| /* |
| * Copyright (C) 2012 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 COMPUTER, 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 RenderMultiColumnSet_h |
| #define RenderMultiColumnSet_h |
| |
| #include "RenderRegionSet.h" |
| |
| namespace WebCore { |
| |
| // RenderMultiColumnSet represents a set of columns that all have the same width and height. By combining runs of same-size columns into a single |
| // object, we significantly reduce the number of unique RenderObjects required to represent columns. |
| // |
| // A simple multi-column block will have exactly one RenderMultiColumnSet child. A simple paginated multi-column block will have three |
| // RenderMultiColumnSet children: one for the content at the bottom of the first page (whose columns will have a shorter height), one |
| // 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 |
| // as well). |
| // |
| // Column spans result in the creation of new column sets as well, since a spanning region has to be placed in between the column sets that |
| // come before and after the span. |
| class RenderMultiColumnSet FINAL : public RenderRegionSet { |
| public: |
| explicit RenderMultiColumnSet(RenderFlowThread&); |
| |
| virtual bool isRenderMultiColumnSet() const OVERRIDE { return true; } |
| |
| unsigned computedColumnCount() const { return m_computedColumnCount; } |
| LayoutUnit computedColumnWidth() const { return m_computedColumnWidth; } |
| LayoutUnit computedColumnHeight() const { return m_computedColumnHeight; } |
| |
| void setComputedColumnWidthAndCount(LayoutUnit width, unsigned count) |
| { |
| m_computedColumnWidth = width; |
| m_computedColumnCount = count; |
| } |
| |
| LayoutUnit heightAdjustedForSetOffset(LayoutUnit height) const; |
| |
| void updateMinimumColumnHeight(LayoutUnit height) { m_minimumColumnHeight = std::max(height, m_minimumColumnHeight); } |
| LayoutUnit minimumColumnHeight() const { return m_minimumColumnHeight; } |
| |
| unsigned forcedBreaksCount() const { return m_forcedBreaksCount; } |
| LayoutUnit forcedBreakOffset() const { return m_forcedBreakOffset; } |
| LayoutUnit maximumDistanceBetweenForcedBreaks() const { return m_maximumDistanceBetweenForcedBreaks; } |
| void clearForcedBreaks() |
| { |
| m_forcedBreaksCount = 0; |
| m_maximumDistanceBetweenForcedBreaks = 0; |
| m_forcedBreakOffset = 0; |
| } |
| void addForcedBreak(LayoutUnit offsetFromFirstPage) |
| { |
| ASSERT(!computedColumnHeight()); |
| LayoutUnit distanceFromLastBreak = offsetFromFirstPage - m_forcedBreakOffset; |
| if (!distanceFromLastBreak) |
| return; |
| m_forcedBreaksCount++; |
| m_maximumDistanceBetweenForcedBreaks = std::max(m_maximumDistanceBetweenForcedBreaks, distanceFromLastBreak); |
| m_forcedBreakOffset = offsetFromFirstPage; |
| } |
| |
| // Calculate the column height when contents are supposed to be balanced. If 'initial' is set, |
| // guess an initial column height; otherwise, stretch the column height a tad. Return true if |
| // column height changed and another layout pass is required. |
| bool calculateBalancedHeight(bool initial); |
| |
| // Record space shortage (the amount of space that would have been enough to prevent some |
| // element from being moved to the next column) at a column break. The smallest amount of space |
| // shortage we find is the amount with which we will stretch the column height, if it turns out |
| // after layout that the columns weren't tall enough. |
| void recordSpaceShortage(LayoutUnit spaceShortage); |
| |
| virtual void updateLogicalWidth() OVERRIDE; |
| |
| void prepareForLayout(); |
| |
| private: |
| virtual void computeLogicalHeight(LayoutUnit logicalHeight, LayoutUnit logicalTop, LogicalExtentComputedValues&) const OVERRIDE; |
| |
| virtual void paintObject(PaintInfo&, const LayoutPoint& paintOffset) OVERRIDE; |
| |
| virtual LayoutUnit pageLogicalWidth() const OVERRIDE { return m_computedColumnWidth; } |
| virtual LayoutUnit pageLogicalHeight() const OVERRIDE { return m_computedColumnHeight; } |
| |
| virtual LayoutUnit pageLogicalTopForOffset(LayoutUnit offset) const OVERRIDE; |
| |
| // FIXME: This will change once we have column sets constrained by enclosing pages, etc. |
| virtual LayoutUnit logicalHeightOfAllFlowThreadContent() const OVERRIDE { return m_computedColumnHeight; } |
| |
| // FIXME: For now we return false, but it's likely we will leverage the auto height region code to do column |
| // balancing. That's why we have an override of this function that is distinct from RenderRegionSet's override. |
| virtual bool shouldHaveAutoLogicalHeight() const OVERRIDE { return false; } |
| |
| virtual void repaintFlowThreadContent(const LayoutRect& repaintRect, bool immediate) const OVERRIDE; |
| |
| virtual void collectLayerFragments(LayerFragments&, const LayoutRect& layerBoundingBox, const LayoutRect& dirtyRect) OVERRIDE; |
| |
| virtual void adjustRegionBoundsFromFlowThreadPortionRect(const IntPoint& layerOffset, IntRect& regionBounds) OVERRIDE; |
| |
| virtual const char* renderName() const; |
| |
| void paintColumnRules(PaintInfo&, const LayoutPoint& paintOffset); |
| |
| LayoutUnit columnGap() const; |
| LayoutRect columnRectAt(unsigned index) const; |
| unsigned columnCount() const; |
| |
| LayoutRect flowThreadPortionRectAt(unsigned index) const; |
| LayoutRect flowThreadPortionOverflowRect(const LayoutRect& flowThreadPortion, unsigned index, unsigned colCount, LayoutUnit colGap) const; |
| |
| enum ColumnIndexCalculationMode { |
| ClampToExistingColumns, // Stay within the range of already existing columns. |
| AssumeNewColumns // Allow column indices outside the range of already existing columns. |
| }; |
| unsigned columnIndexAtOffset(LayoutUnit, ColumnIndexCalculationMode = ClampToExistingColumns) const; |
| |
| void setAndConstrainColumnHeight(LayoutUnit); |
| |
| unsigned m_computedColumnCount; |
| LayoutUnit m_computedColumnWidth; |
| LayoutUnit m_computedColumnHeight; |
| |
| // The following variables are used when balancing the column set. |
| LayoutUnit m_maxColumnHeight; // Maximum column height allowed. |
| LayoutUnit m_minSpaceShortage; // The smallest amout of space shortage that caused a column break. |
| LayoutUnit m_minimumColumnHeight; |
| unsigned m_forcedBreaksCount; // FIXME: We will ultimately need to cache more information to balance around forced breaks properly. |
| LayoutUnit m_maximumDistanceBetweenForcedBreaks; |
| LayoutUnit m_forcedBreakOffset; |
| }; |
| |
| RENDER_OBJECT_TYPE_CASTS(RenderMultiColumnSet, isRenderMultiColumnSet()) |
| |
| } // namespace WebCore |
| |
| #endif // RenderMultiColumnSet_h |
| |