5166aea18583b862f6e0ac75632297edce3d9bd6
[WebKit-https.git] / Source / WebCore / rendering / SimpleLineLayout.cpp
1 /*
2  * Copyright (C) 2013 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. AND ITS CONTRIBUTORS ``AS IS''
14  * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
15  * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
16  * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR ITS CONTRIBUTORS
17  * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
18  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
19  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
20  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
21  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
22  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
23  * THE POSSIBILITY OF SUCH DAMAGE.
24  */
25
26 #include "config.h"
27 #include "SimpleLineLayout.h"
28
29 #include "DocumentMarkerController.h"
30 #include "FontCache.h"
31 #include "Frame.h"
32 #include "GraphicsContext.h"
33 #include "HTMLTextFormControlElement.h"
34 #include "HitTestLocation.h"
35 #include "HitTestRequest.h"
36 #include "HitTestResult.h"
37 #include "Hyphenation.h"
38 #include "InlineTextBox.h"
39 #include "LineWidth.h"
40 #include "Logging.h"
41 #include "PaintInfo.h"
42 #include "RenderBlockFlow.h"
43 #include "RenderChildIterator.h"
44 #include "RenderFragmentedFlow.h"
45 #include "RenderLineBreak.h"
46 #include "RenderMultiColumnFlow.h"
47 #include "RenderStyle.h"
48 #include "RenderText.h"
49 #include "RenderTextControl.h"
50 #include "RenderView.h"
51 #include "Settings.h"
52 #include "SimpleLineLayoutFlowContents.h"
53 #include "SimpleLineLayoutFunctions.h"
54 #include "SimpleLineLayoutResolver.h"
55 #include "SimpleLineLayoutTextFragmentIterator.h"
56 #include "Text.h"
57 #include "TextPaintStyle.h"
58 #include <pal/Logging.h>
59
60 namespace WebCore {
61 namespace SimpleLineLayout {
62
63 #ifndef NDEBUG
64 #define SET_REASON_AND_RETURN_IF_NEEDED(reason, reasons, includeReasons) { \
65         reasons |= reason; \
66         if (includeReasons == IncludeReasons::First) \
67             return reasons; \
68     }
69 #else
70 #define SET_REASON_AND_RETURN_IF_NEEDED(reason, reasons, includeReasons) { \
71         ASSERT_UNUSED(includeReasons, includeReasons == IncludeReasons::First); \
72         reasons |= reason; \
73         return reasons; \
74     }
75 #endif
76
77
78 template <typename CharacterType> AvoidanceReasonFlags canUseForCharacter(CharacterType, bool textIsJustified, IncludeReasons);
79
80 template<> AvoidanceReasonFlags canUseForCharacter(UChar character, bool textIsJustified, IncludeReasons includeReasons)
81 {
82     AvoidanceReasonFlags reasons = { };
83     if (textIsJustified) {
84         // Include characters up to Latin Extended-B and some punctuation range when text is justified.
85         bool isLatinIncludingExtendedB = character <= 0x01FF;
86         bool isPunctuationRange = character >= 0x2010 && character <= 0x2027;
87         if (!(isLatinIncludingExtendedB || isPunctuationRange))
88             SET_REASON_AND_RETURN_IF_NEEDED(FlowHasJustifiedNonLatinText, reasons, includeReasons);
89     }
90
91     if (U16_IS_SURROGATE(character))
92         SET_REASON_AND_RETURN_IF_NEEDED(FlowTextHasSurrogatePair, reasons, includeReasons);
93     
94     UCharDirection direction = u_charDirection(character);
95     if (direction == U_RIGHT_TO_LEFT || direction == U_RIGHT_TO_LEFT_ARABIC
96         || direction == U_RIGHT_TO_LEFT_EMBEDDING || direction == U_RIGHT_TO_LEFT_OVERRIDE
97         || direction == U_LEFT_TO_RIGHT_EMBEDDING || direction == U_LEFT_TO_RIGHT_OVERRIDE
98         || direction == U_POP_DIRECTIONAL_FORMAT || direction == U_BOUNDARY_NEUTRAL)
99         SET_REASON_AND_RETURN_IF_NEEDED(FlowTextHasDirectionCharacter, reasons, includeReasons);
100
101     return reasons;
102 }
103
104 template<> AvoidanceReasonFlags canUseForCharacter(LChar, bool, IncludeReasons)
105 {
106     return { };
107 }
108
109 template <typename CharacterType>
110 static AvoidanceReasonFlags canUseForText(const CharacterType* text, unsigned length, const FontCascade& fontCascade, Optional<float> lineHeightConstraint,
111     bool textIsJustified, IncludeReasons includeReasons)
112 {
113     AvoidanceReasonFlags reasons = { };
114     auto& primaryFont = fontCascade.primaryFont();
115     auto& fontMetrics = primaryFont.fontMetrics();
116     auto availableSpaceForGlyphAscent = fontMetrics.ascent();
117     auto availableSpaceForGlyphDescent = fontMetrics.descent();
118     if (lineHeightConstraint) {
119         auto lineHeightPadding = *lineHeightConstraint - fontMetrics.height();
120         availableSpaceForGlyphAscent += lineHeightPadding / 2;
121         availableSpaceForGlyphDescent += lineHeightPadding / 2;
122     }
123
124     for (unsigned i = 0; i < length; ++i) {
125         auto character = text[i];
126         if (FontCascade::treatAsSpace(character))
127             continue;
128
129         if (character == softHyphen)
130             SET_REASON_AND_RETURN_IF_NEEDED(FlowTextHasSoftHyphen, reasons, includeReasons);
131
132         auto characterReasons = canUseForCharacter(character, textIsJustified, includeReasons);
133         if (characterReasons != NoReason)
134             SET_REASON_AND_RETURN_IF_NEEDED(characterReasons, reasons, includeReasons);
135
136         auto glyphData = fontCascade.glyphDataForCharacter(character, false);
137         if (!glyphData.isValid() || glyphData.font != &primaryFont)
138             SET_REASON_AND_RETURN_IF_NEEDED(FlowPrimaryFontIsInsufficient, reasons, includeReasons);
139
140         if (lineHeightConstraint) {
141             auto bounds = primaryFont.boundsForGlyph(glyphData.glyph);
142             if (ceilf(-bounds.y()) > availableSpaceForGlyphAscent || ceilf(bounds.maxY()) > availableSpaceForGlyphDescent)
143                 SET_REASON_AND_RETURN_IF_NEEDED(FlowFontHasOverflowGlyph, reasons, includeReasons);
144         }
145     }
146     return reasons;
147 }
148
149 static AvoidanceReasonFlags canUseForText(StringView text, const FontCascade& fontCascade, Optional<float> lineHeightConstraint, bool textIsJustified, IncludeReasons includeReasons)
150 {
151     if (text.is8Bit())
152         return canUseForText(text.characters8(), text.length(), fontCascade, lineHeightConstraint, textIsJustified, includeReasons);
153     return canUseForText(text.characters16(), text.length(), fontCascade, lineHeightConstraint, textIsJustified, includeReasons);
154 }
155
156 static AvoidanceReasonFlags canUseForFontAndText(const RenderBlockFlow& flow, IncludeReasons includeReasons)
157 {
158     AvoidanceReasonFlags reasons = { };
159     // We assume that all lines have metrics based purely on the primary font.
