Col width is not honored when dynamically updated and it would not make table narrower

Source/core/rendering/RenderTableCol.cpp

 /*
  * Copyright (C) 1997 Martin Jones (mjones@kde.org)
  *           (C) 1997 Torben Weis (weis@kde.org)
  *           (C) 1998 Waldo Bastian (bastian@kde.org)
  *           (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  * Copyright (C) 2003, 2004, 2005, 2006, 2009 Apple Inc. All rights reserved.
  * Copyright (C) 2008 Nokia Corporation and/or its subsidiary(-ies)
  *
  * This library is free software; you can redistribute it and/or
@@ skipping 33 matching lines @@
     updateFromElement();
 }
 
 void RenderTableCol::styleDidChange(StyleDifference diff, const RenderStyle* oldStyle)
 {
     RenderBox::styleDidChange(diff, oldStyle);
 
     // If border was changed, notify table.
     if (parent()) {
         RenderTable* table = this->table();
-        if (table && !table->selfNeedsLayout() && !table->normalChildNeedsLayout() && oldStyle && oldStyle->border() != style()->border())
+        if (table && !table->selfNeedsLayout() && !table->normalChildNeedsLayout() && oldStyle && oldStyle->border() != style()->border()) {
             table->invalidateCollapsedBorders();
+        } else if (oldStyle && oldStyle->width() != style()->width()) {

[Julien - ping for review, 2014/02/06 22:28:18]

I don't think this is right: you need to check logical direction so it should be
logicalWidth() here, not width().

This should be covered by a vertical writing mode test case too as it was missed
in the code.

+            for (RenderObject* child = table->children()->firstChild(); child; child = child->nextSibling()) {
+                if (child->isTableSection()) {

[Julien - ping for review, 2014/02/06 22:28:18]

We prefer early return so I would expect us to prefer also early continue (to
avoid lost of nested blocks of code).

+                    RenderTableSection* section = toRenderTableSection(child);
+                    unsigned nEffCols = table->numEffCols();
+                    for (unsigned j = 0; j < nEffCols; j++) {
+                        for (unsigned i = 0; i < section->numRows(); i++) {
+                            RenderTableCell* cell = section->primaryCellAt(i, j);
+                            if (!cell)
+                                continue;
+                            cell->setPreferredLogicalWidthsDirty();
+                        }
+                    }
+                }

[Julien - ping for review, 2014/02/06 22:28:18]

You are basically dirtying the preferred logical widths for all the cells, which
is totally overblown.

Only the cells in the current column should need their preferred logical widths
recomputed.

+            }
+        }
     }
 }
 
 void RenderTableCol::updateFromElement()
 {
     unsigned oldSpan = m_span;
     Node* n = node();
     if (n && (n->hasTagName(colTag) || n->hasTagName(colgroupTag))) {
         HTMLTableColElement* tc = toHTMLTableColElement(n);
         m_span = tc->span();
@@ skipping 108 matching lines @@
     return style()->borderStart();
 }
 
 const BorderValue& RenderTableCol::borderAdjoiningCellAfter(const RenderTableCell* cell) const
 {
     ASSERT_UNUSED(cell, table()->colElement(cell->col() - 1) == this);
     return style()->borderEnd();
 }
 
 }