[css-grid] Implement auto-repeat computation

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 cfde1c770390d00cb5a418ebb7f1d54fd22443fa..c007251ba0e73d41af47e48c685757e46e17ea89 100644
--- a/third_party/WebKit/Source/core/layout/LayoutGrid.cpp
+++ b/third_party/WebKit/Source/core/layout/LayoutGrid.cpp
@@ -301,7 +301,8 @@ void LayoutGrid::styleDidChange(StyleDifference diff, const ComputedStyle* oldSt
 
     if (explicitGridDidResize(*oldStyle)
         || namedGridLinesDefinitionDidChange(*oldStyle)
-        || oldStyle->getGridAutoFlow() != styleRef().getGridAutoFlow())
+        || oldStyle->getGridAutoFlow() != styleRef().getGridAutoFlow()
+        || (diff.needsLayout() && (styleRef().gridAutoRepeatColumns().size() || styleRef().gridAutoRepeatRows().size())))
         dirtyGrid();
 }
 
@@ -310,7 +311,9 @@ bool LayoutGrid::explicitGridDidResize(const ComputedStyle& oldStyle) const
     return oldStyle.gridTemplateColumns().size() != styleRef().gridTemplateColumns().size()
         || oldStyle.gridTemplateRows().size() != styleRef().gridTemplateRows().size()
         || oldStyle.namedGridAreaColumnCount() != styleRef().namedGridAreaColumnCount()
-        || oldStyle.namedGridAreaRowCount() != styleRef().namedGridAreaRowCount();
+        || oldStyle.namedGridAreaRowCount() != styleRef().namedGridAreaRowCount()
+        || oldStyle.gridAutoRepeatColumns().size() != styleRef().gridAutoRepeatColumns().size()
+        || oldStyle.gridAutoRepeatRows().size() != styleRef().gridAutoRepeatRows().size();
 }
 
 bool LayoutGrid::namedGridLinesDefinitionDidChange(const ComputedStyle& oldStyle) const
@@ -694,13 +697,40 @@ static bool shouldClearOverrideContainingBlockContentSizeForChild(const LayoutBo
     return child.hasRelativeLogicalHeight() || child.styleRef().logicalHeight().isIntrinsicOrAuto();
 }
 
-GridTrackSize LayoutGrid::gridTrackSize(GridTrackSizingDirection direction, size_t i) const
+const GridTrackSize& LayoutGrid::rawGridTrackSize(GridTrackSizingDirection direction, size_t translatedIndex) const
 {
-    bool isForColumns = direction == ForColumns;
-    const Vector<GridTrackSize>& trackStyles = isForColumns ? style()->gridTemplateColumns() : style()->gridTemplateRows();
-    const GridTrackSize& autoTrackSize = isForColumns ? style()->gridAutoColumns() : style()->gridAutoRows();
-    int translatedIndex = i + (isForColumns ? m_smallestColumnStart : m_smallestRowStart);
-    const GridTrackSize& trackSize = (translatedIndex < 0 || translatedIndex >= static_cast<int>(trackStyles.size())) ? autoTrackSize : trackStyles[translatedIndex];
+    bool isRowAxis = direction == ForColumns;
+    const Vector<GridTrackSize>& trackStyles = isRowAxis ? styleRef().gridTemplateColumns() : styleRef().gridTemplateRows();
+    const Vector<GridTrackSize>& autoRepeatTrackStyles = isRowAxis ? styleRef().gridAutoRepeatColumns() : styleRef().gridAutoRepeatRows();
+    const GridTrackSize& autoTrackSize = isRowAxis ? styleRef().gridAutoColumns() : styleRef().gridAutoRows();
+    size_t insertionPoint = isRowAxis ? styleRef().gridAutoRepeatColumnsInsertionPoint() : styleRef().gridAutoRepeatRowsInsertionPoint();
+    size_t repetitions = autoRepeatCountForDirection(direction);
+
+    // We should not use GridPositionsResolver::explicitGridXXXCount() for this because the
+    // explicit grid might be larger than the number of tracks in grid-template-rows|columns (if
+    // grid-template-areas is specified for example).
+    size_t explicitTracksCount = trackStyles.size() + repetitions;
+
+    int untranslatedIndexAsInt = translatedIndex + (isRowAxis ? m_smallestColumnStart : m_smallestRowStart);
+    if (untranslatedIndexAsInt < 0)
+        return autoTrackSize;
+
+    size_t untranslatedIndex = static_cast<size_t>(untranslatedIndexAsInt);
+    if (untranslatedIndex >= explicitTracksCount)
+        return autoTrackSize;
+
+    if (LIKELY(!repetitions) || untranslatedIndex < insertionPoint)
+        return trackStyles[untranslatedIndex];
+
+    if (untranslatedIndex < (insertionPoint + repetitions))
+        return autoRepeatTrackStyles[0];
+
+    return trackStyles[untranslatedIndex - repetitions];
+}
+
+GridTrackSize LayoutGrid::gridTrackSize(GridTrackSizingDirection direction, size_t translatedIndex) const
+{
+    const GridTrackSize& trackSize = rawGridTrackSize(direction, translatedIndex);
 
