Introduce BlockViewport.

sky/sdk/lib/rendering/object.dart

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 import 'dart:math' as math;
 import 'dart:sky' as sky;
 import 'dart:sky' show Point, Offset, Size, Rect, Color, Paint, Path;
 
 import '../base/hit_test.dart';
 import '../base/node.dart';
@@ skipping 21 matching lines @@
   void paintChild(RenderObject child, Point point) {
     child.paint(this, point.toOffset());
   }
 }
 
 abstract class Constraints {
   const Constraints();
   bool get isTight;
 }
 
+typedef void LayoutCallback(Constraints constraints);
+
 abstract class RenderObject extends AbstractNode implements HitTestTarget {
 
   // LAYOUT
 
   // parentData is only for use by the RenderObject that actually lays this
   // node out, and any other nodes who happen to know exactly what
   // kind of node that is.
   dynamic parentData; // TODO(ianh): change the type of this back to ParentData once the analyzer is cleverer
   void setupParentData(RenderObject child) {
     // override this to setup .parentData correctly for your class
-    assert(!debugDoingLayout);
-    assert(!debugDoingPaint);
+    assert(debugCanPerformMutations);
     if (child.parentData is! ParentData)
       child.parentData = new ParentData();
   }
 
   void adoptChild(RenderObject child) { // only for use by subclasses
     // call this whenever you decide a node is a child
-    assert(!debugDoingLayout);
-    assert(!debugDoingPaint);
+    assert(debugCanPerformMutations);
     assert(child != null);
     setupParentData(child);
     super.adoptChild(child);
     markNeedsLayout();
   }
   void dropChild(RenderObject child) { // only for use by subclasses
-    assert(!debugDoingLayout);
-    assert(!debugDoingPaint);
+    assert(debugCanPerformMutations);
     assert(child != null);
     assert(child.parentData != null);
     child._cleanRelayoutSubtreeRoot();
     child.parentData.detach();
     super.dropChild(child);
     markNeedsLayout();
   }
 
