[css-flexbox] Correctly handle percentage sizing in the main axis

third_party/WebKit/Source/core/layout/LayoutFlexibleBox.cpp

 /*
  * Copyright (C) 2011 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 1077 matching lines @@
         LayoutUnit definiteHeight = computeDefiniteLogicalHeight();
         if (definiteHeight == LayoutUnit(-1))
             return definiteHeight;
 
         childCrossSize = definiteHeight - borderAndPaddingLogicalHeight() - scrollbarLogicalHeight();
         childCrossSize = child.constrainLogicalHeightByMinMax(childCrossSize, LayoutUnit(-1)) - child.scrollbarLogicalHeight() - child.borderAndPaddingLogicalHeight();
     }
     return childCrossSize;
 }
 
+LayoutUnit LayoutFlexibleBox::mainSizeForPercentageResolution(const LayoutBox& child)
+{
+    // This function implements section 9.8. Definite and Indefinite Sizes, case
+    // 2) of the flexbox spec.
+    // We need to check for the flexbox to have a definite main size, and for the
+    // flex item to have a definite flex basis.
+    const Length& flexBasis = flexBasisForChild(child);
+    if (!mainAxisLengthIsDefinite(child, flexBasis))
+        return LayoutUnit(-1);
+    LayoutUnit mainSize = isColumnFlow() ? computeDefiniteLogicalHeight() : computeDefiniteLogicalWidth();
+    if (mainSize == LayoutUnit(-1)) {

[leviw_travelin_and_unemployed, 2016/03/16 00:57:49]

Nit: unnecessary brackets.

+        return mainSize;
+    }
+    if (hasOrthogonalFlow(child)) {

[leviw_travelin_and_unemployed, 2016/03/16 00:57:49]

Ditto.

+        return child.hasOverrideLogicalContentHeight() ? child.overrideLogicalContentHeight() : LayoutUnit(-1);
+    }
+    return child.hasOverrideLogicalContentWidth() ? child.overrideLogicalContentWidth() : LayoutUnit(-1);
+}
+
 LayoutUnit LayoutFlexibleBox::childLogicalHeightForPercentageResolution(const LayoutBox& child)
 {
     if (!hasOrthogonalFlow(child))
         return crossSizeForPercentageResolution(child);
-    return LayoutUnit(-1);
+    return mainSizeForPercentageResolution(child);
 }
 
 LayoutUnit LayoutFlexibleBox::childLogicalWidthForPercentageResolution(const LayoutBox& child)
 {
     if (hasOrthogonalFlow(child))
         return crossSizeForPercentageResolution(child);
-    return LayoutUnit(-1);
+    return mainSizeForPercentageResolution(child);
 }
 
 LayoutUnit LayoutFlexibleBox::adjustChildSizeForAspectRatioCrossAxisMinAndMax(const LayoutBox& child, LayoutUnit childSize)
 {
     Length crossMin = isHorizontalFlow() ? child.style()->minHeight() : child.style()->minWidth();
     Length crossMax = isHorizontalFlow() ? child.style()->maxHeight() : child.style()->maxWidth();
 
 
     if (crossAxisLengthIsDefinite(child, crossMax)) {
         LayoutUnit maxValue = computeMainSizeFromAspectRatioUsing(child, crossMax);
@@ skipping 303 matching lines @@
             prepareChildForPositionedLayout(*child, mainAxisOffset, crossAxisOffset, FlipForRowReverse);
             continue;
         }
 
         // FIXME Investigate if this can be removed based on other flags. crbug.com/370010
         child->setMayNeedPaintInvalidation();
 
         LayoutUnit childPreferredSize = childSizes[i] + mainAxisBorderAndPaddingExtentForChild(*child);
         setOverrideMainAxisSizeForChild(*child, childPreferredSize);
         if (childPreferredSize != mainAxisExtentForChild(*child)) {
+            // We will correctly handle percentage sizing even without re-laying out here, because
+            // if our size was already correct, then percentage resolution was also correct due
+            // to the way percentage sizing is defined by flexbox (ie. it requires a definite flex basis)
+            // TODO(cbiesinger): When flex-basis is used instead of width/height, this is not the case. That
+            // problem is not limited to percentages. See http://crbug.com/531656#c11
             child->setChildNeedsLayout(MarkOnlyThis);
         } else {
             // To avoid double applying margin changes in updateAutoMarginsInCrossAxis, we reset the margins here.
             resetAutoMarginsAndLogicalTopInCrossAxis(*child);
         }
         // We may have already forced relayout for orthogonal flowing children in computeInnerFlexBaseSizeForChild.
         bool forceChildRelayout = relayoutChildren && !childFlexBaseSizeRequiresLayout(*child);
         updateBlockChildDirtyBitsBeforeLayout(forceChildRelayout, *child);
         if (!child->needsLayout())
             child->markForPaginationRelayoutIfNeeded(layoutScope);
@@ skipping 302 matching lines @@
             ASSERT(child);
             LayoutUnit lineCrossAxisExtent = lineContexts[lineNumber].crossAxisExtent;
             LayoutUnit originalOffset = lineContexts[lineNumber].crossAxisOffset - crossAxisStartEdge;
             LayoutUnit newOffset = contentExtent - originalOffset - lineCrossAxisExtent;
             adjustAlignmentForChild(*child, newOffset - originalOffset);
         }
     }
 }
 
 } // namespace blink