cobalt/layout/container_box.h

// Copyright 2015 The Cobalt Authors. All Rights Reserved.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

#ifndef COBALT_LAYOUT_CONTAINER_BOX_H_
#define COBALT_LAYOUT_CONTAINER_BOX_H_

#include <set>
#include <vector>

#include "cobalt/layout/box.h"

namespace cobalt {
namespace layout {

// Defines a base interface for block and inline container boxes that allows
// the box generator to be agnostic to a box type. Implementation-specific,
// not defined in CSS 2.1.
class ContainerBox : public Box, public base::SupportsWeakPtr<ContainerBox> {
 public:
  struct StackingContextChildInfo {
    StackingContextChildInfo(
        Box* box, int z_index, RelationshipToBox containing_block_relationship,
        const ContainingBlocksWithOverflowHidden& overflow_hidden_to_apply)
        : box(box),
          z_index(z_index),
          containing_block_relationship(containing_block_relationship),
          overflow_hidden_to_apply(overflow_hidden_to_apply) {}

    Box* box;
    int z_index;
    RelationshipToBox containing_block_relationship;
    ContainingBlocksWithOverflowHidden overflow_hidden_to_apply;
  };

  ContainerBox(const scoped_refptr<cssom::CSSComputedStyleDeclaration>&
                   css_computed_style_declaration,
               UsedStyleProvider* used_style_provider,
               LayoutStatTracker* layout_stat_tracker);
  ~ContainerBox() override;

  // Attempts to add a child box and takes the ownership if succeeded. Returns
  // true if the child's box level is compatible with the container box. Block
  // container boxes are able to become parents of both block- and inline-level
  // boxes, while inline container boxes are only able to become parents
  // of inline-level boxes.
  virtual bool TryAddChild(const scoped_refptr<Box>& child_box) = 0;
  // Attempts to split the box right before the end. Returns the part after
  // the split if the split succeeded. Only inline boxes are splittable and it's
  // always possible to split them. The returned part is identical to
  // the original container, except that the former is empty.
  //
  // A box generator uses this method to break inline boxes around block-level
  // boxes.
  virtual scoped_refptr<ContainerBox> TrySplitAtEnd() = 0;

  // From |Box|.
  void SplitBidiLevelRuns() override;

  // Invalidates the cross references, indicating that they need to be
  // re-generated the next time they are needed.
  void InvalidateCrossReferencesOfBoxAndAncestors() override;

  ContainerBox* AsContainerBox() override;
  const ContainerBox* AsContainerBox() const override;

  void RenderAndAnimateContent(
      render_tree::CompositionNode::Builder* border_node_builder,
      ContainerBox* stacking_context) const override;

#ifdef COBALT_BOX_DUMP_ENABLED
  void DumpChildrenWithIndent(std::ostream* stream, int indent) const override;
#endif  // COBALT_BOX_DUMP_ENABLED

  // Returns true if the given style allows a container box to act as a
  // containing block for absolutely positioned elements.  For example it will
  // be true if this box's style is itself 'absolute'.
  bool IsContainingBlockForPositionAbsoluteElements() const;

  // Returns true if the given style allows a container box to act as a
  // containing block for fixed positioned elements.  For example it will
  // be true if this box is transformed, as indicated at the bottom of this
  // section: https://www.w3.org/TR/css3-transforms/#transform-rendering.
  bool IsContainingBlockForPositionFixedElements() const;

  // Returns true if the box serves as a stacking context for descendant
  // elements. The core stacking context creation criteria is given here
  // (https://www.w3.org/TR/CSS21/visuren.html#z-index) however it is extended
  // by various other specification documents such as those describing opacity
  // (https://www.w3.org/TR/css3-color/#transparency) and transforms
  // (https://www.w3.org/TR/css3-transforms/#transform-rendering).
  bool IsStackingContext() const override;

 protected:
  class ZIndexComparator {
   public:
    bool operator()(const StackingContextChildInfo& lhs,
                    const StackingContextChildInfo& rhs) const {
      return lhs.z_index < rhs.z_index;
    }
  };
  // Note: find(StackingContextChildInfo) and erase(StackingContextChildInfo) on
  // ZIndexSortedList may not work as expected due to the use of reflexive
  // comparison for equality.
  typedef std::multiset<StackingContextChildInfo, ZIndexComparator>
      ZIndexSortedList;

  void UpdateRectOfPositionedChildBoxes(
      const LayoutParams& relative_child_layout_params,
      const LayoutParams& absolute_child_layout_params);

  // Adds the child box to the end of the list of direct children.
  // NOTE: This should only be called during box generation.
  void PushBackDirectChild(const scoped_refptr<Box>& child_box);

  // Adds the split sibling of the specified child as another direct child.
  // NOTE: This should be called immediately after the split sibling is created.
  Boxes::const_iterator InsertSplitSiblingOfDirectChild(
      Boxes::const_iterator child_position);

