248 lines
12 KiB
C++
248 lines
12 KiB
C++
/*
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* Copyright (C) 2012 Apple Inc. All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY APPLE INC. ``AS IS'' AND ANY
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* EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
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* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR
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* CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
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* EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
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* PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
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* PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
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* OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
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* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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#pragma once
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#include "LayerFragment.h"
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#include "RenderFragmentContainerSet.h"
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#include "RenderMultiColumnFlow.h"
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#include <wtf/Vector.h>
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namespace WebCore {
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// RenderMultiColumnSet represents a set of columns that all have the same width and height. By combining runs of same-size columns into a single
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// object, we significantly reduce the number of unique RenderObjects required to represent columns.
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//
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// A simple multi-column block will have exactly one RenderMultiColumnSet child. A simple paginated multi-column block will have three
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// RenderMultiColumnSet children: one for the content at the bottom of the first page (whose columns will have a shorter height), one
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// for the 2nd to n-1 pages, and then one last column set that will hold the shorter columns on the final page (that may have to be balanced
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// as well).
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//
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// Column spans result in the creation of new column sets as well, since a spanning fragment has to be placed in between the column sets that
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// come before and after the span.
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class RenderMultiColumnSet final : public RenderFragmentContainerSet {
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WTF_MAKE_ISO_ALLOCATED(RenderMultiColumnSet);
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public:
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RenderMultiColumnSet(RenderFragmentedFlow&, RenderStyle&&);
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RenderBlockFlow* multiColumnBlockFlow() const { return downcast<RenderBlockFlow>(parent()); }
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RenderMultiColumnFlow* multiColumnFlow() const { return static_cast<RenderMultiColumnFlow*>(fragmentedFlow()); }
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RenderMultiColumnSet* nextSiblingMultiColumnSet() const;
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RenderMultiColumnSet* previousSiblingMultiColumnSet() const;
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// Return the first object in the flow thread that's rendered inside this set.
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RenderObject* firstRendererInFragmentedFlow() const;
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// Return the last object in the flow thread that's rendered inside this set.
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RenderObject* lastRendererInFragmentedFlow() const;
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// Return true if the specified renderer (descendant of the flow thread) is inside this column set.
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bool containsRendererInFragmentedFlow(const RenderObject&) const;
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void setLogicalTopInFragmentedFlow(LayoutUnit);
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LayoutUnit logicalTopInFragmentedFlow() const { return isHorizontalWritingMode() ? fragmentedFlowPortionRect().y() : fragmentedFlowPortionRect().x(); }
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void setLogicalBottomInFragmentedFlow(LayoutUnit);
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LayoutUnit logicalBottomInFragmentedFlow() const { return isHorizontalWritingMode() ? fragmentedFlowPortionRect().maxY() : fragmentedFlowPortionRect().maxX(); }
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LayoutUnit logicalHeightInFragmentedFlow() const { return isHorizontalWritingMode() ? fragmentedFlowPortionRect().height() : fragmentedFlowPortionRect().width(); }
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unsigned computedColumnCount() const { return m_computedColumnCount; }
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LayoutUnit computedColumnWidth() const { return m_computedColumnWidth; }
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LayoutUnit computedColumnHeight() const { return m_computedColumnHeight; }
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bool columnHeightComputed() const { return m_columnHeightComputed; }
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void setComputedColumnWidthAndCount(LayoutUnit width, unsigned count)
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{
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m_computedColumnWidth = width;
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m_computedColumnCount = count;
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}
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LayoutUnit heightAdjustedForSetOffset(LayoutUnit height) const;
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void updateMinimumColumnHeight(LayoutUnit height) { m_minimumColumnHeight = std::max(height, m_minimumColumnHeight); }
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LayoutUnit minimumColumnHeight() const { return m_minimumColumnHeight; }
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void updateSpaceShortageForSizeContainment(LayoutUnit shortage)
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{
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if (m_spaceShortageForSizeContainment <= 0) {
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m_spaceShortageForSizeContainment = shortage;
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return;
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}
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m_spaceShortageForSizeContainment = std::min(shortage, m_spaceShortageForSizeContainment);
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}
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unsigned forcedBreaksCount() const { return m_contentRuns.size(); }
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void clearForcedBreaks();
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void addForcedBreak(LayoutUnit offsetFromFirstPage);
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// (Re-)calculate the column height. This is first and foremost needed by sets that are to
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// balance the column height, but even when it isn't to be balanced, this is necessary if the
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// multicol container's height is constrained. If |initial| is set, and we are to balance, guess
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// an initial column height; otherwise, stretch the column height a tad. Return true if column
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// height changed and another layout pass is required.
