/* * Copyright (C) 2018 Igalia S.L. All rights reserved. * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: * 1. Redistributions of source code must retain the above copyright * notice, this list of conditions and the following disclaimer. * 2. Redistributions in binary form must reproduce the above copyright * notice, this list of conditions and the following disclaimer in the * documentation and/or other materials provided with the distribution. * * THIS SOFTWARE IS PROVIDED BY APPLE INC. AND ITS CONTRIBUTORS ``AS IS'' * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR ITS CONTRIBUTORS * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF * THE POSSIBILITY OF SUCH DAMAGE. */ #pragma once #include "GridLayoutFunctions.h" namespace WebCore { // These classes are used to implement the Baseline Alignment logic, as described in the CSS Box Alignment // specification. // https://drafts.csswg.org/css-align/#baseline-terms // // A baseline-sharing group is composed of boxes that participate in baseline alignment together. This is // possible only if they: // // * Share an alignment context along an axis perpendicular to their baseline alignment axis. // * Have compatible baseline alignment preferences (i.e., the baselines that want to align are on the same // side of the alignment context). // // Once the BaselineGroup is instantiated, defined by a 'block-direction' (WritingMode) and a 'baseline-preference' // (first/last baseline), it's ready to collect the items that will participate in the Baseline Alignment logic. // class BaselineGroup { public: // It stores an item (if not already present) and update the max_ascent and max_descent associated to this // baseline-sharing group. void update(const RenderBox&, LayoutUnit ascent, LayoutUnit descent); LayoutUnit maxAscent() const { return m_maxAscent; } LayoutUnit maxDescent() const { return m_maxDescent; } int size() const { return m_items.size(); } private: friend class BaselineContext; BaselineGroup(WritingMode blockFlow, ItemPosition childPreference); // Determines whether a baseline-sharing group is compatible with an item, based on its 'block-flow' and // 'baseline-preference' bool isCompatible(WritingMode, ItemPosition) const; // Determines whether the baseline-sharing group's associated block-flow is opposite (LR vs RL) to particular // item's writing-mode. bool isOppositeBlockFlow(WritingMode blockFlow) const; // Determines whether the baseline-sharing group's associated block-flow is orthogonal (vertical vs horizontal) // to particular item's writing-mode. bool isOrthogonalBlockFlow(WritingMode blockFlow) const; WritingMode m_blockFlow; ItemPosition m_preference; LayoutUnit m_maxAscent; LayoutUnit m_maxDescent; HashSet<const RenderBox*> m_items; }; // https://drafts.csswg.org/css-align-3/#shared-alignment-context // Boxes share an alignment context along a particular axis when they are: // // * table cells in the same row, along the table's row (inline) axis // * table cells in the same column, along the table's column (block) axis // * grid items in the same row, along the grid's row (inline) axis // * grid items in the same column, along the grid's colum (block) axis // * flex items in the same flex line, along the flex container's main axis // // https://drafts.csswg.org/css-align-3/#baseline-sharing-group // A Baseline alignment-context may handle several baseline-sharing groups. In order to create an instance, we // need to pass the required data to define the first baseline-sharing group; a Baseline Context must have at // least one baseline-sharing group. // // By adding new items to a Baseline Context, the baseline-sharing groups it handles are automatically updated, // if there is one that is compatible with such item. Otherwise, a new baseline-sharing group is created, // compatible with the new item. class BaselineContext { public: BaselineContext(const RenderBox& child, ItemPosition preference, LayoutUnit ascent, LayoutUnit descent); const BaselineGroup& sharedGroup(const RenderBox& child, ItemPosition preference) const; // Updates the baseline-sharing group compatible with the item. // We pass the item's baseline-preference to avoid dependencies with the LayoutGrid class, which is the one // managing the alignment behavior of the Grid Items. void updateSharedGroup(const RenderBox& child, ItemPosition preference, LayoutUnit ascent, LayoutUnit descent); private: // Returns the baseline-sharing group compatible with an item. // We pass the item's baseline-preference to avoid dependencies with the LayoutGrid class, which is the one // managing the alignment behavior of the Grid Items. // FIXME: Properly implement baseline-group compatibility. // See https://github.com/w3c/csswg-drafts/issues/721 BaselineGroup& findCompatibleSharedGroup(const RenderBox& child, ItemPosition preference); Vector<BaselineGroup> m_sharedGroups; }; static inline bool isBaselinePosition(ItemPosition position) { return position == ItemPosition::Baseline || position == ItemPosition::LastBaseline; } // This is the class that implements the Baseline Alignment logic, using internally the BaselineContext and // BaselineGroupd classes (described above). // // The first phase is to collect the items that will participate in baseline alignment together. During this // phase the required baseline-sharing groups will be created for each Baseline alignment-context shared by // the items participating in the baseline alignment. // // Additionally, the baseline-sharing groups' offsets, max-ascend and max-descent will be computed and stored. // This class also computes the baseline offset for a particular item, based on the max-ascent for its associated // baseline-sharing group. class GridBaselineAlignment { public: // Collects the items participating in baseline alignment and updates the corresponding baseline-sharing // group of the Baseline Context the items belongs to. // All the baseline offsets are updated accordingly based on the added item. void updateBaselineAlignmentContext(ItemPosition, unsigned sharedContext, const RenderBox&, GridAxis); // Returns the baseline offset of a particular item, based on the max-ascent for its associated // baseline-sharing group LayoutUnit baselineOffsetForChild(ItemPosition, unsigned sharedContext, const RenderBox&, GridAxis) const; // Sets the Grid Container's writing-mode so that we can avoid the dependecy of the LayoutGrid class for // determining whether a grid item is orthogonal or not. void setBlockFlow(WritingMode blockFlow) { m_blockFlow = blockFlow; }; // Clearing the Baseline Alignment context and their internal classes and data structures. void clear(GridAxis); private: const BaselineGroup& baselineGroupForChild(ItemPosition, unsigned sharedContext, const RenderBox&, GridAxis) const; LayoutUnit marginOverForChild(const RenderBox&, GridAxis) const; LayoutUnit marginUnderForChild(const RenderBox&, GridAxis) const; LayoutUnit logicalAscentForChild(const RenderBox&, GridAxis) const; LayoutUnit ascentForChild(const RenderBox&, GridAxis) const; LayoutUnit descentForChild(const RenderBox&, LayoutUnit, GridAxis) const; bool isDescentBaselineForChild(const RenderBox&, GridAxis) const; bool isHorizontalBaselineAxis(GridAxis) const; bool isOrthogonalChildForBaseline(const RenderBox&) const; bool isParallelToBaselineAxisForChild(const RenderBox&, GridAxis) const; typedef HashMap<unsigned, std::unique_ptr<BaselineContext>, DefaultHash<unsigned>::Hash, WTF::UnsignedWithZeroKeyHashTraits<unsigned>> BaselineContextsMap; // Grid Container's WritingMode, used to determine grid item's orthogonality. WritingMode m_blockFlow; BaselineContextsMap m_rowAxisAlignmentContext; BaselineContextsMap m_colAxisAlignmentContext; }; } // namespace WebCore