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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 RenderMultiColumnSet_h | |
28 #define RenderMultiColumnSet_h | |
29 | |
30 #include "core/rendering/RenderRegionSet.h" | |
31 | |
32 namespace WebCore { | |
33 | |
34 // RenderMultiColumnSet represents a set of columns that all have the same width
and height. By combining runs of same-size columns into a single | |
35 // object, we significantly reduce the number of unique RenderObjects required t
o represent columns. | |
36 // | |
37 // A simple multi-column block will have exactly one RenderMultiColumnSet child.
A simple paginated multi-column block will have three | |
38 // RenderMultiColumnSet children: one for the content at the bottom of the first
page (whose columns will have a shorter height), one | |
39 // for the 2nd to n-1 pages, and then one last column set that will hold the sho
rter columns on the final page (that may have to be balanced | |
40 // as well). | |
41 // | |
42 // Column spans result in the creation of new column sets as well, since a spann
ing region has to be placed in between the column sets that | |
43 // come before and after the span. | |
44 class RenderMultiColumnSet FINAL : public RenderRegionSet { | |
45 public: | |
46 static RenderMultiColumnSet* createAnonymous(RenderFlowThread*); | |
47 | |
48 virtual bool isRenderMultiColumnSet() const OVERRIDE { return true; } | |
49 | |
50 unsigned computedColumnCount() const { return m_computedColumnCount; } | |
51 LayoutUnit computedColumnWidth() const { return m_computedColumnWidth; } | |
52 LayoutUnit computedColumnHeight() const { return m_computedColumnHeight; } | |
53 | |
54 void setComputedColumnWidthAndCount(LayoutUnit width, unsigned count) | |
55 { | |
56 m_computedColumnWidth = width; | |
57 m_computedColumnCount = count; | |
58 } | |
59 | |
60 LayoutUnit heightAdjustedForSetOffset(LayoutUnit height) const; | |
61 | |
62 void updateMinimumColumnHeight(LayoutUnit height) { m_minimumColumnHeight =
std::max(height, m_minimumColumnHeight); } | |
63 LayoutUnit minimumColumnHeight() const { return m_minimumColumnHeight; } | |
64 | |
65 unsigned forcedBreaksCount() const { return m_forcedBreaksCount; } | |
66 LayoutUnit forcedBreakOffset() const { return m_forcedBreakOffset; } | |
67 LayoutUnit maximumDistanceBetweenForcedBreaks() const { return m_maximumDist
anceBetweenForcedBreaks; } | |
68 void clearForcedBreaks() | |
69 { | |
70 m_forcedBreaksCount = 0; | |
71 m_maximumDistanceBetweenForcedBreaks = 0; | |
72 m_forcedBreakOffset = 0; | |
73 } | |
74 void addForcedBreak(LayoutUnit offsetFromFirstPage) | |
75 { | |
76 ASSERT(!computedColumnHeight()); | |
77 LayoutUnit distanceFromLastBreak = offsetFromFirstPage - m_forcedBreakOf
fset; | |
78 if (!distanceFromLastBreak) | |
79 return; | |
80 m_forcedBreaksCount++; | |
81 m_maximumDistanceBetweenForcedBreaks = std::max(m_maximumDistanceBetween
ForcedBreaks, distanceFromLastBreak); | |
82 m_forcedBreakOffset = offsetFromFirstPage; | |
83 } | |
84 | |
85 // Calculate the column height when contents are supposed to be balanced. If
'initial' is set, | |
86 // guess an initial column height; otherwise, stretch the column height a ta
d. Return true if | |
87 // column height changed and another layout pass is required. | |
88 bool calculateBalancedHeight(bool initial); | |
89 | |
90 // Record space shortage (the amount of space that would have been enough to
prevent some | |
91 // element from being moved to the next column) at a column break. The small
est amount of space | |
