the discretion /// of the registry. The use of texture IDs currently unknown to the registry /// will silently result in a blank rectangle. /// /// Once inserted into the layer tree, texture layers are repainted autonomously /// as dictated by the backend (e.g. on arrival of a video frame). Such /// repainting generally does not involve executing Dart code. /// /// Texture layers are always leaves in the layer tree. /// /// See also: /// /// * <https://api.flutter.dev/javadoc/io/flutter/view/TextureRegistry.html> /// for how to create and manage backend textures on Android. /// * <https://api.flutter.dev/objcdoc/Protocols/FlutterTextureRegistry.html> /// for how to create and manage backend textures on iOS. class TextureLayer extends Layer { /// Creates a texture layer bounded by [rect] and with backend texture /// identified by [textureId], if [freeze] is true new texture frames will not be /// populated to the texture, and use [filterQuality] to set layer's [FilterQuality]. TextureLayer({ required this.rect, required this.textureId, this.freeze = false, this.filterQuality = ui.FilterQuality.low, }) : assert(rect != null), assert(textureId != null); /// Bounding rectangle of this layer. final Rect rect; /// The identity of the backend texture. final int textureId; /// When true the texture that will not be updated with new frames. /// /// This is used when resizing an embedded Android views: When resizing there /// is a short period during which the framework cannot tell if the newest /// texture frame has the previous or new size, to workaround this the /// framework "freezes" the texture just before resizing the Android view and /// un-freezes it when it is certain that a frame with the new size is ready. final bool freeze; /// {@macro flutter.widgets.Texture.filterQuality} final ui.FilterQuality filterQuality; @override void addToScene(ui.SceneBuilder builder, [ Offset layerOffset = Offset.zero ]) { final Rect shiftedRect = layerOffset == Offset.zero ? rect : rect.shift(layerOffset); builder.addTexture( textureId, offset: shiftedRect.topLeft, width: shiftedRect.width, height: shiftedRect.height, freeze: freeze, filterQuality: filterQuality, ); } @override bool findAnnotations<S extends Object>(AnnotationResult<S> result, Offset localPosition, { required bool onlyFirst }) { return false; } } /// A layer that shows an embedded [UIView](https://developer.apple.com/documentation/uikit/uiview) /// on iOS. class PlatformViewLayer extends Layer { /// Creates a platform view layer. /// /// The `rect` and `viewId` parameters must not be null. PlatformViewLayer({ required this.rect, required this.viewId, }) : assert(rect != null), assert(viewId != null); /// Bounding rectangle of this layer in the global coordinate space. final Rect rect; /// The unique identifier of the UIView displayed on this layer. /// /// A UIView with this identifier must have been created by [PlatformViewsService.initUiKitView]. final int viewId; @override void addToScene(ui.SceneBuilder builder, [ Offset layerOffset = Offset.zero ]) { final Rect shiftedRect = layerOffset == Offset.zero ? rect : rect.shift(layerOffset); builder.addPlatformView( viewId, offset: shiftedRect.topLeft, width: shiftedRect.width, height: shiftedRect.height, ); } } /// A layer that indicates to the compositor that it should display /// certain performance statistics within it. /// /// Performance overlay layers are always leaves in the layer tree. class PerformanceOverlayLayer extends Layer { /// Creates a layer that displays a performance overlay. PerformanceOverlayLayer({ required Rect overlayRect, required this.optionsMask, required this.rasterizerThreshold, required this.checkerboardRasterCacheImages, required this.checkerboardOffscreenLayers, }) : _overlayRect = overlayRect; /// The rectangle in this layer's coordinate system that the overlay should occupy. /// /// The scene must be explicitly recomposited after this property is changed /// (as described at [Layer]). Rect get overlayRect => _overlayRect; Rect _overlayRect; set overlayRect(Rect value) { if (value != _overlayRect) { _overlayRect = value; markNeedsAddToScene(); } } /// The mask is created by shifting 1 by the index of the specific /// [PerformanceOverlayOption] to enable. final int optionsMask; /// The rasterizer threshold is an integer specifying the number of frame /// intervals that the rasterizer must miss before it decides that the frame /// is suitable for capturing an SkPicture trace for further analysis. final int rasterizerThreshold; /// Whether the raster cache should checkerboard cached entries. /// /// The compositor can sometimes decide to cache certain portions of the /// widget hierarchy. Such portions typically don't change often from frame to /// frame and are expensive to render. This can speed up overall rendering. However, /// there is certain upfront cost to constructing these cache entries. And, if /// the cache entries are not used very often, this cost may not be worth the /// speedup in rendering of subsequent frames. If the developer wants to be certain /// that populating the raster cache is not causing stutters, this option can be /// set. Depending on the observations made, hints can be provided to the compositor /// that aid it in making better decisions about caching. final bool checkerboardRasterCacheImages; /// Whether the compositor should checkerboard layers that are rendered to offscreen /// bitmaps. This can be useful for debugging rendering performance. /// /// Render target switches are caused by using opacity layers (via a [FadeTransition] or /// [Opacity] widget), clips, shader mask layers, etc. Selecting a new render target /// and merging it with the rest of the scene has a performance cost. This can sometimes /// be avoided by using equivalent widgets that do not require these layers (for example, /// replacing an [Opacity] widget with an [widgets.Image] using a [BlendMode]). final bool checkerboardOffscreenLayers; @override void addToScene(ui.SceneBuilder builder, [ Offset layerOffset = Offset.zero ]) { assert(optionsMask != null); final Rect shiftedOverlayRect = layerOffset == Offset.zero ? overlayRect : overlayRect.shift(layerOffset); builder.addPerformanceOverlay(optionsMask, shiftedOverlayRect); builder.setRasterizerTracingThreshold(rasterizerThreshold); builder.setCheckerboardRasterCacheImages(checkerboardRasterCacheImages); builder.setCheckerboardOffscreenLayers(checkerboardOffscreenLayers); } @override bool findAnnotations<S extends Object>(AnnotationResult<S> result, Offset localPosition, { required bool onlyFirst }) { return false; } } /// A composited layer that has a list of children. /// /// A [ContainerLayer] instance merely takes a list of children and inserts them /// into the composited rendering in order. There are subclasses of /// [ContainerLayer] which apply more elaborate effects in the process. class ContainerLayer extends Layer { /// The first composited layer in this layer's child list. Layer? get firstChild => _firstChild; Layer? _firstChild; /// The last composited layer in this layer's child list. Layer? get lastChild => _lastChild; Layer? _lastChild; /// Returns whether this layer has at least one child layer. bool get hasChildren => _firstChild != null; /// Consider this layer as the root and build a scene (a tree of layers) /// in the engine. // The reason this method is in the `ContainerLayer` class rather than // `PipelineOwner` or other singleton level is because this method can be used // both to render the whole layer tree (e.g. a normal application frame) and // to render a subtree (e.g. `OffsetLayer.toImage`). ui.Scene buildScene(ui.SceneBuilder builder) { List<PictureLayer>? temporaryLayers; assert(() { if (debugCheckElevationsEnabled) { temporaryLayers = _debugCheckElevations(); } return true; }()); updateSubtreeNeedsAddToScene(); addToScene(builder); // Clearing the flag _after_ calling `addToScene`, not _before_. This is // because `addToScene` calls children's `addToScene` methods, which may // mark this layer as dirty. _needsAddToScene = false; final ui.Scene scene = builder.build(); assert(() { // We should remove any layers that got added to highlight the incorrect // PhysicalModelLayers. If we don't, we'll end up adding duplicate layers // or continuing to render stale outlines. if (temporaryLayers != null) { for (final PictureLayer temporaryLayer in temporaryLayers!) { temporaryLayer.remove(); } } return true; }()); return scene; } bool _debugUltimatePreviousSiblingOf(Layer child, { Layer? equals }) { assert(child.attached == attached); while (child.previousSibling != null) { assert(child.previousSibling != child); child = child.previousSibling!; assert(child.attached == attached); } return child == equals; } bool _debugUltimateNextSiblingOf(Layer child, { Layer? equals }) { assert(child.attached == attached); while (child._nextSibling != null) { assert(child._nextSibling != child); child = child._nextSibling!; assert(child.attached == attached); } return child == equals; } PictureLayer _highlightConflictingLayer(PhysicalModelLayer child) { final ui.PictureRecorder recorder = ui.PictureRecorder(); final Canvas canvas = Canvas(recorder); canvas.drawPath( child.clipPath!, Paint() ..color = const Color(0xFFAA0000) ..style = PaintingStyle.stroke // The elevation may be 0 or otherwise too small to notice. // Adding 10 to it makes it more visually obvious. ..strokeWidth = child.elevation! + 10.0, ); final PictureLayer pictureLayer = PictureLayer(child.clipPath!.getBounds()) ..picture = recorder.endRecording() ..debugCreator = child; child.append(pictureLayer); return pictureLayer; } List<PictureLayer> _processConflictingPhysicalLayers(PhysicalModelLayer predecessor, PhysicalModelLayer child) { FlutterError.reportError(FlutterErrorDetails( exception: FlutterError('Painting order is out of order with respect to elevation.\n' 'See https://api.flutter.dev/flutter/rendering/debugCheckElevationsEnabled.html ' 'for more details.'), library: 'rendering library', context: ErrorDescription('during compositing'), informationCollector: () { return <DiagnosticsNode>[ child.toDiagnosticsNode(name: 'Attempted to composite layer', style: DiagnosticsTreeStyle.errorProperty), predecessor.toDiagnosticsNode(name: 'after layer', style: DiagnosticsTreeStyle.errorProperty), ErrorDescription('which occupies the same area at a higher elevation.'), ]; }, )); return <PictureLayer>[ _highlightConflictingLayer(predecessor), _highlightConflictingLayer(child), ]; } /// Checks that no [PhysicalModelLayer] would paint after another overlapping /// [PhysicalModelLayer] that has a higher elevation. /// /// Returns a list of [PictureLayer] objects it added to the tree to highlight /// bad nodes. These layers should be removed from the tree after building the /// [Scene]. List<PictureLayer> _debugCheckElevations() { final List<PhysicalModelLayer> physicalModelLayers = depthFirstIterateChildren().whereType<PhysicalModelLayer>().toList(); final List<PictureLayer> addedLayers = <PictureLayer>[]; for (int i = 0; i < physicalModelLayers.length; i++) { final PhysicalModelLayer physicalModelLayer = physicalModelLayers[i]; assert( physicalModelLayer.lastChild?.debugCreator != physicalModelLayer, 'debugCheckElevations has either already visited this layer or failed ' 'to remove the added picture from it.', ); double accumulatedElevation = physicalModelLayer.elevation!; Layer? ancestor = physicalModelLayer.parent; while (ancestor != null) { if (ancestor is PhysicalModelLayer) { accumulatedElevation += ancestor.elevation!; } ancestor = ancestor.parent; } for (int j = 0; j <= i; j++) { final PhysicalModelLayer predecessor = physicalModelLayers[j]; double predecessorAccumulatedElevation = predecessor.elevation!; ancestor = predecessor.parent; while (ancestor != null) { if (ancestor == predecessor) { continue; } if (ancestor is PhysicalModelLayer) { predecessorAccumulatedElevation += ancestor.elevation!; } ancestor = ancestor.parent; } if (predecessorAccumulatedElevation <= accumulatedElevation) { continue; } final Path intersection = Path.combine( PathOperation.intersect, predecessor._debugTransformedClipPath, physicalModelLayer._debugTransformedClipPath, ); if (intersection != null && intersection.computeMetrics().any((ui.PathMetric metric) => metric.length > 0)) { addedLayers.addAll(_processConflictingPhysicalLayers(predecessor, physicalModelLayer)); } } } return addedLayers; } @override void updateSubtreeNeedsAddToScene() { super.updateSubtreeNeedsAddToScene(); Layer? child = firstChild; while (child != null) { child.updateSubtreeNeedsAddToScene(); _needsAddToScene = _needsAddToScene || child._needsAddToScene; child = child.nextSibling; } } @override bool findAnnotations<S extends Object>(AnnotationResult<S> result, Offset localPosition, { required bool onlyFirst }) { for (Layer? child = lastChild; child != null; child = child.previousSibling) { final bool isAbsorbed = child.findAnnotations<S>(result, localPosition, onlyFirst: onlyFirst); if (isAbsorbed) return true; if (onlyFirst && result.entries.isNotEmpty) return isAbsorbed; } return false; } @override void attach(Object owner) { super.attach(owner); Layer? child = firstChild; while (child != null) { child.attach(owner); child = child.nextSibling; } } @override void detach() { super.detach(); Layer? child = firstChild; while (child != null) { child.detach(); child = child.nextSibling; } } /// Adds the given layer to the end of this layer's child list. void append(Layer child) { assert(child != this); assert(child != firstChild); assert(child != lastChild); assert(child.parent == null); assert(!child.attached); assert(child.nextSibling == null); assert(child.previousSibling == null); assert(() { Layer node = this; while (node.parent != null) node = node.parent!; assert(node != child); // indicates we are about to create a cycle return true; }()); adoptChild(child); child._previousSibling = lastChild; if (lastChild != null) lastChild!._nextSibling = child; _lastChild = child; _firstChild ??= child; assert(child.attached == attached); } // Implementation of [Layer.remove]. void _removeChild(Layer child) { assert(child.parent == this); assert(child.attached == attached); assert(_debugUltimatePreviousSiblingOf(child, equals: firstChild)); assert(_debugUltimateNextSiblingOf(child, equals: lastChild)); if (child._previousSibling == null) { assert(_firstChild == child); _firstChild = child._nextSibling; } else { child._previousSibling!._nextSibling = child.nextSibling; } if (child._nextSibling == null) { assert(lastChild == child); _lastChild = child.previousSibling; } else { child.nextSibling!._previousSibling = child.previousSibling; } assert((firstChild == null) == (lastChild == null)); assert(firstChild == null || firstChild!.attached == attached); assert(lastChild == null || lastChild!.attached == attached); assert(firstChild == null || _debugUltimateNextSiblingOf(firstChild!, equals: lastChild)); assert(lastChild == null || _debugUltimatePreviousSiblingOf(lastChild!, equals: firstChild)); child._previousSibling = null; child._nextSibling = null; dropChild(child); assert(!child.attached); } /// Removes all of this layer's children from its child list. void removeAllChildren() { Layer? child = firstChild; while (child != null) { final Layer? next = child.nextSibling; child._previousSibling = null; child._nextSibling = null; assert(child.attached == attached); dropChild(child); child = next; } _firstChild = null; _lastChild = null; } @override void addToScene(ui.SceneBuilder builder, [ Offset layerOffset = Offset.zero ]) { addChildrenToScene(builder, layerOffset); } /// Uploads all of this layer's children to the engine. /// /// This method is typically used by [addToScene] to insert the children into /// the scene. Subclasses of [ContainerLayer] typically override [addToScene] /// to apply effects to the scene using the [SceneBuilder] API, then insert /// their children using [addChildrenToScene], then reverse the aforementioned /// effects before returning from [addToScene]. void addChildrenToScene(ui.SceneBuilder builder, [ Offset childOffset = Offset.zero ]) { Layer? child = firstChild; while (child != null) { if (childOffset == Offset.zero) { child._addToSceneWithRetainedRendering(builder); } else { child.addToScene(builder, childOffset); } child = child.nextSibling; } } /// Applies the transform that would be applied when compositing the given /// child to the given matrix. /// /// Specifically, this should apply the transform that is applied to child's /// _origin_. When using [applyTransform] with a chain of layers, results will /// be unreliable unless the deepest layer in the chain collapses the /// `layerOffset` in [addToScene] to zero, meaning that it passes /// [Offset.zero] to its children, and bakes any incoming `layerOffset` into /// the [SceneBuilder] as (for instance) a transform (which is then also /// included in the transformation applied by [applyTransform]). /// /// For example, if [addToScene] applies the `layerOffset` and then /// passes [Offset.zero] to the children, then it should be included in the /// transform applied here, whereas if [addToScene] just passes the /// `layerOffset` to the child, then it should not be included in the /// transform applied here. /// /// This method is only valid immediately after [addToScene] has been called, /// before any of the properties have been changed. /// /// The default implementation does nothing, since [ContainerLayer], by /// default, composites its children at the origin of the [ContainerLayer] /// itself. /// /// The `child` argument should generally not be null, since in principle a /// layer could transform each child independently. However, certain layers /// may explicitly allow null as a value, for example if they know that they /// transform all their children identically. /// /// The `transform` argument must not be null. /// /// Used by [FollowerLayer] to transform its child to a [LeaderLayer]'s /// position. void applyTransform(Layer? child, Matrix4 transform) { assert(child != null); assert(transform != null); } /// Returns the descendants of this layer in depth first order. @visibleForTesting List<Layer> depthFirstIterateChildren() { if (firstChild == null) return <Layer>[]; final List<Layer> children = <Layer>[]; Layer? child = firstChild; while(child != null) { children.add(child); if (child is ContainerLayer) { children.addAll(child.depthFirstIterateChildren()); } child = child.nextSibling; } return children; } @override List<DiagnosticsNode> debugDescribeChildren() { final List<DiagnosticsNode> children = <DiagnosticsNode>[]; if (firstChild == null) return children; Layer? child = firstChild; int count = 1; while (true) { children.add(child!.toDiagnosticsNode(name: 'child $count')); if (child == lastChild) break; count += 1; child = child.nextSibling; } return children; } } /// A layer that is displayed at an offset from its parent layer. /// /// Offset layers are key to efficient repainting because they are created by /// repaint boundaries in the [RenderObject] tree (see /// [RenderObject.isRepaintBoundary]). When a render object that is a repaint /// boundary is asked to paint at given offset in a [PaintingContext], the /// render object first checks whether it needs to repaint itself. If not, it /// reuses its existing [OffsetLayer] (and its entire subtree) by mutating its /// [offset] property, cutting off the paint walk. class OffsetLayer extends ContainerLayer { /// Creates an offset layer. /// /// By default, [offset] is zero. It must be non-null before the compositing /// phase of the pipeline. OffsetLayer({ Offset offset = Offset.zero }) : _offset = offset; /// Offset from parent in the parent's coordinate system. /// /// The scene must be explicitly recomposited after this property is changed /// (as described at [Layer]). /// /// The [offset] property must be non-null before the compositing phase of the /// pipeline. Offset get offset => _offset; Offset _offset; set offset(Offset value) { if (value != _offset) { markNeedsAddToScene(); } _offset = value; } @override bool findAnnotations<S extends Object>(AnnotationResult<S> result, Offset localPosition, { required bool onlyFirst }) { return super.findAnnotations<S>(result, localPosition - offset, onlyFirst: onlyFirst); } @override void applyTransform(Layer? child, Matrix4 transform) { assert(child != null); assert(transform != null); transform.multiply(Matrix4.translationValues(offset.dx, offset.dy, 0.0)); } @override void addToScene(ui.SceneBuilder builder, [ Offset layerOffset = Offset.zero ]) { // Skia has a fast path for concatenating scale/translation only matrices. // Hence pushing a translation-only transform layer should be fast. For // retained rendering, we don't want to push the offset down to each leaf // node. Otherwise, changing an offset layer on the very high level could // cascade the change to too many leaves. engineLayer = builder.pushOffset( layerOffset.dx + offset.dx, layerOffset.dy + offset.dy, oldLayer: _engineLayer as ui.OffsetEngineLayer?, ); addChildrenToScene(builder); builder.pop(); } @override void debugFillProperties(DiagnosticPropertiesBuilder properties) { super.debugFillProperties(properties); properties.add(DiagnosticsProperty<Offset>('offset', offset)); } /// Capture an image of the current state of this layer and its children. /// /// The returned [ui.Image] has uncompressed raw RGBA bytes, will be offset /// by the top-left corner of [bounds], and have dimensions equal to the size /// of [bounds] multiplied by [pixelRatio]. /// /// The [pixelRatio] describes the scale between the logical pixels and the /// size of the output image. It is independent of the /// [dart:ui.FlutterView.devicePixelRatio] for the device, so specifying 1.0 /// (the default) will give you a 1:1 mapping between logical pixels and the /// output pixels in the image. /// /// See also: /// /// * [RenderRepaintBoundary.toImage] for a similar API at the render object level. /// * [dart:ui.Scene.toImage] for more information about the image returned. Future<ui.Image> toImage(Rect bounds, { double pixelRatio = 1.0 }) async { assert(bounds != null); assert(pixelRatio != null); final ui.SceneBuilder builder = ui.SceneBuilder(); final Matrix4 transform = Matrix4.translationValues( (-bounds.left - offset.dx) * pixelRatio, (-bounds.top - offset.dy) * pixelRatio, 0.0, ); transform.scale(pixelRatio, pixelRatio); builder.pushTransform(transform.storage); final ui.Scene scene = buildScene(builder); try { // Size is rounded up to the next pixel to make sure we don't clip off // anything. return await scene.toImage( (pixelRatio * bounds.width).ceil(), (pixelRatio * bounds.height).ceil(), ); } finally { scene.dispose(); } } } /// A composite layer that clips its children using a rectangle. /// /// When debugging, setting [debugDisableClipLayers] to true will cause this /// layer to be skipped (directly replaced by its children). This can be helpful /// to track down the cause of performance problems. class ClipRectLayer extends ContainerLayer { /// Creates a layer with a rectangular clip. /// /// The [clipRect] argument must not be null before the compositing phase of /// the pipeline. /// /// The [clipBehavior] argument must not be null, and must not be [Clip.none]. ClipRectLayer({ Rect? clipRect, Clip clipBehavior = Clip.hardEdge, }) : _clipRect = clipRect, _clipBehavior = clipBehavior, assert(clipBehavior != null), assert(clipBehavior != Clip.none); /// The rectangle to clip in the parent's coordinate system. /// /// The scene must be explicitly recomposited after this property is changed /// (as described at [Layer]). Rect? get clipRect => _clipRect; Rect? _clipRect; set clipRect(Rect? value) { if (value != _clipRect) { _clipRect = value; markNeedsAddToScene(); } } /// {@template flutter.rendering.ClipRectLayer.clipBehavior} /// Controls how to clip. /// /// Must not be set to null or [Clip.none]. /// {@endtemplate} /// /// Defaults to [Clip.hardEdge]. Clip get clipBehavior => _clipBehavior; Clip _clipBehavior; set clipBehavior(Clip value) { assert(value != null); assert(value != Clip.none); if (value != _clipBehavior) { _clipBehavior = value; markNeedsAddToScene(); } } @override bool findAnnotations<S extends Object>(AnnotationResult<S> result, Offset localPosition, { required bool