Split getIntrinsicDimensions into four pieces

sky/sdk/lib/framework/rendering/block.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 'box.dart';
 import 'object.dart';
 
 class BlockParentData extends BoxParentData with ContainerParentDataMixin<RenderBox> { }
 
 class RenderBlock extends RenderBox with ContainerRenderObjectMixin<RenderBox, BlockParentData>,
                                          RenderBoxContainerDefaultsMixin<RenderBox, BlockParentData> {
   // lays out RenderBox children in a vertical stack
   // uses the maximum width provided by the parent
   // sizes itself to the height of its child stack
 
   RenderBlock({
     List<RenderBox> children
   }) {
     if (children != null)
       children.forEach((child) { add(child); });
   }
 
   void setParentData(RenderBox child) {
     if (child.parentData is! BlockParentData)
       child.parentData = new BlockParentData();
   }
 
-  // override this to report what dimensions you would have if you
-  // were laid out with the given constraints this can walk the tree
-  // if it must, but it should be as cheap as possible; just get the
-  // dimensions and nothing else (e.g. don't calculate hypothetical
-  // child positions if they're not needed to determine dimensions)
-  Size getIntrinsicDimensions(BoxConstraints constraints) {
+  double getMinIntrinsicWidth(BoxConstraints constraints) {
+    double width = 0.0;
+    BoxConstraints innerConstraints = new BoxConstraints(
+        minWidth: constraints.minWidth, maxWidth: constraints.maxWidth);
+    RenderBox child = firstChild;
+    while (child != null) {
+      width = math.max(width, child.getMinIntrinsicWidth(innerConstraints));
+      child = child.parentData.nextSibling;
+    }
+    return width;
+  }
+
+  double getMaxIntrinsicWidth(BoxConstraints constraints) {
+    double width = 0.0;
+    BoxConstraints innerConstraints = new BoxConstraints(
+        minWidth: constraints.minWidth, maxWidth: constraints.maxWidth);
+    RenderBox child = firstChild;
+    while (child != null) {
+      width = math.max(width, child.getMaxIntrinsicWidth(innerConstraints));
+      child = child.parentData.nextSibling;
+    }
+    return width;
+  }
+
+  double _getIntrinsicHeight(BoxConstraints constraints) {
     double height = 0.0;
     double width = constraints.constrainWidth(constraints.maxWidth);
     assert(width < double.INFINITY);
-    RenderBox child = firstChild;
     BoxConstraints innerConstraints = new BoxConstraints(minWidth: width,
                                                          maxWidth: width);
+    RenderBox child = firstChild;
     while (child != null) {
-      height += child.getIntrinsicDimensions(innerConstraints).height;
-      assert(child.parentData is BlockParentData);
+      double childHeight = child.getMinIntrinsicHeight(innerConstraints);
+      assert(childHeight == child.getMaxIntrinsicHeight(innerConstraints));
+      height += childHeight;
       child = child.parentData.nextSibling;
     }
+    return height;
+  }
 
-    return new Size(width, constraints.constrainHeight(height));
+  double getMinIntrinsicHeight(BoxConstraints constraints) {
+    return _getIntrinsicHeight(constraints);
+  }
+
+  double getMaxIntrinsicHeight(BoxConstraints constraints) {
+    return _getIntrinsicHeight(constraints);
   }
 
   void performLayout() {
     assert(constraints is BoxConstraints);
     double width = constraints.constrainWidth(constraints.maxWidth);
     double y = 0.0;
     RenderBox child = firstChild;
     while (child != null) {
       child.layout(new BoxConstraints(minWidth: width, maxWidth: width), parentUsesSize: true);
       assert(child.parentData is BlockParentData);
       child.parentData.position = new Point(0.0, y);
       y += child.size.height;
       child = child.parentData.nextSibling;
     }
     size = new Size(width, constraints.constrainHeight(y));
     assert(size.width < double.INFINITY);
     assert(size.height < double.INFINITY);
   }
 
   void hitTestChildren(HitTestResult result, { Point position }) {
     defaultHitTestChildren(result, position: position);
   }
 
   void paint(RenderObjectDisplayList canvas) {
     defaultPaint(canvas);
   }
 
 }