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 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#pragma once
27
28#include "LayerFragment.h"
29#include "RenderFragmentContainerSet.h"
30#include "RenderMultiColumnFlow.h"
31#include <wtf/Vector.h>
32
33namespace WebCore {
34
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
36// object, we significantly reduce the number of unique RenderObjects required to represent columns.
37//
38// A simple multi-column block will have exactly one RenderMultiColumnSet child. A simple paginated multi-column block will have three
39// RenderMultiColumnSet children: one for the content at the bottom of the first page (whose columns will have a shorter height), one
40// 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
41// as well).
42//
43// Column spans result in the creation of new column sets as well, since a spanning fragment has to be placed in between the column sets that
44// come before and after the span.
45class RenderMultiColumnSet final : public RenderFragmentContainerSet {
46 WTF_MAKE_ISO_ALLOCATED(RenderMultiColumnSet);
47public:
48 RenderMultiColumnSet(RenderFragmentedFlow&, RenderStyle&&);
49
50 RenderBlockFlow* multiColumnBlockFlow() const { return downcast<RenderBlockFlow>(parent()); }
51 RenderMultiColumnFlow* multiColumnFlow() const { return static_cast<RenderMultiColumnFlow*>(fragmentedFlow()); }
52
53 RenderMultiColumnSet* nextSiblingMultiColumnSet() const;
54 RenderMultiColumnSet* previousSiblingMultiColumnSet() const;
55
56 // Return the first object in the flow thread that's rendered inside this set.
57 RenderObject* firstRendererInFragmentedFlow() const;
58 // Return the last object in the flow thread that's rendered inside this set.
59 RenderObject* lastRendererInFragmentedFlow() const;
60
61 // Return true if the specified renderer (descendant of the flow thread) is inside this column set.
62 bool containsRendererInFragmentedFlow(const RenderObject&) const;
63
64 void setLogicalTopInFragmentedFlow(LayoutUnit);
65 LayoutUnit logicalTopInFragmentedFlow() const { return isHorizontalWritingMode() ? fragmentedFlowPortionRect().y() : fragmentedFlowPortionRect().x(); }
66 void setLogicalBottomInFragmentedFlow(LayoutUnit);
67 LayoutUnit logicalBottomInFragmentedFlow() const { return isHorizontalWritingMode() ? fragmentedFlowPortionRect().maxY() : fragmentedFlowPortionRect().maxX(); }
68 LayoutUnit logicalHeightInFragmentedFlow() const { return isHorizontalWritingMode() ? fragmentedFlowPortionRect().height() : fragmentedFlowPortionRect().width(); }
69
70 unsigned computedColumnCount() const { return m_computedColumnCount; }
71 LayoutUnit computedColumnWidth() const { return m_computedColumnWidth; }
72 LayoutUnit computedColumnHeight() const { return m_computedColumnHeight; }
73 bool columnHeightComputed() const { return m_columnHeightComputed; }
74
75 void setComputedColumnWidthAndCount(LayoutUnit width, unsigned count)
76 {
77 m_computedColumnWidth = width;
78 m_computedColumnCount = count;
79 }
80
81 LayoutUnit heightAdjustedForSetOffset(LayoutUnit height) const;
82
83 void updateMinimumColumnHeight(LayoutUnit height) { m_minimumColumnHeight = std::max(height, m_minimumColumnHeight); }
84 LayoutUnit minimumColumnHeight() const { return m_minimumColumnHeight; }
85
86 unsigned forcedBreaksCount() const { return m_contentRuns.size(); }
87 void clearForcedBreaks();
88 void addForcedBreak(LayoutUnit offsetFromFirstPage);
89
90 // (Re-)calculate the column height. This is first and foremost needed by sets that are to
91 // balance the column height, but even when it isn't to be balanced, this is necessary if the
92 // multicol container's height is constrained. If |initial| is set, and we are to balance, guess
93 // an initial column height; otherwise, stretch the column height a tad. Return true if column
94 // height changed and another layout pass is required.
95 bool recalculateColumnHeight(bool initial);
96
97 // Record space shortage (the amount of space that would have been enough to prevent some
98 // element from being moved to the next column) at a column break. The smallest amount of space
99 // shortage we find is the amount with which we will stretch the column height, if it turns out
100 // after layout that the columns weren't tall enough.
101 void recordSpaceShortage(LayoutUnit spaceShortage);
102
103 void updateLogicalWidth() override;
104
105 void prepareForLayout(bool initial);
106 // Begin laying out content for this column set. This happens at the beginning of flow thread
107 // layout, and when advancing from a previous column set or spanner to this one.
108 void beginFlow(RenderBlock* container);
109 // Finish laying out content for this column set. This happens at end of flow thread layout, and
110 // when advancing to the next column set or spanner.
111 void endFlow(RenderBlock* container, LayoutUnit bottomInContainer);
112 // Has this set been flowed in this layout pass?
