Paint tree logic for layout2.dart

sky/sdk/lib/framework/layout2.dart

Index: sky/sdk/lib/framework/layout2.dart
diff --git a/sky/sdk/lib/framework/layout2.dart b/sky/sdk/lib/framework/layout2.dart
index e3773e2bcc67bea48bdb19bafce41577409a2637..5837577113eb2105f6ec7a31d0b58664dc80a9f2 100644
--- a/sky/sdk/lib/framework/layout2.dart
+++ b/sky/sdk/lib/framework/layout2.dart
@@ -32,14 +32,27 @@ double clamp({double min: 0.0, double value: 0.0, double max: double.INFINITY})
 
 class RenderNodeDisplayList extends sky.PictureRecorder {
   RenderNodeDisplayList(double width, double height) : super(width, height);
+  List<RenderNode> _children; // used by _doPaint() to find out which RenderNodes to ask to paint
   void paintChild(RenderNode child, double x, double y) {
-    save();
-    translate(x, y);
-    child.paint(this);
-    restore();
+    if (child.createNewDisplayList) {
+      if (_children == null)
+        _children = new List<RenderNode>();
+      assert(!_children.contains(child));
+      _children.add(child);
+      drawPaintNode(child._paintNode, transform: new Matrix.translate(x, y));
+    } else {
+      save();
+      translate(x, y);
+      child.paint(this);
+      restore();
+    }
   }
 }
 
+class PaintOptions {
+  Matrix transform = Matrix.IDENTITY;
+}
+
 abstract class RenderNode extends AbstractNode {
 
   // LAYOUT
@@ -222,15 +235,57 @@ abstract class RenderNode extends AbstractNode {
 
   // PAINTING
 
+  static List<RenderNode> _nodesNeedingPaint = new List<RenderNode>();
   static bool _debugDoingPaint = false;
+  PaintNode _paintNode; // only set if createNewDisplayList is true
+  bool _needsPaint = true;
+  bool get needsPaint => _needsPaint;
+  bool get createNewDisplayList => false;
   void markNeedsPaint() {
     assert(!_debugDoingPaint);
-    var ancestor = this;
-    while (ancestor.parent != null)
-      ancestor = ancestor.parent;
-    assert(ancestor is Screen);
-    ancestor.paintFrame();
+    if (_needsPaint) return;
+    if (createNewDisplayList) {
+      _needsPaint = true;
+      _nodesNeedingPaint.add(this);
+    } else {
+      assert(parent != null);
+      parent.markNeedsPaint();
+    }
+  }
+  static void flushPaint() {
+    List<RenderNode> dirtyNodes = _nodesNeedingPaint;
+    _nodesNeedingPaint = new List<RenderNode>();
+    dirtyNodes..sort((a, b) => a.depth - b.depth)..forEach((node) {
+      if (node._needsPaint && node.attached)
+        node._doPaint();
+    });
   }
+  void _doPaint() {
+    assert(!_needsLayout);
+    assert(createNewDisplayList);
+    RenderNodeDisplayList newDisplayList = new RenderNodeDisplayList();
+    _needsPaint = false;
+    try {
+      paint(newDisplayList);
+    } catch (e, stack) {
+      print('Exception raised during paint of ${this}: ${e}');
+      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
+    _paintNode.setDisplayList(newDisplayList);
+    if (newDisplayList._children != null)
+      newDisplayList._children.forEach((node) {
+        assert(node.attached == attached);
+        if (node._needsPaint)
+          node._doPaint();
+      });
+  }
+
+  PaintOptions paintOptions;
+  // only set this to a subclass of PaintOptions that this class of RenderNode knows how to deal with
+
   void paint(RenderNodeDisplayList canvas) { }
 
 }