Make rendering use PaintingNodes for increased efficiency.

sky/sdk/lib/rendering/object.dart

Index: sky/sdk/lib/rendering/object.dart
diff --git a/sky/sdk/lib/rendering/object.dart b/sky/sdk/lib/rendering/object.dart
index b384d029deb69cd6a74e850ff5500b1c7c57906b..e201ce26bd17b78ce1174e359b91f8365c00d8bc 100644
--- a/sky/sdk/lib/rendering/object.dart
+++ b/sky/sdk/lib/rendering/object.dart
@@ -27,10 +27,22 @@ class ParentData {
 }
 
 class PaintingCanvas extends sky.Canvas {
-  PaintingCanvas(sky.PictureRecorder recorder, Size bounds) : super(recorder, bounds);
+  PaintingCanvas(sky.PictureRecorder recorder, Rect bounds) : super(recorder, bounds);
 
+  List<RenderObject> _children; // used by _doPaint() to find out which RenderObjects to ask to paint

[Hixie, 2015/07/02 00:19:54]

rename this to _descendantsWithPaintNodes or some such

[iansf, 2015/07/06 18:22:01]

Done.

   void paintChild(RenderObject child, Point point) {
-    child.paint(this, point.toOffset());
+    if (child.createNewDisplayList) {
+      if (_children == null)
+        _children = new List<RenderObject>();
+      assert(!_children.contains(child));
+      _children.add(child);
+

[Hixie, 2015/07/02 00:19:54]

remove this blank line

[iansf, 2015/07/06 18:22:01]

Done.

+      translate(point.x, point.y);
+      drawPaintingNode(child._paintingNode);
+      translate(-point.x, -point.y);
+    } else {
+      child.performPaint(this, point.toOffset());
+    }
   }
 }
 
@@ -138,6 +150,7 @@ abstract class RenderObject extends AbstractNode implements HitTestTarget {
     assert(_relayoutSubtreeRoot == null);
     _relayoutSubtreeRoot = this;
     _nodesNeedingLayout.add(this);
+    _nodesNeedingPaint.add(this);
     scheduler.ensureVisualUpdate();
   }
   static void flushLayout() {
@@ -238,10 +251,79 @@ abstract class RenderObject extends AbstractNode implements HitTestTarget {
 
   // PAINTING
 
-  static bool debugDoingPaint = false;
+  static List<RenderObject> _nodesNeedingPaint = new List<RenderObject>();
+  static bool _debugDoingPaint = false;
+  static bool get debugDoingPaint => _debugDoingPaint;
+
+  sky.PaintingNode _paintingNode = new sky.PaintingNode(); // only set if createNewDisplayList is true
+  sky.PaintingNode get paintingNode => _paintingNode;
+  bool _needsPaint = true;
+  bool get needsPaint => _needsPaint;
+  bool get createNewDisplayList => true;
+
   void markNeedsPaint() {
     assert(!debugDoingPaint);
-    scheduler.ensureVisualUpdate();
+    if (_needsPaint) return;
+    if (createNewDisplayList) {
+      _needsPaint = true;
+      _nodesNeedingPaint.add(this);
+

[Hixie, 2015/07/02 00:19:54]

remove this random blank line :-)

[iansf, 2015/07/06 18:22:01]

Done.

+      scheduler.ensureVisualUpdate();
+    } else if (parent != null) {
+      if (parent is RenderObject) {
+        (parent as RenderObject).markNeedsPaint(); // TODO(ianh): remove the cast once the analyzer is cleverer
+      }
+    }
+  }
+
+  static void flushPaint() {
+    _debugDoingPaint = true;
+    List<RenderObject> dirtyNodes = _nodesNeedingPaint;
+    _nodesNeedingPaint = new List<RenderObject>();
+    dirtyNodes..sort((a, b) => a.depth - b.depth)..forEach((node) {
+      if (node._needsPaint && node.attached)
+        node._doPaint();
+    });
+    assert(_nodesNeedingPaint.length == 0);
+    _debugDoingPaint = false;
+  }
+
+  void _doPaint() {

[Hixie, 2015/07/02 00:19:54]

call this _paintOnPaintNode() or _updatePaintNode() or some such.

[iansf, 2015/07/06 18:22:01]

Done.

+    assert(!_needsLayout);
+    assert(createNewDisplayList);
+    sky.PictureRecorder recorder = new sky.PictureRecorder();
+    PaintingCanvas canvas = new PaintingCanvas(recorder, paintBounds);
+    _needsPaint = false;
+    try {
+      performPaint(canvas, Point.origin.toOffset());

[Hixie, 2015/07/02 00:19:54]

use Offset.zero instead

[iansf, 2015/07/06 18:22:01]

Done.

+    } catch (e, stack) {
+      print('Exception raised during paint of ${this.runtimeType}: ${e}');

[Hixie, 2015/07/02 00:19:54]

make this match the style in layout()

[iansf, 2015/07/06 18:22:01]

Done.

+      print(stack);
+      return;
+    }
+    assert(!_needsLayout); // check that the paint() method didn't mark us dirty again
+    assert(!_needsPaint); // check that the paint() method didn't mark us dirty again
+    _paintingNode.setBackingDrawable(recorder.endRecordingAsDrawable());
+
+    if (canvas._children != null) {
+      canvas._children.forEach((node) {
+        assert(node.attached == attached);
+        if (node._needsPaint)
+          node._doPaint();
+      });
+    }
+
+  }
+
+  Rect get paintBounds;

[Hixie, 2015/07/02 00:19:54]

move this below performPaint()

[iansf, 2015/07/06 18:22:01]

Done.

+
+  void performPaint(PaintingCanvas canvas, Offset offset) {

[Hixie, 2015/07/02 00:19:54]

call this _paintOnCanvas() or some such.

[iansf, 2015/07/06 18:22:01]

Done.

+    _needsPaint = false;
+    paint(canvas, offset);
+    assert(!_needsPaint);
+  }
+
+
   }
   void paint(PaintingCanvas canvas, Offset offset) { }