Allow independent rendering pipelines

Fixes #2723

packages/flutter/benchmark/stocks/layout_bench.dart

@@ -31,7 +31,7 @@ void main() {
 
   for (int i = 0; i < _kNumberOfIterations || _kRunForever; ++i) {
     renderView.configuration = (i % 2 == 0) ? big : small;
-    RenderObject.flushLayout();
+    WidgetFlutterBinding.instance.pipelineOwner.flushLayout();
   }
 
   watch.stop();

packages/flutter/lib/src/rendering/README.md

@@ -20,8 +20,8 @@ The last phase of a frame is the Semantics phase. This only occurs if
 a semantics server has been installed, for example if the user is
 using an accessibility tool.
 
-Each frame, the semantics phase starts with a call to the static
-`RenderObject.flushSemantics()` method from the `Renderer` binding's
+Each frame, the semantics phase starts with a call to the
+`PipelineOwner.flushSemantics()` method from the `Renderer` binding's
 `beginFrame()` method.
 
 Each node marked as needing semantics (which initially is just the

packages/flutter/lib/src/rendering/binding.dart

@@ -48,6 +48,10 @@ abstract class Renderer extends Object with Scheduler, Services
     handleMetricsChanged(); // configures renderView's metrics
   }
 
+  /// The render tree's owner, which maintains dirty state for layout,
+  /// composite, paint, and accessibility semantics
+  final PipelineOwner pipelineOwner = new PipelineOwner();
+
   /// The render tree that's attached to the output surface.
   RenderView get renderView => _renderView;
   RenderView _renderView;
@@ -58,7 +62,7 @@ abstract class Renderer extends Object with Scheduler, Services
     if (_renderView != null)
       _renderView.detach();
     _renderView = value;
-    _renderView.attach();
+    _renderView.attach(pipelineOwner);
   }
 
   void handleMetricsChanged() {
@@ -81,12 +85,12 @@ abstract class Renderer extends Object with Scheduler, Services
   /// Pump the rendering pipeline to generate a frame.
   void beginFrame() {
     assert(renderView != null);
-    RenderObject.flushLayout();
-    RenderObject.flushCompositingBits();
-    RenderObject.flushPaint();
+    pipelineOwner.flushLayout();
+    pipelineOwner.flushCompositingBits();
+    pipelineOwner.flushPaint();
     renderView.compositeFrame(); // this sends the bits to the GPU
     if (SemanticsNode.hasListeners) {
-      RenderObject.flushSemantics();
+      pipelineOwner.flushSemantics();
       SemanticsNode.sendSemanticsTree();
     }
   }

packages/flutter/lib/src/rendering/block.dart

@@ -337,8 +337,8 @@ class RenderBlockViewport extends RenderBlockBase {
   }
 
   @override
-  void attach() {
-    super.attach();
+  void attach(PipelineOwner owner) {
+    super.attach(owner);
     _overlayPainter?.attach(this);
   }
 

packages/flutter/lib/src/rendering/box.dart

@@ -388,12 +388,7 @@ class BoxHitTestEntry extends HitTestEntry {
 /// Parent data used by [RenderBox] and its subclasses.
 class BoxParentData extends ParentData {
   /// The offset at which to paint the child in the parent's coordinate system
-  Offset get offset => _offset;
-  Offset _offset = Offset.zero;
-  void set offset(Offset value) {
-    assert(RenderObject.debugDoingLayout);
-    _offset = value;
-  }
+  Offset offset = Offset.zero;
 
