Support getting baseline from paint as well as layout.

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/debug.dart';
 import '../base/hit_test.dart';
 import '../base/node.dart';
 import '../base/scheduler.dart' as scheduler;
 
 export 'dart:sky' show Point, Offset, Size, Rect, Color, Paint, Path;
 export '../base/hit_test.dart' show HitTestTarget, HitTestEntry, HitTestResult;
 
 
 class ParentData {
   void detach() {
@@ skipping 175 matching lines @@
       performLayout();
       assert(() {
         _debugActiveLayout = debugPreviousActiveLayout;
         _debugDoingThisLayout = false;
         _debugCanParentUseSize = null;
         _debugMutationsLocked = false;
         return true;
       });
     } catch (e) {
       print('Exception raised during layout:\n${e}\nContext:\n${this}');
+      if (inDebugBuild)
+        rethrow;
       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;
@@ skipping 77 matching lines @@
 
   void rotate({
     int oldAngle, // 0..3
     int newAngle, // 0..3
     Duration time
   }) { }
 
 
   // PAINTING
 
-  static List<RenderObject> _nodesNeedingPaint = new List<RenderObject>();
   static bool _debugDoingPaint = false;
   static bool get debugDoingPaint => _debugDoingPaint;
-  static void set debugDoingPaint(bool debug) {
-    _debugDoingPaint = debug;
-  }
+  bool _debugDoingThisPaint = false;
+  bool get debugDoingThisPaint => _debugDoingThisPaint;
+  static RenderObject _debugActivePaint = null;
+  static RenderObject get debugActivePaint => _debugActivePaint;
+
+  static List<RenderObject> _nodesNeedingPaint = new List<RenderObject>();
 
   final sky.PaintingNode _paintingNode = new sky.PaintingNode();
   sky.PaintingNode get paintingNode {
     assert(createNewDisplayList);
     return _paintingNode;
   }
   bool _needsPaint = true;
   bool get needsPaint => _needsPaint;
-  bool get createNewDisplayList => false;
 
   void markNeedsPaint() {
     assert(!debugDoingPaint);
     if (!attached) return; // Don't try painting things that aren't in the hierarchy
     if (_needsPaint) return;
     if (createNewDisplayList) {
       _needsPaint = true;
       _nodesNeedingPaint.add(this);
       scheduler.ensureVisualUpdate();
     } else {
       assert(parent != null); // parent always exists on this path because the root node is a RenderView, which sets createNewDisplayList.
       if (parent is RenderObject) {
         (parent as RenderObject).markNeedsPaint(); // TODO(ianh): remove the cast once the analyzer is cleverer
       }
     }
   }
 
   static void flushPaint() {
     try {
       _debugDoingPaint = true;
       List<RenderObject> dirtyNodes = _nodesNeedingPaint;
       _nodesNeedingPaint = new List<RenderObject>();
       for (RenderObject node in dirtyNodes..sort((a, b) => a.depth - b.depth)) {
         if (node._needsPaint && node.attached)
           node._updatePaintingCanvas();
       };
       assert(_nodesNeedingPaint.length == 0);
-    } catch (e) {
-      print('Exception raised during flushPaint:\n${e}');
     } finally {
       _debugDoingPaint = false;
     }
   }
 
   void _updatePaintingCanvas() {
     assert(!_needsLayout);
     assert(createNewDisplayList);
     sky.PictureRecorder recorder = new sky.PictureRecorder();
     PaintingCanvas canvas = new PaintingCanvas(recorder, paintBounds);
     _needsPaint = false;
     try {
       _paintOnCanvas(canvas, Offset.zero);
     } catch (e) {
       print('Exception raised during _updatePaintingCanvas:\n${e}\nContext:\n${this}');
+      if (inDebugBuild)
+        rethrow;
       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._descendentsWithPaintingCanvases != null) {
       for (RenderObject node in canvas._descendentsWithPaintingCanvases) {
         assert(node.attached == attached);
         if (node._needsPaint)
           node._updatePaintingCanvas();
       };
     }
   }
 
   void _paintOnCanvas(PaintingCanvas canvas, Offset offset) {
     _needsPaint = false;
+    assert(!_debugDoingThisPaint);
+    RenderObject debugLastActivePaint;
+    assert(() {
+      _debugDoingThisPaint = true;
+      debugLastActivePaint = _debugActivePaint;
+      _debugActivePaint = this;
+      return true;
+    });
     paint(canvas, offset);
+    assert(() {
+      _debugActivePaint = debugLastActivePaint;
+      _debugDoingThisPaint = false;
+      return true;
+    });
     assert(!_needsPaint);
   }
 
+  bool get createNewDisplayList => false;
   Rect get paintBounds;
-
   void paint(PaintingCanvas canvas, Offset offset) { }
 
 
   // EVENTS
 
   void handleEvent(sky.Event event, HitTestEntry entry) {
     // override this if you have a client, to hand it to the client
     // override this if you want to do anything with the event
   }
 
@@ skipping 287 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;
   }
 }