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

/*
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#ifndef FlexibleBoxAlgorithm_h
#define FlexibleBoxAlgorithm_h

#include "core/CoreExport.h"
#include "core/layout/OrderIterator.h"
#include "core/style/ComputedStyle.h"
#include "platform/LayoutUnit.h"
#include "platform/wtf/Noncopyable.h"
#include "platform/wtf/Vector.h"

namespace blink {

class LayoutBox;

enum FlexSign {
  kPositiveFlexibility,
  kNegativeFlexibility,
};

class FlexItem {
 public:
  FlexItem(LayoutBox*,
           LayoutUnit flex_base_content_size,
           LayoutUnit hypothetical_main_content_size,
           LayoutUnit main_axis_border_and_padding,
           LayoutUnit main_axis_margin);

  LayoutUnit HypotheticalMainAxisMarginBoxSize() const {
    return hypothetical_main_content_size + main_axis_border_and_padding +
           main_axis_margin;
  }

  LayoutUnit FlexBaseMarginBoxSize() const {
    return flex_base_content_size + main_axis_border_and_padding +
           main_axis_margin;
  }

  LayoutUnit FlexedMarginBoxSize() const {
    return flexed_content_size + main_axis_border_and_padding +
           main_axis_margin;
  }

  LayoutBox* box;
  const LayoutUnit flex_base_content_size;
  const LayoutUnit hypothetical_main_content_size;
  const LayoutUnit main_axis_border_and_padding;
  const LayoutUnit main_axis_margin;
  LayoutUnit flexed_content_size;
  bool frozen;
};

class FlexLine {
 public:
  FlexLine() {
    total_flex_grow = total_flex_shrink = total_weighted_flex_shrink = 0;
  }

  FlexSign Sign() const {
    return sum_hypothetical_main_size < container_main_inner_size
               ? kPositiveFlexibility
               : kNegativeFlexibility;
  }

  void SetContainerMainInnerSize(LayoutUnit size) {
    container_main_inner_size = size;
  }

  void FreezeInflexibleItems();

  // This modifies remaining_free_space.
  void FreezeViolations(Vector<FlexItem*>& violations);

  // These fields get filled in by ComputeNextFlexLine.
  // TODO(cbiesinger): Consider moving to a constructor.
  Vector<FlexItem> line_items;
  LayoutUnit sum_flex_base_size;
  double total_flex_grow;
  double total_flex_shrink;
  double total_weighted_flex_shrink;
  // The hypothetical main size of an item is the flex base size clamped
  // according to its min and max main size properties
  LayoutUnit sum_hypothetical_main_size;

  // This gets set by SetContainerMainInnerSize
  LayoutUnit container_main_inner_size;
  // initial_free_space is the initial amount of free space in this flexbox.
  // remaining_free_space starts out at the same value but as we place and lay
  // out flex items we subtract from it. Note that both values can be
  // negative.
  // These get set by FreezeInflexibleItems, see spec:
  // https://drafts.csswg.org/css-flexbox/#resolve-flexible-lengths step 3
  LayoutUnit initial_free_space;
  LayoutUnit remaining_free_space;

  // These get filled in by LayoutAndPlaceChildren (for now)
  // TODO(cbiesinger): Move that to FlexibleBoxAlgorithm.
  LayoutUnit cross_axis_offset;
  LayoutUnit cross_axis_extent;
  LayoutUnit max_ascent;
};

class FlexLayoutAlgorithm {
  WTF_MAKE_NONCOPYABLE(FlexLayoutAlgorithm);

 public:
  FlexLayoutAlgorithm(const ComputedStyle*,
                      LayoutUnit line_break_length,
                      const Vector<FlexItem>& all_items);

  Vector<FlexLine>& FlexLines() { return flex_lines_; }

  // Computes the next flex line, stores it in FlexLines(), and returns a
  // pointer to it. Returns nullptr if there are no more lines.
  FlexLine* ComputeNextFlexLine();

 private:
  bool IsMultiline() const { return style_->FlexWrap() != EFlexWrap::kNowrap; }

  const ComputedStyle* style_;
  LayoutUnit line_break_length_;
  const Vector<FlexItem>& all_items_;
  Vector<FlexLine> flex_lines_;
  size_t next_item_index_;
};

}  // namespace blink

#endif  // FlexibleBoxAlgorithm_h