  // Moves all of the direct children starting with the iterator from this
  // container to its split sibling.
  // NOTE: This should be called immediately after the split sibling is created
  // and prior to it being inserted into the tree.
  void MoveDirectChildrenToSplitSibling(Boxes::const_iterator start_position);

  const Boxes& child_boxes() const { return child_boxes_; }

  void UpdateCrossReferencesOfContainerBox(
      ContainerBox* source_box, RelationshipToBox nearest_containing_block,
      RelationshipToBox nearest_absolute_containing_block,
      RelationshipToBox nearest_fixed_containing_block,
      RelationshipToBox nearest_stacking_context,
      StackingContextContainerBoxStack* stacking_context_container_box_stack)
      override;

  bool ValidateUpdateSizeInputs(const LayoutParams& params) override;
  void InvalidateUpdateSizeInputs() { update_size_results_valid_ = false; }

  // Add a box and all of its descendants that are contained within the
  // specified stacking context to the stacking context's draw order. This is
  // used when a render tree node that is already cached is encountered to
  // ensure that it maintains the proper draw order in its stacking context.
  void AddBoxAndDescendantsToDrawOrderInStackingContext(
      ContainerBox* stacking_context) override;

 private:
  static Boxes::iterator RemoveConst(Boxes* container,
                                     Boxes::const_iterator const_iter);
  ContainerBox* FindContainingBlock(Box* box);

  // Update the cross references of the container box if they are invalid.
  void UpdateCrossReferences();

  // These helper functions are called from
  // Box::UpdateCrossReferencesOfContainerBox().
  void AddContainingBlockChild(Box* child_box);
  void AddStackingContextChild(
      Box* child_box, int z_index,
      RelationshipToBox containing_block_relationship,
      const ContainingBlocksWithOverflowHidden&
          containing_blocks_with_overflow_hidden_to_apply);

  // Returns whether or not the container has any stacking context children.
  bool HasStackingContextChildren() const;

  // Updates used values of left/top/right/bottom given the child_box's
  // 'position' property is set to 'relative'.
  //    https://www.w3.org/TR/CSS21/visuren.html#relative-positioning
  void UpdateOffsetOfRelativelyPositionedChildBox(
      Box* child_box, const LayoutParams& child_layout_params);

  // Updates the sizes of the fixed position child box.
  // This is meant to be called by UpdateRectOfPositionedChildBoxes(), after the
  // child has gone through the in-flow layout.
  //    https://www.w3.org/TR/CSS21/visuren.html#absolute-positioning
  void UpdateRectOfAbsolutelyPositionedChildBox(
      Box* child_box, const LayoutParams& child_layout_params);

  // Add children (sorted by z-index) that belong to our stacking context to the
  // render tree.  The specific list of children to be rendered must be passed
  // in also, though it will likely only ever be either negative_z_index_child_
  // or non_negative_z_index_child_.
  void RenderAndAnimateStackingContextChildren(
      const ZIndexSortedList& z_index_child_list,
      render_tree::CompositionNode::Builder* border_node_builder,
      const Vector2dLayoutUnit& offset_from_parent_node,
      ContainerBox* stacking_context) const;

  // Called by a box within this stacking context when it is being added to the
  // render tree so that it can get its position in the stacking context's
  // draw order.
  size_t AddToDrawOrderInThisStackingContext();

  // A list of our direct children.  If a box is one of our child boxes, we
  // are that box's parent.  We may not be the box's containing block (such
  // as for 'absolute' or 'fixed' position elements).
  Boxes child_boxes_;

  // A list of our positioned child boxes.  For each box in our list of
  // positioned_child_boxes_, we are that child's containing block.  This is
  // used for properly positioning and sizing positioned child elements.
  std::vector<Box*> positioned_child_boxes_;

  // A list of descendant positioned boxes and stacking context children within
  // our stacking context that should be drawn after this box, sorted by
  // z-index.
  ZIndexSortedList negative_z_index_stacking_context_children_;
  ZIndexSortedList non_negative_z_index_stacking_context_children_;

  bool update_size_results_valid_;

  // Whether or not the cross references--which refers to positioned children
  // and z-index children of the container--are valid, and do not need to be
  // updated the next time cross references are needed.
  bool are_cross_references_valid_;

  // Whether or not bidi level run splitting has already occurred. This is
  // tracked so it will never be attempted more than once.
  bool are_bidi_levels_runs_split_;

  // The next draw order position within this box's stacking context.
  size_t next_draw_order_position_;

  // Boxes and ContainerBoxes are closely related.  For example, when
  // Box::SetupAsPositionedChild() is called, it will internally call
  // ContainerBox::AddContainingBlockChild() and
  // ContainerBox::AddStackingContextChild().
  // This mutual friendship is a result of the need to maintain 2-way links
  // between boxes and containers.
  friend class Box;
  friend class LayoutBoxes;
  friend class FlexContainerBox;

  DISALLOW_COPY_AND_ASSIGN(ContainerBox);
};

}  // namespace layout
}  // namespace cobalt

#endif  // COBALT_LAYOUT_CONTAINER_BOX_H_