160     const auto& style = flow.style();
161     auto& fontCascade = style.fontCascade();
162     if (fontCascade.primaryFont().isInterstitial())
163         SET_REASON_AND_RETURN_IF_NEEDED(FlowIsMissingPrimaryFont, reasons, includeReasons);
164     Optional<float> lineHeightConstraint;
165     if (style.lineBoxContain() & LineBoxContainGlyphs)
166         lineHeightConstraint = lineHeightFromFlow(flow).toFloat();
167     bool flowIsJustified = style.textAlign() == TextAlignMode::Justify;
168     for (const auto& textRenderer : childrenOfType<RenderText>(flow)) {
169         // FIXME: Do not return until after checking all children.
170         if (textRenderer.text().isEmpty())
171             SET_REASON_AND_RETURN_IF_NEEDED(FlowTextIsEmpty, reasons, includeReasons);
172         if (textRenderer.isCombineText())
173             SET_REASON_AND_RETURN_IF_NEEDED(FlowTextIsCombineText, reasons, includeReasons);
174         if (textRenderer.isCounter())
175             SET_REASON_AND_RETURN_IF_NEEDED(FlowTextIsRenderCounter, reasons, includeReasons);
176         if (textRenderer.isQuote())
177             SET_REASON_AND_RETURN_IF_NEEDED(FlowTextIsRenderQuote, reasons, includeReasons);
178         if (textRenderer.isTextFragment())
179             SET_REASON_AND_RETURN_IF_NEEDED(FlowTextIsTextFragment, reasons, includeReasons);
180         if (textRenderer.isSVGInlineText())
181             SET_REASON_AND_RETURN_IF_NEEDED(FlowTextIsSVGInlineText, reasons, includeReasons);
182         if (!textRenderer.canUseSimpleFontCodePath()) {
183             // No need to check the code path at this point. We already know it can't be simple.
184             SET_REASON_AND_RETURN_IF_NEEDED(FlowHasComplexFontCodePath, reasons, includeReasons);
185         } else {
186             TextRun run(String(textRenderer.text()));
187             run.setCharacterScanForCodePath(false);
188             if (style.fontCascade().codePath(run) != FontCascade::Simple)
189                 SET_REASON_AND_RETURN_IF_NEEDED(FlowHasComplexFontCodePath, reasons, includeReasons);
190         }
191
192         auto textReasons = canUseForText(textRenderer.stringView(), fontCascade, lineHeightConstraint, flowIsJustified, includeReasons);
193         if (textReasons != NoReason)
194             SET_REASON_AND_RETURN_IF_NEEDED(textReasons, reasons, includeReasons);
195     }
196     return reasons;
197 }
198
199 static AvoidanceReasonFlags canUseForStyle(const RenderStyle& style, IncludeReasons includeReasons)
200 {
201     AvoidanceReasonFlags reasons = { };
202     if (style.textOverflow() == TextOverflow::Ellipsis)
203         SET_REASON_AND_RETURN_IF_NEEDED(FlowHasTextOverflow, reasons, includeReasons);
204     if (style.textUnderlinePosition() != TextUnderlinePosition::Auto || !style.textUnderlineOffset().isAuto() || !style.textDecorationThickness().isAuto())
205         SET_REASON_AND_RETURN_IF_NEEDED(FlowHasUnsupportedUnderlineDecoration, reasons, includeReasons);
206     // Non-visible overflow should be pretty easy to support.
207     if (style.overflowX() != Overflow::Visible || style.overflowY() != Overflow::Visible)
208         SET_REASON_AND_RETURN_IF_NEEDED(FlowHasOverflowNotVisible, reasons, includeReasons);
209     if (!style.isLeftToRightDirection())
210         SET_REASON_AND_RETURN_IF_NEEDED(FlowIsNotLTR, reasons, includeReasons);
211     if (!(style.lineBoxContain() & LineBoxContainBlock))
212         SET_REASON_AND_RETURN_IF_NEEDED(FlowHasLineBoxContainProperty, reasons, includeReasons);
213     if (style.writingMode() != TopToBottomWritingMode)
214         SET_REASON_AND_RETURN_IF_NEEDED(FlowIsNotTopToBottom, reasons, includeReasons);
215     if (style.lineBreak() != LineBreak::Auto)
216         SET_REASON_AND_RETURN_IF_NEEDED(FlowHasLineBreak, reasons, includeReasons);
217     if (style.unicodeBidi() != UBNormal)
218         SET_REASON_AND_RETURN_IF_NEEDED(FlowHasNonNormalUnicodeBiDi, reasons, includeReasons);
219     if (style.rtlOrdering() != Order::Logical)
220         SET_REASON_AND_RETURN_IF_NEEDED(FlowHasRTLOrdering, reasons, includeReasons);
221     if (style.lineAlign() != LineAlign::None)
222         SET_REASON_AND_RETURN_IF_NEEDED(FlowHasLineAlignEdges, reasons, includeReasons);
223     if (style.lineSnap() != LineSnap::None)
224         SET_REASON_AND_RETURN_IF_NEEDED(FlowHasLineSnap, reasons, includeReasons);
225     if (style.textEmphasisFill() != TextEmphasisFill::Filled || style.textEmphasisMark() != TextEmphasisMark::None)
226         SET_REASON_AND_RETURN_IF_NEEDED(FlowHasTextEmphasisFillOrMark, reasons, includeReasons);
227     if (style.textShadow())
228         SET_REASON_AND_RETURN_IF_NEEDED(FlowHasTextShadow, reasons, includeReasons);
229     if (style.hasPseudoStyle(PseudoId::FirstLine))
230         SET_REASON_AND_RETURN_IF_NEEDED(FlowHasPseudoFirstLine, reasons, includeReasons);
231     if (style.hasPseudoStyle(PseudoId::FirstLetter))
