[css-grid] Implementation of Baseline Self-Alignment

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

Index: third_party/WebKit/Source/core/layout/LayoutGrid.cpp
diff --git a/third_party/WebKit/Source/core/layout/LayoutGrid.cpp b/third_party/WebKit/Source/core/layout/LayoutGrid.cpp
index 05a01b709fbfee65abbd54397c163e4667c2d148..4a875da30a31861c3789dca318362ac7192c66ab 100644
--- a/third_party/WebKit/Source/core/layout/LayoutGrid.cpp
+++ b/third_party/WebKit/Source/core/layout/LayoutGrid.cpp
@@ -32,6 +32,7 @@
 #include "core/style/ComputedStyle.h"
 #include "core/style/GridArea.h"
 #include "platform/LengthFunctions.h"
+#include "platform/text/WritingMode.h"
 #include "wtf/PtrUtil.h"
 #include <algorithm>
 #include <memory>
@@ -140,6 +141,66 @@ struct ContentAlignmentData {
   LayoutUnit distributionOffset = LayoutUnit(-1);
 };
 
+class BaselineGroup {
+ public:
+  BaselineGroup() {}
+
+  void update(LayoutUnit ascent, LayoutUnit descent) {
+    m_maxAscent = std::max(m_maxAscent, ascent);
+    m_maxDescent = std::max(m_maxDescent, descent);
+    m_size++;
+  }
+  LayoutUnit maxAscent() const { return m_maxAscent; }
+  LayoutUnit maxDescent() const { return m_maxDescent; }
+  LayoutUnit size() const { return m_size; }
+
+ private:
+  LayoutUnit m_maxAscent;
+  LayoutUnit m_maxDescent;
+  LayoutUnit m_size;
+};
+
+class BaselineContext {
+ public:
+  BaselineContext(const LayoutBox& child,
+                  ItemPosition preference,
+                  LayoutUnit ascent,
+                  LayoutUnit descent) {
+    updateSharedGroup(child, preference, ascent, descent);
+  }
+
+  const BaselineGroup& getSharedGroup(const LayoutBox& child,
+                                      ItemPosition preference) const {
+    if (isAscentBaseline(child.styleRef().getWritingMode(), preference))
+      return m_ascentSharedGroup;
+    return m_descentSharedGroup;
+  }
+
+  void updateSharedGroup(const LayoutBox& child,
+                         ItemPosition preference,
+                         LayoutUnit ascent,
+                         LayoutUnit descent) {
+    if (isAscentBaseline(child.styleRef().getWritingMode(), preference))
+      m_ascentSharedGroup.update(ascent, descent);
+    else
+      m_descentSharedGroup.update(ascent, descent);
+  }
+
+ private:
+  bool isAscentBaseline(WritingMode blockDirection,
+                        ItemPosition preference) const {
+    return ((blockDirection == TopToBottomWritingMode &&
+             preference == ItemPositionBaseline) ||
+            (blockDirection == LeftToRightWritingMode &&
+             preference == ItemPositionBaseline) ||
+            (blockDirection == RightToLeftWritingMode &&
+             preference == ItemPositionLastBaseline));
+  }
+
+  BaselineGroup m_ascentSharedGroup;
+  BaselineGroup m_descentSharedGroup;
+};
+
 enum TrackSizeRestriction {
   AllowInfinity,
   ForbidInfinity,
@@ -247,6 +308,12 @@ class LayoutGrid::GridIterator {
   size_t m_childIndex;
 };
 
+typedef HashMap<unsigned,
+                std::unique_ptr<BaselineContext>,
+                DefaultHash<unsigned>::Hash,
+                WTF::UnsignedWithZeroKeyHashTraits<unsigned>>
+    BaselineContextsMap;
+
 struct LayoutGrid::GridSizingData {
   WTF_MAKE_NONCOPYABLE(GridSizingData);
   STACK_ALLOCATED();
@@ -259,6 +326,9 @@ struct LayoutGrid::GridSizingData {
   Vector<GridTrack> rowTracks;
   Vector<size_t> contentSizedTracksIndex;
 
