[css tables] Don't pass table width increase due to % columns to parents

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

 /*
  * Copyright (C) 2002 Lars Knoll (knoll@kde.org)
  *           (C) 2002 Dirk Mueller (mueller@kde.org)
  * Copyright (C) 2003, 2006, 2008, 2010 Apple Inc. 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
  * version 2 of the License.
  *
@@ skipping 15 matching lines @@
 #include "core/layout/LayoutTableCol.h"
 #include "core/layout/LayoutTableSection.h"
 #include "core/layout/TextAutosizer.h"
 
 namespace blink {
 
 TableLayoutAlgorithmAuto::TableLayoutAlgorithmAuto(LayoutTable* table)
     : TableLayoutAlgorithm(table)
     , m_hasPercent(false)
     , m_effectiveLogicalWidthDirty(true)
+    , m_scaledWidthFromPercentColumns(0)

[mstensho (USE GERRIT), 2016/05/18 19:50:17]

No need to explicitly initialize LayoutUnit to 0. Actually it's kind of bad to
do it, since we'd perform saturation checks and stuff. :)

[dgrogan, 2016/05/18 22:28:33]

Done.

 {
 }
 
 TableLayoutAlgorithmAuto::~TableLayoutAlgorithmAuto()
 {
 }
 
 void TableLayoutAlgorithmAuto::recalcColumn(unsigned effCol)
 {
     Layout& columnLayout = m_layoutStruct[effCol];
@@ skipping 124 matching lines @@
 
         // For the last column in a column-group, we invalidate our group logical width.
         if (column->isTableColumn() && !column->nextSibling())
             groupLogicalWidth = Length();
     }
 
     for (unsigned i = 0; i < nEffCols; i++)
         recalcColumn(i);
 }
 
+static bool shouldScaleColumnsForParent(LayoutTable* table)
+{
+    LayoutBlock* cb = table->containingBlock();
+    while (!cb->isLayoutView()) {
+        // It doesn't matter if our table is auto or fixed: auto means we don't
+        // scale. Fixed doesn't care if we do or not because it doesn't depend
+        // on the cell contents' preferred widths.
+        if (cb->isTableCell())
+            return false;
+        cb = cb->containingBlock();
+    }
+    return true;
+}
+
 // FIXME: This needs to be adapted for vertical writing modes.
-static bool shouldScaleColumns(LayoutTable* table)
+static bool shouldScaleColumnsForSelf(LayoutTable* table)
 {
+    // Normally, scale all columns to satisfy this from CSS2.2:
+    // "A percentage value for a column width is relative to the table width.
+    // If the table has 'width: auto', a percentage represents a constraint on the column's width"
+
     // A special case.  If this table is not fixed width and contained inside
     // a cell, then don't bloat the maxwidth by examining percentage growth.
     while (true) {
         Length tw = table->style()->width();
         if ((!tw.isAuto() && !tw.hasPercent()) || table->isOutOfFlowPositioned())
             return true;
         LayoutBlock* cb = table->containingBlock();
 
         while (!cb->isLayoutView() && !cb->isTableCell()
             && cb->style()->width().isAuto() && !cb->isOutOfFlowPositioned())
@@ skipping 17 matching lines @@
 {
     TextAutosizer::TableLayoutScope textAutosizerTableLayoutScope(m_table);
 
     fullRecalc();
 
     int spanMaxLogicalWidth = calcEffectiveLogicalWidth();
     minWidth = LayoutUnit();
     maxWidth = LayoutUnit();
     float maxPercent = 0;
     float maxNonPercent = 0;
-    bool scaleColumns = shouldScaleColumns(m_table);
+    bool scaleColumnsForSelf = shouldScaleColumnsForSelf(m_table);
 