   @override
   String toString() => 'offset=$offset';
@@ -556,9 +551,9 @@ abstract class RenderBox extends RenderObject {
     assert(!_debugDoingBaseline);
     assert(() {
       final RenderObject parent = this.parent;
-      if (RenderObject.debugDoingLayout)
+      if (owner.debugDoingLayout)
         return (RenderObject.debugActiveLayout == parent) && parent.debugDoingThisLayout;
-      if (RenderObject.debugDoingPaint)
+      if (owner.debugDoingPaint)
         return ((RenderObject.debugActivePaint == parent) && parent.debugDoingThisPaint) ||
                ((RenderObject.debugActivePaint == this) && debugDoingThisPaint);
       assert(parent == this.parent);

packages/flutter/lib/src/rendering/child_view.dart

@@ -171,8 +171,8 @@ class RenderChildView extends RenderBox {
   }
 
   @override
-  void attach() {
-    super.attach();
+  void attach(PipelineOwner owner) {
+    super.attach(owner);
     _child?._attach();
   }
 

packages/flutter/lib/src/rendering/node.dart

@@ -51,7 +51,7 @@ class AbstractNode {
 
   /// Call only from overrides of [redepthChildren]
   void redepthChild(AbstractNode child) {
-    assert(child._attached == _attached);
+    assert(child.owner == owner);
     if (child._depth <= _depth) {
       child._depth = _depth + 1;
       child.redepthChildren();
@@ -62,16 +62,21 @@ class AbstractNode {
   /// redepthChild(child) for each child. Do not call directly.
   void redepthChildren() { }
 
-  bool _attached = false;
+  Object _owner;
+  /// The owner for this node (null if unattached).
+  Object get owner => _owner;
+
   /// Whether this node is in a tree whose root is attached to something.
-  bool get attached => _attached;
+  bool get attached => _owner != null;
 
-  /// Mark this node as attached.
+  /// Mark this node as attached to the given owner.
   ///
   /// Typically called only from the parent's attach(), and to mark the root of
   /// a tree attached.
-  void attach() {
-    _attached = true;
+  void attach(Object owner) {
+    assert(owner != null);
+    assert(_owner == null);
+    _owner = owner;
   }
 
   /// Mark this node as detached.
@@ -79,7 +84,8 @@ class AbstractNode {
   /// Typically called only from the parent's detach(), and to mark the root of
   /// a tree detached.
   void detach() {
-    _attached = false;
+    assert(_owner != null);
+    _owner = null;
   }
 
   AbstractNode _parent;
@@ -99,7 +105,7 @@ class AbstractNode {
     });
     child._parent = this;
     if (attached)
-      child.attach();
+      child.attach(_owner);
     redepthChild(child);
   }
 

packages/flutter/lib/src/rendering/proxy_box.dart

@@ -1035,8 +1035,8 @@ class RenderDecoratedBox extends RenderProxyBox {
   }
 
   @override
-  void attach() {
-    super.attach();
+  void attach(PipelineOwner owner) {
+    super.attach(owner);
     _addListenerIfNeeded();
   }
 

packages/flutter/lib/src/rendering/semantics.dart

@@ -58,10 +58,11 @@ class SemanticsNode extends AbstractNode {
        _actionHandler = handler;
 
   SemanticsNode.root({
-    SemanticActionHandler handler
+    SemanticActionHandler handler,
+    Object owner
   }) : _id = 0,
        _actionHandler = handler {
-    attach();
+    attach(owner);
   }
 
   static int _lastIdentifier = 0;
@@ -265,8 +266,8 @@ class SemanticsNode extends AbstractNode {
   static Set<SemanticsNode> _detachedNodes = new Set<SemanticsNode>();
 
   @override
-  void attach() {
-    super.attach();
+  void attach(Object owner) {
+    super.attach(owner);
     assert(!_nodes.containsKey(_id));
     _nodes[_id] = this;
     _detachedNodes.remove(this);
@@ -274,7 +275,7 @@ class SemanticsNode extends AbstractNode {
       _inheritedMergeAllDescendantsIntoThisNode = parent._shouldMergeAllDescendantsIntoThisNode;
     if (_children != null) {
       for (SemanticsNode child in _children)
-        child.attach();
+        child.attach(owner);
     }
   }
 

packages/flutter/lib/src/rendering/view.dart

@@ -33,7 +33,7 @@ class ViewConfiguration {
 /// The root of the render tree.
 ///
 /// The view represents the total output surface of the render tree and handles
-/// bootstraping the rendering pipeline. The view has a unique child
+/// bootstrapping the rendering pipeline. The view has a unique child
 /// [RenderBox], which is required to fill the entire output surface.
 class RenderView extends RenderObject with RenderObjectWithChildMixin<RenderBox> {
   RenderView({

packages/flutter/lib/src/rendering/viewport.dart

@@ -168,8 +168,8 @@ class RenderViewportBase extends RenderBox implements HasMainAxis {
   }
 
