[css-grid] Performance optimization on the baseline-self alignment logic

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

 /*
  * Copyright (C) 2011 Apple Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 313 matching lines @@
           kForRows, LogicalHeight() - track_based_logical_height);
     }
 
     // TODO (lajava): We need to compute baselines after step 2 so
     // items with a relative size (percentages) can resolve it before
     // determining its baseline. However, we only set item's grid area
     // (via override sizes) as part of the content-sized tracks sizing
     // logic. Hence, items located at fixed or flexible tracks can't
     // resolve correctly their size at this stage, which may lead to
     // an incorrect computation of their shared context's baseline.
-    ComputeBaselineAlignmentContext();
+    // ComputeBaselineAlignmentContext();
 
     // 3- If the min-content contribution of any grid items have changed based
     // on the row sizes calculated in step 2, steps 1 and 2 are repeated with
     // the new min-content contribution (once only).
     RepeatTracksSizingIfNeeded(available_space_for_columns,
                                ContentLogicalHeight());
 
     // Grid container should have the minimum height of a line if it's editable.
     // That doesn't affect track sizing though.
     if (HasLineIfEmpty())
@@ skipping 1781 matching lines @@
 }
 
 LayoutUnit LayoutGrid::ColumnAxisOffsetForChild(const LayoutBox& child) const {
   const GridSpan& rows_span =
       track_sizing_algorithm_.GetGrid().GridItemSpan(child, kForRows);
   size_t child_start_line = rows_span.StartLine();
   LayoutUnit start_of_row = row_positions_[child_start_line];
   LayoutUnit start_position = start_of_row + MarginBeforeForChild(child);
   if (HasAutoMarginsInColumnAxis(child))
     return start_position;
+  if (IsBaselineAlignmentForChild(child, kGridColumnAxis))
+    start_position += ColumnAxisBaselineOffsetForChild(child);
   GridAxisPosition axis_position = ColumnAxisPositionForChild(child);
   switch (axis_position) {
     case kGridAxisStart:
-      return start_position + ColumnAxisBaselineOffsetForChild(child);
+      return start_position;
     case kGridAxisEnd:
     case kGridAxisCenter: {
       size_t child_end_line = rows_span.EndLine();
       LayoutUnit end_of_row = row_positions_[child_end_line];
       // m_rowPositions include distribution offset (because of content
       // alignment) and gutters so we need to subtract them to get the actual
       // end position for a given row (this does not have to be done for the
       // last track as there are no more m_columnPositions after it).
       LayoutUnit track_gap = GridGap(kForRows);
       if (child_end_line < row_positions_.size() - 1) {
@@ skipping 18 matching lines @@
 }
 
 LayoutUnit LayoutGrid::RowAxisOffsetForChild(const LayoutBox& child) const {
   const GridSpan& columns_span =
       track_sizing_algorithm_.GetGrid().GridItemSpan(child, kForColumns);
   size_t child_start_line = columns_span.StartLine();
   LayoutUnit start_of_column = column_positions_[child_start_line];
   LayoutUnit start_position = start_of_column + MarginStartForChild(child);
   if (HasAutoMarginsInRowAxis(child))
     return start_position;
+  if (IsBaselineAlignmentForChild(child, kGridRowAxis))
+    start_position += RowAxisBaselineOffsetForChild(child);
   GridAxisPosition axis_position = RowAxisPositionForChild(child);
   switch (axis_position) {
     case kGridAxisStart:
-      return start_position + RowAxisBaselineOffsetForChild(child);
+      return start_position;
     case kGridAxisEnd:
     case kGridAxisCenter: {
       size_t child_end_line = columns_span.EndLine();
       LayoutUnit end_of_column = column_positions_[child_end_line];
       // m_columnPositions include distribution offset (because of content
       // alignment) and gutters so we need to subtract them to get the actual
       // end position for a given column (this does not have to be done for the
       // last track as there are no more m_columnPositions after it).
       LayoutUnit track_gap = GridGap(kForColumns);
       if (child_end_line < column_positions_.size() - 1) {
@@ skipping 212 matching lines @@
   if (direction == kForRows)
     return grid.NumTracks(kForRows);
 
   return grid.NumTracks(kForRows)
              ? grid.NumTracks(kForColumns)
              : GridPositionsResolver::ExplicitGridColumnCount(
                    StyleRef(), grid.AutoRepeatTracks(kForColumns));
 }
 
 }  // namespace blink