+  BaselineContextsMap rowAxisAlignmentContext;
+  BaselineContextsMap colAxisAlignmentContext;
+
   // Performance optimization: hold onto these Vectors until the end of Layout
   // to avoid repeated malloc / free.
   Vector<GridTrack*> filteredTracks;
@@ -790,8 +860,18 @@ void LayoutGrid::computeUsedBreadthOfGridTracks(
         track.setGrowthLimitCap(valueForLength(gridLength.length(), maxSize));
     }
 
-    if (trackSize.isContentSized())
+    if (trackSize.isContentSized()) {
       sizingData.contentSizedTracksIndex.append(i);
+    } else if (!m_gridItemArea.isEmpty()) {
+      GridIterator iterator(m_grid, direction, i);
+      while (LayoutBox* gridItem = iterator.nextGridItem()) {
+        if (isBaselineAlignment(*gridItem) &&
+            (sizingData.sizingOperation != IntrinsicSizeComputation ||
+             direction == ForRows))
+          gridItem->layoutIfNeeded();
+        updateBaselineAlignmentContextIfNeeded(*gridItem, sizingData);
+      }
+    }
     if (trackSize.maxTrackBreadth().isFlex())
       flexibleSizedTracksIndex.append(i);
   }
@@ -1104,7 +1184,8 @@ GridTrackSize LayoutGrid::gridTrackSize(GridTrackSizingDirection direction,
     }
   }
 
-  // Flex sizes are invalid as a min sizing function. However we still can have
+  // Flex sizes Laare invalid as a min sizing function. However we still can

[kojii, 2016/11/15 04:21:15]

typo?

[jfernandez, 2016/11/16 11:51:24]

Done.

+  // have
   // a flexible |minTrackBreadth| if the track had a flex size directly (e.g.
   // "1fr"), the spec says that in this case it implies an automatic minimum.
   if (minTrackBreadth.isFlex())
@@ -1136,7 +1217,11 @@ LayoutUnit LayoutGrid::logicalHeightForChild(LayoutBox& child,
     child.clearOverrideLogicalContentHeight();
 
   child.layoutIfNeeded();
-  return child.logicalHeight() + child.marginLogicalHeight();
+  LayoutUnit baselineOffset =
+      updateBaselineAlignmentContextIfNeeded(child, sizingData);
+  return baselineOffset > 0
+             ? baselineOffset
+             : child.logicalHeight() + child.marginLogicalHeight();
 }
 
 GridTrackSizingDirection LayoutGrid::flowAwareDirectionForChild(
@@ -1232,7 +1317,11 @@ LayoutUnit LayoutGrid::minContentForChild(LayoutBox& child,
   if (direction == ForColumns &&
       sizingData.sizingOperation == IntrinsicSizeComputation) {
     DCHECK(isOrthogonalChild(child));
-    return child.logicalHeight() + child.marginLogicalHeight();
+    LayoutUnit baselineOffset =
+        updateBaselineAlignmentContextIfNeeded(child, sizingData);
+    return baselineOffset > 0
+               ? baselineOffset
+               : child.logicalHeight() + child.marginLogicalHeight();
   }
 
   if (updateOverrideContainingBlockContentSizeForChild(
@@ -2746,6 +2835,11 @@ LayoutUnit LayoutGrid::marginLogicalHeightForChild(
   return isHorizontalWritingMode() ? child.marginHeight() : child.marginWidth();
 }
 
+LayoutUnit LayoutGrid::marginLogicalWidthForChild(
+    const LayoutBox& child) const {
+  return isHorizontalWritingMode() ? child.marginWidth() : child.marginHeight();
+}
+
 LayoutUnit LayoutGrid::computeMarginLogicalSizeForChild(
     MarginDirection forDirection,
     const LayoutBox& child) const {
@@ -2929,6 +3023,110 @@ static int synthesizedBaselineFromBorderBox(const LayoutBox& box,
 