-  static List<RenderObject> _nodesNeedingLayout = new List<RenderObject>();
   static bool _debugDoingLayout = false;
   static bool get debugDoingLayout => _debugDoingLayout;
   bool _debugDoingThisResize = false;
   bool get debugDoingThisResize => _debugDoingThisResize;
   bool _debugDoingThisLayout = false;
   bool get debugDoingThisLayout => _debugDoingThisLayout;
   static RenderObject _debugActiveLayout = null;
   static RenderObject get debugActiveLayout => _debugActiveLayout;
+  bool _debugDoingThisLayoutWithCallback = false;
+  bool _debugMutationsLocked = false;
   bool _debugCanParentUseSize;
   bool get debugCanParentUseSize => _debugCanParentUseSize;
+  bool get debugCanPerformMutations {
+    RenderObject node = this;
+    while (true) {
+      if (node._debugDoingThisLayoutWithCallback)
+        return true;
+      if (node._debugMutationsLocked)
+        return false;
+      if (node.parent is! RenderObject)
+        return true;
+      node = node.parent;
+    }
+  }
+
+  static List<RenderObject> _nodesNeedingLayout = new List<RenderObject>();
   bool _needsLayout = true;
   bool get needsLayout => _needsLayout;
   RenderObject _relayoutSubtreeRoot;
   Constraints _constraints;
   Constraints get constraints => _constraints;
   bool debugDoesMeetConstraints(); // override this in a subclass to verify that your state matches the constraints object
   bool debugAncestorsAlreadyMarkedNeedsLayout() {
     if (_relayoutSubtreeRoot == null)
       return true; // we haven't yet done layout even once, so there's nothing for us to do
     RenderObject node = this;
     while (node != _relayoutSubtreeRoot) {
       assert(node._relayoutSubtreeRoot == _relayoutSubtreeRoot);
       assert(node.parent != null);
       node = node.parent as RenderObject;
       if (!node._needsLayout)
         return false;
     }
     assert(node._relayoutSubtreeRoot == node);
     return true;
   }
   void markNeedsLayout() {
-    assert(!debugDoingLayout);
-    assert(!debugDoingPaint);
+    assert(debugCanPerformMutations);
     if (_needsLayout) {
       assert(debugAncestorsAlreadyMarkedNeedsLayout());
       return;
     }
     _needsLayout = true;
     assert(_relayoutSubtreeRoot != null);
     if (_relayoutSubtreeRoot != this) {
       final parent = this.parent; // TODO(ianh): Remove this once the analyzer is cleverer
       assert(parent is RenderObject);
       parent.markNeedsLayout();
@@ skipping 30 matching lines @@
           node.layoutWithoutResize();
       });
     } finally {
       _debugDoingLayout = false;
       sky.tracing.end('RenderObject.flushLayout');
     }
   }
   void layoutWithoutResize() {
     try {
       assert(_relayoutSubtreeRoot == this);
-      _debugCanParentUseSize = false;
-      _debugDoingThisLayout = true;
-      RenderObject debugPreviousActiveLayout = _debugActiveLayout;
-      _debugActiveLayout = this;
+      RenderObject debugPreviousActiveLayout;
+      assert(!_debugMutationsLocked);
+      assert(!_debugDoingThisLayoutWithCallback);
+      assert(() {
+        _debugMutationsLocked = true;
+        _debugCanParentUseSize = false;
+        _debugDoingThisLayout = true;
+        debugPreviousActiveLayout = _debugActiveLayout;
+        _debugActiveLayout = this;
+        return true;
+      });
       performLayout();
-      _debugActiveLayout = debugPreviousActiveLayout;
-      _debugDoingThisLayout = false;
-      _debugCanParentUseSize = null;
+      assert(() {
+        _debugActiveLayout = debugPreviousActiveLayout;
+        _debugDoingThisLayout = false;
+        _debugCanParentUseSize = null;
+        _debugMutationsLocked = false;
+        return true;
+      });
     } catch (e, stack) {
       print('Exception raised during layout:\n${e}\nContext:\n${this}');
       print(stack);
       return;
     }
     _needsLayout = false;
     markNeedsPaint();
   }
   void layout(Constraints constraints, { bool parentUsesSize: false }) {
     final parent = this.parent; // TODO(ianh): Remove this once the analyzer is cleverer
     RenderObject relayoutSubtreeRoot;
     if (!parentUsesSize || sizedByParent || constraints.isTight || parent is! RenderObject)
       relayoutSubtreeRoot = this;
     else
       relayoutSubtreeRoot = parent._relayoutSubtreeRoot;
     assert(parent == this.parent); // TODO(ianh): Remove this once the analyzer is cleverer
     if (!needsLayout && constraints == _constraints && relayoutSubtreeRoot == _relayoutSubtreeRoot)
       return;
     _constraints = constraints;
     _relayoutSubtreeRoot = relayoutSubtreeRoot;
-    _debugCanParentUseSize = parentUsesSize;
+    assert(!_debugMutationsLocked);
+    assert(!_debugDoingThisLayoutWithCallback);
+    assert(() {
+      _debugMutationsLocked = true;
+      _debugCanParentUseSize = parentUsesSize;
+      return true;
+    });
     if (sizedByParent) {
-      _debugDoingThisResize = true;
+      assert(() { _debugDoingThisResize = true; return true; });
       performResize();
-      _debugDoingThisResize = false;
+      assert(() { _debugDoingThisResize = false; return true; });
     }
-    _debugDoingThisLayout = true;
-    RenderObject debugPreviousActiveLayout = _debugActiveLayout;
-    _debugActiveLayout = this;
+    RenderObject debugPreviousActiveLayout;
+    assert(() {
+      _debugDoingThisLayout = true;
+      debugPreviousActiveLayout = _debugActiveLayout;
+      _debugActiveLayout = this;
+      return true;
+    });
     performLayout();
-    _debugActiveLayout = debugPreviousActiveLayout;
-    _debugDoingThisLayout = false;
-    _debugCanParentUseSize = null;
+    assert(() {
+      _debugActiveLayout = debugPreviousActiveLayout;
+      _debugDoingThisLayout = false;
+      _debugCanParentUseSize = null;
+      _debugMutationsLocked = false;
+      return true;
+    });
     assert(debugDoesMeetConstraints());
     _needsLayout = false;
     markNeedsPaint();
     assert(parent == this.parent); // TODO(ianh): Remove this once the analyzer is cleverer
   }
   bool get sizedByParent => false; // return true if the constraints are the only input to the sizing algorithm (in particular, child nodes have no impact)
   void performResize(); // set the local dimensions, using only the constraints (only called if sizedByParent is true)
   void performLayout();
     // Override this to perform relayout without your parent's
     // involvement.
     //
     // This is called during layout. If sizedByParent is true, then
     // performLayout() should not change your dimensions, only do that
     // in performResize(). If sizedByParent is false, then set both
     // your dimensions and do your children's layout here.
     //
     // When calling layout() on your children, pass in
     // "parentUsesSize: true" if your size or layout is dependent on
     // your child's size or intrinsic dimensions.
+  void invokeLayoutCallback(LayoutCallback callback) {
+    assert(_debugMutationsLocked);
+    assert(_debugDoingThisLayout);
+    assert(!_debugDoingThisLayoutWithCallback);
+    assert(() {
+      _debugDoingThisLayoutWithCallback = true;
+      return true;
+    });
+    callback(constraints);
+    assert(() {
+      _debugDoingThisLayoutWithCallback = false;
+      return true;
+    });
+  }
 
