Fill out some more documentation about building RenderBox subclasses.

sky/sdk/lib/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 'dart:math' as math;
 
 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); });
+      for (RenderBox child in children)

[hansmuller, 2015/06/24 20:30:14]

Maybe just define addAll(children) in ContainerRenderObjectMixin and have it do
all of this, even the null check?

[Hixie, 2015/06/25 19:15:31]

Good idea. Done.

+        add(child);

[hansmuller, 2015/06/24 19:53:31]

https://www.dartlang.org/articles/style-guide/#do-use-curly-braces-for-all-fl...

[Hixie, 2015/06/25 19:15:31]

I updated our style guide to disagree with this. Adding extra braces where
they're not needed harms readability. There's no dangling-else issue here.

   }
 
   void setParentData(RenderBox child) {

[hansmuller, 2015/06/24 20:32:49]

Could setParentData() be defined in RenderBoxContainerDefaultsMixin?

[Hixie, 2015/06/25 19:15:32]

Sadly not. You can't call "new" on a generic type argument for some reason. If
you could, it'd be in the Container mixin. (The Defaults mixin is just for some
helper functions, it shouldn't override actual methods.)

     if (child.parentData is! BlockParentData)
       child.parentData = new BlockParentData();
   }
 
   double getMinIntrinsicWidth(BoxConstraints constraints) {
     double width = 0.0;
     BoxConstraints innerConstraints = new BoxConstraints(
         minWidth: constraints.minWidth, maxWidth: constraints.maxWidth);
     RenderBox child = firstChild;
     while (child != null) {
@@ skipping 63 matching lines @@
   void hitTestChildren(HitTestResult result, { Point position }) {
     defaultHitTestChildren(result, position: position);
   }
 
   void paint(RenderCanvas canvas) {
     defaultPaint(canvas);
   }
 
 }