onlyFirst }) { if (!clipRect!.contains(localPosition)) return false; return super.findAnnotations<S>(result, localPosition, onlyFirst: onlyFirst); } @override void addToScene(ui.SceneBuilder builder, [ Offset layerOffset = Offset.zero ]) { assert(clipRect != null); assert(clipBehavior != null); bool enabled = true; assert(() { enabled = !debugDisableClipLayers; return true; }()); if (enabled) { final Rect shiftedClipRect = layerOffset == Offset.zero ? clipRect! : clipRect!.shift(layerOffset); engineLayer = builder.pushClipRect( shiftedClipRect, clipBehavior: clipBehavior, oldLayer: _engineLayer as ui.ClipRectEngineLayer?, ); } else { engineLayer = null; } addChildrenToScene(builder, layerOffset); if (enabled) builder.pop(); } @override void debugFillProperties(DiagnosticPropertiesBuilder properties) { super.debugFillProperties(properties); properties.add(DiagnosticsProperty<Rect>('clipRect', clipRect)); properties.add(DiagnosticsProperty<Clip>('clipBehavior', clipBehavior)); } } /// A composite layer that clips its children using a rounded rectangle. /// /// When debugging, setting [debugDisableClipLayers] to true will cause this /// layer to be skipped (directly replaced by its children). This can be helpful /// to track down the cause of performance problems. class ClipRRectLayer extends ContainerLayer { /// Creates a layer with a rounded-rectangular clip. /// /// The [clipRRect] and [clipBehavior] properties must be non-null before the /// compositing phase of the pipeline. ClipRRectLayer({ RRect? clipRRect, Clip clipBehavior = Clip.antiAlias, }) : _clipRRect = clipRRect, _clipBehavior = clipBehavior, assert(clipBehavior != null), assert(clipBehavior != Clip.none); /// The rounded-rect to clip in the parent's coordinate system. /// /// The scene must be explicitly recomposited after this property is changed /// (as described at [Layer]). RRect? get clipRRect => _clipRRect; RRect? _clipRRect; set clipRRect(RRect? value) { if (value != _clipRRect) { _clipRRect = value; markNeedsAddToScene(); } } /// {@macro flutter.rendering.ClipRectLayer.clipBehavior} /// /// Defaults to [Clip.antiAlias]. Clip get clipBehavior => _clipBehavior; Clip _clipBehavior; set clipBehavior(Clip value) { assert(value != null); assert(value != Clip.none); if (value != _clipBehavior) { _clipBehavior = value; markNeedsAddToScene(); } } @override bool findAnnotations<S extends Object>(AnnotationResult<S> result, Offset localPosition, { required bool onlyFirst }) { if (!clipRRect!.contains(localPosition)) return false; return super.findAnnotations<S>(result, localPosition, onlyFirst: onlyFirst); } @override void addToScene(ui.SceneBuilder builder, [ Offset layerOffset = Offset.zero ]) { assert(clipRRect != null); assert(clipBehavior != null); bool enabled = true; assert(() { enabled = !debugDisableClipLayers; return true; }()); if (enabled) { final RRect shiftedClipRRect = layerOffset == Offset.zero ? clipRRect! : clipRRect!.shift(layerOffset); engineLayer = builder.pushClipRRect( shiftedClipRRect, clipBehavior: clipBehavior, oldLayer: _engineLayer as ui.ClipRRectEngineLayer?, ); } else { engineLayer = null; } addChildrenToScene(builder, layerOffset); if (enabled) builder.pop(); } @override void debugFillProperties(DiagnosticPropertiesBuilder properties) { super.debugFillProperties(properties); properties.add(DiagnosticsProperty<RRect>('clipRRect', clipRRect)); properties.add(DiagnosticsProperty<Clip>('clipBehavior', clipBehavior)); } } /// A composite layer that clips its children using a path. /// /// When debugging, setting [debugDisableClipLayers] to true will cause this /// layer to be skipped (directly replaced by its children). This can be helpful /// to track down the cause of performance problems. class ClipPathLayer extends ContainerLayer { /// Creates a layer with a path-based clip. /// /// The [clipPath] and [clipBehavior] properties must be non-null before the /// compositing phase of the pipeline. ClipPathLayer({ Path? clipPath, Clip clipBehavior = Clip.antiAlias, }) : _clipPath = clipPath, _clipBehavior = clipBehavior, assert(clipBehavior != null), assert(clipBehavior != Clip.none); /// The path to clip in the parent's coordinate system. /// /// The scene must be explicitly recomposited after this property is changed /// (as described at [Layer]). Path? get clipPath => _clipPath; Path? _clipPath; set clipPath(Path? value) { if (value != _clipPath) { _clipPath = value; markNeedsAddToScene(); } } /// {@macro flutter.rendering.ClipRectLayer.clipBehavior} /// /// Defaults to [Clip.antiAlias]. Clip get clipBehavior => _clipBehavior; Clip _clipBehavior; set clipBehavior(Clip value) { assert(value != null); assert(value != Clip.none); if (value != _clipBehavior) { _clipBehavior = value; markNeedsAddToScene(); } } @override bool findAnnotations<S extends Object>(AnnotationResult<S> result, Offset localPosition, { required bool onlyFirst }) { if (!clipPath!.contains(localPosition)) return false; return super.findAnnotations<S>(result, localPosition, onlyFirst: onlyFirst); } @override void addToScene(ui.SceneBuilder builder, [ Offset layerOffset = Offset.zero ]) { assert(clipPath != null); assert(clipBehavior != null); bool enabled = true; assert(() { enabled = !debugDisableClipLayers; return true; }()); if (enabled) { final Path shiftedPath = layerOffset == Offset.zero ? clipPath! : clipPath!.shift(layerOffset); engineLayer = builder.pushClipPath( shiftedPath, clipBehavior: clipBehavior, oldLayer: _engineLayer as ui.ClipPathEngineLayer?, ); } else { engineLayer = null; } addChildrenToScene(builder, layerOffset); if (enabled) builder.pop(); } @override void debugFillProperties(DiagnosticPropertiesBuilder properties) { super.debugFillProperties(properties); properties.add(DiagnosticsProperty<Clip>('clipBehavior', clipBehavior)); } } /// A composite layer that applies a [ColorFilter] to its children. class ColorFilterLayer extends ContainerLayer { /// Creates a layer that applies a [ColorFilter] to its children. /// /// The [colorFilter] property must be non-null before the compositing phase /// of the pipeline. ColorFilterLayer({ ColorFilter? colorFilter, }) : _colorFilter = colorFilter; /// The color filter to apply to children. /// /// The scene must be explicitly recomposited after this property is changed /// (as described at [Layer]). ColorFilter? get colorFilter => _colorFilter; ColorFilter? _colorFilter; set colorFilter(ColorFilter? value) { assert(value != null); if (value != _colorFilter) { _colorFilter = value; markNeedsAddToScene(); } } @override void addToScene(ui.SceneBuilder builder, [ Offset layerOffset = Offset.zero ]) { assert(colorFilter != null); engineLayer = builder.pushColorFilter( colorFilter!, oldLayer: _engineLayer as ui.ColorFilterEngineLayer?, ); addChildrenToScene(builder, layerOffset); builder.pop(); } @override void debugFillProperties(DiagnosticPropertiesBuilder properties) { super.debugFillProperties(properties); properties.add(DiagnosticsProperty<ColorFilter>('colorFilter', colorFilter)); } } /// A composite layer that applies an [ImageFilter] to its children. class ImageFilterLayer extends ContainerLayer { /// Creates a layer that applies an [ImageFilter] to its children. /// /// The [imageFilter] property must be non-null before the compositing phase /// of the pipeline. ImageFilterLayer({ ui.ImageFilter? imageFilter, }) : _imageFilter = imageFilter; /// The image filter to apply to children. /// /// The scene must be explicitly recomposited after this property is changed /// (as described at [Layer]). ui.ImageFilter? get imageFilter => _imageFilter; ui.ImageFilter? _imageFilter; set imageFilter(ui.ImageFilter? value) { assert(value != null); if (value != _imageFilter) { _imageFilter = value; markNeedsAddToScene(); } } @override void addToScene(ui.SceneBuilder builder, [ Offset layerOffset = Offset.zero ]) { assert(imageFilter != null); engineLayer = builder.pushImageFilter( imageFilter!, oldLayer: _engineLayer as ui.ImageFilterEngineLayer?, ); addChildrenToScene(builder, layerOffset); builder.pop(); } @override void debugFillProperties(DiagnosticPropertiesBuilder