   // when the parent has rotated (e.g. when the screen has been turned
   // 90 degrees), immediately prior to layout() being called for the
   // new dimensions, rotate() is called with the old and new angles.
   // The next time paint() is called, the coordinate space will have
   // been rotated N quarter-turns clockwise, where:
   //    N = newAngle-oldAngle
   // ...but the rendering is expected to remain the same, pixel for
   // pixel, on the output device. Then, the layout() method or
   // equivalent will be invoked.
@@ skipping 212 matching lines @@
   }
   void addAll(List<ChildType> children) {
     if (children != null)
       for (ChildType child in children)
         add(child);
   }
   void _removeFromChildList(ChildType child) {
     assert(child.parentData is ParentDataType);
     assert(_debugUltimatePreviousSiblingOf(child, equals: _firstChild));
     assert(_debugUltimateNextSiblingOf(child, equals: _lastChild));
-    _childCount -= 1;
     assert(_childCount >= 0);
     if (child.parentData.previousSibling == null) {
       assert(_firstChild == child);
       _firstChild = child.parentData.nextSibling;
     } else {
       assert(child.parentData.previousSibling.parentData is ParentDataType);
       child.parentData.previousSibling.parentData.nextSibling = child.parentData.nextSibling;
     }
     if (child.parentData.nextSibling == null) {
       assert(_lastChild == child);
       _lastChild = child.parentData.previousSibling;
     } else {
       assert(child.parentData.nextSibling.parentData is ParentDataType);
       child.parentData.nextSibling.parentData.previousSibling = child.parentData.previousSibling;
     }
     child.parentData.previousSibling = null;
     child.parentData.nextSibling = null;
+    _childCount -= 1;
   }
   void remove(ChildType child) {
     _removeFromChildList(child);
     dropChild(child);
   }
+  void removeAll() {
+    ChildType child = _firstChild;
+    while (child != null) {
+      assert(child.parentData is ParentDataType);
+      ChildType next = child.parentData.nextSibling;
+      child.parentData.previousSibling = null;
+      child.parentData.nextSibling = null;
+      dropChild(child);
+      child = next;
+    }
+    _firstChild = null;
+    _lastChild = null;
+    _childCount = 0;
+  }
   void move(ChildType child, { ChildType before }) {
     assert(child != this);
     assert(before != this);
     assert(child != before);
     assert(child.parent == this);
     assert(child.parentData is ParentDataType);
     if (child.parentData.nextSibling == before)
       return;
     _removeFromChildList(child);
     _addToChildList(child, before: before);
@@ skipping 43 matching lines @@
     int count = 1;
     ChildType child = _firstChild;
     while (child != null) {
       result += '${prefix}child ${count}: ${child.toString(prefix)}';
       count += 1;
       child = child.parentData.nextSibling;
     }
     return result;
   }
 }