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// 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:developer';
import 'package:flutter/foundation.dart';
import 'package:flutter/gestures.dart';
import 'package:flutter/scheduler.dart';
import 'package:flutter/semantics.dart';
import 'package:flutter/services.dart';
import 'box.dart';
import 'debug.dart';
import 'mouse_tracking.dart';
import 'object.dart';
import 'view.dart';
export 'package:flutter/gestures.dart' show HitTestResult;
// Examples can assume:
// dynamic context;
/// The glue between the render tree and the Flutter engine.
mixin RendererBinding on BindingBase, ServicesBinding, SchedulerBinding, GestureBinding, SemanticsBinding, HitTestable {
@override
void initInstances() {
super.initInstances();
_instance = this;
_pipelineOwner = PipelineOwner(
onNeedVisualUpdate: ensureVisualUpdate,
onSemanticsOwnerCreated: _handleSemanticsOwnerCreated,
onSemanticsOwnerDisposed: _handleSemanticsOwnerDisposed,
);
window
..onMetricsChanged = handleMetricsChanged
..onTextScaleFactorChanged = handleTextScaleFactorChanged
..onPlatformBrightnessChanged = handlePlatformBrightnessChanged
..onSemanticsEnabledChanged = _handleSemanticsEnabledChanged
..onSemanticsAction = _handleSemanticsAction;
initRenderView();
_handleSemanticsEnabledChanged();
assert(renderView != null);
addPersistentFrameCallback(_handlePersistentFrameCallback);
initMouseTracker();
if (kIsWeb) {
addPostFrameCallback(_handleWebFirstFrame);
}
}
/// The current [RendererBinding], if one has been created.
static RendererBinding? get instance => _instance;
static RendererBinding? _instance;
@override
void initServiceExtensions() {
super.initServiceExtensions();
assert(() {
// these service extensions only work in debug mode
registerBoolServiceExtension(
name: 'invertOversizedImages',
getter: () async => debugInvertOversizedImages,
setter: (bool value) async {
if (debugInvertOversizedImages != value) {
debugInvertOversizedImages = value;
return _forceRepaint();
}
return Future<void>.value();
},
);
registerBoolServiceExtension(
name: 'debugPaint',
getter: () async => debugPaintSizeEnabled,
setter: (bool value) {
if (debugPaintSizeEnabled == value)
return Future<void>.value();
debugPaintSizeEnabled = value;
return _forceRepaint();
},
);
registerBoolServiceExtension(
name: 'debugPaintBaselinesEnabled',
getter: () async => debugPaintBaselinesEnabled,
setter: (bool value) {
if (debugPaintBaselinesEnabled == value)
return Future<void>.value();
debugPaintBaselinesEnabled = value;
return _forceRepaint();
},
);
registerBoolServiceExtension(
name: 'repaintRainbow',
getter: () async => debugRepaintRainbowEnabled,
setter: (bool value) {
final bool repaint = debugRepaintRainbowEnabled && !value;
debugRepaintRainbowEnabled = value;
if (repaint)
return _forceRepaint();
return Future<void>.value();
},
);
registerBoolServiceExtension(
name: 'debugCheckElevationsEnabled',
getter: () async => debugCheckElevationsEnabled,
setter: (bool value) {
if (debugCheckElevationsEnabled == value) {
return Future<void>.value();
}
debugCheckElevationsEnabled = value;
return _forceRepaint();
},
);
registerSignalServiceExtension(
name: 'debugDumpLayerTree',
callback: () {
debugDumpLayerTree();
return debugPrintDone;
},
);
return true;
}());
if (!kReleaseMode) {
// these service extensions work in debug or profile mode
registerSignalServiceExtension(
name: 'debugDumpRenderTree',
callback: () {
debugDumpRenderTree();
return debugPrintDone;
},
);
registerSignalServiceExtension(
name: 'debugDumpSemanticsTreeInTraversalOrder',
callback: () {
debugDumpSemanticsTree(DebugSemanticsDumpOrder.traversalOrder);
return debugPrintDone;
},
);
registerSignalServiceExtension(
name: 'debugDumpSemanticsTreeInInverseHitTestOrder',
callback: () {
debugDumpSemanticsTree(DebugSemanticsDumpOrder.inverseHitTest);
return debugPrintDone;
},
);
}
}
/// Creates a [RenderView] object to be the root of the
/// [RenderObject] rendering tree, and initializes it so that it
/// will be rendered when the next frame is requested.