113 bool hasBeenFlowed() const { return logicalBottomInFragmentedFlow() != RenderFragmentedFlow::maxLogicalHeight(); }
114
115 bool requiresBalancing() const;
116
117 LayoutPoint columnTranslationForOffset(const LayoutUnit&) const;
118
119 void paintColumnRules(PaintInfo&, const LayoutPoint& paintOffset) override;
120
121 enum ColumnHitTestTranslationMode {
122 ClampHitTestTranslationToColumns,
123 DoNotClampHitTestTranslationToColumns
124 };
125 LayoutPoint translateFragmentPointToFragmentedFlow(const LayoutPoint & logicalPoint, ColumnHitTestTranslationMode = DoNotClampHitTestTranslationToColumns) const;
126
127 void updateHitTestResult(HitTestResult&, const LayoutPoint&) override;
128
129 LayoutRect columnRectAt(unsigned index) const;
130 unsigned columnCount() const;
131
132protected:
133 void addOverflowFromChildren() override;
134
135private:
136 bool isRenderMultiColumnSet() const override { return true; }
137 void layout() override;
138
139 LogicalExtentComputedValues computeLogicalHeight(LayoutUnit logicalHeight, LayoutUnit logicalTop) const override;
140
141 void paintObject(PaintInfo&, const LayoutPoint&) override { }
142
143 LayoutUnit pageLogicalWidth() const override { return m_computedColumnWidth; }
144 LayoutUnit pageLogicalHeight() const override { return m_computedColumnHeight; }
145
146 LayoutUnit pageLogicalTopForOffset(LayoutUnit offset) const override;
147
148 LayoutUnit logicalHeightOfAllFragmentedFlowContent() const override { return logicalHeightInFragmentedFlow(); }
149
150 void repaintFragmentedFlowContent(const LayoutRect& repaintRect) override;
151
152 void collectLayerFragments(LayerFragments&, const LayoutRect& layerBoundingBox, const LayoutRect& dirtyRect) override;
153
154 void adjustFragmentBoundsFromFragmentedFlowPortionRect(LayoutRect& fragmentBounds) const override;
155
156 VisiblePosition positionForPoint(const LayoutPoint&, const RenderFragmentContainer*) override;
157
158 const char* renderName() const override;
159
160 LayoutUnit calculateMaxColumnHeight() const;
161 LayoutUnit columnGap() const;
162
163 LayoutUnit columnLogicalLeft(unsigned) const;
164 LayoutUnit columnLogicalTop(unsigned) const;
165
166 LayoutRect fragmentedFlowPortionRectAt(unsigned index) const;
167 LayoutRect fragmentedFlowPortionOverflowRect(const LayoutRect& fragmentedFlowPortion, unsigned index, unsigned colCount, LayoutUnit colGap);
168
169 LayoutUnit initialBlockOffsetForPainting() const;
170
171 enum ColumnIndexCalculationMode {
172 ClampToExistingColumns, // Stay within the range of already existing columns.
173 AssumeNewColumns // Allow column indices outside the range of already existing columns.
174 };
175 unsigned columnIndexAtOffset(LayoutUnit, ColumnIndexCalculationMode = ClampToExistingColumns) const;
176
177 void setAndConstrainColumnHeight(LayoutUnit);
178
179 // Return the index of the content run with the currently tallest columns, taking all implicit
180 // breaks assumed so far into account.
181 unsigned findRunWithTallestColumns() const;
182
183 // Given the current list of content runs, make assumptions about where we need to insert
184 // implicit breaks (if there's room for any at all; depending on the number of explicit breaks),
185 // and store the results. This is needed in order to balance the columns.
186 void distributeImplicitBreaks();
187
188 LayoutUnit calculateBalancedHeight(bool initial) const;
189
190 unsigned m_computedColumnCount; // Used column count (the resulting 'N' from the pseudo-algorithm in the multicol spec)
191 LayoutUnit m_computedColumnWidth; // Used column width (the resulting 'W' from the pseudo-algorithm in the multicol spec)
192 LayoutUnit m_computedColumnHeight;
193 LayoutUnit m_availableColumnHeight;
194 bool m_columnHeightComputed;
195
196 // The following variables are used when balancing the column set.
197 LayoutUnit m_maxColumnHeight; // Maximum column height allowed.
198 LayoutUnit m_minSpaceShortage; // The smallest amout of space shortage that caused a column break.
199 LayoutUnit m_minimumColumnHeight;
200
201 // A run of content without explicit (forced) breaks; i.e. a flow thread portion between two
202 // explicit breaks, between flow thread start and an explicit break, between an explicit break
203 // and flow thread end, or, in cases when there are no explicit breaks at all: between flow flow
204 // thread start and flow thread end. We need to know where the explicit breaks are, in order to
205 // figure out where the implicit breaks will end up, so that we get the columns properly
206 // balanced. A content run starts out as representing one single column, and will represent one
207 // additional column for each implicit break "inserted" there.
208 class ContentRun {
209 public:
210 ContentRun(LayoutUnit breakOffset)
211 : m_breakOffset(breakOffset)
212 , m_assumedImplicitBreaks(0) { }
213
214 unsigned assumedImplicitBreaks() const { return m_assumedImplicitBreaks; }
215 void assumeAnotherImplicitBreak() { m_assumedImplicitBreaks++; }
216 LayoutUnit breakOffset() const { return m_breakOffset; }
217
218 // Return the column height that this content run would require, considering the implicit
219 // breaks assumed so far.
220 LayoutUnit columnLogicalHeight(LayoutUnit startOffset) const { return ceilf(float(m_breakOffset - startOffset) / float(m_assumedImplicitBreaks + 1)); }
221
222 private:
223 LayoutUnit m_breakOffset; // Flow thread offset where this run ends.
224 unsigned m_assumedImplicitBreaks; // Number of implicit breaks in this run assumed so far.
225 };
226 Vector<ContentRun, 1> m_contentRuns;
227};
228
229} // namespace WebCore
230
231SPECIALIZE_TYPE_TRAITS_RENDER_OBJECT(RenderMultiColumnSet, isRenderMultiColumnSet())
232