[css-grid] Move the track sizing algorithm to its own class

third_party/WebKit/Source/core/layout/GridTrackSizingAlgorithm.h

+// Copyright 2017 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef GridTrackSizingAlgorithm_h
+#define GridTrackSizingAlgorithm_h
+
+#include "core/style/GridPositionsResolver.h"
+#include "core/style/GridTrackSize.h"
+#include "platform/LayoutUnit.h"
+#include "wtf/HashSet.h"
+#include "wtf/Optional.h"
+#include <memory>
+
+namespace blink {
+
+static const int infinity = -1;
+
+class Grid;
+class GridTrackSizingAlgorithmStrategy;
+class LayoutGrid;
+
+enum SizingOperation { TrackSizing, IntrinsicSizeComputation };
+
+enum TrackSizeComputationPhase {
+  ResolveIntrinsicMinimums,
+  ResolveContentBasedMinimums,
+  ResolveMaxContentMinimums,
+  ResolveIntrinsicMaximums,
+  ResolveMaxContentMaximums,
+  MaximizeTracks,
+};
+
+class GridTrack {
+ public:
+  GridTrack() : m_infinitelyGrowable(false) {}
+
+  LayoutUnit baseSize() const;
+  void setBaseSize(LayoutUnit);
+
+  LayoutUnit growthLimit() const;
+  void setGrowthLimit(LayoutUnit);
+
+  bool infiniteGrowthPotential() const;
+
+  LayoutUnit plannedSize() const { return m_plannedSize; }
+  void setPlannedSize(LayoutUnit);
+
+  LayoutUnit sizeDuringDistribution() const { return m_sizeDuringDistribution; }
+  void setSizeDuringDistribution(LayoutUnit);
+
+  void growSizeDuringDistribution(LayoutUnit);
+
+  bool infinitelyGrowable() const { return m_infinitelyGrowable; }
+  void setInfinitelyGrowable(bool);
+
+  Optional<LayoutUnit> growthLimitCap() const { return m_growthLimitCap; }
+  void setGrowthLimitCap(Optional<LayoutUnit>);
+
+ private:
+  bool growthLimitIsInfinite() const { return m_growthLimit == infinity; }
+  bool isGrowthLimitBiggerThanBaseSize() const;
+  void ensureGrowthLimitIsBiggerThanBaseSize();
+
+  LayoutUnit m_baseSize;
+  LayoutUnit m_growthLimit;
+  LayoutUnit m_plannedSize;
+  LayoutUnit m_sizeDuringDistribution;
+  Optional<LayoutUnit> m_growthLimitCap;
+  bool m_infinitelyGrowable;
+};
+
+class GridTrackSizingAlgorithm final {
+ public:
+  GridTrackSizingAlgorithm(const LayoutGrid* layoutGrid, Grid& grid)
+      : m_grid(grid),
+        m_layoutGrid(layoutGrid),
+        m_sizingState(ColumnSizingFirstIteration) {}
+
+  // setup() must be run before calling run() as it configures the behaviour of
+  // the algorithm.
+  void setup(GridTrackSizingDirection,
+             size_t numTracks,
+             SizingOperation,
+             LayoutUnit availableSpace,
+             LayoutUnit freeSpace);
+  void run();
+  void reset();
+
+  // Required by LayoutGrid. Try to minimize the exposed surface.
