[css-grid] Fix painting in RTL

third_party/WebKit/Source/core/paint/GridPainter.cpp

Index: third_party/WebKit/Source/core/paint/GridPainter.cpp
diff --git a/third_party/WebKit/Source/core/paint/GridPainter.cpp b/third_party/WebKit/Source/core/paint/GridPainter.cpp
index 299e603a4b8777827661fa081b084b95af6cc753..61e1098ca9f37a7cb3f234c7416e18b8ea409e8e 100644
--- a/third_party/WebKit/Source/core/paint/GridPainter.cpp
+++ b/third_party/WebKit/Source/core/paint/GridPainter.cpp
@@ -46,9 +46,24 @@ void GridPainter::paintChildren(const PaintInfo& paintInfo, const LayoutPoint& p
     LayoutRect localPaintInvalidationRect = LayoutRect(paintInfo.cullRect().m_rect);
     localPaintInvalidationRect.moveBy(-paintOffset);
 
-    GridSpan dirtiedColumns = dirtiedGridAreas(m_layoutGrid.columnPositions(), localPaintInvalidationRect.x(), localPaintInvalidationRect.maxX());
+    Vector<LayoutUnit> columnPositions = m_layoutGrid.columnPositions();
+    if (!m_layoutGrid.styleRef().isLeftToRightDirection()) {
+        // Translate columnPositions in RTL as we need the physical coordinates of the columns in order to call dirtiedGridAreas().
+        for (size_t i = 0; i < columnPositions.size(); i++)
+            columnPositions[i] = m_layoutGrid.translateRTLCoordinate(columnPositions[i]);

[cbiesinger, 2016/04/12 20:07:51]

Why not make this translation inside of dirtiedGrisAreas?

[Manuel Rego, 2016/04/13 08:42:55]

Because we only need to do it for columns, not for rows.
So we'd need to add an extra param to dirtiedGrisAreas()
to know if we're processing columns or rows.

Anyway I can do it, if you think it's better.

+        // We change the order of tracks in columnPositions, as in RTL the leftmost track will be the last one.
+        std::sort(columnPositions.begin(), columnPositions.end());
+    }
+
+    GridSpan dirtiedColumns = dirtiedGridAreas(columnPositions, localPaintInvalidationRect.x(), localPaintInvalidationRect.maxX());
     GridSpan dirtiedRows = dirtiedGridAreas(m_layoutGrid.rowPositions(), localPaintInvalidationRect.y(), localPaintInvalidationRect.maxY());
 
+    if (!m_layoutGrid.styleRef().isLeftToRightDirection()) {
+        // As we changed the order of tracks previously, we need to swap the dirtied columns in RTL.
+        size_t lastLine = columnPositions.size() - 1;
+        dirtiedColumns = GridSpan::translatedDefiniteGridSpan(lastLine - dirtiedColumns.endLine(), lastLine - dirtiedColumns.startLine());
+    }
+
     Vector<std::pair<LayoutBox*, size_t>> gridItemsToBePainted;
 
     for (const auto& row : dirtiedRows) {