Don't stretch margin: auto items in a vertical flexbox

Source/core/rendering/RenderBox.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2005 Allan Sandfeld Jensen (kde@carewolf.com)
  *           (C) 2005, 2006 Samuel Weinig (sam.weinig@gmail.com)
  * Copyright (C) 2005, 2006, 2007, 2008, 2009, 2010 Apple Inc. All rights reserved.
  * Copyright (C) 2013 Adobe Systems Incorporated. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
@@ skipping 2207 matching lines @@
         EMarqueeDirection dir = parent()->style()->marqueeDirection();
         if (dir == MAUTO || dir == MFORWARD || dir == MBACKWARD || dir == MLEFT || dir == MRIGHT)
             return true;
     }
 
     // Flexible box items should shrink wrap, so we lay them out at their intrinsic widths.
     // In the case of columns that have a stretch alignment, we go ahead and layout at the
     // stretched size to avoid an extra layout when applying alignment.
     if (parent()->isFlexibleBox()) {
         // For multiline columns, we need to apply align-content first, so we can't stretch now.
         if (!parent()->style()->isColumnFlexDirection() || parent()->style()->flexWrap() != FlexNoWrap)

[ojan, 2013/05/24 01:21:57]

It's not obvious to me that this new code is right for flex-wrapping. Mind
adding a wrapping + margin:auto test case as well?

             return true;
         if (!flexItemHasStretchAlignment(this))
             return true;
+        if (parent()->style()->isColumnFlexDirection() && (style()->marginLeft().isAuto() || style()->marginRight().isAuto())) {
+            // Auto margins means we want centering, not stretching, so we want to return true here
+            return true;
+        }
     }
 
     // Flexible horizontal boxes lay out children at their intrinsic widths.  Also vertical boxes
     // that don't stretch their kids lay out their children at their intrinsic widths.
     // FIXME: Think about block-flow here.
     // https://bugs.webkit.org/show_bug.cgi?id=46473
     if (parent()->isDeprecatedFlexibleBox() && (parent()->style()->boxOrient() == HORIZONTAL || parent()->style()->boxAlign() != BSTRETCH))
         return true;
 
     // Button, input, select, textarea, and legend treat width value of 'auto' as 'intrinsic' unless it's in a
@@ skipping 2349 matching lines @@
 
 void RenderBox::reportStaticMembersMemoryUsage(MemoryInstrumentation* memoryInstrumentation)
 {
     memoryInstrumentation->addRootObject(gOverrideHeightMap, WebCoreMemoryTypes::RenderingStructures);
     memoryInstrumentation->addRootObject(gOverrideWidthMap, WebCoreMemoryTypes::RenderingStructures);
     memoryInstrumentation->addRootObject(gOverrideContainingBlockLogicalHeightMap, WebCoreMemoryTypes::RenderingStructures);
     memoryInstrumentation->addRootObject(gOverrideContainingBlockLogicalWidthMap, WebCoreMemoryTypes::RenderingStructures);
 }
 
 } // namespace WebCore