232         SET_REASON_AND_RETURN_IF_NEEDED(FlowHasPseudoFirstLetter, reasons, includeReasons);
233     if (style.hasTextCombine())
234         SET_REASON_AND_RETURN_IF_NEEDED(FlowHasTextCombine, reasons, includeReasons);
235     if (style.backgroundClip() == FillBox::Text)
236         SET_REASON_AND_RETURN_IF_NEEDED(FlowHasTextFillBox, reasons, includeReasons);
237     if (style.borderFit() == BorderFit::Lines)
238         SET_REASON_AND_RETURN_IF_NEEDED(FlowHasBorderFitLines, reasons, includeReasons);
239     if (style.lineBreak() != LineBreak::Auto)
240         SET_REASON_AND_RETURN_IF_NEEDED(FlowHasNonAutoLineBreak, reasons, includeReasons);
241     if (style.nbspMode() != NBSPMode::Normal)
242         SET_REASON_AND_RETURN_IF_NEEDED(FlowHasWebKitNBSPMode, reasons, includeReasons);
243     if (style.hyphens() == Hyphens::Auto) {
244         auto textReasons = canUseForText(style.hyphenString(), style.fontCascade(), WTF::nullopt, false, includeReasons);
245         if (textReasons != NoReason)
246             SET_REASON_AND_RETURN_IF_NEEDED(textReasons, reasons, includeReasons);
247     }
248     return reasons;
249 }
250
251 AvoidanceReasonFlags canUseForWithReason(const RenderBlockFlow& flow, IncludeReasons includeReasons)
252 {
253 #ifndef NDEBUG
254     static std::once_flag onceFlag;
255     std::call_once(onceFlag, [] {
256         PAL::registerNotifyCallback("com.apple.WebKit.showSimpleLineLayoutCoverage", WTF::Function<void()> { printSimpleLineLayoutCoverage });
257         PAL::registerNotifyCallback("com.apple.WebKit.showSimpleLineLayoutReasons", WTF::Function<void()> { printSimpleLineLayoutBlockList });
258         PAL::registerNotifyCallback("com.apple.WebKit.toggleSimpleLineLayout", WTF::Function<void()> { toggleSimpleLineLayout });
259     });
260 #endif
261     AvoidanceReasonFlags reasons = { };
262     if (!flow.settings().simpleLineLayoutEnabled())
263         SET_REASON_AND_RETURN_IF_NEEDED(FeatureIsDisabled, reasons, includeReasons);
264     if (!flow.parent())
265         SET_REASON_AND_RETURN_IF_NEEDED(FlowHasNoParent, reasons, includeReasons);
266     if (!flow.firstChild())
267         SET_REASON_AND_RETURN_IF_NEEDED(FlowHasNoChild, reasons, includeReasons);
268     if (flow.fragmentedFlowState() != RenderObject::NotInsideFragmentedFlow) {
269         auto* fragmentedFlow = flow.enclosingFragmentedFlow();
270         if (!is<RenderMultiColumnFlow>(fragmentedFlow))
271             SET_REASON_AND_RETURN_IF_NEEDED(FlowIsInsideANonMultiColumnThread, reasons, includeReasons);
272         auto& columnThread = downcast<RenderMultiColumnFlow>(*fragmentedFlow);
273         if (columnThread.parent() != &flow.view())
274             SET_REASON_AND_RETURN_IF_NEEDED(MultiColumnFlowIsNotTopLevel, reasons, includeReasons);
275         if (columnThread.hasColumnSpanner())
276             SET_REASON_AND_RETURN_IF_NEEDED(MultiColumnFlowHasColumnSpanner, reasons, includeReasons);
277         auto& style = flow.style();
278         if (style.verticalAlign() != VerticalAlign::Baseline)
279             SET_REASON_AND_RETURN_IF_NEEDED(MultiColumnFlowVerticalAlign, reasons, includeReasons);
280         if (style.isFloating())
281             SET_REASON_AND_RETURN_IF_NEEDED(MultiColumnFlowIsFloating, reasons, includeReasons);
282     }
283     if (!flow.isHorizontalWritingMode())
284         SET_REASON_AND_RETURN_IF_NEEDED(FlowHasHorizonalWritingMode, reasons, includeReasons);
285     if (flow.hasOutline())
286         SET_REASON_AND_RETURN_IF_NEEDED(FlowHasOutline, reasons, includeReasons);
287     if (flow.isRubyText() || flow.isRubyBase())
288         SET_REASON_AND_RETURN_IF_NEEDED(FlowIsRuby, reasons, includeReasons);
289     if (!flow.style().hangingPunctuation().isEmpty())
290         SET_REASON_AND_RETURN_IF_NEEDED(FlowHasHangingPunctuation, reasons, includeReasons);
291     
292     // Printing does pagination without a flow thread.
293     if (flow.document().paginated())
294         SET_REASON_AND_RETURN_IF_NEEDED(FlowIsPaginated, reasons, includeReasons);
295     if (flow.firstLineBlock())
296         SET_REASON_AND_RETURN_IF_NEEDED(FlowHasPseudoFirstLine, reasons, includeReasons);
297     if (flow.isAnonymousBlock() && flow.parent()->style().textOverflow() == TextOverflow::Ellipsis)
298         SET_REASON_AND_RETURN_IF_NEEDED(FlowHasTextOverflow, reasons, includeReasons);
299     if (flow.parent()->isDeprecatedFlexibleBox())
300         SET_REASON_AND_RETURN_IF_NEEDED(FlowIsDepricatedFlexBox, reasons, includeReasons);
301     // FIXME: Placeholders do something strange.
302     if (is<RenderTextControl>(*flow.parent()) && downcast<RenderTextControl>(*flow.parent()).textFormControlElement().placeholderElement())
303         SET_REASON_AND_RETURN_IF_NEEDED(FlowParentIsPlaceholderElement, reasons, includeReasons);
304     // FIXME: Implementation of wrap=hard looks into lineboxes.