///
/// Called automatically when the binding is created.
void initRenderView() {
assert(!_debugIsRenderViewInitialized);
assert(() {
_debugIsRenderViewInitialized = true;
return true;
}());
renderView = RenderView(configuration: createViewConfiguration(), window: window);
renderView.prepareInitialFrame();
}
bool _debugIsRenderViewInitialized = false;
/// The object that manages state about currently connected mice, for hover
/// notification.
MouseTracker get mouseTracker => _mouseTracker!;
MouseTracker? _mouseTracker;
/// The render tree's owner, which maintains dirty state for layout,
/// composite, paint, and accessibility semantics.
PipelineOwner get pipelineOwner => _pipelineOwner;
late PipelineOwner _pipelineOwner;
/// The render tree that's attached to the output surface.
RenderView get renderView => _pipelineOwner.rootNode! as RenderView;
/// Sets the given [RenderView] object (which must not be null), and its tree, to
/// be the new render tree to display. The previous tree, if any, is detached.
set renderView(RenderView value) {
assert(value != null);
_pipelineOwner.rootNode = value;
}
/// Called when the system metrics change.
///
/// See [dart:ui.PlatformDispatcher.onMetricsChanged].
@protected
void handleMetricsChanged() {
assert(renderView != null);
renderView.configuration = createViewConfiguration();
scheduleForcedFrame();
}
/// Called when the platform text scale factor changes.
///
/// See [dart:ui.PlatformDispatcher.onTextScaleFactorChanged].
@protected
void handleTextScaleFactorChanged() { }
/// Called when the platform brightness changes.
///
/// The current platform brightness can be queried from a Flutter binding or
/// from a [MediaQuery] widget. The latter is preferred from widgets because
/// it causes the widget to be automatically rebuilt when the brightness
/// changes.
///
/// {@tool snippet}
/// Querying [MediaQuery] directly. Preferred.
///
/// ```dart
/// final Brightness brightness = MediaQuery.platformBrightnessOf(context);
/// ```
/// {@end-tool}
///
/// {@tool snippet}
/// Querying [PlatformDispatcher.platformBrightness].
///
/// ```dart
/// final Brightness brightness = WidgetsBinding.instance!.platformDispatcher.platformBrightness;
/// ```
/// {@end-tool}
///
/// {@tool snippet}
/// Querying [MediaQueryData].
///
/// ```dart
/// final MediaQueryData mediaQueryData = MediaQuery.of(context);
/// final Brightness brightness = mediaQueryData.platformBrightness;
/// ```
/// {@end-tool}
///
/// See [dart:ui.PlatformDispatcher.onPlatformBrightnessChanged].
@protected
void handlePlatformBrightnessChanged() { }
/// Returns a [ViewConfiguration] configured for the [RenderView] based on the
/// current environment.
///
/// This is called during construction and also in response to changes to the
/// system metrics.
///
/// Bindings can override this method to change what size or device pixel
/// ratio the [RenderView] will use. For example, the testing framework uses
/// this to force the display into 800x600 when a test is run on the device
/// using `flutter run`.
ViewConfiguration createViewConfiguration() {
final double devicePixelRatio = window.devicePixelRatio;
return ViewConfiguration(
size: window.physicalSize / devicePixelRatio,
devicePixelRatio: devicePixelRatio,
);
}
SemanticsHandle? _semanticsHandle;
/// Creates a [MouseTracker] which manages state about currently connected
/// mice, for hover notification.
///
/// Used by testing framework to reinitialize the mouse tracker between tests.
@visibleForTesting
void initMouseTracker([MouseTracker? tracker]) {
_mouseTracker?.dispose();
_mouseTracker = tracker ?? MouseTracker();
}
@override // from GestureBinding
void dispatchEvent(PointerEvent event, HitTestResult? hitTestResult) {
if (hitTestResult != null ||
event is PointerAddedEvent ||
event is PointerRemovedEvent) {
assert(event.position != null);
_mouseTracker!.updateWithEvent(event,
() => hitTestResult ?? renderView.hitTestMouseTrackers(event.position));
}
super.dispatchEvent(event, hitTestResult);
}
void _handleSemanticsEnabledChanged() {
setSemanticsEnabled(window.semanticsEnabled);
}
/// Whether the render tree associated with this binding should produce a tree
/// of [SemanticsNode] objects.