     GridLength minTrackBreadth = trackSize.minTrackBreadth();
     GridLength maxTrackBreadth = trackSize.maxTrackBreadth();
@@ -1182,8 +1212,77 @@ void LayoutGrid::insertItemIntoGrid(LayoutBox& child, const GridArea& area)
 
 size_t LayoutGrid::computeAutoRepeatTracksCount(GridTrackSizingDirection direction) const
 {
-    // TODO(svillar): implement the algorithm to compute the number of auto repeat tracks.
-    return 0;
+    bool isRowAxis = direction == ForColumns;
+    const auto& autoRepeatTracks = isRowAxis ? styleRef().gridAutoRepeatColumns() : styleRef().gridAutoRepeatRows();
+
+    if (!autoRepeatTracks.size())
+        return 0;
+
+    DCHECK_EQ(autoRepeatTracks.size(), static_cast<size_t>(1));
+    auto autoTrackSize = autoRepeatTracks.at(0);
+    DCHECK(autoTrackSize.minTrackBreadth().isLength());
+    DCHECK(!autoTrackSize.minTrackBreadth().isContentSized());
+
+    LayoutUnit availableSize = isRowAxis ? availableLogicalWidth() : computeContentLogicalHeight(MainOrPreferredSize, styleRef().logicalHeight(), LayoutUnit(-1));
+    if (availableSize == -1) {
+        const Length& maxLength = isRowAxis ? styleRef().logicalMaxWidth() : styleRef().logicalMaxHeight();
+        if (!maxLength.isMaxSizeNone()) {
+            availableSize = isRowAxis
+                ? computeLogicalWidthUsing(MaxSize, maxLength, containingBlockLogicalWidthForContent(), containingBlock())
+                : computeContentLogicalHeight(MaxSize, maxLength, LayoutUnit(-1));
+        }
+    } else {
+        availableSize = isRowAxis
+            ? constrainLogicalWidthByMinMax(availableSize, availableLogicalWidth(), containingBlock())
+            : constrainLogicalHeightByMinMax(availableSize, LayoutUnit(-1));
+    }
+
+    bool needsToFulfillMinimumSize = false;
+    bool indefiniteMainAndMaxSizes = availableSize == LayoutUnit(-1);
+    if (indefiniteMainAndMaxSizes) {
+        const Length& minSize = isRowAxis ? styleRef().logicalMinWidth() : styleRef().logicalMinHeight();
+        if (!minSize.isSpecified())
+            return 1;
+
+        LayoutUnit containingBlockAvailableSize = isRowAxis ? containingBlockLogicalWidthForContent() : containingBlockLogicalHeightForContent(ExcludeMarginBorderPadding);
+        availableSize = valueForLength(minSize, containingBlockAvailableSize);
+        needsToFulfillMinimumSize = true;
+    }
+
+    bool hasDefiniteMaxTrackSizingFunction = autoTrackSize.maxTrackBreadth().isLength() && !autoTrackSize.maxTrackBreadth().isContentSized();
+    const Length trackLength = hasDefiniteMaxTrackSizingFunction ? autoTrackSize.maxTrackBreadth().length() : autoTrackSize.minTrackBreadth().length();
+    // For the purpose of finding the number of auto-repeated tracks, the UA must floor the track size to a UA-specified
+    // value to avoid division by zero. It is suggested that this floor be 1px.
+    LayoutUnit autoRepeatTrackSize = std::max<LayoutUnit>(LayoutUnit(1), valueForLength(trackLength, availableSize));
+
+    // There will be always at least 1 auto-repeat track, so take it already into account when computing the total track size.
+    LayoutUnit tracksSize = autoRepeatTrackSize;
+    const Vector<GridTrackSize>& trackSizes = isRowAxis ? styleRef().gridTemplateColumns() : styleRef().gridTemplateRows();
+
+    for (const auto& track : trackSizes) {
+        bool hasDefiniteMaxTrackBreadth = track.maxTrackBreadth().isLength() && !track.maxTrackBreadth().isContentSized();
+        DCHECK(hasDefiniteMaxTrackBreadth || (track.minTrackBreadth().isLength() && !track.minTrackBreadth().isContentSized()));
+        tracksSize += valueForLength(hasDefiniteMaxTrackBreadth ? track.maxTrackBreadth().length() : track.minTrackBreadth().length(), availableSize);
+    }
+
+    // Add gutters as if there where only 1 auto repeat track. Gaps between auto repeat tracks will be added later when
+    // computing the repetitions.
+    LayoutUnit gapSize = guttersSize(direction, 2);
+    tracksSize += gapSize * trackSizes.size();
+
+    LayoutUnit freeSpace = availableSize - tracksSize;
+    if (freeSpace <= 0)
+        return 1;
+
+    size_t repetitions = 1 + (freeSpace / (autoRepeatTrackSize + gapSize)).toInt();
+
+    // Provided the grid container does not have a definite size or max-size in the relevant axis,
+    // if the min size is definite then the number of repetitions is the largest possible positive
+    // integer that fulfills that minimum requirement.
+    if (needsToFulfillMinimumSize)
+        ++repetitions;
+
+    return repetitions;
 }
 
 void LayoutGrid::placeItemsOnGrid()