305     if (flow.parent()->isTextArea() && flow.parent()->element()->hasAttributeWithoutSynchronization(HTMLNames::wrapAttr))
306         SET_REASON_AND_RETURN_IF_NEEDED(FlowParentIsTextAreaWithWrapping, reasons, includeReasons);
307     // This currently covers <blockflow>#text</blockflow>, <blockflow>#text<br></blockflow> and mutiple (sibling) RenderText cases.
308     // The <blockflow><inline>#text</inline></blockflow> case is also popular and should be relatively easy to cover.
309     for (const auto* child = flow.firstChild(); child;) {
310         if (child->selectionState() != RenderObject::SelectionNone)
311             SET_REASON_AND_RETURN_IF_NEEDED(FlowChildIsSelected, reasons, includeReasons);
312         if (is<RenderText>(*child)) {
313             const auto& renderText = downcast<RenderText>(*child);
314             if (renderText.textNode() && !renderText.document().markers().markersFor(*renderText.textNode()).isEmpty())
315                 SET_REASON_AND_RETURN_IF_NEEDED(FlowIncludesDocumentMarkers, reasons, includeReasons);
316             child = child->nextSibling();
317             continue;
318         }
319         if (is<RenderLineBreak>(child) && !downcast<RenderLineBreak>(*child).isWBR() && child->style().clear() == Clear::None) {
320             child = child->nextSibling();
321             continue;
322         }
323         SET_REASON_AND_RETURN_IF_NEEDED(FlowHasNonSupportedChild, reasons, includeReasons);
324         break;
325     }
326     auto styleReasons = canUseForStyle(flow.style(), includeReasons);
327     if (styleReasons != NoReason)
328         SET_REASON_AND_RETURN_IF_NEEDED(styleReasons, reasons, includeReasons);
329     // We can't use the code path if any lines would need to be shifted below floats. This is because we don't keep per-line y coordinates.
330     if (flow.containsFloats()) {
331         float minimumWidthNeeded = std::numeric_limits<float>::max();
332         for (const auto& textRenderer : childrenOfType<RenderText>(flow)) {
333             minimumWidthNeeded = std::min(minimumWidthNeeded, textRenderer.minLogicalWidth());
334
335             for (auto& floatingObject : *flow.floatingObjectSet()) {
336                 ASSERT(floatingObject);
337                 // if a float has a shape, we cannot tell if content will need to be shifted until after we lay it out,
338                 // since the amount of space is not uniform for the height of the float.
339                 if (floatingObject->renderer().shapeOutsideInfo())
340                     SET_REASON_AND_RETURN_IF_NEEDED(FlowHasUnsupportedFloat, reasons, includeReasons);
341                 float availableWidth = flow.availableLogicalWidthForLine(floatingObject->y(), DoNotIndentText);
342                 if (availableWidth < minimumWidthNeeded)
343                     SET_REASON_AND_RETURN_IF_NEEDED(FlowHasUnsupportedFloat, reasons, includeReasons);
344             }
345         }
346     }
347     auto fontAndTextReasons = canUseForFontAndText(flow, includeReasons);
348     if (fontAndTextReasons != NoReason)
349         SET_REASON_AND_RETURN_IF_NEEDED(fontAndTextReasons, reasons, includeReasons);
350     return reasons;
351 }
352
353 bool canUseFor(const RenderBlockFlow& flow)
354 {
355     return canUseForWithReason(flow, IncludeReasons::First) == NoReason;
356 }
357
358 static float computeLineLeft(TextAlignMode textAlign, float availableWidth, float committedWidth, float logicalLeftOffset)
359 {
360     float remainingWidth = availableWidth - committedWidth;
361     float left = logicalLeftOffset;
362     switch (textAlign) {
363     case TextAlignMode::Left:
364     case TextAlignMode::WebKitLeft:
365     case TextAlignMode::Start:
366         return left;
367     case TextAlignMode::Right:
368     case TextAlignMode::WebKitRight:
369     case TextAlignMode::End:
370         return left + std::max<float>(remainingWidth, 0);
371     case TextAlignMode::Center:
372     case TextAlignMode::WebKitCenter:
373         return left + std::max<float>(remainingWidth / 2, 0);
374     case TextAlignMode::Justify:
375         ASSERT_NOT_REACHED();
376         break;
377     }
378     ASSERT_NOT_REACHED();
379     return 0;
380 }
381
382 static void revertAllRunsOnCurrentLine(Layout::RunVector& runs)
383 {
384     while (!runs.isEmpty() && !runs.last().isEndOfLine)
385         runs.removeLast();
386 }
387
388 static void revertRuns(Layout::RunVector& runs, unsigned positionToRevertTo, float width)
389 {
390     while (runs.size()) {
391         auto& lastRun = runs.last();
392         if (lastRun.end <= positionToRevertTo)
393             break;
394         if (lastRun.start >= positionToRevertTo) {
395             // Revert this run completely.
396             width -= (lastRun.logicalRight - lastRun.logicalLeft);
397             runs.removeLast();
398         } else {
399             lastRun.logicalRight -= width;
400             width = 0;
401             lastRun.end = positionToRevertTo;
402             // Partial removal.
403             break;
404         }
405     }
406 }
407
408 class LineState {
409 public:
410     void setAvailableWidth(float width) { m_availableWidth = width; }
411     void setCollapedWhitespaceWidth(float width) { m_collapsedWhitespaceWidth = width; }
412     void setLogicalLeftOffset(float offset) { m_logicalLeftOffset = offset; }
413     void setOverflowedFragment(const TextFragmentIterator::TextFragment& fragment) { m_overflowedFragment = fragment; }
414     void setNeedsAllFragments()
415     {
416         ASSERT(!m_fragments);
417         m_fragments.emplace();
418     }
419     void setHyphenationDisabled() { m_hyphenationDisabled = true; }
420     bool isHyphenationDisabled() const { return m_hyphenationDisabled; }
421
422     float availableWidth() const { return m_availableWidth; }
423     float logicalLeftOffset() const { return m_logicalLeftOffset; }
424     const TextFragmentIterator::TextFragment& overflowedFragment() const { return m_overflowedFragment; }
425     bool hasTrailingWhitespace() const { return m_lastFragment.type() == TextFragmentIterator::TextFragment::Whitespace && m_lastFragment.length() > 0; }
426     bool hasWhitespaceFragments() const { return m_lastWhitespaceFragment != WTF::nullopt; }
427     TextFragmentIterator::TextFragment lastFragment() const { return m_lastFragment; }
428     bool isWhitespaceOnly() const { return m_trailingWhitespaceWidth && m_runsWidth == m_trailingWhitespaceWidth; }
429     bool fits(float extra) const { return m_availableWidth >= m_runsWidth + extra; }
430     bool firstCharacterFits() const { return m_firstCharacterFits; }
431     float width() const { return m_runsWidth; }
432     std::pair<unsigned, bool> expansionOpportunityCount(unsigned from, unsigned to) const
433     {
434         ASSERT(m_fragments);
435         // linebreak runs are special.
