| /* |
| * Copyright (C) 2007 Apple Inc. 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. ``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 |
| * 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. |
| */ |
| |
| #ifndef LayoutState_h |
| #define LayoutState_h |
| |
| #include "platform/geometry/LayoutRect.h" |
| #include "platform/wtf/Allocator.h" |
| #include "platform/wtf/HashMap.h" |
| #include "platform/wtf/Noncopyable.h" |
| |
| namespace blink { |
| |
| class LayoutBox; |
| class LayoutFlowThread; |
| class LayoutObject; |
| class LayoutView; |
| |
| // LayoutState is an optimization used during layout. |
| // |
| // LayoutState's purpose is to cache information as we walk down the container |
| // block chain during layout. In particular, the absolute layout offset for the |
| // current LayoutObject is O(1) when using LayoutState, when it is |
| // O(depthOfTree) without it (thus potentially making layout O(N^2)). |
| // LayoutState incurs some memory overhead and is pretty intrusive (see next |
| // paragraphs about those downsides). |
| // |
| // To use LayoutState, the layout() functions have to allocate a new LayoutSTate |
| // object on the stack whenever the LayoutObject creates a new coordinate system |
| // (which is pretty much all objects but LayoutTableRow). |
| // |
| // LayoutStates are linked together with a single linked list, acting in |
| // practice like a stack that we push / pop. LayoutView holds the top-most |
| // pointer to this stack. |
| // |
| // See the layout() functions on how to set it up during layout. |
| // See e.g LayoutBox::offsetFromLogicalTopOfFirstPage on how to use LayoutState |
| // for computations. |
| class LayoutState { |
| // LayoutState is always allocated on the stack. |
| // The reason is that it is scoped to layout, thus we can avoid expensive |
| // mallocs. |
| DISALLOW_NEW(); |
| WTF_MAKE_NONCOPYABLE(LayoutState); |
| |
| public: |
| // Constructor for root LayoutState created by LayoutView |
| explicit LayoutState(LayoutView&); |
| // Constructor for sub-tree layout and orthogonal writing-mode roots |
| explicit LayoutState(LayoutObject& root); |
| |
| LayoutState(LayoutBox&, bool containing_block_logical_width_changed = false); |
| |
| ~LayoutState(); |
| |
| bool IsPaginated() const { return is_paginated_; } |
| |
| // The page logical offset is the object's offset from the top of the page in |
| // the page progression direction (so an x-offset in vertical text and a |
| // y-offset for horizontal text). |
| LayoutUnit PageLogicalOffset(const LayoutBox&, |
| const LayoutUnit& child_logical_offset) const; |
| |
| LayoutUnit HeightOffsetForTableHeaders() const { |
| return height_offset_for_table_headers_; |
| } |
| void SetHeightOffsetForTableHeaders(LayoutUnit offset) { |
| height_offset_for_table_headers_ = offset; |
| } |
| |
| const LayoutSize& PaginationOffset() const { return pagination_offset_; } |
| bool ContainingBlockLogicalWidthChanged() const { |
| return containing_block_logical_width_changed_; |
| } |
| |
| bool PaginationStateChanged() const { return pagination_state_changed_; } |
| void SetPaginationStateChanged() { pagination_state_changed_ = true; } |
| |
| LayoutState* Next() const { return next_; } |
| |
| LayoutFlowThread* FlowThread() const { return flow_thread_; } |
| |
| LayoutObject& GetLayoutObject() const { return layout_object_; } |
| |
| private: |
| // Do not add anything apart from bitfields until after m_flowThread. See |
| // https://bugs.webkit.org/show_bug.cgi?id=100173 |
| bool is_paginated_ : 1; |
| |
| bool containing_block_logical_width_changed_ : 1; |
| bool pagination_state_changed_ : 1; |
| |
| LayoutFlowThread* flow_thread_; |
| |
| LayoutState* next_; |
| |
| // x/y offset from the logical top / start of the first page. Does not include |
| // relative positioning or scroll offsets. |
| LayoutSize pagination_offset_; |
| |
| // The height we need to make available for repeating table headers in |
| // paginated layout. |
| LayoutUnit height_offset_for_table_headers_; |
| |
| LayoutObject& layout_object_; |
| }; |
| |
| } // namespace blink |
| |
| #endif // LayoutState_h |