 // TODO(lajava): This logic is shared by LayoutFlexibleBox, so it might be
 // refactored somehow.
+bool LayoutGrid::isBaselineAlignment(const LayoutBox& child) const {
+  bool isChildInlineFlowAlongRowAxis = !isOrthogonalChild(child);
+  ItemPosition align = isChildInlineFlowAlongRowAxis
+                           ? alignSelfForChild(child).position()
+                           : justifySelfForChild(child).position();
+  bool hasAutoMargins = isChildInlineFlowAlongRowAxis
+                            ? hasAutoMarginsInColumnAxis(child)
+                            : hasAutoMarginsInRowAxis(child);
+  return (
+      (align == ItemPositionBaseline || align == ItemPositionLastBaseline) &&
+      !hasAutoMargins);
+}
+
+LayoutUnit LayoutGrid::updateBaselineAlignmentContextIfNeeded(
+    LayoutBox& child,
+    GridSizingData& sizingData) const {
+  if (!isBaselineAlignment(child))
+    return LayoutUnit();
+
+  bool isChildInlineFlowAlongRowAxis = !isOrthogonalChild(child);
+  ItemPosition align = isChildInlineFlowAlongRowAxis
+                           ? alignSelfForChild(child).position()
+                           : justifySelfForChild(child).position();
+  const GridSpan& span = isChildInlineFlowAlongRowAxis
+                             ? cachedGridSpan(child, ForRows)
+                             : cachedGridSpan(child, ForColumns);
+  LayoutUnit ascent = firstLineBoxBaselineForChild(child);
+  LayoutUnit descent = descentBaselineForChild(child, ascent);
+  BaselineContextsMap& baselineContexts =
+      isChildInlineFlowAlongRowAxis ? sizingData.rowAxisAlignmentContext
+                                    : sizingData.colAxisAlignmentContext;
+  BaselineContext* context = nullptr;
+  BaselineContextsMap::AddResult addResult = baselineContexts.add(
+      span.startLine(), std::unique_ptr<BaselineContext>());
+  if (addResult.isNewEntry) {
+    context = new BaselineContext(child, align, ascent, descent);
+    addResult.storedValue->value = wrapUnique(context);
+  } else {
+    context = addResult.storedValue->value.get();
+    context->updateSharedGroup(child, align, ascent, descent);
+  }
+  auto group = context->getSharedGroup(child, align);
+  return group.maxAscent() + group.maxDescent();
+}
+
+LayoutUnit LayoutGrid::firstLineBoxBaselineForChild(
+    const LayoutBox& child) const {
+  LayoutUnit baseline(child.firstLineBoxBaseline());
+  // We take content-box's bottom if no valid baseline.
+  if (baseline == -1)
+    baseline = LayoutBlock::logicalHeightForChild(child);
+  return baseline + marginBeforeForChild(child);
+}
+
+LayoutUnit LayoutGrid::descentBaselineForChild(const LayoutBox& child,
+                                               LayoutUnit ascent) const {
+  bool isChildInlineFlowAlongRowAxis = !isOrthogonalChild(child);
+  return isChildInlineFlowAlongRowAxis
+             ? (marginLogicalHeightForChild(child) +
+                LayoutBlock::logicalHeightForChild(child)) -
+                   ascent
+             : (marginLogicalWidthForChild(child) +
+                logicalWidthForChild(child)) -
+                   ascent;
+}
+
+LayoutUnit LayoutGrid::columnAxisBaselineOffsetForChild(
+    const LayoutBox& child,
+    const GridSizingData& sizingData) const {
+  // only parallel items participating in baseline alignment along
+  // the grid's row axis have an offset in the column axis.
+  if (!isInlineBaselineAlignedChild(child))
+    return LayoutUnit();
+
+  const GridSpan& span = cachedGridSpan(child, ForRows);
+  const BaselineContext* context =
+      sizingData.rowAxisAlignmentContext.get(span.startLine());
+  DCHECK(context);
+  const BaselineGroup& group =
+      context->getSharedGroup(child, alignSelfForChild(child).position());
+  // TODO (lajava): We could just return LayoutUnit() if there is only
+  // 1 child in the group.
+  return group.maxAscent() - firstLineBoxBaselineForChild(child);
+}
+
+LayoutUnit LayoutGrid::rowAxisBaselineOffsetForChild(
+    const LayoutBox& child,
+    const GridSizingData& sizingData) const {
+  // only orthogonal items participating in baseline alignment along
+  // the grid's column axis have an offset in the row axis.
+  if (!isBlockBaselineAlignedChild(child))
+    return LayoutUnit();
+
+  const GridSpan& span = cachedGridSpan(child, ForColumns);
+  const BaselineContext* context =
+      sizingData.colAxisAlignmentContext.get(span.startLine());
+  DCHECK(context);
+  const BaselineGroup& group =
+      context->getSharedGroup(child, justifySelfForChild(child).position());
+  // TODO (lajava): We could just return LayoutUnit() if there is only
+  // 1 child in the group.
+  return group.maxAscent() - firstLineBoxBaselineForChild(child);
+}
+
 int LayoutGrid::baselinePosition(FontBaseline,
                                  bool,
                                  LineDirectionMode direction,
@@ -2942,9 +3140,12 @@ int LayoutGrid::baselinePosition(FontBaseline,
   return baseline + beforeMarginInLineDirection(direction);
 }
 