properties) { super.debugFillProperties(properties); properties.add(DiagnosticsProperty<ui.ImageFilter>('imageFilter', imageFilter)); } } /// A composited layer that applies a given transformation matrix to its /// children. /// /// This class inherits from [OffsetLayer] to make it one of the layers that /// can be used at the root of a [RenderObject] hierarchy. class TransformLayer extends OffsetLayer { /// Creates a transform layer. /// /// The [transform] and [offset] properties must be non-null before the /// compositing phase of the pipeline. TransformLayer({ Matrix4? transform, Offset offset = Offset.zero }) : _transform = transform, super(offset: offset); /// The matrix to apply. /// /// The scene must be explicitly recomposited after this property is changed /// (as described at [Layer]). /// /// This transform is applied before [offset], if both are set. /// /// The [transform] property must be non-null before the compositing phase of /// the pipeline. Matrix4? get transform => _transform; Matrix4? _transform; set transform(Matrix4? value) { assert(value != null); assert(value!.storage.every((double component) => component.isFinite)); if (value == _transform) return; _transform = value; _inverseDirty = true; markNeedsAddToScene(); } Matrix4? _lastEffectiveTransform; Matrix4? _invertedTransform; bool _inverseDirty = true; @override void addToScene(ui.SceneBuilder builder, [ Offset layerOffset = Offset.zero ]) { assert(transform != null); _lastEffectiveTransform = transform; final Offset totalOffset = offset + layerOffset; if (totalOffset != Offset.zero) { _lastEffectiveTransform = Matrix4.translationValues(totalOffset.dx, totalOffset.dy, 0.0) ..multiply(_lastEffectiveTransform!); } engineLayer = builder.pushTransform( _lastEffectiveTransform!.storage, oldLayer: _engineLayer as ui.TransformEngineLayer?, ); addChildrenToScene(builder); builder.pop(); } Offset? _transformOffset(Offset localPosition) { if (_inverseDirty) { _invertedTransform = Matrix4.tryInvert( PointerEvent.removePerspectiveTransform(transform!) ); _inverseDirty = false; } if (_invertedTransform == null) return null; return MatrixUtils.transformPoint(_invertedTransform!, localPosition); } @override bool findAnnotations<S extends Object>(AnnotationResult<S> result, Offset localPosition, { required bool onlyFirst }) { final Offset? transformedOffset = _transformOffset(localPosition); if (transformedOffset == null) return false; return super.findAnnotations<S>(result, transformedOffset, onlyFirst: onlyFirst); } @override void applyTransform(Layer? child, Matrix4 transform) { assert(child != null); assert(transform != null); assert(_lastEffectiveTransform != null || this.transform != null); if (_lastEffectiveTransform == null) { transform.multiply(this.transform!); } else { transform.multiply(_lastEffectiveTransform!); } } @override void debugFillProperties(DiagnosticPropertiesBuilder properties) { super.debugFillProperties(properties); properties.add(TransformProperty('transform', transform)); } } /// A composited layer that makes its children partially transparent. /// /// When debugging, setting [debugDisableOpacityLayers] to true will cause this /// layer to be skipped (directly replaced by its children). This can be helpful /// to track down the cause of performance problems. /// /// Try to avoid an [OpacityLayer] with no children. Remove that layer if /// possible to save some tree walks. class OpacityLayer extends ContainerLayer { /// Creates an opacity layer. /// /// The [alpha] property must be non-null before the compositing phase of /// the pipeline. OpacityLayer({ int? alpha, Offset offset = Offset.zero, }) : _alpha = alpha, _offset = offset; /// The amount to multiply into the alpha channel. /// /// The opacity is expressed as an integer from 0 to 255, where 0 is fully /// transparent and 255 is fully opaque. /// /// The scene must be explicitly recomposited after this property is changed /// (as described at [Layer]). int? get alpha => _alpha; int? _alpha; set alpha(int? value) { assert(value != null); if (value != _alpha) { _alpha = value; markNeedsAddToScene(); } } /// Offset from parent in the parent's coordinate system. Offset? get offset => _offset; Offset? _offset; set offset(Offset? value) { if (value != _offset) { _offset = value; markNeedsAddToScene(); } } @override void applyTransform(Layer? child, Matrix4 transform) { assert(child != null); assert(transform != null); transform.translate(offset!.dx, offset!.dy); } @override void addToScene(ui.SceneBuilder builder, [ Offset layerOffset = Offset.zero ]) { assert(alpha != null); bool enabled = firstChild != null; // don't add this layer if there's no child assert(() { enabled = enabled && !debugDisableOpacityLayers; return true; }()); if (enabled) engineLayer = builder.pushOpacity( alpha!, offset: offset! + layerOffset, oldLayer: _engineLayer as ui.OpacityEngineLayer?, ); else engineLayer = null; addChildrenToScene(builder); if (enabled) builder.pop(); } @override void debugFillProperties(DiagnosticPropertiesBuilder properties) { super.debugFillProperties(properties); properties.add(IntProperty('alpha', alpha)); properties.add(DiagnosticsProperty<Offset>('offset', offset)); } } /// A composited layer that applies a shader to its children. /// /// The shader is only applied inside the given [maskRect]. The shader itself /// uses the top left of the [maskRect] as its origin. /// /// The [maskRect] does not affect the positions of any child layers. class ShaderMaskLayer extends ContainerLayer { /// Creates a shader mask layer. /// /// The [shader], [maskRect], and [blendMode] properties must be non-null /// before the compositing phase of the pipeline. ShaderMaskLayer({ Shader? shader, Rect? maskRect, BlendMode? blendMode, }) : _shader = shader, _maskRect = maskRect, _blendMode = blendMode; /// The shader to apply to the children. /// /// The origin of the shader (e.g. of the coordinate system used by the `from` /// and `to` arguments to [ui.Gradient.linear]) is at the top left of the /// [maskRect]. /// /// The scene must be explicitly recomposited after this property is changed /// (as described at [Layer]). /// /// See also: /// /// * [ui.Gradient] and [ui.ImageShader], two shader types that can be used. Shader? get shader => _shader; Shader? _shader; set shader(Shader? value) { if (value != _shader) { _shader = value; markNeedsAddToScene(); } } /// The position and size of the shader. /// /// The [shader] is only rendered inside this rectangle, using the top left of /// the rectangle as its origin. /// /// The scene must be explicitly recomposited after this property is changed /// (as described at [Layer]). Rect? get maskRect => _maskRect; Rect? _maskRect; set maskRect(Rect? value) { if (value != _maskRect) { _maskRect = value; markNeedsAddToScene(); } } /// The blend mode to apply when blending the shader with the children. /// /// The scene must be explicitly recomposited after this property is changed /// (as described at [Layer]). BlendMode? get blendMode => _blendMode; BlendMode? _blendMode; set blendMode(BlendMode? value) { if (value != _blendMode) { _blendMode = value; markNeedsAddToScene(); } } @override void addToScene(ui.SceneBuilder builder, [ Offset layerOffset = Offset.zero ]) { assert(shader != null); assert(maskRect != null); assert(blendMode != null); assert(layerOffset != null); final Rect shiftedMaskRect = layerOffset == Offset.zero ? maskRect! : maskRect!.shift(layerOffset); engineLayer = builder.pushShaderMask( shader!, shiftedMaskRect, blendMode!, oldLayer: _engineLayer as ui.ShaderMaskEngineLayer?, ); addChildrenToScene(builder, layerOffset); builder.pop(); } @override void debugFillProperties(DiagnosticPropertiesBuilder properties) { super.debugFillProperties(properties); properties.add(DiagnosticsProperty<Shader>('shader', shader)); properties.add(DiagnosticsProperty<Rect>('maskRect', maskRect)); properties.add(DiagnosticsProperty<BlendMode>('blendMode', blendMode)); } } /// A composited layer that applies a filter to the existing contents of the scene. class BackdropFilterLayer extends ContainerLayer { /// Creates a