     // We substitute 0 percent by (epsilon / percentScaleFactor) percent in two places below to avoid division by zero.
     // FIXME: Handle the 0% cases properly.
     const float epsilon = 1 / 128.0f;
 
     float remainingPercent = 100;
+
     for (size_t i = 0; i < m_layoutStruct.size(); ++i) {
         minWidth += m_layoutStruct[i].effectiveMinLogicalWidth;
         maxWidth += m_layoutStruct[i].effectiveMaxLogicalWidth;
-        if (scaleColumns) {
+        if (scaleColumnsForSelf) {
             if (m_layoutStruct[i].effectiveLogicalWidth.hasPercent()) {
                 float percent = std::min(static_cast<float>(m_layoutStruct[i].effectiveLogicalWidth.percent()), remainingPercent);
                 float logicalWidth = static_cast<float>(m_layoutStruct[i].effectiveMaxLogicalWidth) * 100 / std::max(percent, epsilon);
                 maxPercent = std::max(logicalWidth,  maxPercent);
                 remainingPercent -= percent;
             } else {
                 maxNonPercent += m_layoutStruct[i].effectiveMaxLogicalWidth;
             }
         }
     }
-
-    if (scaleColumns) {
+    if (scaleColumnsForSelf) {
         maxNonPercent = maxNonPercent * 100 / std::max(remainingPercent, epsilon);
-        maxWidth = std::max(maxWidth, LayoutUnit(std::min(maxNonPercent, static_cast<float>(tableMaxWidth))));
-        maxWidth = std::max(maxWidth, LayoutUnit(std::min(maxPercent, static_cast<float>(tableMaxWidth))));
+        m_scaledWidthFromPercentColumns = LayoutUnit(std::min(maxNonPercent, static_cast<float>(tableMaxWidth)));
+        m_scaledWidthFromPercentColumns = std::max(m_scaledWidthFromPercentColumns, LayoutUnit(std::min(maxPercent, static_cast<float>(tableMaxWidth))));
     }
 
+    if (shouldScaleColumnsForParent(m_table)) {

[mstensho (USE GERRIT), 2016/05/18 19:50:17]

Should probably check |scaleColumnsForSelf| first, since this may be expensive,
given a deep enough tree. Maybe we should also check if
m_scaledWidthFromPercentColumns is different from maxWidth before (potentially)
walking to the root.

[dgrogan, 2016/05/18 22:28:33]

Done. Well, I changed to checking to see if m_scaledWidthFromPercentColumns >
maxWidth, since that's the only way it could have an effect.

+        DCHECK(scaleColumnsForSelf);
+        maxWidth = std::max(m_scaledWidthFromPercentColumns, maxWidth);
+    }
     maxWidth = LayoutUnit(std::max(maxWidth.floor(), spanMaxLogicalWidth));
 }
 
+LayoutUnit TableLayoutAlgorithmAuto::scaledWidthFromPercentColumns()

[mstensho (USE GERRIT), 2016/05/18 19:50:17]

Make this inline?

[dgrogan, 2016/05/18 22:28:33]

Done.

+{
+    return m_scaledWidthFromPercentColumns;
+}
+
 void TableLayoutAlgorithmAuto::applyPreferredLogicalWidthQuirks(LayoutUnit& minWidth, LayoutUnit& maxWidth) const
 {
     Length tableLogicalWidth = m_table->style()->logicalWidth();
     if (tableLogicalWidth.isFixed() && tableLogicalWidth.isPositive()) {
         // |minWidth| is the result of measuring the intrinsic content's size. Keep it to
         // make sure we are *never* smaller than the actual content.
         LayoutUnit minContentWidth = minWidth;
         // FIXME: This line looks REALLY suspicious as it could allow the minimum
         // preferred logical width to be smaller than the table content. This has
         // to be cross-checked against other browsers.
@@ skipping 433 matching lines @@
             int reduce = available * minMaxDiff / logicalWidthBeyondMin;
             m_layoutStruct[i].computedLogicalWidth += reduce;
             available -= reduce;
             logicalWidthBeyondMin -= minMaxDiff;
             if (available >= 0)
                 break;
         }
     }
 }
 } // namespace blink