92 // shortage we find is the amount with which we will stretch the column heig
ht, if it turns out | |
93 // after layout that the columns weren't tall enough. | |
94 void recordSpaceShortage(LayoutUnit spaceShortage); | |
95 | |
96 virtual void updateLogicalWidth() OVERRIDE; | |
97 | |
98 void prepareForLayout(); | |
99 | |
100 private: | |
101 RenderMultiColumnSet(RenderFlowThread*); | |
102 | |
103 virtual void computeLogicalHeight(LayoutUnit logicalHeight, LayoutUnit logic
alTop, LogicalExtentComputedValues&) const OVERRIDE; | |
104 | |
105 virtual void paintObject(PaintInfo&, const LayoutPoint& paintOffset) OVERRID
E; | |
106 | |
107 virtual LayoutUnit pageLogicalWidth() const OVERRIDE { return m_computedColu
mnWidth; } | |
108 virtual LayoutUnit pageLogicalHeight() const OVERRIDE { return m_computedCol
umnHeight; } | |
109 | |
110 virtual LayoutUnit pageLogicalTopForOffset(LayoutUnit offset) const OVERRIDE
; | |
111 | |
112 // FIXME: This will change once we have column sets constrained by enclosing
pages, etc. | |
113 virtual LayoutUnit logicalHeightOfAllFlowThreadContent() const OVERRIDE { re
turn m_computedColumnHeight; } | |
114 | |
115 // FIXME: For now we return false, but it's likely we will leverage the auto
height region code to do column | |
116 // balancing. That's why we have an override of this function that is distin
ct from RenderRegionSet's override. | |
117 virtual bool shouldHaveAutoLogicalHeight() const OVERRIDE { return false; } | |
118 | |
119 virtual void repaintFlowThreadContent(const LayoutRect& repaintRect) const O
VERRIDE; | |
120 | |
121 virtual void collectLayerFragments(LayerFragments&, const LayoutRect& layerB
oundingBox, const LayoutRect& dirtyRect) OVERRIDE; | |
122 | |
123 virtual const char* renderName() const OVERRIDE; | |
124 | |
125 void paintColumnRules(PaintInfo&, const LayoutPoint& paintOffset); | |
126 | |
127 LayoutUnit columnGap() const; | |
128 LayoutRect columnRectAt(unsigned index) const; | |
129 unsigned columnCount() const; | |
130 | |
131 LayoutRect flowThreadPortionRectAt(unsigned index) const; | |
132 LayoutRect flowThreadPortionOverflowRect(const LayoutRect& flowThreadPortion
, unsigned index, unsigned colCount, LayoutUnit colGap) const; | |
133 | |
134 enum ColumnIndexCalculationMode { | |
135 ClampToExistingColumns, // Stay within the range of already existing col
umns. | |
136 AssumeNewColumns // Allow column indices outside the range of already ex
isting columns. | |
137 }; | |
138 unsigned columnIndexAtOffset(LayoutUnit, ColumnIndexCalculationMode = ClampT
oExistingColumns) const; | |
139 | |
140 void setAndConstrainColumnHeight(LayoutUnit); | |
141 | |
142 unsigned m_computedColumnCount; | |
143 LayoutUnit m_computedColumnWidth; | |
144 LayoutUnit m_computedColumnHeight; | |
145 | |
146 // The following variables are used when balancing the column set. | |
147 LayoutUnit m_maxColumnHeight; // Maximum column height allowed. | |
148 LayoutUnit m_minSpaceShortage; // The smallest amout of space shortage that
caused a column break. | |
149 LayoutUnit m_minimumColumnHeight; | |
150 unsigned m_forcedBreaksCount; // FIXME: We will ultimately need to cache mor
e information to balance around forced breaks properly. | |
151 LayoutUnit m_maximumDistanceBetweenForcedBreaks; | |
152 LayoutUnit m_forcedBreakOffset; | |
153 }; | |
154 | |
155 DEFINE_RENDER_OBJECT_TYPE_CASTS(RenderMultiColumnSet, isRenderMultiColumnSet()); | |
156 | |
157 } // namespace WebCore | |
158 | |
159 #endif // RenderMultiColumnSet_h | |
160 | |
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