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1 /* | 1 /* |
2 * Copyright (C) 2012 Apple Inc. All rights reserved. | 2 * Copyright (C) 2012 Apple Inc. All rights reserved. |
3 * | 3 * |
4 * Redistribution and use in source and binary forms, with or without | 4 * Redistribution and use in source and binary forms, with or without |
5 * modification, are permitted provided that the following conditions | 5 * modification, are permitted provided that the following conditions |
6 * are met: | 6 * are met: |
7 * 1. Redistributions of source code must retain the above copyright | 7 * 1. Redistributions of source code must retain the above copyright |
8 * notice, this list of conditions and the following disclaimer. | 8 * notice, this list of conditions and the following disclaimer. |
9 * 2. Redistributions in binary form must reproduce the above copyright | 9 * 2. Redistributions in binary form must reproduce the above copyright |
10 * notice, this list of conditions and the following disclaimer in the | 10 * notice, this list of conditions and the following disclaimer in the |
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21 * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT | 21 * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT |
22 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE | 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. | 23 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. |
24 */ | 24 */ |
25 | 25 |
26 | 26 |
27 #ifndef RenderMultiColumnSet_h | 27 #ifndef RenderMultiColumnSet_h |
28 #define RenderMultiColumnSet_h | 28 #define RenderMultiColumnSet_h |
29 | 29 |
30 #include "core/rendering/RenderRegionSet.h" | 30 #include "core/rendering/RenderRegionSet.h" |
| 31 #include "wtf/Vector.h" |
31 | 32 |
32 namespace WebCore { | 33 namespace WebCore { |
33 | 34 |
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 // 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 // object, we significantly reduce the number of unique RenderObjects required t
o represent columns. |
36 // | 37 // |
37 // A simple multi-column block will have exactly one RenderMultiColumnSet child.
A simple paginated multi-column block will have three | 38 // 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 // 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 // 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 // as well). |
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55 { | 56 { |
56 m_computedColumnWidth = width; | 57 m_computedColumnWidth = width; |
57 m_computedColumnCount = count; | 58 m_computedColumnCount = count; |
58 } | 59 } |
59 | 60 |
60 LayoutUnit heightAdjustedForSetOffset(LayoutUnit height) const; | 61 LayoutUnit heightAdjustedForSetOffset(LayoutUnit height) const; |
61 | 62 |
62 void updateMinimumColumnHeight(LayoutUnit height) { m_minimumColumnHeight =
std::max(height, m_minimumColumnHeight); } | 63 void updateMinimumColumnHeight(LayoutUnit height) { m_minimumColumnHeight =
std::max(height, m_minimumColumnHeight); } |
63 LayoutUnit minimumColumnHeight() const { return m_minimumColumnHeight; } | 64 LayoutUnit minimumColumnHeight() const { return m_minimumColumnHeight; } |
64 | 65 |
65 unsigned forcedBreaksCount() const { return m_forcedBreaksCount; } | 66 unsigned forcedBreaksCount() const { return m_contentRuns.size(); } |
66 LayoutUnit forcedBreakOffset() const { return m_forcedBreakOffset; } | 67 void clearForcedBreaks(); |
67 LayoutUnit maximumDistanceBetweenForcedBreaks() const { return m_maximumDist
anceBetweenForcedBreaks; } | 68 void addForcedBreak(LayoutUnit offsetFromFirstPage); |
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 | 69 |
85 // Calculate the column height when contents are supposed to be balanced. If
'initial' is set, | 70 // (Re-)calculate the column height when contents are supposed to be balance
d. If 'initial' is |
86 // guess an initial column height; otherwise, stretch the column height a ta
d. Return true if | 71 // set, guess an initial column height; otherwise, stretch the column height
a tad. Return true |
87 // column height changed and another layout pass is required. | 72 // if column height changed and another layout pass is required. |
88 bool calculateBalancedHeight(bool initial); | 73 bool recalculateBalancedHeight(bool initial); |
89 | 74 |
90 // Record space shortage (the amount of space that would have been enough to
prevent some | 75 // 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 | 76 // 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 | 77 // 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. | 78 // after layout that the columns weren't tall enough. |
94 void recordSpaceShortage(LayoutUnit spaceShortage); | 79 void recordSpaceShortage(LayoutUnit spaceShortage); |
95 | 80 |
96 virtual void updateLogicalWidth() OVERRIDE; | 81 virtual void updateLogicalWidth() OVERRIDE; |
97 | 82 |
98 void prepareForLayout(); | 83 void prepareForLayout(); |
