An align attribute should not be applied for wider children

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 2126 matching lines @@
     if ((marginStartLength.isAuto() && marginEndLength.isAuto() && marginBoxWidth < availableWidth)
         || (!marginStartLength.isAuto() && !marginEndLength.isAuto() && containingBlockStyle->textAlign() == WEBKIT_CENTER)) {
         // Other browsers center the margin box for align=center elements so we match them here.
         LayoutUnit centeredMarginBoxStart = std::max(LayoutUnit(), (availableWidth - childWidth - marginStartWidth - marginEndWidth) / 2);
         marginStart = centeredMarginBoxStart + marginStartWidth;
         marginEnd = availableWidth - childWidth - marginStart + marginEndWidth;
         return;
     }
 
     // CSS 2.1: "If there is exactly one value specified as 'auto', its used value follows from the equality."
-    if (marginEndLength.isAuto() && marginBoxWidth < availableWidth) {
-        marginStart = marginStartWidth;
-        marginEnd = availableWidth - childWidth - marginStart;
-        return;
-    }
+    if (marginBoxWidth < availableWidth) {

[mstensho (USE GERRIT), 2014/12/10 10:45:05]

Should move this check to include center alignment (above) too.

[Kyungtae Kim, 2014/12/10 11:50:38]

Done.

+        bool adjustFromTextAlign = !marginEndLength.isAuto() && ((!containingBlockStyle->isLeftToRightDirection() && containingBlockStyle->textAlign() == WEBKIT_LEFT)
+            || (containingBlockStyle->isLeftToRightDirection() && containingBlockStyle->textAlign() == WEBKIT_RIGHT));
+        bool hasInvertedDirection = containingBlockStyle->isLeftToRightDirection() != style()->isLeftToRightDirection();
 
-    bool adjustFromTextAlign = !marginEndLength.isAuto() && ((!containingBlockStyle->isLeftToRightDirection() && containingBlockStyle->textAlign() == WEBKIT_LEFT)
-        || (containingBlockStyle->isLeftToRightDirection() && containingBlockStyle->textAlign() == WEBKIT_RIGHT));
-    bool hasInvertedDirection = containingBlockStyle->isLeftToRightDirection() != style()->isLeftToRightDirection();
+        if (marginEndLength.isAuto() || (adjustFromTextAlign && hasInvertedDirection && !marginStartLength.isAuto())) {

[mstensho (USE GERRIT), 2014/12/10 10:45:05]

Now is a good time to get rid of adjustFromTextAlign and hasInvertedDirection,
and just set marginEndLength and/or marginStartLength to Auto when align is
left, center or right.

[Kyungtae Kim, 2014/12/10 11:50:38]

 I think it could be confusing.
Because auto margins always have a priority over align,
we need to check many combinations before setting it.
How do you think about that?

[mstensho (USE GERRIT), 2014/12/10 23:27:00]

The code for WEBKIT_CENTER needs to remain special, because it actually aligns
the margin box, not the border box, in that case. But for WEBKIT_LEFT and
WEBKIT_RIGHT, something like this:

if (containingBlockStyle->textAlign() == WEBKIT_LEFT ||
containingBlockStyle->textAlign() == WEBKIT_RIGHT) {
    enum BlockAlign { None, Start, End };
    BlockAlign blockAlign = None;
    if (containingBlockStyle->textAlign() == WEBKIT_LEFT) {
        if (!containingBlockStyle->isLeftToRightDirection())
            blockAlign = style()->isLeftToRightDirection() ? Start : End;
    } else { // WEBKIT_RIGHT
        if (containingBlockStyle->isLeftToRightDirection())
            blockAlign = !style()->isLeftToRightDirection() ? Start : End;
    }
    if (blockAlign == Start) {
        if (!marginStartLength.isAuto())
            marginEndLength = Length(Auto);
    } else if (blockAlign == End) {
        if (!marginEndLength.isAuto())
            marginStartLength = Length(Auto);
    }
}

And then just handle the auto margins according to the CSS spec, without the
need for any of the two flags.

+            marginStart = marginStartWidth;
+            marginEnd = availableWidth - childWidth - marginStart;
+            return;
+        }
 
-    if ((marginStartLength.isAuto() && marginBoxWidth < availableWidth) || (adjustFromTextAlign && !hasInvertedDirection)) {
-        marginEnd = marginEndWidth;
-        marginStart = availableWidth - childWidth - marginEnd;
-        return;
-    }
-
-    if (adjustFromTextAlign && hasInvertedDirection) {
-        marginStart = marginStartWidth;
-        marginEnd = availableWidth - childWidth - marginStart;
-        return;
+        if (marginStartLength.isAuto() || adjustFromTextAlign) {
+            marginEnd = marginEndWidth;
+            marginStart = availableWidth - childWidth - marginEnd;
+            return;
+        }
     }
 
     // Either no auto margins, or our margin box width is >= the container width, auto margins will just turn into 0.
     marginStart = marginStartWidth;
     marginEnd = marginEndWidth;
 }
 
 void RenderBox::updateLogicalHeight()
 {
     m_intrinsicContentLogicalHeight = contentLogicalHeight();
@@ skipping 2315 matching lines @@
     computedValues.m_margins.m_end = marginEnd();
 
     setLogicalTop(oldLogicalTop);
     setLogicalWidth(oldLogicalWidth);
     setLogicalLeft(oldLogicalLeft);
     setMarginLeft(oldMarginLeft);
     setMarginRight(oldMarginRight);
 }
 
 } // namespace blink