| // 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 NGColumnMapper_h |
| #define NGColumnMapper_h |
| |
| #include "core/CoreExport.h" |
| #include "core/layout/ng/ng_block_break_token.h" |
| #include "platform/heap/Handle.h" |
| |
| namespace blink { |
| |
| // Keeps track of the current column, and is used to map offsets from the |
| // coordinate established by the fragmented flow [1] to visual coordinates. |
| // |
| // [1] https://drafts.csswg.org/css-break/#fragmented-flow |
| // |
| // TODO(mstensho): Add a NGFragmentainerMapper super class. There are other |
| // fragmentation types than multicol (regions, pagination for printing). |
| class CORE_EXPORT NGColumnMapper |
| : public GarbageCollectedFinalized<NGColumnMapper> { |
| public: |
| NGColumnMapper(LayoutUnit inline_progression, LayoutUnit block_size) |
| : inline_progression_(inline_progression), block_size_(block_size) {} |
| |
| // Column block length. |
| LayoutUnit BlockSize() const { return block_size_; } |
| |
| // Offset for next break, in the fragmented flow coordinate space. |
| LayoutUnit NextBreakOffset() const { |
| return last_break_block_offset_ + block_size_; |
| } |
| |
| // Convert an offset in the fragmented flow coordinate space to the visual |
| // coordinate space. |
| void ToVisualOffset(NGLogicalOffset& offset) { |
| offset.inline_offset += inline_offset_; |
| offset.block_offset -= last_break_block_offset_; |
| } |
| |
| // Specify where in the content to start layout of the next column. |
| void SetBreakToken(NGBlockBreakToken* token) { |
| DCHECK(!break_token_); |
| break_token_ = token; |
| } |
| bool HasBreakToken() const { return break_token_; } |
| |
| // Advance to the next column. Returns the break token to resume at. If |
| // nullptr is returned, there's no more content to process. |
| NGBlockBreakToken* Advance() { |
| NGBlockBreakToken* token = break_token_; |
| break_token_ = nullptr; |
| if (token) { |
| inline_offset_ += inline_progression_; |
| last_break_block_offset_ += block_size_; |
| } |
| return token; |
| } |
| |
| DEFINE_INLINE_TRACE() { visitor->trace(break_token_); } |
| |
| private: |
| // Where to resume in the next column. |
| Member<NGBlockBreakToken> break_token_; |
| |
| // The sum of used column-width and column_gap. |
| LayoutUnit inline_progression_; |
| |
| // Inline offset to the current column. |
| LayoutUnit inline_offset_; |
| |
| // Block size of a column. |
| LayoutUnit block_size_; |
| |
| // Amount of content held by previous columns. |
| LayoutUnit last_break_block_offset_; |
| }; |
| |
| } // namespace blink |
| |
| #endif // NGColumnMapper_h |