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132 LayoutRect flowThreadPortionOverflowRect(const LayoutRect& flowThreadPortion
, unsigned index, unsigned colCount, LayoutUnit colGap) const; | 117 LayoutRect flowThreadPortionOverflowRect(const LayoutRect& flowThreadPortion
, unsigned index, unsigned colCount, LayoutUnit colGap) const; |
133 | 118 |
134 enum ColumnIndexCalculationMode { | 119 enum ColumnIndexCalculationMode { |
135 ClampToExistingColumns, // Stay within the range of already existing col
umns. | 120 ClampToExistingColumns, // Stay within the range of already existing col
umns. |
136 AssumeNewColumns // Allow column indices outside the range of already ex
isting columns. | 121 AssumeNewColumns // Allow column indices outside the range of already ex
isting columns. |
137 }; | 122 }; |
138 unsigned columnIndexAtOffset(LayoutUnit, ColumnIndexCalculationMode = ClampT
oExistingColumns) const; | 123 unsigned columnIndexAtOffset(LayoutUnit, ColumnIndexCalculationMode = ClampT
oExistingColumns) const; |
139 | 124 |
140 void setAndConstrainColumnHeight(LayoutUnit); | 125 void setAndConstrainColumnHeight(LayoutUnit); |
141 | 126 |
142 unsigned m_computedColumnCount; | 127 // Return the index of the content run with the currently tallest columns, t
aking all implicit |
143 LayoutUnit m_computedColumnWidth; | 128 // breaks assumed so far into account. |
| 129 unsigned findRunWithTallestColumns() const; |
| 130 |
| 131 // Given the current list of content runs, make assumptions about where we n
eed to insert |
| 132 // implicit breaks (if there's room for any at all; depending on the number
of explicit breaks), |
| 133 // and store the results. This is needed in order to balance the columns. |
| 134 void distributeImplicitBreaks(); |
| 135 |
| 136 LayoutUnit calculateBalancedHeight(bool initial) const; |
| 137 |
| 138 unsigned m_computedColumnCount; // Used column count (the resulting 'N' from
the pseudo-algorithm in the multicol spec) |
| 139 LayoutUnit m_computedColumnWidth; // Used column width (the resulting 'W' fr
om the pseudo-algorithm in the multicol spec) |
144 LayoutUnit m_computedColumnHeight; | 140 LayoutUnit m_computedColumnHeight; |
145 | 141 |
146 // The following variables are used when balancing the column set. | 142 // The following variables are used when balancing the column set. |
147 LayoutUnit m_maxColumnHeight; // Maximum column height allowed. | 143 LayoutUnit m_maxColumnHeight; // Maximum column height allowed. |
148 LayoutUnit m_minSpaceShortage; // The smallest amout of space shortage that
caused a column break. | 144 LayoutUnit m_minSpaceShortage; // The smallest amout of space shortage that
caused a column break. |
149 LayoutUnit m_minimumColumnHeight; | 145 LayoutUnit m_minimumColumnHeight; |
150 unsigned m_forcedBreaksCount; // FIXME: We will ultimately need to cache mor
e information to balance around forced breaks properly. | 146 |
151 LayoutUnit m_maximumDistanceBetweenForcedBreaks; | 147 // A run of content without explicit (forced) breaks; i.e. a flow thread por
tion between two |
152 LayoutUnit m_forcedBreakOffset; | 148 // explicit breaks, between flow thread start and an explicit break, between
an explicit break |
| 149 // and flow thread end, or, in cases when there are no explicit breaks at al
l: between flow flow |
| 150 // thread start and flow thread end. We need to know where the explicit brea
ks are, in order to |
| 151 // figure out where the implicit breaks will end up, so that we get the colu
mns properly |
| 152 // balanced. A content run starts out as representing one single column, and
will represent one |
| 153 // additional column for each implicit break "inserted" there. |
| 154 class ContentRun { |
| 155 public: |
| 156 ContentRun(LayoutUnit breakOffset) |
| 157 : m_breakOffset(breakOffset) |
| 158 , m_assumedImplicitBreaks(0) { } |
| 159 |
| 160 unsigned assumedImplicitBreaks() const { return m_assumedImplicitBreaks;
} |
| 161 void assumeAnotherImplicitBreak() { m_assumedImplicitBreaks++; } |
| 162 LayoutUnit breakOffset() const { return m_breakOffset; } |
| 163 |
| 164 // Return the column height that this content run would require, conside
ring the implicit |
| 165 // breaks assumed so far. |
| 166 LayoutUnit columnLogicalHeight(LayoutUnit startOffset) const { return ce
ilf(float(m_breakOffset - startOffset) / float(m_assumedImplicitBreaks + 1)); } |
| 167 |
| 168 private: |
| 169 LayoutUnit m_breakOffset; // Flow thread offset where this run ends. |
| 170 unsigned m_assumedImplicitBreaks; // Number of implicit breaks in this r
un assumed so far. |
| 171 }; |
| 172 Vector<ContentRun, 1> m_contentRuns; |
153 }; | 173 }; |
154 | 174 |
155 DEFINE_RENDER_OBJECT_TYPE_CASTS(RenderMultiColumnSet, isRenderMultiColumnSet()); | 175 DEFINE_RENDER_OBJECT_TYPE_CASTS(RenderMultiColumnSet, isRenderMultiColumnSet()); |
156 | 176 |
157 } // namespace WebCore | 177 } // namespace WebCore |
158 | 178 |
159 #endif // RenderMultiColumnSet_h | 179 #endif // RenderMultiColumnSet_h |
160 | 180 |
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