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bool recalculateColumnHeight(bool initial);
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// Record space shortage (the amount of space that would have been enough to prevent some
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// element from being moved to the next column) at a column break. The smallest amount of space
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// shortage we find is the amount with which we will stretch the column height, if it turns out
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// after layout that the columns weren't tall enough.
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void recordSpaceShortage(LayoutUnit spaceShortage);
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void updateLogicalWidth() override;
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void prepareForLayout(bool initial);
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// Begin laying out content for this column set. This happens at the beginning of flow thread
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// layout, and when advancing from a previous column set or spanner to this one.
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void beginFlow(RenderBlock* container);
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// Finish laying out content for this column set. This happens at end of flow thread layout, and
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// when advancing to the next column set or spanner.
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void endFlow(RenderBlock* container, LayoutUnit bottomInContainer);
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// Has this set been flowed in this layout pass?
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bool hasBeenFlowed() const { return logicalBottomInFragmentedFlow() != RenderFragmentedFlow::maxLogicalHeight(); }
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bool requiresBalancing() const;
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LayoutPoint columnTranslationForOffset(const LayoutUnit&) const;
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void paintColumnRules(PaintInfo&, const LayoutPoint& paintOffset) override;
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enum ColumnHitTestTranslationMode {
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ClampHitTestTranslationToColumns,
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DoNotClampHitTestTranslationToColumns
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};
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LayoutPoint translateFragmentPointToFragmentedFlow(const LayoutPoint & logicalPoint, ColumnHitTestTranslationMode = DoNotClampHitTestTranslationToColumns) const;
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void updateHitTestResult(HitTestResult&, const LayoutPoint&) override;
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LayoutRect columnRectAt(unsigned index) const;
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unsigned columnCount() const;
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LayoutUnit columnGap() const;
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private:
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void addOverflowFromChildren() override;
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bool isRenderMultiColumnSet() const override { return true; }
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void layout() override;
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Node* nodeForHitTest() const override;
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LogicalExtentComputedValues computeLogicalHeight(LayoutUnit logicalHeight, LayoutUnit logicalTop) const override;
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void paintObject(PaintInfo&, const LayoutPoint&) override { }
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LayoutUnit pageLogicalWidth() const override { return m_computedColumnWidth; }
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LayoutUnit pageLogicalHeight() const override { return m_computedColumnHeight; }
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LayoutUnit pageLogicalTopForOffset(LayoutUnit offset) const override;
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LayoutUnit logicalHeightOfAllFragmentedFlowContent() const override { return logicalHeightInFragmentedFlow(); }
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void repaintFragmentedFlowContent(const LayoutRect& repaintRect) override;
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void collectLayerFragments(LayerFragments&, const LayoutRect& layerBoundingBox, const LayoutRect& dirtyRect) override;
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void adjustFragmentBoundsFromFragmentedFlowPortionRect(LayoutRect& fragmentBounds) const override;
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Vector<LayoutRect> fragmentRectsForFlowContentRect(const LayoutRect&) final;
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VisiblePosition positionForPoint(const LayoutPoint&, const RenderFragmentContainer*) override;
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const char* renderName() const override;
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LayoutUnit calculateMaxColumnHeight() const;
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LayoutUnit columnLogicalLeft(unsigned) const;
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LayoutUnit columnLogicalTop(unsigned) const;
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LayoutRect fragmentedFlowPortionRectAt(unsigned index) const;
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LayoutRect fragmentedFlowPortionOverflowRect(const LayoutRect& fragmentedFlowPortion, unsigned index, unsigned colCount, LayoutUnit colGap);
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LayoutUnit initialBlockOffsetForPainting() const;
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enum ColumnIndexCalculationMode {
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ClampToExistingColumns, // Stay within the range of already existing columns.