backdrop filter layer. /// /// The [filter] property must be non-null before the compositing phase of the /// pipeline. BackdropFilterLayer({ ui.ImageFilter? filter }) : _filter = filter; /// The filter to apply to the existing contents of the scene. /// /// The scene must be explicitly recomposited after this property is changed /// (as described at [Layer]). ui.ImageFilter? get filter => _filter; ui.ImageFilter? _filter; set filter(ui.ImageFilter? value) { if (value != _filter) { _filter = value; markNeedsAddToScene(); } } @override void addToScene(ui.SceneBuilder builder, [ Offset layerOffset = Offset.zero ]) { assert(filter != null); engineLayer = builder.pushBackdropFilter( filter!, oldLayer: _engineLayer as ui.BackdropFilterEngineLayer?, ); addChildrenToScene(builder, layerOffset); builder.pop(); } } /// A composited layer that uses a physical model to producing lighting effects. /// /// For example, the layer casts a shadow according to its geometry and the /// relative position of lights and other physically modeled objects in the /// scene. /// /// When debugging, setting [debugDisablePhysicalShapeLayers] to true will cause this /// layer to be skipped (directly replaced by its children). This can be helpful /// to track down the cause of performance problems. class PhysicalModelLayer extends ContainerLayer { /// Creates a composited layer that uses a physical model to producing /// lighting effects. /// /// The [clipPath], [clipBehavior], [elevation], [color], and [shadowColor] /// arguments must be non-null before the compositing phase of the pipeline. PhysicalModelLayer({ Path? clipPath, Clip clipBehavior = Clip.none, double? elevation, Color? color, Color? shadowColor, }) : _clipPath = clipPath, _clipBehavior = clipBehavior, _elevation = elevation, _color = color, _shadowColor = shadowColor; /// The path to clip in the parent's coordinate system. /// /// The scene must be explicitly recomposited after this property is changed /// (as described at [Layer]). Path? get clipPath => _clipPath; Path? _clipPath; set clipPath(Path? value) { if (value != _clipPath) { _clipPath = value; markNeedsAddToScene(); } } Path get _debugTransformedClipPath { ContainerLayer? ancestor = parent; final Matrix4 matrix = Matrix4.identity(); while (ancestor != null && ancestor.parent != null) { ancestor.applyTransform(this, matrix); ancestor = ancestor.parent; } return clipPath!.transform(matrix.storage); } /// {@macro flutter.material.Material.clipBehavior} Clip get clipBehavior => _clipBehavior; Clip _clipBehavior; set clipBehavior(Clip value) { assert(value != null); if (value != _clipBehavior) { _clipBehavior = value; markNeedsAddToScene(); } } /// The z-coordinate at which to place this physical object. /// /// The scene must be explicitly recomposited after this property is changed /// (as described at [Layer]). /// /// In tests, the [debugDisableShadows] flag is set to true by default. /// Several widgets and render objects force all elevations to zero when this /// flag is set. For this reason, this property will often be set to zero in /// tests even if the layer should be raised. To verify the actual value, /// consider setting [debugDisableShadows] to false in your test. double? get elevation => _elevation; double? _elevation; set elevation(double? value) { if (value != _elevation) { _elevation = value; markNeedsAddToScene(); } } /// The background color. /// /// The scene must be explicitly recomposited after this property is changed /// (as described at [Layer]). Color? get color => _color; Color? _color; set color(Color? value) { if (value != _color) { _color = value; markNeedsAddToScene(); } } /// The shadow color. Color? get shadowColor => _shadowColor; Color? _shadowColor; set shadowColor(Color? value) { if (value != _shadowColor) { _shadowColor = value; markNeedsAddToScene(); } } @override bool findAnnotations<S extends Object>(AnnotationResult<S> result, Offset localPosition, { required bool onlyFirst }) { if (!clipPath!.contains(localPosition)) return false; return super.findAnnotations<S>(result, localPosition, onlyFirst: onlyFirst); } @override void addToScene(ui.SceneBuilder builder, [ Offset layerOffset = Offset.zero ]) { assert(clipPath != null); assert(clipBehavior != null); assert(elevation != null); assert(color != null); assert(shadowColor != null); bool enabled = true; assert(() { enabled = !debugDisablePhysicalShapeLayers; return true; }()); if (enabled) { engineLayer = builder.pushPhysicalShape( path: layerOffset == Offset.zero ? clipPath! : clipPath!.shift(layerOffset), elevation: elevation!, color: color!, shadowColor: shadowColor, clipBehavior: clipBehavior, oldLayer: _engineLayer as ui.PhysicalShapeEngineLayer?, ); } else { engineLayer = null; } addChildrenToScene(builder, layerOffset); if (enabled) builder.pop(); } @override void debugFillProperties(DiagnosticPropertiesBuilder properties) { super.debugFillProperties(properties); properties.add(DoubleProperty('elevation', elevation)); properties.add(ColorProperty('color', color)); } } /// An object that a [LeaderLayer] can register with. /// /// An instance of this class should be provided as the [LeaderLayer.link] and /// the [FollowerLayer.link] properties to cause the [FollowerLayer] to follow /// the [LeaderLayer]. /// /// See also: /// /// * [CompositedTransformTarget], the widget that creates a [LeaderLayer]. /// * [CompositedTransformFollower], the widget that creates a [FollowerLayer]. /// * [RenderLeaderLayer] and [RenderFollowerLayer], the corresponding /// render objects. class LayerLink { /// The currently-registered [LeaderLayer], if any. LeaderLayer? get leader => _leader; LeaderLayer? _leader; /// The total size of [leader]'s contents. /// /// Generally this should be set by the [RenderObject] that paints on the /// registered [leader] layer (for instance a [RenderLeaderLayer] that shares /// this link with its followers). This size may be outdated before and during /// layout. Size? leaderSize; @override String toString() => '${describeIdentity(this)}(${ _leader != null ? "<linked>" : "<dangling>" })'; } /// A composited layer that can be followed by a [FollowerLayer]. /// /// This layer collapses the accumulated offset into a transform and passes /// [Offset.zero] to its child layers in the [addToScene]/[addChildrenToScene] /// methods, so that [applyTransform] will work reliably. class LeaderLayer extends ContainerLayer { /// Creates a leader layer. /// /// The [link] property must not be null, and must not have been provided to /// any other [LeaderLayer] layers that are [attached] to the layer tree at /// the same time. /// /// The [offset] property must be non-null before the compositing phase of the /// pipeline. LeaderLayer({ required LayerLink link, this.offset = Offset.zero }) : assert(link != null), _link = link; /// The object with which this layer should register. /// /// The link will be established when this layer is [attach]ed, and will be /// cleared when this layer is [detach]ed. LayerLink get link => _link; set link(LayerLink value) { assert(value != null); _link = value; } LayerLink _link; /// Offset from parent in the parent's coordinate system. /// /// The scene must be explicitly recomposited after this property is changed /// (as described at [Layer]). /// /// The [offset] property must be non-null before the compositing phase of the /// pipeline. Offset offset; /// {@macro flutter.rendering.FollowerLayer.alwaysNeedsAddToScene} @override bool get alwaysNeedsAddToScene => true; @override void attach(Object owner) { super.attach(owner); assert(link.leader == null); _lastOffset = null; link._leader = this; } @override void detach() { assert(link.leader == this); link._leader = null; _lastOffset = null; super.detach(); } /// The offset the last time this layer was composited. /// /// This is reset to null when the layer is attached or detached, to help /// catch cases where the follower layer ends up before the leader layer, but /// not every case can be detected. Offset? _lastOffset; @override bool findAnnotations<S extends Object>(AnnotationResult<S> result, Offset