436         if (from == to)
437             return std::make_pair(0, false);
438         unsigned expansionOpportunityCount = 0;
439         auto previousFragmentType = TextFragmentIterator::TextFragment::ContentEnd;
440         for (const auto& fragment : *m_fragments) {
441             if (fragment.end() <= from)
442                 continue;
443             auto currentFragmentType = fragment.type();
444             auto expansionOpportunity = this->expansionOpportunity(currentFragmentType, previousFragmentType);
445             if (expansionOpportunity)
446                 ++expansionOpportunityCount;
447             previousFragmentType = currentFragmentType;
448             if (fragment.end() >= to)
449                 return std::make_pair(expansionOpportunityCount, expansionOpportunity);
450         }
451         ASSERT_NOT_REACHED();
452         return std::make_pair(expansionOpportunityCount, false);
453     }
454
455     bool isEmpty() const
456     {
457         if (!m_lastFragment.isValid())
458             return true;
459         if (!m_lastCompleteFragment.isEmpty())
460             return false;
461         return m_lastFragment.overlapsToNextRenderer();
462     }
463
464     static inline unsigned endPositionForCollapsedFragment(const TextFragmentIterator::TextFragment& fragment)
465     {
466         return fragment.isCollapsed() ? fragment.start() + 1 : fragment.end();
467     }
468
469     void appendFragmentAndCreateRunIfNeeded(const TextFragmentIterator::TextFragment& fragment, Layout::RunVector& runs)
470     {
471         // Adjust end position while collapsing.
472         unsigned endPosition = endPositionForCollapsedFragment(fragment);
473         // New line needs new run.
474         if (!m_runsWidth) {
475             ASSERT(!m_uncompletedWidth);
476             runs.append(Run(fragment.start(), endPosition, m_runsWidth, m_runsWidth + fragment.width(), false, fragment.hasHyphen(), fragment.isLineBreak()));
477         } else {
478             // Advance last completed fragment when the previous fragment is all set (including multiple parts across renderers)
479             if ((m_lastFragment.type() != fragment.type()) || !m_lastFragment.overlapsToNextRenderer()) {
480                 m_lastCompleteFragment = m_lastFragment;
481                 m_uncompletedWidth = fragment.width();
482             } else
483                 m_uncompletedWidth += fragment.width();
484             // Collapse neighbouring whitespace, if they are across multiple renderers and are not collapsed yet.
485             if (m_lastFragment.isCollapsible() && fragment.isCollapsible()) {
486                 ASSERT(m_lastFragment.isLastInRenderer());
487                 if (!m_lastFragment.isCollapsed()) {
488                     // Line width needs to be adjusted so that now it takes collapsing into consideration.
489                     m_runsWidth -= (m_lastFragment.width() - m_collapsedWhitespaceWidth);
490                 }
491                 // This fragment is collapsed completely. No run is needed.
492                 return;
493             }
494             if (m_lastFragment.isLastInRenderer() || m_lastFragment.isCollapsed())
495                 runs.append(Run(fragment.start(), endPosition, m_runsWidth, m_runsWidth + fragment.width(), false, fragment.hasHyphen(), fragment.isLineBreak()));
496             else {
497                 Run& lastRun = runs.last();
498                 lastRun.end = endPosition;
499                 lastRun.logicalRight += fragment.width();
500                 ASSERT(!lastRun.hasHyphen);
501                 lastRun.hasHyphen = fragment.hasHyphen();
502             }
503         }
504         m_runsWidth += fragment.width();
505         m_lastFragment = fragment;
506         if (m_fragments)
507             (*m_fragments).append(fragment);
508
509         if (fragment.type() == TextFragmentIterator::TextFragment::Whitespace) {
510             m_trailingWhitespaceWidth += fragment.width();
511             m_lastWhitespaceFragment = fragment;
512         } else {
513             m_trailingWhitespaceWidth = 0;
514             m_lastNonWhitespaceFragment = fragment;
515         }
516
517         if (!m_firstCharacterFits)
518             m_firstCharacterFits = fragment.start() + 1 > endPosition || m_runsWidth <= m_availableWidth;
519     }
520
521     TextFragmentIterator::TextFragment revertToLastCompleteFragment(Layout::RunVector& runs)
522     {
523         if (!m_uncompletedWidth) {
524             ASSERT(m_lastFragment == m_lastCompleteFragment);
525             return m_lastFragment;
526         }
527         ASSERT(m_lastFragment.isValid());
528         m_runsWidth -= m_uncompletedWidth;
529         revertRuns(runs, endPositionForCollapsedFragment(m_lastCompleteFragment), m_uncompletedWidth);
530         m_uncompletedWidth = 0;
531         ASSERT(m_lastCompleteFragment.isValid());
532         return m_lastCompleteFragment;
533     }
534
535     void removeTrailingWhitespace(Layout::RunVector& runs)
536     {
537         if (m_lastFragment.type() != TextFragmentIterator::TextFragment::Whitespace)
538             return;
539         if (m_lastNonWhitespaceFragment) {
540             auto needsReverting = m_lastNonWhitespaceFragment->end() != m_lastFragment.end();
541             // Trailing whitespace fragment might actually have zero length.
542             ASSERT(needsReverting || !m_trailingWhitespaceWidth);
543             if (needsReverting) {
544                 revertRuns(runs, m_lastNonWhitespaceFragment->end(), m_trailingWhitespaceWidth);
545                 m_runsWidth -= m_trailingWhitespaceWidth;
546             }
547             m_trailingWhitespaceWidth = 0;
548             m_lastFragment = *m_lastNonWhitespaceFragment;
549             return;
550         }
551         // This line is all whitespace.
552         revertAllRunsOnCurrentLine(runs);
553         m_runsWidth = 0;
554         m_trailingWhitespaceWidth = 0;
555         // FIXME: Make m_lastFragment optional.