void setSemanticsEnabled(bool enabled) {
if (enabled) {
_semanticsHandle ??= _pipelineOwner.ensureSemantics();
} else {
_semanticsHandle?.dispose();
_semanticsHandle = null;
}
}
void _handleWebFirstFrame(Duration _) {
assert(kIsWeb);
const MethodChannel methodChannel = MethodChannel('flutter/service_worker');
methodChannel.invokeMethod<void>('first-frame');
}
void _handleSemanticsAction(int id, SemanticsAction action, ByteData? args) {
_pipelineOwner.semanticsOwner?.performAction(
id,
action,
args != null ? const StandardMessageCodec().decodeMessage(args) : null,
);
}
void _handleSemanticsOwnerCreated() {
renderView.scheduleInitialSemantics();
}
void _handleSemanticsOwnerDisposed() {
renderView.clearSemantics();
}
void _handlePersistentFrameCallback(Duration timeStamp) {
drawFrame();
_scheduleMouseTrackerUpdate();
}
bool _debugMouseTrackerUpdateScheduled = false;
void _scheduleMouseTrackerUpdate() {
assert(!_debugMouseTrackerUpdateScheduled);
assert(() {
_debugMouseTrackerUpdateScheduled = true;
return true;
}());
SchedulerBinding.instance!.addPostFrameCallback((Duration duration) {
assert(_debugMouseTrackerUpdateScheduled);
assert(() {
_debugMouseTrackerUpdateScheduled = false;
return true;
}());
_mouseTracker!.updateAllDevices(renderView.hitTestMouseTrackers);
});
}
int _firstFrameDeferredCount = 0;
bool _firstFrameSent = false;
/// Whether frames produced by [drawFrame] are sent to the engine.
///
/// If false the framework will do all the work to produce a frame,
/// but the frame is never sent to the engine to actually appear on screen.
///
/// See also:
///
/// * [deferFirstFrame], which defers when the first frame is sent to the
/// engine.
bool get sendFramesToEngine => _firstFrameSent || _firstFrameDeferredCount == 0;
/// Tell the framework to not send the first frames to the engine until there
/// is a corresponding call to [allowFirstFrame].
///
/// Call this to perform asynchronous initialization work before the first
/// frame is rendered (which takes down the splash screen). The framework
/// will still do all the work to produce frames, but those frames are never
/// sent to the engine and will not appear on screen.
///
/// Calling this has no effect after the first frame has been sent to the
/// engine.
void deferFirstFrame() {
assert(_firstFrameDeferredCount >= 0);
_firstFrameDeferredCount += 1;
}
/// Called after [deferFirstFrame] to tell the framework that it is ok to
/// send the first frame to the engine now.
///
/// For best performance, this method should only be called while the
/// [schedulerPhase] is [SchedulerPhase.idle].
///
/// This method may only be called once for each corresponding call
/// to [deferFirstFrame].
void allowFirstFrame() {
assert(_firstFrameDeferredCount > 0);
_firstFrameDeferredCount -= 1;
// Always schedule a warm up frame even if the deferral count is not down to
// zero yet since the removal of a deferral may uncover new deferrals that
// are lower in the widget tree.
if (!_firstFrameSent)
scheduleWarmUpFrame();
}
/// Call this to pretend that no frames have been sent to the engine yet.
///
/// This is useful for tests that want to call [deferFirstFrame] and
/// [allowFirstFrame] since those methods only have an effect if no frames
/// have been sent to the engine yet.
void resetFirstFrameSent() {
_firstFrameSent = false;
}
/// Pump the rendering pipeline to generate a frame.
///
/// This method is called by [handleDrawFrame], which itself is called
/// automatically by the engine when it is time to lay out and paint a frame.
///
/// Each frame consists of the following phases:
///
/// 1. The animation phase: The [handleBeginFrame] method, which is registered
/// with [PlatformDispatcher.onBeginFrame], invokes all the transient frame
/// callbacks registered with [scheduleFrameCallback], in registration order.
/// This includes all the [Ticker] instances that are driving
/// [AnimationController] objects, which means all of the active [Animation]
/// objects tick at this point.
///
/// 2. Microtasks: After [handleBeginFrame] returns, any microtasks that got
/// scheduled by transient frame callbacks get to run. This typically includes
/// callbacks for futures from [Ticker]s and [AnimationController]s that
/// completed this frame.
