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

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

Index: third_party/WebKit/Source/core/layout/TableLayoutAlgorithmAuto.cpp
diff --git a/third_party/WebKit/Source/core/layout/TableLayoutAlgorithmAuto.cpp b/third_party/WebKit/Source/core/layout/TableLayoutAlgorithmAuto.cpp
index 0ff2aad54ee239d5a6080cad371f6bc07eecb043..27d9aec8d6d21ec6c8c998fcc45ed43ac9ff17b8 100644
--- a/third_party/WebKit/Source/core/layout/TableLayoutAlgorithmAuto.cpp
+++ b/third_party/WebKit/Source/core/layout/TableLayoutAlgorithmAuto.cpp
@@ -33,6 +33,7 @@ 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.

 {
 }
 
@@ -177,9 +178,27 @@ void TableLayoutAlgorithmAuto::fullRecalc()
         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) {
@@ -217,17 +236,18 @@ void TableLayoutAlgorithmAuto::computeIntrinsicLogicalWidths(LayoutUnit& minWidt
     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);
@@ -238,16 +258,24 @@ void TableLayoutAlgorithmAuto::computeIntrinsicLogicalWidths(LayoutUnit& minWidt
             }
         }
     }
-
-    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();