556         m_lastFragment = TextFragmentIterator::TextFragment();
557     }
558
559 private:
560     bool expansionOpportunity(TextFragmentIterator::TextFragment::Type currentFragmentType, TextFragmentIterator::TextFragment::Type previousFragmentType) const
561     {
562         return (currentFragmentType == TextFragmentIterator::TextFragment::Whitespace
563             || (currentFragmentType == TextFragmentIterator::TextFragment::NonWhitespace && previousFragmentType == TextFragmentIterator::TextFragment::NonWhitespace));
564     }
565
566     float m_availableWidth { 0 };
567     float m_logicalLeftOffset { 0 };
568     float m_runsWidth { 0 };
569     TextFragmentIterator::TextFragment m_overflowedFragment;
570     TextFragmentIterator::TextFragment m_lastFragment;
571     Optional<TextFragmentIterator::TextFragment> m_lastNonWhitespaceFragment;
572     Optional<TextFragmentIterator::TextFragment> m_lastWhitespaceFragment;
573     TextFragmentIterator::TextFragment m_lastCompleteFragment;
574     float m_uncompletedWidth { 0 };
575     float m_trailingWhitespaceWidth { 0 }; // Use this to remove trailing whitespace without re-mesuring the text.
576     float m_collapsedWhitespaceWidth { 0 };
577     // Having one character on the line does not necessarily mean it actually fits.
578     // First character of the first fragment might be forced on to the current line even if it does not fit.
579     bool m_firstCharacterFits { false };
580     bool m_hyphenationDisabled { false };
581     Optional<Vector<TextFragmentIterator::TextFragment, 30>> m_fragments;
582 };
583
584 static bool preWrap(const TextFragmentIterator::Style& style)
585 {
586     return style.wrapLines && !style.collapseWhitespace;
587 }
588     
589 static void removeTrailingWhitespace(LineState& lineState, Layout::RunVector& runs, const TextFragmentIterator& textFragmentIterator)
590 {
591     if (!lineState.hasTrailingWhitespace())
592         return;
593     // Remove collapsed whitespace, or non-collapsed pre-wrap whitespace, unless it's the only content on the line -so removing the whitesapce
594     // would produce an empty line.
595     const auto& style = textFragmentIterator.style();
596     bool collapseWhitespace = style.collapseWhitespace || (!style.breakSpaces && preWrap(style));
597     if (!collapseWhitespace)
598         return;
599     if (preWrap(style) && lineState.isWhitespaceOnly())
600         return;
601     lineState.removeTrailingWhitespace(runs);
602 }
603
604 static void updateLineConstrains(const RenderBlockFlow& flow, LineState& line, const LineState& previousLine, unsigned& numberOfPrecedingLinesWithHyphen, const TextFragmentIterator::Style& style, bool isFirstLine)
605 {
606     bool shouldApplyTextIndent = !flow.isAnonymous() || flow.parent()->firstChild() == &flow;
607     LayoutUnit height = flow.logicalHeight();
608     LayoutUnit logicalHeight = flow.minLineHeightForReplacedRenderer(false, 0);
609     line.setLogicalLeftOffset(flow.logicalLeftOffsetForLine(height, DoNotIndentText, logicalHeight) + (shouldApplyTextIndent && isFirstLine ? flow.textIndentOffset() : 0_lu));
610     float logicalRightOffset = flow.logicalRightOffsetForLine(height, DoNotIndentText, logicalHeight);
611     line.setAvailableWidth(std::max<float>(0, logicalRightOffset - line.logicalLeftOffset()));
612     if (style.textAlign == TextAlignMode::Justify)
613         line.setNeedsAllFragments();
614     numberOfPrecedingLinesWithHyphen = (previousLine.isEmpty() || !previousLine.lastFragment().hasHyphen()) ? 0 : numberOfPrecedingLinesWithHyphen + 1;
615     if (style.hyphenLimitLines && numberOfPrecedingLinesWithHyphen >= *style.hyphenLimitLines)
616         line.setHyphenationDisabled();
617     line.setCollapedWhitespaceWidth(style.font.spaceWidth() + style.wordSpacing);
618 }
619
620 struct SplitFragmentData {
621     unsigned position;
622     float width;
623 };
624 static Optional<unsigned> hyphenPositionForFragment(SplitFragmentData splitData, const TextFragmentIterator::TextFragment& fragmentToSplit,
625     const LineState& line, const TextFragmentIterator& textFragmentIterator, float availableWidth)
626 {
627     auto& style = textFragmentIterator.style();
628     if (!style.shouldHyphenate || line.isHyphenationDisabled())
629         return WTF::nullopt;
630
631     // FIXME: This is a workaround for webkit.org/b/169613. See maxPrefixWidth computation in tryHyphenating().
632     // It does not work properly with non-collapsed leading tabs when font is enlarged.
633     auto adjustedAvailableWidth = availableWidth - style.hyphenStringWidth;
634     if (!line.isEmpty())
635         adjustedAvailableWidth += style.font.spaceWidth();
636     if (!enoughWidthForHyphenation(adjustedAvailableWidth, style.font.pixelSize()))
637         return WTF::nullopt;
638
639     // We might be able to fit the hyphen at the split position.
640     auto splitPositionWithHyphen = splitData.position;
641     // Find a splitting position where hyphen surely fits.
642     unsigned start = fragmentToSplit.start();
643     auto leftSideWidth = splitData.width;
644     while (leftSideWidth + style.hyphenStringWidth > availableWidth) {
645         if (--splitPositionWithHyphen <= start)
646             return WTF::nullopt; // No space for hyphen.
647         leftSideWidth -= textFragmentIterator.textWidth(splitPositionWithHyphen, splitPositionWithHyphen + 1, 0);
648     }
649     ASSERT(splitPositionWithHyphen > start);
650     return textFragmentIterator.lastHyphenPosition(fragmentToSplit, splitPositionWithHyphen + 1);
651 }
652
653 static SplitFragmentData split(const TextFragmentIterator::TextFragment& fragment, float availableWidth,
654     const TextFragmentIterator& textFragmentIterator)
655 {
656     ASSERT(availableWidth >= 0);
657     auto left = fragment.start();
658     // Pathological case of (extremely)long string and narrow lines.
659     // Adjust the range so that we can pick a reasonable midpoint.
660     auto averageCharacterWidth = fragment.width() / fragment.length();
661     auto right = std::min<unsigned>(left + (2 * availableWidth / averageCharacterWidth), fragment.end() - 1);
662     // Preserve the left width for the final split position so that we don't need to remeasure the left side again.
