third_party/WebKit/Source/core/layout/LayoutMultiColumnSet.h

   1 /*
   2  * Copyright (C) 2012 Apple Inc.  All rights reserved.
   3  *
   4  * Redistribution and use in source and binary forms, with or without
   5  * modification, are permitted provided that the following conditions
   6  * are met:
   7  * 1. Redistributions of source code must retain the above copyright
   8  *    notice, this list of conditions and the following disclaimer.
   9  * 2. Redistributions in binary form must reproduce the above copyright
  10  *    notice, this list of conditions and the following disclaimer in the
  11  *    documentation and/or other materials provided with the distribution.
  12  *
  13  * THIS SOFTWARE IS PROVIDED BY APPLE INC. ``AS IS'' AND ANY
  14  * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  15  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
  16  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL APPLE COMPUTER, INC. OR
  17  * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
  18  * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
  19  * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
  20  * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
  21  * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  22  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  23  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  24  */
  25
  26
  27 #ifndef LayoutMultiColumnSet_h
  28 #define LayoutMultiColumnSet_h
  29
  30 #include "core/CoreExport.h"
  31 #include "core/layout/LayoutMultiColumnFlowThread.h"
  32 #include "core/layout/MultiColumnFragmentainerGroup.h"
  33 #include "wtf/Vector.h"
  34
  35 namespace blink {
  36
  37 // A set of columns in a multicol container. A column set is inserted as an anonymous child of the
  38 // actual multicol container (i.e. the layoutObject whose style computes to non-auto column-count and/or
  39 // column-width), next to the flow thread. There'll be one column set for each contiguous run of
  40 // column content. The only thing that can interrupt a contiguous run of column content is a column
  41 // spanner, which means that if there are no spanners, there'll only be one column set.
  42 //
  43 // Since a spanner interrupts an otherwise contiguous run of column content, inserting one may
  44 // result in the creation of additional new column sets. A placeholder for the spanning layoutObject has
  45 // to be placed in between the column sets that come before and after the spanner, if there's
  46 // actually column content both before and after the spanner.
  47 //
  48 // A column set has no children on its own, but is merely used to slice a portion of the tall
  49 // "single-column" flow thread into actual columns visually, to convert from flow thread coordinates
  50 // to visual ones. It is in charge of both positioning columns correctly relatively to the parent
  51 // multicol container, and to calculate the correct translation for each column's contents, and to
  52 // paint any rules between them. LayoutMultiColumnSet objects are used for painting, hit testing,
  53 // and any other type of operation that requires mapping from flow thread coordinates to visual
  54 // coordinates.
  55 //
  56 // Columns are normally laid out in the inline progression direction, but if the multicol container
  57 // is inside another fragmentation context (e.g. paged media, or an another multicol container), we
  58 // may need to group the columns, so that we get one MultiColumnFragmentainerGroup for each outer
  59 // fragmentainer (page / column) that the inner multicol container lives in. Each fragmentainer
  60 // group has its own column height, but the column height is uniform within a group.
  61 class CORE_EXPORT LayoutMultiColumnSet : public LayoutBlockFlow {
  62 public:
  63     static LayoutMultiColumnSet* createAnonymous(LayoutFlowThread&, const ComputedStyle& parentStyle);
  64
  65     const MultiColumnFragmentainerGroup& firstFragmentainerGroup() const { return m_fragmentainerGroups.first(); }
  66     const MultiColumnFragmentainerGroup& lastFragmentainerGroup() const { return m_fragmentainerGroups.last(); }
  67     MultiColumnFragmentainerGroup& fragmentainerGroupAtFlowThreadOffset(LayoutUnit flowThreadOffset)
  68     {
  69         return m_fragmentainerGroups[fragmentainerGroupIndexAtFlowThreadOffset(flowThreadOffset)];
  70     }
  71     const MultiColumnFragmentainerGroup& fragmentainerGroupAtFlowThreadOffset(LayoutUnit flowThreadOffset) const
  72     {
  73         return m_fragmentainerGroups[fragmentainerGroupIndexAtFlowThreadOffset(flowThreadOffset)];
  74     }
  75     const MultiColumnFragmentainerGroup& fragmentainerGroupAtVisualPoint(const LayoutPoint&) const;
  76
  77     bool isOfType(LayoutObjectType type) const override { return type == LayoutObjectLayoutMultiColumnSet || LayoutBlockFlow::isOfType(type); }
  78     bool canHaveChildren() const final { return false; }
  79
  80     // Return the width and height of a single column or page in the set.