///
/// After [handleBeginFrame], [handleDrawFrame], which is registered with
/// [dart:ui.PlatformDispatcher.onDrawFrame], is called, which invokes all the
/// persistent frame callbacks, of which the most notable is this method,
/// [drawFrame], which proceeds as follows:
///
/// 3. The layout phase: All the dirty [RenderObject]s in the system are laid
/// out (see [RenderObject.performLayout]). See [RenderObject.markNeedsLayout]
/// for further details on marking an object dirty for layout.
///
/// 4. The compositing bits phase: The compositing bits on any dirty
/// [RenderObject] objects are updated. See
/// [RenderObject.markNeedsCompositingBitsUpdate].
///
/// 5. The paint phase: All the dirty [RenderObject]s in the system are
/// repainted (see [RenderObject.paint]). This generates the [Layer] tree. See
/// [RenderObject.markNeedsPaint] for further details on marking an object
/// dirty for paint.
///
/// 6. The compositing phase: The layer tree is turned into a [Scene] and
/// sent to the GPU.
///
/// 7. The semantics phase: All the dirty [RenderObject]s in the system have
/// their semantics updated. This generates the [SemanticsNode] tree. See
/// [RenderObject.markNeedsSemanticsUpdate] for further details on marking an
/// object dirty for semantics.
///
/// For more details on steps 3-7, see [PipelineOwner].
///
/// 8. The finalization phase: After [drawFrame] returns, [handleDrawFrame]
/// then invokes post-frame callbacks (registered with [addPostFrameCallback]).
///
/// Some bindings (for example, the [WidgetsBinding]) add extra steps to this
/// list (for example, see [WidgetsBinding.drawFrame]).
//
// When editing the above, also update widgets/binding.dart's copy.
@protected
void drawFrame() {
assert(renderView != null);
pipelineOwner.flushLayout();
pipelineOwner.flushCompositingBits();
pipelineOwner.flushPaint();
if (sendFramesToEngine) {
renderView.compositeFrame(); // this sends the bits to the GPU
pipelineOwner.flushSemantics(); // this also sends the semantics to the OS.
_firstFrameSent = true;
}
}
@override
Future<void> performReassemble() async {
await super.performReassemble();
Timeline.startSync('Dirty Render Tree', arguments: timelineArgumentsIndicatingLandmarkEvent);
try {
renderView.reassemble();
} finally {
Timeline.finishSync();
}
scheduleWarmUpFrame();
await endOfFrame;
}
@override
void hitTest(HitTestResult result, Offset position) {
assert(renderView != null);
assert(result != null);
assert(position != null);
renderView.hitTest(result, position: position);
super.hitTest(result, position);
}
Future<void> _forceRepaint() {
late RenderObjectVisitor visitor;
visitor = (RenderObject child) {
child.markNeedsPaint();
child.visitChildren(visitor);
};
instance?.renderView.visitChildren(visitor);
return endOfFrame;
}
}
/// Prints a textual representation of the entire render tree.
void debugDumpRenderTree() {
debugPrint(RendererBinding.instance?.renderView.toStringDeep() ?? 'Render tree unavailable.');
}
/// Prints a textual representation of the entire layer tree.
void debugDumpLayerTree() {
debugPrint(RendererBinding.instance?.renderView.debugLayer?.toStringDeep() ?? 'Layer tree unavailable.');
}
/// Prints a textual representation of the entire semantics tree.
/// This will only work if there is a semantics client attached.
/// Otherwise, a notice that no semantics are available will be printed.
///
/// The order in which the children of a [SemanticsNode] will be printed is
/// controlled by the [childOrder] parameter.
void debugDumpSemanticsTree(DebugSemanticsDumpOrder childOrder) {
debugPrint(RendererBinding.instance?.renderView.debugSemantics?.toStringDeep(childOrder: childOrder) ?? 'Semantics not collected.');
}
/// A concrete binding for applications that use the Rendering framework
/// directly. This is the glue that binds the framework to the Flutter engine.
///
/// You would only use this binding if you are writing to the
/// rendering layer directly. If you are writing to a higher-level
/// library, such as the Flutter Widgets library, then you would use
/// that layer's binding.
class RenderingFlutterBinding extends BindingBase with GestureBinding, SchedulerBinding, ServicesBinding, SemanticsBinding, PaintingBinding, RendererBinding {
/// Creates a binding for the rendering layer.
///
/// The `root` render box is attached directly to the [renderView] and is
/// given constraints that require it to fill the window.
RenderingFlutterBinding({ RenderBox? root }) {
assert(renderView != null);
renderView.child = root;
}
}