663     float leftSideWidth = 0;
664     while (left < right) {
665         auto middle = (left + right) / 2;
666         auto width = textFragmentIterator.textWidth(fragment.start(), middle + 1, 0);
667         if (width < availableWidth) {
668             left = middle + 1;
669             leftSideWidth = width;
670         } else if (width > availableWidth)
671             right = middle;
672         else {
673             right = middle + 1;
674             leftSideWidth = width;
675             break;
676         }
677     }
678     return { right, leftSideWidth };
679 }
680
681 static TextFragmentIterator::TextFragment splitFragmentToFitLine(TextFragmentIterator::TextFragment& fragmentToSplit,
682     const LineState& line, const TextFragmentIterator& textFragmentIterator)
683 {
684     auto availableWidth = line.availableWidth() - line.width();
685     auto splitFragmentData = split(fragmentToSplit, availableWidth, textFragmentIterator);
686     Optional<unsigned> hyphenPosition = WTF::nullopt;
687     // Does first character fit this line?
688     if (splitFragmentData.position == fragmentToSplit.start()) {
689         // Keep at least one character on empty lines.
690         if (line.isEmpty())
691             splitFragmentData.width = textFragmentIterator.textWidth(fragmentToSplit.start(), ++splitFragmentData.position, 0);
692     } else {
693         hyphenPosition = hyphenPositionForFragment(splitFragmentData, fragmentToSplit, line, textFragmentIterator, availableWidth);
694         if (hyphenPosition) {
695             splitFragmentData.position = *hyphenPosition;
696             splitFragmentData.width = textFragmentIterator.textWidth(fragmentToSplit.start(), splitFragmentData.position, 0);
697         }
698     }
699     // If the right side surely does not fit the (next)line, we don't need the width to be kerning/ligature adjusted.
700     // Part of it gets re-measured as the left side during next split.
701     // This saves measuring long chunk of text repeatedly (see pathological case at ::split).
702     auto rightSideWidth = fragmentToSplit.width() - splitFragmentData.width;
703     if (rightSideWidth < 2 * availableWidth)
704         rightSideWidth = textFragmentIterator.textWidth(splitFragmentData.position, fragmentToSplit.end(), 0);
705     return hyphenPosition ? fragmentToSplit.splitWithHyphen(splitFragmentData.position, textFragmentIterator.style().hyphenStringWidth,
706         splitFragmentData.width, rightSideWidth) : fragmentToSplit.split(splitFragmentData.position, splitFragmentData.width, rightSideWidth);
707 }
708
709 enum PreWrapLineBreakRule { Preserve, Ignore };
710
711 static TextFragmentIterator::TextFragment consumeLineBreakIfNeeded(const TextFragmentIterator::TextFragment& fragment, TextFragmentIterator& textFragmentIterator, LineState& line, Layout::RunVector& runs,
712     PreWrapLineBreakRule preWrapLineBreakRule = PreWrapLineBreakRule::Preserve)
713 {
714     if (!fragment.isLineBreak())
715         return fragment;
716
717     bool isHardLinebreak = fragment.type() == TextFragmentIterator::TextFragment::HardLineBreak;
718     // <br> always produces a run. (required by testing output)
719     if (isHardLinebreak)
720         line.appendFragmentAndCreateRunIfNeeded(fragment, runs);
721
722     auto& style = textFragmentIterator.style();
723     if (style.preserveNewline && preWrapLineBreakRule == PreWrapLineBreakRule::Preserve) {
724         if (!isHardLinebreak)
725             return fragment;
726     }
727     return textFragmentIterator.nextTextFragment();
728 }
729
730 static TextFragmentIterator::TextFragment skipWhitespaceIfNeeded(const TextFragmentIterator::TextFragment& fragment, TextFragmentIterator& textFragmentIterator)
731 {
732     if (!textFragmentIterator.style().collapseWhitespace)
733         return fragment;
734
735     TextFragmentIterator::TextFragment firstNonWhitespaceFragment = fragment;
736     while (firstNonWhitespaceFragment.type() == TextFragmentIterator::TextFragment::Whitespace)
737         firstNonWhitespaceFragment = textFragmentIterator.nextTextFragment();
738     return firstNonWhitespaceFragment;
739 }
740
741 static TextFragmentIterator::TextFragment firstFragment(TextFragmentIterator& textFragmentIterator, LineState& currentLine, const LineState& previousLine, Layout::RunVector& runs)
742 {
743     // Handle overflow fragment from previous line.
744     auto overflowedFragment = previousLine.overflowedFragment();
745     if (overflowedFragment.isEmpty())
746         return skipWhitespaceIfNeeded(textFragmentIterator.nextTextFragment(), textFragmentIterator);
747
748     if (overflowedFragment.type() != TextFragmentIterator::TextFragment::Whitespace)
749         return overflowedFragment;
750
751     // Leading whitespace handling.
752     auto& style = textFragmentIterator.style();
753     if (style.breakSpaces) {
754         // Leading whitespace created after breaking the previous line.
755         // Breaking before the first space after a word is only allowed in combination with break-all or break-word.
756         if (style.breakFirstWordOnOverflow || previousLine.hasTrailingWhitespace())
757             return overflowedFragment;
758     }
759     // Special overflow pre-wrap whitespace handling: skip the overflowed whitespace (even when style says not-collapsible)
760     // if we manage to fit at least one character on the previous line.
761     auto preWrapIsOn = preWrap(style);
762     if ((style.collapseWhitespace || preWrapIsOn) && previousLine.firstCharacterFits()) {
763         // If skipping the whitespace puts us on a newline, skip the newline too as we already wrapped the line.
764         auto firstFragmentCandidate = consumeLineBreakIfNeeded(textFragmentIterator.nextTextFragment(), textFragmentIterator, currentLine, runs,
765             preWrapIsOn ? PreWrapLineBreakRule::Ignore : PreWrapLineBreakRule::Preserve);
766         return skipWhitespaceIfNeeded(firstFragmentCandidate, textFragmentIterator);
767     }
768     return skipWhitespaceIfNeeded(overflowedFragment, textFragmentIterator);
769 }
770
771 static void forceFragmentToLine(LineState& line, TextFragmentIterator& textFragmentIterator, Layout::RunVector& runs, const TextFragmentIterator::TextFragment& fragment)
772 {
773     line.appendFragmentAndCreateRunIfNeeded(fragment, runs);
774     // Check if there are more fragments to add to the current line.
