Fix behaviour of empty cells in tables with colspans

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 244d9f4a9bbaf1b9e3fea1b14d39bb324cd1bc1c..2a158d9932dc24b29a57a2a8ba4d21f9dc79e100 100644
--- a/third_party/WebKit/Source/core/layout/TableLayoutAlgorithmAuto.cpp
+++ b/third_party/WebKit/Source/core/layout/TableLayoutAlgorithmAuto.cpp
@@ -67,8 +67,8 @@ void TableLayoutAlgorithmAuto::recalcColumn(unsigned effCol)
 
                 if (cell->maxPreferredLogicalWidth())
                     columnLayout.emptyCellsOnly = false;
-
                 if (cell->colSpan() == 1) {
+
                     columnLayout.minLogicalWidth = std::max<int>(cell->minPreferredLogicalWidth(), columnLayout.minLogicalWidth);
                     if (cell->maxPreferredLogicalWidth() > columnLayout.maxLogicalWidth) {
                         columnLayout.maxLogicalWidth = cell->maxPreferredLogicalWidth();
@@ -115,9 +115,6 @@ void TableLayoutAlgorithmAuto::recalcColumn(unsigned effCol)
                         break;
                     }
                 } else if (!effCol || section->primaryCellAt(i, effCol - 1) != cell) {
-                    // If a cell originates in this spanning column ensure we have a min/max width of at least 1px for it.
-                    columnLayout.minLogicalWidth = std::max<int>(columnLayout.minLogicalWidth, cell->maxPreferredLogicalWidth() ? 1 : 0);
-
                     // This spanning cell originates in this column. Insert the cell into spanning cells list.
                     insertSpanCell(cell);
                 }
@@ -312,6 +309,7 @@ int TableLayoutAlgorithmAuto::calcEffectiveLogicalWidth()
         bool haveAuto = false;
         bool spanHasEmptyCellsOnly = true;
         int fixedWidth = 0;
+        int numAuto = 0;
         while (lastCol < nEffCols && span > 0) {
             Layout& columnLayout = m_layoutStruct[lastCol];
             switch (columnLayout.logicalWidth.type()) {
@@ -330,6 +328,8 @@ int TableLayoutAlgorithmAuto::calcEffectiveLogicalWidth()
                 // fall through
             case Auto:
                 haveAuto = true;
+                if (!columnLayout.columnHasNoCells)
+                    numAuto++;
                 // fall through
             default:
                 // If the column is a percentage width, do not let the spanning cell overwrite the
@@ -370,16 +370,17 @@ int TableLayoutAlgorithmAuto::calcEffectiveLogicalWidth()
                 float percentMissing = cellLogicalWidth.percent() - totalPercent;
                 int totalWidth = 0;
                 for (unsigned pos = effCol; pos < lastCol; ++pos) {
-                    if (!m_layoutStruct[pos].effectiveLogicalWidth.hasPercent())
+                    if (!m_layoutStruct[pos].effectiveLogicalWidth.hasPercent() && (!m_layoutStruct[pos].emptyCellsOnly || spanHasEmptyCellsOnly))
                         totalWidth += m_layoutStruct[pos].clampedEffectiveMaxLogicalWidth();
                 }
 
                 for (unsigned pos = effCol; pos < lastCol && totalWidth > 0; ++pos) {
-                    if (!m_layoutStruct[pos].effectiveLogicalWidth.hasPercent()) {
-                        float percent = percentMissing * static_cast<float>(m_layoutStruct[pos].effectiveMaxLogicalWidth) / totalWidth;
+                    // Empty columns shouldn't get any share of a span's percent width.
+                    if (!m_layoutStruct[pos].effectiveLogicalWidth.hasPercent() && (!m_layoutStruct[pos].emptyCellsOnly || spanHasEmptyCellsOnly)) {
+                        float percent = percentMissing * static_cast<float>(m_layoutStruct[pos].clampedEffectiveMaxLogicalWidth()) / totalWidth;
                         totalWidth -= m_layoutStruct[pos].clampedEffectiveMaxLogicalWidth();
                         percentMissing -= percent;
-                        if (percent > 0)
+                        if (percent > 0 && !m_layoutStruct[pos].columnHasNoCells)
                             m_layoutStruct[pos].effectiveLogicalWidth.setValue(Percent, percent);
                         else
                             m_layoutStruct[pos].effectiveLogicalWidth = Length();
@@ -447,11 +448,14 @@ int TableLayoutAlgorithmAuto::calcEffectiveLogicalWidth()
         }
         if (!cellLogicalWidth.hasPercent()) {
             if (cellMaxLogicalWidth > spanMaxLogicalWidth) {
+                int widthAvailableToAuto = cellMaxLogicalWidth - fixedWidth;
                 for (unsigned pos = effCol; spanMaxLogicalWidth >= 0 && pos < lastCol; ++pos) {
                     int colMaxLogicalWidth = std::max(m_layoutStruct[pos].effectiveMaxLogicalWidth, static_cast<int>(spanMaxLogicalWidth ? cellMaxLogicalWidth * static_cast<float>(m_layoutStruct[pos].effectiveMaxLogicalWidth) / spanMaxLogicalWidth : cellMaxLogicalWidth));
                     spanMaxLogicalWidth -= m_layoutStruct[pos].effectiveMaxLogicalWidth;
                     cellMaxLogicalWidth -= colMaxLogicalWidth;
                     m_layoutStruct[pos].effectiveMaxLogicalWidth = colMaxLogicalWidth;
+                    if (m_layoutStruct[pos].logicalWidth.isAuto() && m_layoutStruct[pos].emptyCellsOnly && !m_layoutStruct[pos].columnHasNoCells && !spanHasEmptyCellsOnly)
+                        m_layoutStruct[pos].effectiveMinLogicalWidth = widthAvailableToAuto / numAuto;
                 }
             }
         } else {
@@ -541,7 +545,8 @@ void TableLayoutAlgorithmAuto::layout()
             break;
         case Auto:
             if (m_layoutStruct[i].emptyCellsOnly) {
-                numAutoEmptyCellsOnly++;
+                if (!m_layoutStruct[i].columnHasNoCells)
+                    numAutoEmptyCellsOnly++;
             } else {
                 numAuto++;
                 totalAuto += m_layoutStruct[i].clampedEffectiveMaxLogicalWidth();