localPosition, { required bool onlyFirst }) { return super.findAnnotations<S>(result, localPosition - offset, onlyFirst: onlyFirst); } @override void addToScene(ui.SceneBuilder builder, [ Offset layerOffset = Offset.zero ]) { assert(offset != null); _lastOffset = offset + layerOffset; if (_lastOffset != Offset.zero) engineLayer = builder.pushTransform( Matrix4.translationValues(_lastOffset!.dx, _lastOffset!.dy, 0.0).storage, oldLayer: _engineLayer as ui.TransformEngineLayer?, ); addChildrenToScene(builder); if (_lastOffset != Offset.zero) builder.pop(); } /// Applies the transform that would be applied when compositing the given /// child to the given matrix. /// /// See [ContainerLayer.applyTransform] for details. /// /// The `child` argument may be null, as the same transform is applied to all /// children. @override void applyTransform(Layer? child, Matrix4 transform) { assert(_lastOffset != null); if (_lastOffset != Offset.zero) transform.translate(_lastOffset!.dx, _lastOffset!.dy); } @override void debugFillProperties(DiagnosticPropertiesBuilder properties) { super.debugFillProperties(properties); properties.add(DiagnosticsProperty<Offset>('offset', offset)); properties.add(DiagnosticsProperty<LayerLink>('link', link)); } } /// A composited layer that applies a transformation matrix to its children such /// that they are positioned to match a [LeaderLayer]. /// /// If any of the ancestors of this layer have a degenerate matrix (e.g. scaling /// by zero), then the [FollowerLayer] will not be able to transform its child /// to the coordinate space of the [LeaderLayer]. /// /// A [linkedOffset] property can be provided to further offset the child layer /// from the leader layer, for example if the child is to follow the linked /// layer at a distance rather than directly overlapping it. class FollowerLayer extends ContainerLayer { /// Creates a follower layer. /// /// The [link] property must not be null. /// /// The [unlinkedOffset], [linkedOffset], and [showWhenUnlinked] properties /// must be non-null before the compositing phase of the pipeline. FollowerLayer({ required LayerLink link, this.showWhenUnlinked = true, this.unlinkedOffset = Offset.zero, this.linkedOffset = Offset.zero, }) : assert(link != null), _link = link; /// The link to the [LeaderLayer]. /// /// The same object should be provided to a [LeaderLayer] that is earlier in /// the layer tree. When this layer is composited, it will apply a transform /// that moves its children to match the position of the [LeaderLayer]. LayerLink get link => _link; set link(LayerLink value) { assert(value != null); _link = value; } LayerLink _link; /// Whether to show the layer's contents when the [link] does not point to a /// [LeaderLayer]. /// /// When the layer is linked, children layers are positioned such that they /// have the same global position as the linked [LeaderLayer]. /// /// When the layer is not linked, then: if [showWhenUnlinked] is true, /// children are positioned as if the [FollowerLayer] was a [ContainerLayer]; /// if it is false, then children are hidden. /// /// The [showWhenUnlinked] property must be non-null before the compositing /// phase of the pipeline. bool? showWhenUnlinked; /// Offset from parent in the parent's coordinate system, used when the layer /// is not linked to a [LeaderLayer]. /// /// The scene must be explicitly recomposited after this property is changed /// (as described at [Layer]). /// /// The [unlinkedOffset] property must be non-null before the compositing /// phase of the pipeline. /// /// See also: /// /// * [linkedOffset], for when the layers are linked. Offset? unlinkedOffset; /// Offset from the origin of the leader layer to the origin of the child /// layers, used when the layer is linked to a [LeaderLayer]. /// /// The scene must be explicitly recomposited after this property is changed /// (as described at [Layer]). /// /// The [linkedOffset] property must be non-null before the compositing phase /// of the pipeline. /// /// See also: /// /// * [unlinkedOffset], for when the layer is not linked. Offset? linkedOffset; Offset? _lastOffset; Matrix4? _lastTransform; Matrix4? _invertedTransform; bool _inverseDirty = true; Offset? _transformOffset(Offset localPosition) { if (_inverseDirty) { _invertedTransform = Matrix4.tryInvert(getLastTransform()!); _inverseDirty = false; } if (_invertedTransform == null) return null; final Vector4 vector = Vector4(localPosition.dx, localPosition.dy, 0.0, 1.0); final Vector4 result = _invertedTransform!.transform(vector); return Offset(result[0] - linkedOffset!.dx, result[1] - linkedOffset!.dy); } @override bool findAnnotations<S extends Object>(AnnotationResult<S> result, Offset localPosition, { required bool onlyFirst }) { if (link.leader == null) { if (showWhenUnlinked!) { return super.findAnnotations(result, localPosition - unlinkedOffset!, onlyFirst: onlyFirst); } return false; } final Offset? transformedOffset = _transformOffset(localPosition); if (transformedOffset == null) { return false; } return super.findAnnotations<S>(result, transformedOffset, onlyFirst: onlyFirst); } /// The transform that was used during the last composition phase. /// /// If the [link] was not linked to a [LeaderLayer], or if this layer has /// a degenerate matrix applied, then this will be null. /// /// This method returns a new [Matrix4] instance each time it is invoked. Matrix4? getLastTransform() { if (_lastTransform == null) return null; final Matrix4 result = Matrix4.translationValues(-_lastOffset!.dx, -_lastOffset!.dy, 0.0); result.multiply(_lastTransform!); return result; } /// Call [applyTransform] for each layer in the provided list. /// /// The list is in reverse order (deepest first). The first layer will be /// treated as the child of the second, and so forth. The first layer in the /// list won't have [applyTransform] called on it. The first layer may be /// null. static Matrix4 _collectTransformForLayerChain(List<ContainerLayer?> layers) { // Initialize our result matrix. final Matrix4 result = Matrix4.identity(); // Apply each layer to the matrix in turn, starting from the last layer, // and providing the previous layer as the child. for (int index = layers.length - 1; index > 0; index -= 1) layers[index]?.applyTransform(layers[index - 1], result); return result; } /// Find the common ancestor of two layers [a] and [b] by searching towards /// the root of the tree, and append each ancestor of [a] or [b] visited along /// the path to [ancestorsA] and [ancestorsB] respectively. /// /// Returns null if [a] [b] do not share a common ancestor, in which case the /// results in [ancestorsA] and [ancestorsB] are undefined. static Layer? _pathsToCommonAncestor( Layer? a, Layer? b, List<ContainerLayer?> ancestorsA, List<ContainerLayer?> ancestorsB, ) { // No common ancestor found. if (a == null || b == null) return null; if (identical(a, b)) return a; if (a.depth < b.depth) { ancestorsB.add(b.parent); return _pathsToCommonAncestor(a, b.parent, ancestorsA, ancestorsB); } else if (a.depth > b.depth){ ancestorsA.add(a.parent); return _pathsToCommonAncestor(a.parent, b, ancestorsA, ancestorsB); } ancestorsA.add(a.parent); ancestorsB.add(b.parent); return _pathsToCommonAncestor(a.parent, b.parent, ancestorsA, ancestorsB); } /// Populate [_lastTransform] given the current state of the tree. void _establishTransform() { assert(link != null); _lastTransform = null; final LeaderLayer? leader = link.leader; // Check to see if we are linked. if (leader == null) return; // If we're linked, check the link is valid. assert( leader.owner == owner, 'Linked LeaderLayer anchor is not in the same layer tree as the FollowerLayer.', ); assert( leader._lastOffset != null, 'LeaderLayer anchor must come before FollowerLayer in paint order, but the reverse was true.', ); // Stores [leader, ..., commonAncestor] after calling _pathsToCommonAncestor. final List<ContainerLayer?> forwardLayers = <ContainerLayer>[leader]; // Stores [this (follower), ..., commonAncestor] after calling // _pathsToCommonAncestor. final List<ContainerLayer?