  81     LayoutUnit pageLogicalWidth() const { return flowThread()->logicalWidth(); }
  82     LayoutUnit pageLogicalHeightForOffset(LayoutUnit) const;
  83     LayoutUnit pageRemainingLogicalHeightForOffset(LayoutUnit, PageBoundaryRule) const;
  84     bool isPageLogicalHeightKnown() const;
  85
  86     LayoutFlowThread* flowThread() const { return m_flowThread; }
  87
  88     LayoutBlockFlow* multiColumnBlockFlow() const { return toLayoutBlockFlow(parent()); }
  89     LayoutMultiColumnFlowThread* multiColumnFlowThread() const { return toLayoutMultiColumnFlowThread(flowThread()); }
  90
  91     LayoutMultiColumnSet* nextSiblingMultiColumnSet() const;
  92     LayoutMultiColumnSet* previousSiblingMultiColumnSet() const;
  93
  94     MultiColumnFragmentainerGroup& appendNewFragmentainerGroup();
  95
  96     LayoutUnit logicalTopInFlowThread() const;
  97     LayoutUnit logicalBottomInFlowThread() const;
  98     LayoutUnit logicalHeightInFlowThread() const { return logicalBottomInFlowThread() - logicalTopInFlowThread(); }
  99     LayoutRect flowThreadPortionRect() const;
 100     LayoutRect flowThreadPortionOverflowRect() const;
 101     LayoutRect overflowRectForFlowThreadPortion(const LayoutRect& flowThreadPortionRect, bool isFirstPortion, bool isLastPortion) const;
 102
 103     // The used CSS value of column-count, i.e. how many columns there are room for without overflowing.
 104     unsigned usedColumnCount() const { return multiColumnFlowThread()->columnCount(); }
 105
 106     bool heightIsAuto() const;
 107
 108     // Find the column that contains the given block offset, and return the translation needed to
 109     // get from flow thread coordinates to visual coordinates.
 110     LayoutSize flowThreadTranslationAtOffset(LayoutUnit) const;
 111
 112     LayoutPoint visualPointToFlowThreadPoint(const LayoutPoint& visualPoint) const;
 113
 114     void updateMinimumColumnHeight(LayoutUnit offsetInFlowThread, LayoutUnit height);
 115
 116     // Add a content run, specified by its end position. A content run is appended at every
 117     // forced/explicit break and at the end of the column set. The content runs are used to
 118     // determine where implicit/soft breaks will occur, in order to calculate an initial column
 119     // height.
 120     void addContentRun(LayoutUnit endOffsetFromFirstPage);
 121
 122     // (Re-)calculate the column height if it's auto. This is first and foremost needed by sets that
 123     // are to balance the column height, but even when it isn't to be balanced, this is necessary if
 124     // the multicol container's height is constrained.
 125     bool recalculateColumnHeight(BalancedColumnHeightCalculation);
 126
 127     // Record space shortage (the amount of space that would have been enough to prevent some
 128     // element from being moved to the next column) at a column break. The smallest amount of space
 129     // shortage we find is the amount with which we will stretch the column height, if it turns out
 130     // after layout that the columns weren't tall enough.
 131     void recordSpaceShortage(LayoutUnit offsetInFlowThread, LayoutUnit);
 132
 133     // Reset previously calculated column height. Will mark for layout if needed.
 134     void resetColumnHeight();
 135
 136     // Layout of flow thread content that's to be rendered inside this column set begins. This
 137     // happens at the beginning of flow thread layout, and when advancing from a previous column set
 138     // or spanner to this one.
 139     void beginFlow(LayoutUnit offsetInFlowThread);
 140
 141     // Layout of flow thread content that was to be rendered inside this column set has
 142     // finished. This happens at end of flow thread layout, and when advancing to the next column
 143     // set or spanner.
 144     void endFlow(LayoutUnit offsetInFlowThread);
 145
 146     void computeIntrinsicLogicalWidths(LayoutUnit& minLogicalWidth, LayoutUnit& maxLogicalWidth) const final;
 147
 148     void attachToFlowThread();
 149     void detachFromFlowThread();
 150
 151     // The top of the page nearest to the specified block offset. All in flowthread coordinates.
 152     LayoutUnit pageLogicalTopForOffset(LayoutUnit offset) const;
 153
 154     LayoutRect fragmentsBoundingBox(const LayoutRect& boundingBoxInFlowThread) const;
 155
 156     void collectLayerFragments(DeprecatedPaintLayerFragments&, const LayoutRect& layerBoundingBox, const LayoutRect& dirtyRect);
 157
 158     LayoutUnit columnGap() const;
 159
 160     // The "CSS actual" value of column-count. This includes overflowing columns, if any.
 161     unsigned actualColumnCount() const;
 162
 163     const char* name() const override { return "LayoutMultiColumnSet"; }
 164
 165 protected:
 166     LayoutMultiColumnSet(LayoutFlowThread*);
 167
 168 private:
 169     unsigned fragmentainerGroupIndexAtFlowThreadOffset(LayoutUnit) const;
 170
 171     void insertedIntoTree() final;
 172     void willBeRemovedFromTree() final;
 173
 174     bool isSelfCollapsingBlock() const override { return false; }
 175
 176     void computeLogicalHeight(LayoutUnit logicalHeight, LayoutUnit logicalTop, LogicalExtentComputedValues&) const override;
 177     PositionWithAffinity positionForPoint(const LayoutPoint&) override;
 178
 179     void paintObject(const PaintInfo&, const LayoutPoint& paintOffset) override;
 180
 181     void addOverflowFromChildren() override;
 182
 183     MultiColumnFragmentainerGroupList m_fragmentainerGroups;
 184     LayoutFlowThread* m_flowThread;
 185 };
 186
 187 DEFINE_LAYOUT_OBJECT_TYPE_CASTS(LayoutMultiColumnSet, isLayoutMultiColumnSet());
 188
 189 } // namespace blink
 190
 191 #endif // LayoutMultiColumnSet_h
 192