-bool LayoutGrid::isInlineBaselineAlignedChild(const LayoutBox* child) const {
-  return alignSelfForChild(*child).position() == ItemPositionBaseline &&
-         !isOrthogonalChild(*child) && !hasAutoMarginsInColumnAxis(*child);
+bool LayoutGrid::isInlineBaselineAlignedChild(const LayoutBox& child) const {
+  return !isOrthogonalChild(child) && isBaselineAlignment(child);
+}
+
+bool LayoutGrid::isBlockBaselineAlignedChild(const LayoutBox& child) const {
+  return isOrthogonalChild(child) && isBaselineAlignment(child);
 }
 
 int LayoutGrid::firstLineBoxBaseline() const {
@@ -2959,8 +3160,8 @@ int LayoutGrid::firstLineBoxBaseline() const {
     for (size_t index = 0; index < m_grid[0][column].size(); index++) {
       const LayoutBox* child = m_grid[0][column][index];
       DCHECK(!child->isOutOfFlowPositioned());
-      // If an item participates in baseline alignmen, we select such item.
-      if (isInlineBaselineAlignedChild(child)) {
+      // If an item participates in baseline alignment, we select such item.
+      if (isInlineBaselineAlignedChild(*child)) {
         // TODO (lajava): self-baseline and content-baseline alignment
         // still not implemented.
         baselineChild = child;
@@ -3079,8 +3280,6 @@ GridAxisPosition LayoutGrid::columnAxisPositionForChild(
       return GridAxisStart;
     case ItemPositionBaseline:
     case ItemPositionLastBaseline:
-      // FIXME: These two require implementing Baseline Alignment. For now, we
-      // always 'start' align the child. crbug.com/234191
       return GridAxisStart;
     case ItemPositionAuto:
     case ItemPositionNormal:
@@ -3158,8 +3357,6 @@ GridAxisPosition LayoutGrid::rowAxisPositionForChild(
       return GridAxisStart;
     case ItemPositionBaseline:
     case ItemPositionLastBaseline:
-      // FIXME: These two require implementing Baseline Alignment. For now, we
-      // always 'start' align the child. crbug.com/234191
       return GridAxisStart;
     case ItemPositionAuto:
     case ItemPositionNormal:
@@ -3182,7 +3379,8 @@ LayoutUnit LayoutGrid::columnAxisOffsetForChild(
   GridAxisPosition axisPosition = columnAxisPositionForChild(child);
   switch (axisPosition) {
     case GridAxisStart:
-      return startPosition;
+      return startPosition +
+             columnAxisBaselineOffsetForChild(child, sizingData);
     case GridAxisEnd:
     case GridAxisCenter: {
       size_t childEndLine = rowsSpan.endLine();
@@ -3225,7 +3423,7 @@ LayoutUnit LayoutGrid::rowAxisOffsetForChild(const LayoutBox& child,
   GridAxisPosition axisPosition = rowAxisPositionForChild(child);
   switch (axisPosition) {
     case GridAxisStart:
-      return startPosition;
+      return startPosition + rowAxisBaselineOffsetForChild(child, sizingData);
     case GridAxisEnd:
     case GridAxisCenter: {
       size_t childEndLine = columnsSpan.endLine();