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AssumeNewColumns // Allow column indices outside the range of already existing columns.
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};
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unsigned columnIndexAtOffset(LayoutUnit, ColumnIndexCalculationMode = ClampToExistingColumns) const;
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std::pair<unsigned, unsigned> firstAndLastColumnsFromOffsets(LayoutUnit topOffset, LayoutUnit bottomOffset) const;
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void setAndConstrainColumnHeight(LayoutUnit);
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// Return the index of the content run with the currently tallest columns, taking all implicit
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// breaks assumed so far into account.
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unsigned findRunWithTallestColumns() const;
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// Given the current list of content runs, make assumptions about where we need to insert
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// implicit breaks (if there's room for any at all; depending on the number of explicit breaks),
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// and store the results. This is needed in order to balance the columns.
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void distributeImplicitBreaks();
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LayoutUnit calculateBalancedHeight(bool initial) const;
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unsigned m_computedColumnCount { 1 }; // Used column count (the resulting 'N' from the pseudo-algorithm in the multicol spec)
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LayoutUnit m_computedColumnWidth; // Used column width (the resulting 'W' from the pseudo-algorithm in the multicol spec)
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LayoutUnit m_computedColumnHeight;
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LayoutUnit m_availableColumnHeight;
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bool m_columnHeightComputed { false };
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// The following variables are used when balancing the column set.
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LayoutUnit m_maxColumnHeight; // Maximum column height allowed.
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LayoutUnit m_minSpaceShortage; // The smallest amout of space shortage that caused a column break.
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LayoutUnit m_minimumColumnHeight;
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LayoutUnit m_spaceShortageForSizeContainment; // The shortage space that keeps size containment monolithic.
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// A run of content without explicit (forced) breaks; i.e. a flow thread portion between two
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// explicit breaks, between flow thread start and an explicit break, between an explicit break
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// and flow thread end, or, in cases when there are no explicit breaks at all: between flow flow
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// thread start and flow thread end. We need to know where the explicit breaks are, in order to
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// figure out where the implicit breaks will end up, so that we get the columns properly
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// balanced. A content run starts out as representing one single column, and will represent one
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// additional column for each implicit break "inserted" there.
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class ContentRun {
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public:
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ContentRun(LayoutUnit breakOffset)
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: m_breakOffset(breakOffset)
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{ }
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unsigned assumedImplicitBreaks() const { return m_assumedImplicitBreaks; }
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void assumeAnotherImplicitBreak() { m_assumedImplicitBreaks++; }
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LayoutUnit breakOffset() const { return m_breakOffset; }
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// Return the column height that this content run would require, considering the implicit
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// breaks assumed so far.
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LayoutUnit columnLogicalHeight(LayoutUnit startOffset) const { return LayoutUnit(ceilf(float(m_breakOffset - startOffset) / float(m_assumedImplicitBreaks + 1))); }
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private:
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LayoutUnit m_breakOffset; // Flow thread offset where this run ends.
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unsigned m_assumedImplicitBreaks { 0 }; // Number of implicit breaks in this run assumed so far.
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};
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Vector<ContentRun, 1> m_contentRuns;
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};
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} // namespace WebCore
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SPECIALIZE_TYPE_TRAITS_RENDER_OBJECT(RenderMultiColumnSet, isRenderMultiColumnSet())
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