+  const Grid& grid() const { return m_grid; }
+  GridTrackSize gridTrackSize(GridTrackSizingDirection,
+                              size_t translatedIndex,
+                              SizingOperation) const;
+  LayoutUnit minContentSize() const { return m_minContentSize; };
+  LayoutUnit maxContentSize() const { return m_maxContentSize; };
+
+  Vector<GridTrack>& tracks(GridTrackSizingDirection);
+  const Vector<GridTrack>& tracks(GridTrackSizingDirection) const;
+
+  LayoutUnit& freeSpace(GridTrackSizingDirection);
+
+#if DCHECK_IS_ON()
+  bool tracksAreWiderThanMinTrackBreadth() const;
+#endif
+
+ private:
+  GridTrackSize gridTrackSize(GridTrackSizingDirection,
+                              size_t translatedIndex) const;
+  GridTrackSize rawGridTrackSize(GridTrackSizingDirection,
+                                 size_t translatedIndex) const;
+  LayoutUnit assumedRowsSizeForOrthogonalChild(const LayoutBox&) const;
+  LayoutUnit computeTrackBasedSize() const;
+
+  // Helper methods for step 1. initializeTrackSizes().
+  LayoutUnit initialBaseSize(const GridTrackSize&) const;
+  LayoutUnit initialGrowthLimit(const GridTrackSize&,
+                                LayoutUnit baseSize) const;
+
+  // Helper methods for step 2. resolveIntrinsicTrackSizes().
+  void sizeTrackToFitNonSpanningItem(const GridSpan&,
+                                     LayoutBox& gridItem,
+                                     GridTrack&);
+  bool spanningItemCrossesFlexibleSizedTracks(const GridSpan&) const;
+  typedef struct GridItemsSpanGroupRange GridItemsSpanGroupRange;
+  template <TrackSizeComputationPhase phase>
+  void increaseSizesToAccommodateSpanningItems(
+      const GridItemsSpanGroupRange& gridItemsWithSpan);
+  LayoutUnit itemSizeForTrackSizeComputationPhase(TrackSizeComputationPhase,
+                                                  LayoutBox&) const;
+  template <TrackSizeComputationPhase phase>
+  void distributeSpaceToTracks(Vector<GridTrack*>& tracks,
+                               Vector<GridTrack*>* growBeyondGrowthLimitsTracks,
+                               LayoutUnit& availableLogicalSpace) const;
+  LayoutUnit gridAreaBreadthForChild(const LayoutBox&,
+                                     GridTrackSizingDirection);
+
+  void computeGridContainerIntrinsicSizes();
+
+  // Helper methods for step 4. Strech flexible tracks.
+  typedef HashSet<size_t,
+                  DefaultHash<size_t>::Hash,
+                  WTF::UnsignedWithZeroKeyHashTraits<size_t>>
+      TrackIndexSet;
+  double computeFlexFactorUnitSize(
+      const Vector<GridTrack>& tracks,
+      double flexFactorSum,
+      LayoutUnit& leftOverSpace,
+      const Vector<size_t, 8>& flexibleTracksIndexes,
+      std::unique_ptr<TrackIndexSet> tracksToTreatAsInflexible = nullptr) const;
+  void computeFlexSizedTracksGrowth(double flexFraction,
+                                    Vector<LayoutUnit>& increments,
+                                    LayoutUnit& totalGrowth) const;
+  double findFrUnitSize(const GridSpan& tracksSpan,
+                        LayoutUnit leftOverSpace) const;
+
+  // Track sizing algorithm steps. Note that the "Maximize Tracks" step is done
+  // entirely inside the strategies, that's why we don't need an additional
+  // method at thise level.
+  void initializeTrackSizes();
+  void resolveIntrinsicTrackSizes();
+  void stretchFlexibleTracks(LayoutUnit freeSpace);
+
+  // State machine.
+  void advanceNextState();
+  bool isValidTransition() const;
+
+  // Data.
+  bool m_needsSetup{true};
+  LayoutUnit m_availableSpace;
+
+  LayoutUnit m_freeSpaceColumns;
+  LayoutUnit m_freeSpaceRows;
+
+  // We need to keep both alive in order to properly size grids with orthogonal
+  // writing modes.