   @override
-  void attach() {
-    super.attach();
+  void attach(PipelineOwner owner) {
+    super.attach(owner);
     _overlayPainter?.attach(this);
   }
 

packages/flutter/lib/src/widgets/gesture_detector.dart

@@ -335,7 +335,11 @@ class RawGestureDetectorState extends State<RawGestureDetector> {
   /// the gesture detector should be enabled.
   void replaceGestureRecognizers(Map<Type, GestureRecognizerFactory> gestures) {
     assert(() {
-      if (!RenderObject.debugDoingLayout) {
+      // TODO kgiesing This assert will trigger if the owner of the current
+      // tree is different from the owner assigned to the renderer instance.
+      // Once elements have a notion of owners this assertion can be written
+      // more clearly.
+      if (!Renderer.instance.pipelineOwner.debugDoingLayout) {
         throw new FlutterError(
           'Unexpected call to replaceGestureRecognizers() method of RawGestureDetectorState.\n'
           'The replaceGestureRecognizers() method can only be called during the layout phase. '

packages/flutter/test/rendering/independent_layout_test.dart

+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import 'package:flutter/material.dart';
+import 'package:flutter/rendering.dart';
+import 'package:test/test.dart';
+
+import 'rendering_tester.dart';
+
+class TestLayout {
+  TestLayout() {
+    // viewport incoming constraints are tight 800x600
+    // viewport is vertical by default
+    root = new RenderViewport(
+      child: new RenderCustomPaint(
+        painter: new TestCallbackPainter(
+          onPaint: () { painted = true; }
+        ),
+        child: child = new RenderConstrainedBox(
+          additionalConstraints: new BoxConstraints.tightFor(height: 10.0, width: 10.0)
+        )
+      )
+    );
+  }
+  RenderBox root;
+  RenderBox child;
+  bool painted = false;
+}
+
+void main() {
+  test('onscreen layout does not affect offscreen', () {
+    TestLayout onscreen = new TestLayout();
+    TestLayout offscreen = new TestLayout();
+    expect(onscreen.child.hasSize, isFalse);
+    expect(onscreen.painted, isFalse);
+    expect(offscreen.child.hasSize, isFalse);
+    expect(offscreen.painted, isFalse);
+    // Attach the offscreen to a custom render view and owner
+    RenderView renderView = new TestRenderView();
+    PipelineOwner pipelineOwner = new PipelineOwner();
+    renderView.attach(pipelineOwner);
+    renderView.child = offscreen.root;
+    renderView.scheduleInitialFrame();
+    // Lay out the onscreen in the default binding
+    layout(onscreen.root, phase: EnginePhase.layout);
+    expect(onscreen.child.hasSize, isTrue);
+    expect(onscreen.painted, isFalse);
+    expect(onscreen.child.size, equals(const Size(800.0, 10.0)));
+    // Make sure the offscreen didn't get laid out
+    expect(offscreen.child.hasSize, isFalse);
+    expect(offscreen.painted, isFalse);
+    // Now lay out the offscreen
+    pipelineOwner.flushLayout();
+    expect(offscreen.child.hasSize, isTrue);
+    expect(offscreen.painted, isFalse);
+  });
+  test('offscreen layout does not affect onscreen', () {
+    TestLayout onscreen = new TestLayout();
+    TestLayout offscreen = new TestLayout();
+    expect(onscreen.child.hasSize, isFalse);
+    expect(onscreen.painted, isFalse);
+    expect(offscreen.child.hasSize, isFalse);
+    expect(offscreen.painted, isFalse);
+    // Attach the offscreen to a custom render view and owner
+    RenderView renderView = new TestRenderView();
+    PipelineOwner pipelineOwner = new PipelineOwner();
+    renderView.attach(pipelineOwner);
+    renderView.child = offscreen.root;
+    renderView.scheduleInitialFrame();
+    // Lay out the offscreen
+    pipelineOwner.flushLayout();
+    expect(offscreen.child.hasSize, isTrue);
+    expect(offscreen.painted, isFalse);
+    // Make sure the onscreen didn't get laid out
+    expect(onscreen.child.hasSize, isFalse);
+    expect(onscreen.painted, isFalse);
+    // Now lay out the onscreen in the default binding
+    layout(onscreen.root, phase: EnginePhase.layout);
+    expect(onscreen.child.hasSize, isTrue);
+    expect(onscreen.painted, isFalse);
+    expect(onscreen.child.size, equals(const Size(800.0, 10.0)));
+  });
+}

