[layoutng] Create a more correct constraint space for children

third_party/WebKit/Source/core/layout/ng/ng_block_layout_algorithm.cc

 // Copyright 2016 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.
 
 #include "core/layout/ng/ng_block_layout_algorithm.h"
 
 #include "core/layout/LayoutBox.h"
 #include "core/layout/ng/ng_constraint_space.h"
 #include "core/layout/ng/ng_fragment.h"
 #include "core/layout/ng/ng_length_utils.h"
 #include "core/layout/ng/ng_margin_strut.h"
 #include "core/style/ComputedStyle.h"
 #include "platform/LengthFunctions.h"
 
 namespace blink {
 
 NGBlockLayoutAlgorithm::NGBlockLayoutAlgorithm(
     PassRefPtr<const ComputedStyle> style,
     NGBoxIterator boxIterator)
     : m_style(style), m_boxIterator(boxIterator) {}
 
 NGFragment* NGBlockLayoutAlgorithm::layout(
     const NGConstraintSpace& constraintSpace) {
   LayoutUnit inlineSize =
       computeInlineSizeForFragment(constraintSpace, *m_style);
+  LayoutUnit blockSize =
+      computeBlockSizeForFragment(constraintSpace, *m_style, LayoutUnit(-1));

[ikilpatrick, 2016/08/23 00:49:04]

Is the -1 correct? Should it be LayoutUnit(0) instead?
 - height percentages will get resolved to zero in this case?

(and constraintSpace.blockSize() for quirks mode?) :P

[cbiesinger, 2016/08/23 01:06:54]

They don't get resolved to zero -- indefinite percentages get resolved to auto =
the height of their content.

(You're right about quirks mode, I'll add a TODO)

+  NGConstraintSpace constraint_space_for_children(
+      constraintSpace, NGLogicalSize(inlineSize, blockSize));
 
   HeapVector<Member<const NGFragmentBase>> childFragments;
   LayoutUnit contentSize;
   for (NGBox box : m_boxIterator) {
-    NGBoxMargins childMargins = computeMargins(constraintSpace, *box.style());
-    NGFragment* fragment = box.layout(constraintSpace);
+    NGBoxMargins childMargins =
+        computeMargins(constraint_space_for_children, *box.style());
+    NGFragment* fragment = box.layout(constraint_space_for_children);
     // TODO(layout-ng): Support auto margins
     fragment->setOffset(childMargins.inlineStart,
                         contentSize + childMargins.blockStart);
     box.positionUpdated(*fragment);
     contentSize += fragment->blockSize() + childMargins.blockSum();
     childFragments.append(fragment);
   }
 
-  LayoutUnit blockSize =
+  // Recompute the block-axis size now that we know our content size

[ikilpatrick, 2016/08/23 00:49:04]

grammar-Nit: period and end?

(I don't really care if this isn't a rule).

[cbiesinger, 2016/08/23 01:06:54]

Done.

+  blockSize =
       computeBlockSizeForFragment(constraintSpace, *m_style, contentSize);
   NGFragment* returnFragment =
       new NGFragment(inlineSize, blockSize, inlineSize, blockSize,
                      HorizontalTopBottom, LeftToRight);
   returnFragment->swapChildren(childFragments);
   return returnFragment;
 }
 
 }  // namespace blink