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/*
* 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 "core/rendering/RenderMultiColumnFlowThread.h"
#include "core/rendering/RenderRegion.h"
#include "wtf/Vector.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.
//
// Column sets are inserted as anonymous children of the actual multicol container (i.e. the
// renderer whose style computes to non-auto column-count and/or column-width).
//
// Being a "region", a column set has no children on its own, but is merely used to slice a portion
// of the tall "single-column" flow thread into actual columns visually, to convert from flow thread
// coordinates to visual ones. It is in charge of both positioning columns correctly relatively to
// the parent multicol container, and to calculate the correct translation for each column's
// contents, and to paint any rules between them. RenderMultiColumnSet objects are used for
// painting, hit testing, and any other type of operation that requires mapping from flow thread
// coordinates to visual coordinates.
//
// Column spans result in the creation of new column sets, since a spanning renderer has to be
// placed in between the column sets that come before and after the span.
class RenderMultiColumnSet FINAL : public RenderRegion {
public:
enum BalancedHeightCalculation { GuessFromFlowThreadPortion, StretchBySpaceShortage };
static RenderMultiColumnSet* createAnonymous(RenderFlowThread*, RenderStyle* parentStyle);
virtual bool isRenderMultiColumnSet() const OVERRIDE { return true; }
virtual LayoutUnit pageLogicalWidth() const OVERRIDE FINAL { return flowThread()->logicalWidth(); }
virtual LayoutUnit pageLogicalHeight() const OVERRIDE FINAL { return m_columnHeight; }
RenderBlockFlow* multiColumnBlockFlow() const { return toRenderBlockFlow(parent()); }
RenderMultiColumnFlowThread* multiColumnFlowThread() const
{
ASSERT_WITH_SECURITY_IMPLICATION(!flowThread() || flowThread()->isRenderMultiColumnFlowThread());
return static_cast<RenderMultiColumnFlowThread*>(flowThread());
}
RenderMultiColumnSet* nextSiblingMultiColumnSet() const;
RenderMultiColumnSet* previousSiblingMultiColumnSet() const;
LayoutUnit logicalTopInFlowThread() const { return isHorizontalWritingMode() ? flowThreadPortionRect().y() : flowThreadPortionRect().x(); }
LayoutUnit logicalBottomInFlowThread() const { return isHorizontalWritingMode() ? flowThreadPortionRect().maxY() : flowThreadPortionRect().maxX(); }
LayoutUnit logicalHeightInFlowThread() const { return isHorizontalWritingMode() ? flowThreadPortionRect().height() : flowThreadPortionRect().width(); }
// The used CSS value of column-count, i.e. how many columns there are room for without overflowing.
unsigned usedColumnCount() const { return multiColumnFlowThread()->columnCount(); }
// Find the column that contains the given block offset, and return the translation needed to
// get from flow thread coordinates to visual coordinates.
LayoutSize flowThreadTranslationAtOffset(LayoutUnit) const;
LayoutUnit heightAdjustedForSetOffset(LayoutUnit height) const;
void updateMinimumColumnHeight(LayoutUnit height) { m_minimumColumnHeight = std::max(height, m_minimumColumnHeight); }
LayoutUnit minimumColumnHeight() const { return m_minimumColumnHeight; }
// Add a content run, specified by its end position. A content run is appended at every
// forced/explicit break and at the end of the column set. The content runs are used to
// determine where implicit/soft breaks will occur, in order to calculate an initial column
// height.
void addContentRun(LayoutUnit endOffsetFromFirstPage);
// (Re-)calculate the column height if it's auto.
bool recalculateColumnHeight(BalancedHeightCalculation);
// 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);
// Reset previously calculated column height. Will mark for layout if needed.
void resetColumnHeight();
// Expand this set's flow thread portion rectangle to contain all trailing flow thread
// overflow. Only to be called on the last set.
void expandToEncompassFlowThreadContentsIfNeeded();
private:
RenderMultiColumnSet(RenderFlowThread*);
virtual void computeLogicalHeight(LayoutUnit logicalHeight, LayoutUnit logicalTop, LogicalExtentComputedValues&) const OVERRIDE;
virtual void paintObject(PaintInfo&, const LayoutPoint& paintOffset) OVERRIDE;
virtual LayoutUnit pageLogicalTopForOffset(LayoutUnit offset) const OVERRIDE;
virtual LayoutUnit logicalHeightOfAllFlowThreadContent() const OVERRIDE { return logicalHeightInFlowThread(); }
virtual void repaintFlowThreadContent(const LayoutRect& repaintRect) const OVERRIDE;
virtual void collectLayerFragments(LayerFragments&, const LayoutRect& layerBoundingBox, const LayoutRect& dirtyRect) OVERRIDE;
virtual void addOverflowFromChildren() OVERRIDE;
virtual const char* renderName() const OVERRIDE;
void paintColumnRules(PaintInfo&, const LayoutPoint& paintOffset);
LayoutUnit calculateMaxColumnHeight() const;
LayoutUnit columnGap() const;
LayoutRect columnRectAt(unsigned index) const;
// The "CSS actual" value of column-count. This includes overflowing columns, if any.
unsigned actualColumnCount() 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);
// Return the index of the content run with the currently tallest columns, taking all implicit
// breaks assumed so far into account.
unsigned findRunWithTallestColumns() const;
// Given the current list of content runs, make assumptions about where we need to insert
// implicit breaks (if there's room for any at all; depending on the number of explicit breaks),
// and store the results. This is needed in order to balance the columns.
void distributeImplicitBreaks();
LayoutUnit calculateColumnHeight(BalancedHeightCalculation) const;
LayoutUnit m_columnHeight;
// 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;
// A run of content without explicit (forced) breaks; i.e. a flow thread portion between two
// explicit breaks, between flow thread start and an explicit break, between an explicit break
// and flow thread end, or, in cases when there are no explicit breaks at all: between flow
// thread portion start and flow thread portion end. We need to know where the explicit breaks
// are, in order to figure out where the implicit breaks will end up, so that we get the columns
// properly balanced. A content run starts out as representing one single column, and will
// represent one additional column for each implicit break "inserted" there.
class ContentRun {
public:
ContentRun(LayoutUnit breakOffset)
: m_breakOffset(breakOffset)
, m_assumedImplicitBreaks(0) { }
unsigned assumedImplicitBreaks() const { return m_assumedImplicitBreaks; }
void assumeAnotherImplicitBreak() { m_assumedImplicitBreaks++; }
LayoutUnit breakOffset() const { return m_breakOffset; }
// Return the column height that this content run would require, considering the implicit
// breaks assumed so far.
LayoutUnit columnLogicalHeight(LayoutUnit startOffset) const { return ceilf((m_breakOffset - startOffset).toFloat() / float(m_assumedImplicitBreaks + 1)); }
private:
LayoutUnit m_breakOffset; // Flow thread offset where this run ends.
unsigned m_assumedImplicitBreaks; // Number of implicit breaks in this run assumed so far.
};
Vector<ContentRun, 1> m_contentRuns;
};
DEFINE_RENDER_OBJECT_TYPE_CASTS(RenderMultiColumnSet, isRenderMultiColumnSet());
} // namespace WebCore
#endif // RenderMultiColumnSet_h
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