> inverseLayers = <ContainerLayer>[this]; final Layer? ancestor = _pathsToCommonAncestor( leader, this, forwardLayers, inverseLayers, ); assert(ancestor != null); final Matrix4 forwardTransform = _collectTransformForLayerChain(forwardLayers); // Further transforms the coordinate system to a hypothetical child (null) // of the leader layer, to account for the leader's additional paint offset // and layer offset (LeaderLayer._lastOffset). leader.applyTransform(null, forwardTransform); forwardTransform.translate(linkedOffset!.dx, linkedOffset!.dy); final Matrix4 inverseTransform = _collectTransformForLayerChain(inverseLayers); if (inverseTransform.invert() == 0.0) { // We are in a degenerate transform, so there's not much we can do. return; } // Combine the matrices and store the result. inverseTransform.multiply(forwardTransform); _lastTransform = inverseTransform; _inverseDirty = true; } /// {@template flutter.rendering.FollowerLayer.alwaysNeedsAddToScene} /// This disables retained rendering. /// /// A [FollowerLayer] copies changes from a [LeaderLayer] that could be anywhere /// in the Layer tree, and that leader layer could change without notifying the /// follower layer. Therefore we have to always call a follower layer's /// [addToScene]. In order to call follower layer's [addToScene], leader layer's /// [addToScene] must be called first so leader layer must also be considered /// as [alwaysNeedsAddToScene]. /// {@endtemplate} @override bool get alwaysNeedsAddToScene => true; @override void addToScene(ui.SceneBuilder builder, [ Offset layerOffset = Offset.zero ]) { assert(link != null); assert(showWhenUnlinked != null); if (link.leader == null && !showWhenUnlinked!) { _lastTransform = null; _lastOffset = null; _inverseDirty = true; engineLayer = null; return; } _establishTransform(); if (_lastTransform != null) { engineLayer = builder.pushTransform( _lastTransform!.storage, oldLayer: _engineLayer as ui.TransformEngineLayer?, ); addChildrenToScene(builder); builder.pop(); _lastOffset = unlinkedOffset! + layerOffset; } else { _lastOffset = null; final Matrix4 matrix = Matrix4.translationValues(unlinkedOffset!.dx, unlinkedOffset!.dy, .0); engineLayer = builder.pushTransform( matrix.storage, oldLayer: _engineLayer as ui.TransformEngineLayer?, ); addChildrenToScene(builder); builder.pop(); } _inverseDirty = true; } @override void applyTransform(Layer? child, Matrix4 transform) { assert(child != null); assert(transform != null); if (_lastTransform != null) { transform.multiply(_lastTransform!); } else { transform.multiply(Matrix4.translationValues(unlinkedOffset!.dx, unlinkedOffset!.dy, 0)); } } @override void debugFillProperties(DiagnosticPropertiesBuilder properties) { super.debugFillProperties(properties); properties.add(DiagnosticsProperty<LayerLink>('link', link)); properties.add(TransformProperty('transform', getLastTransform(), defaultValue: null)); } } /// A composited layer which annotates its children with a value. Pushing this /// layer to the tree is the common way of adding an annotation. /// /// An annotation is an optional object of any type that, when attached with a /// layer, can be retrieved using [Layer.find] or [Layer.findAllAnnotations] /// with a position. The search process is done recursively, controlled by a /// concept of being opaque to a type of annotation, explained in the document /// of [Layer.findAnnotations]. /// /// When an annotation search arrives, this layer defers the same search to each /// of this layer's children, respecting their opacity. Then it adds this /// layer's annotation if all of the following restrictions are met: /// /// {@template flutter.rendering.AnnotatedRegionLayer.restrictions} /// * The target type must be identical to the annotated type `T`. /// * If [size] is provided, the target position must be contained within the /// rectangle formed by [size] and [offset]. /// {@endtemplate} /// /// This layer is opaque to a type of annotation if any child is also opaque, or /// if [opaque] is true and the layer's annotation is added. class AnnotatedRegionLayer<T extends Object> extends ContainerLayer { /// Creates a new layer that annotates its children with [value]. /// /// The [value] provided cannot be null. AnnotatedRegionLayer( this.value, { this.size, Offset? offset, this.opaque = false, }) : assert(value != null), assert(opaque != null), offset = offset ?? Offset.zero; /// The annotated object, which is added to the result if all restrictions are /// met. final T value; /// The size of the annotated object. /// /// If [size] is provided, then the annotation is found only if the target /// position is contained by the rectangle formed by [size] and [offset]. /// Otherwise no such restriction is applied, and clipping can only be done by /// the ancestor layers. final Size? size; /// The position of the annotated object. /// /// The [offset] defaults to [Offset.zero] if not provided, and is ignored if /// [size] is not set. /// /// The [offset] only offsets the clipping rectangle, and does not affect /// how the painting or annotation search is propagated to its children. final Offset offset; /// Whether the annotation of this layer should be opaque during an annotation /// search of type `T`, preventing siblings visually behind it from being /// searched. /// /// If [opaque] is true, and this layer does add its annotation [value], /// then the layer will always be opaque during the search. /// /// If [opaque] is false, or if this layer does not add its annotation, /// then the opacity of this layer will be the one returned by the children, /// meaning that it will be opaque if any child is opaque. /// /// The [opaque] defaults to false. /// /// The [opaque] is effectively useless during [Layer.find] (more /// specifically, [Layer.findAnnotations] with `onlyFirst: true`), since the /// search process then skips the remaining tree after finding the first /// annotation. /// /// See also: /// /// * [Layer.findAnnotations], which explains the concept of being opaque /// to a type of annotation as the return value. /// * [HitTestBehavior], which controls similar logic when hit-testing in the /// render tree. final bool opaque; /// Searches the subtree for annotations of type `S` at the location /// `localPosition`, then adds the annotation [value] if applicable. /// /// This method always searches its children, and if any child returns `true`, /// the remaining children are skipped. Regardless of what the children /// return, this method then adds this layer's annotation if all of the /// following restrictions are met: /// /// {@macro flutter.rendering.AnnotatedRegionLayer.restrictions} /// /// This search process respects `onlyFirst`, meaning that when `onlyFirst` is /// true, the search will stop when it finds the first annotation from the /// children, and the layer's own annotation is checked only when none is /// given by the children. /// /// The return value is true if any child returns `true`, or if [opaque] is /// true and the layer's annotation is added. /// /// For explanation of layer annotations, parameters and return value, refer /// to [Layer.findAnnotations]. @override bool findAnnotations<S extends Object>(AnnotationResult<S> result, Offset localPosition, { required bool onlyFirst }) { bool isAbsorbed = super.findAnnotations(result, localPosition, onlyFirst: onlyFirst); if (result.entries.isNotEmpty && onlyFirst) return isAbsorbed; if (size != null && !(offset & size!).contains(localPosition)) { return isAbsorbed; } if (T == S) { isAbsorbed = isAbsorbed || opaque; final Object untypedValue = value; final S typedValue = untypedValue as S; result.add(AnnotationEntry<S>( annotation: typedValue, localPosition: localPosition - offset, )); } return isAbsorbed; } @override void debugFillProperties(DiagnosticPropertiesBuilder properties) { super.debugFillProperties(properties); properties.add(DiagnosticsProperty<T>('value', value)); properties.add(DiagnosticsProperty<Size>('size', size, defaultValue: null)); properties.add(DiagnosticsProperty<Offset>('offset', offset, defaultValue: null)); properties.add(DiagnosticsProperty<bool>('opaque', opaque, defaultValue: false)); } }