packages/flutter/test/rendering/rendering_tester.dart

@@ -41,16 +41,16 @@ class TestRenderingFlutterBinding extends BindingBase with Scheduler, Services,
 
   @override
   void beginFrame() {
-    RenderObject.flushLayout();
+    pipelineOwner.flushLayout();
     if (phase == EnginePhase.layout)
       return;
-    RenderObject.flushCompositingBits();
+    pipelineOwner.flushCompositingBits();
     if (phase == EnginePhase.compositingBits)
       return;
-    RenderObject.flushPaint();
+    pipelineOwner.flushPaint();
     if (phase == EnginePhase.paint)
       return;
-    renderer.renderView.compositeFrame();
+    renderView.compositeFrame();
   }
 }
 

packages/flutter_sprites/lib/src/sprite_box.dart

@@ -58,8 +58,8 @@ class SpriteBox extends RenderBox {
   }
 
   @override
-  void attach() {
-    super.attach();
+  void attach(PipelineOwner owner) {
+    super.attach(owner);
     _scheduleTick();
   }
 

packages/flutter_test/lib/src/widget_tester.dart

@@ -46,20 +46,20 @@ class _SteppedWidgetFlutterBinding extends WidgetFlutterBinding {
   // Cloned from Renderer.beginFrame() but with early-exit semantics.
   void _beginFrame() {
     assert(renderView != null);
-    RenderObject.flushLayout();
+    pipelineOwner.flushLayout();
     if (phase == EnginePhase.layout)
       return;
-    RenderObject.flushCompositingBits();
+    pipelineOwner.flushCompositingBits();
     if (phase == EnginePhase.compositingBits)
       return;
-    RenderObject.flushPaint();
+    pipelineOwner.flushPaint();
     if (phase == EnginePhase.paint)
       return;
     renderView.compositeFrame(); // this sends the bits to the GPU
     if (phase == EnginePhase.composite)
       return;
     if (SemanticsNode.hasListeners) {
-      RenderObject.flushSemantics();
+      pipelineOwner.flushSemantics();
       if (phase == EnginePhase.flushSemantics)
         return;
       SemanticsNode.sendSemanticsTree();

packages/flutter_tools/lib/src/commands/analyze.dart

@@ -347,6 +347,7 @@ class AnalyzeCommand extends FlutterCommand {
       new RegExp('^\\[(hint|error)\\] Unused import \\(${mainFile.path},'),
       new RegExp(r'^\[.+\] .+ \(.+/\.pub-cache/.+'),
       new RegExp('\\[warning\\] Missing concrete implementation of \'RenderObject\\.applyPaintTransform\''), // https://github.com/dart-lang/sdk/issues/25232
+      new RegExp('\\[warning\\] Missing concrete implementation of \'AbstractNode\\.attach\''), // https://github.com/dart-lang/sdk/issues/25232
       new RegExp(r'[0-9]+ (error|warning|hint|lint).+found\.'),
       new RegExp(r'^$'),
     ];