Improve multicol preferred/intrinsic width calculation.

Source/core/rendering/RenderBlock.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2007 David Smith (catfish.man@gmail.com)
  * Copyright (C) 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011 Apple Inc. All rights reserved.
  * Copyright (C) Research In Motion Limited 2010. 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
  * License as published by the Free Software Foundation; either
@@ skipping 5693 matching lines @@
 void RenderBlock::computeIntrinsicLogicalWidths(LayoutUnit& minLogicalWidth, LayoutUnit& maxLogicalWidth) const
 {
     if (childrenInline()) {
         // FIXME: Remove this const_cast.
         const_cast<RenderBlock*>(this)->computeInlinePreferredLogicalWidths(minLogicalWidth, maxLogicalWidth);
     } else
         computeBlockPreferredLogicalWidths(minLogicalWidth, maxLogicalWidth);
 
     maxLogicalWidth = max(minLogicalWidth, maxLogicalWidth);
 
+    adjustIntrinsicLogicalWidthsForColumns(minLogicalWidth, maxLogicalWidth);
+
     // A horizontal marquee with inline children has no minimum width.
     if (childrenInline() && isMarquee() && toRenderMarquee(this)->isHorizontal())
         minLogicalWidth = 0;
 
     if (isTableCell()) {
         Length tableCellWidth = toRenderTableCell(this)->styleOrColLogicalWidth();
         if (tableCellWidth.isFixed() && tableCellWidth.value() > 0)
             maxLogicalWidth = max(minLogicalWidth, adjustContentBoxLogicalWidthForBoxSizing(tableCellWidth.value()));
     }
 
@@ skipping 36 matching lines @@
         m_maxPreferredLogicalWidth = m_maxPreferredLogicalWidth.ceil();
     }
 
     LayoutUnit borderAndPadding = borderAndPaddingLogicalWidth();
     m_minPreferredLogicalWidth += borderAndPadding;
     m_maxPreferredLogicalWidth += borderAndPadding;
 
     clearPreferredLogicalWidthsDirty();
 }
 
+void RenderBlock::adjustIntrinsicLogicalWidthsForColumns(LayoutUnit& minLogicalWidth, LayoutUnit& maxLogicalWidth) const
+{
+    // FIXME: make this method virtual and move the code to RenderMultiColumnBlock once the old
+    // multicol code is gone.
+
+    if (!style()->hasAutoColumnCount() || !style()->hasAutoColumnWidth()) {
+        // The min/max intrinsic widths calculated really tell how much space elements need when
+        // laid out inside the columns. In order to eventually end up with the desired column width,
+        // we need to convert them to values pertaining to the multicol container.
+        int columnCount = style()->hasAutoColumnCount() ? 1 : style()->columnCount();
+        LayoutUnit columnWidth;
+        LayoutUnit gapExtra = (columnCount - 1) * columnGap();
+        if (style()->hasAutoColumnWidth()) {
+            minLogicalWidth = minLogicalWidth * columnCount + gapExtra;
+        } else {
+            columnWidth = style()->columnWidth();
+            minLogicalWidth = min(minLogicalWidth, columnWidth);
+        }
+        // FIXME: If column-count is auto here, we should resolve it to calculate the maximum
+        // intrinsic width, instead of pretending that it's 1. The only way to do that is by
+        // performing a layout pass, but this is not an appropriate time or place for layout. The
+        // good news is that if height is unconstrained and there are no explicit breaks, the
+        // resolved column-count really should be 1.
+        maxLogicalWidth = max(maxLogicalWidth, columnWidth) * columnCount + gapExtra;
+    }
+}
+
 struct InlineMinMaxIterator {
 /* InlineMinMaxIterator is a class that will iterate over all render objects that contribute to
    inline min/max width calculations.  Note the following about the way it walks:
    (1) Positioned content is skipped (since it does not contribute to min/max width of a block)
    (2) We do not drill into the children of floats or replaced elements, since you can't break
        in the middle of such an element.
    (3) Inline flows (e.g., <a>, <span>, <i>) are walked twice, since each side can have
        distinct borders/margin/padding that contribute to the min/max width.
 */
     RenderObject* parent;
@@ skipping 2197 matching lines @@
 void RenderBlock::showLineTreeAndMark(const InlineBox* markedBox1, const char* markedLabel1, const InlineBox* markedBox2, const char* markedLabel2, const RenderObject* obj) const
 {
     showRenderObject();
     for (const RootInlineBox* root = firstRootBox(); root; root = root->nextRootBox())
         root->showLineTreeAndMark(markedBox1, markedLabel1, markedBox2, markedLabel2, obj, 1);
 }
 
 #endif
 
 } // namespace WebCore