+  Vector<GridTrack> m_columns;
+  Vector<GridTrack> m_rows;
+  Vector<size_t> m_contentSizedTracksIndex;
+  Vector<size_t> m_flexibleSizedTracksIndex;
+
+  GridTrackSizingDirection m_direction;
+  SizingOperation m_sizingOperation;
+
+  Grid& m_grid;
+
+  const LayoutGrid* m_layoutGrid;
+  std::unique_ptr<GridTrackSizingAlgorithmStrategy> m_strategy;
+
+  // The track sizing algorithm is used for both layout and intrinsic size
+  // computation. We're normally just interested in intrinsic inline sizes
+  // (a.k.a widths in most of the cases) for the computeIntrinsicLogicalWidths()
+  // computations. That's why we don't need to keep around different values for
+  // rows/columns.
+  LayoutUnit m_minContentSize;
+  LayoutUnit m_maxContentSize;
+
+  enum SizingState {
+    ColumnSizingFirstIteration,
+    RowSizingFirstIteration,
+    ColumnSizingSecondIteration,
+    RowSizingSecondIteration
+  };
+  SizingState m_sizingState;
+
+  // This is a RAII class used to ensure that the track sizing algorithm is
+  // executed as it is suppossed to be, i.e., first resolve columns and then
+  // rows. Only if required a second iteration is run following the same order,
+  // first columns and then rows.
+  class MachineState {
+   public:
+    MachineState(GridTrackSizingAlgorithm&);
+    ~MachineState();
+
+   private:
+    GridTrackSizingAlgorithm& m_algorithm;
+  };
+
+  friend class GridTrackSizingAlgorithmStrategy;
+};
+
+class GridTrackSizingAlgorithmStrategy {
+  WTF_MAKE_NONCOPYABLE(GridTrackSizingAlgorithmStrategy);
+  USING_FAST_MALLOC(GridTrackSizingAlgorithmStrategy);
+
+ public:
+  LayoutUnit minContentForChild(LayoutBox&) const;
+  LayoutUnit maxContentForChild(LayoutBox&) const;
+  LayoutUnit minSizeForChild(LayoutBox&) const;
+
+  virtual void maximizeTracks(Vector<GridTrack>&, LayoutUnit& freeSpace);
+  virtual double findUsedFlexFraction(Vector<size_t>& flexibleSizedTracksIndex,
+                                      GridTrackSizingDirection,
+                                      LayoutUnit initialFreeSpace) const;
+  virtual bool recomputeUsedFlexFractionIfNeeded(
+      Vector<size_t>& flexibleSizedTracksIndex,
+      double& flexFraction,
+      Vector<LayoutUnit>& increments,
+      LayoutUnit& totalGrowth) const;
+
+ protected:
+  GridTrackSizingAlgorithmStrategy(GridTrackSizingAlgorithm& algorithm)
+      : m_algorithm(algorithm) {}
+
+  virtual bool canPerformLayout() const = 0;
+  virtual LayoutUnit minLogicalWidthForChild(
+      LayoutBox&,
+      Length childMinSize,
+      GridTrackSizingDirection) const = 0;
+  virtual void layoutGridItemForMinSizeComputation(
+      LayoutBox&,
+      bool overrideSizeHasChanged) const = 0;
+
+  LayoutUnit logicalHeightForChild(LayoutBox&) const;
+
+  bool updateOverrideContainingBlockContentSizeForChild(
+      LayoutBox&,
+      GridTrackSizingDirection) const;
+  LayoutUnit computeTrackBasedSize() const;
+  GridTrackSizingDirection direction() const { return m_algorithm.m_direction; }
+  double findFrUnitSize(const GridSpan& tracksSpan,
+                        LayoutUnit leftOverSpace) const;
+  void distributeSpaceToTracks(Vector<GridTrack*>& tracks,
+                               LayoutUnit& availableLogicalSpace) const;
+  const LayoutGrid* layoutGrid() const { return m_algorithm.m_layoutGrid; }
+
+  GridTrackSizingAlgorithm& m_algorithm;
+};
+}
+
+#endif  // GridTrackSizingAlgorithm_h