775     auto nextFragment = textFragmentIterator.nextTextFragment();
776     if (fragment.overlapsToNextRenderer()) {
777         while (true) {
778             if (nextFragment.type() != fragment.type())
779                 break;
780             line.appendFragmentAndCreateRunIfNeeded(nextFragment, runs);
781             // Does it overlap to the next segment?
782             if (!nextFragment.overlapsToNextRenderer())
783                 return;
784             nextFragment = textFragmentIterator.nextTextFragment();
785         }
786     }
787     // When the forced fragment is followed by either whitespace and/or line break, consume them too, otherwise we end up with an extra whitespace and/or line break.
788     nextFragment = skipWhitespaceIfNeeded(nextFragment, textFragmentIterator);
789     nextFragment = consumeLineBreakIfNeeded(nextFragment, textFragmentIterator, line, runs);
790     line.setOverflowedFragment(nextFragment);
791 }
792
793 static bool createLineRuns(LineState& line, const LineState& previousLine, Layout::RunVector& runs, TextFragmentIterator& textFragmentIterator)
794 {
795     const auto& style = textFragmentIterator.style();
796     bool lineCanBeWrapped = style.wrapLines || style.breakFirstWordOnOverflow || style.breakAnyWordOnOverflow;
797     auto fragment = firstFragment(textFragmentIterator, line, previousLine, runs);
798     while (fragment.type() != TextFragmentIterator::TextFragment::ContentEnd) {
799         // Hard and soft linebreaks.
800         if (fragment.isLineBreak()) {
801             // Add the new line fragment only if there's nothing on the line. (otherwise the extra new line character would show up at the end of the content.)
802             if (line.isEmpty() || fragment.type() == TextFragmentIterator::TextFragment::HardLineBreak) {
803                 if (style.textAlign == TextAlignMode::Right || style.textAlign == TextAlignMode::WebKitRight)
804                     line.removeTrailingWhitespace(runs);
805                 line.appendFragmentAndCreateRunIfNeeded(fragment, runs);
806             }
807             break;
808         }
809         if (lineCanBeWrapped && !line.fits(fragment.width())) {
810             // Overflow wrapping behaviour:
811             // 1. Whitesapce collapse on: whitespace is skipped. Jump to next line.
812             // 2. Whitespace collapse off: whitespace is wrapped.
813             // 3. First, non-whitespace fragment is either wrapped or kept on the line. (depends on overflow-wrap)
814             // 5. Non-whitespace fragment when there's already another fragment on the line either gets wrapped (word-break: break-all)
815             // or gets pushed to the next line.
816             bool emptyLine = line.isEmpty();
817             // Whitespace fragment.
818             if (fragment.type() == TextFragmentIterator::TextFragment::Whitespace) {
819                 if (style.collapseWhitespace) {
820                     // Push collapased whitespace to the next line.
821                     line.setOverflowedFragment(fragment);
822                     break;
823                 }
824                 if (style.breakSpaces && line.hasWhitespaceFragments() && fragment.length() == 1) {
825                     // Breaking before the first space after a word is not allowed if there are previous breaking opportunities in the line.
826                     textFragmentIterator.revertToEndOfFragment(line.revertToLastCompleteFragment(runs));
827                     break;
828                 }
829                 // Split the whitespace; left part stays on this line, right is pushed to next line.
830                 line.setOverflowedFragment(splitFragmentToFitLine(fragment, line, textFragmentIterator));
831                 line.appendFragmentAndCreateRunIfNeeded(fragment, runs);
832                 break;
833             }
834             // Non-whitespace fragment. (!style.wrapLines: bug138102(preserve existing behavior)
835             if (((emptyLine && style.breakFirstWordOnOverflow) || style.breakAnyWordOnOverflow) || !style.wrapLines) {
836                 // Split the fragment; (modified)fragment stays on this line, overflowedFragment is pushed to next line.
837                 line.setOverflowedFragment(splitFragmentToFitLine(fragment, line, textFragmentIterator));
838                 line.appendFragmentAndCreateRunIfNeeded(fragment, runs);
839                 break;
840             }
841             ASSERT(fragment.type() == TextFragmentIterator::TextFragment::NonWhitespace);
842             // Find out if this non-whitespace fragment has a hyphen where we can break.
843             if (style.shouldHyphenate) {
844                 auto fragmentToSplit = fragment;
845                 // Split and check if we actually ended up with a hyphen.
846                 auto overflowFragment = splitFragmentToFitLine(fragmentToSplit, line, textFragmentIterator);
847                 if (fragmentToSplit.hasHyphen()) {
848                     line.setOverflowedFragment(overflowFragment);
849                     line.appendFragmentAndCreateRunIfNeeded(fragmentToSplit, runs);
850                     break;
851                 }
852                 // No hyphen, no split.
853             }
854             // Non-breakable non-whitespace first fragment. Add it to the current line. -it overflows though.
855             if (emptyLine) {
856                 forceFragmentToLine(line, textFragmentIterator, runs, fragment);
857                 break;
858             }
859             // Non-breakable non-whitespace fragment when there's already content on the line. Push it to the next line.
860             ASSERT(line.lastFragment().isValid());
861             if (line.lastFragment().overlapsToNextRenderer()) {
862                 // Check if this fragment is a continuation of a previous segment. In such cases, we need to remove them all.
863                 textFragmentIterator.revertToEndOfFragment(line.revertToLastCompleteFragment(runs));
864                 break;
865             }
866             line.setOverflowedFragment(fragment);
867             break;
868         }
869         line.appendFragmentAndCreateRunIfNeeded(fragment, runs);
870         // Find the next text fragment.
871         fragment = textFragmentIterator.nextTextFragment(line.width());
872     }
873     return (fragment.type() == TextFragmentIterator::TextFragment::ContentEnd && line.overflowedFragment().isEmpty()) || line.overflowedFragment().type() == TextFragmentIterator::TextFragment::ContentEnd;
874 }
875
876 static ExpansionBehavior expansionBehavior(bool isAfterExpansion, bool lastRunOnLine)
877 {
878     ExpansionBehavior expansionBehavior;
879     expansionBehavior = isAfterExpansion ? ForbidLeadingExpansion : AllowLeadingExpansion;
880     expansionBehavior |= lastRunOnLine ? ForbidTrailingExpansion : AllowTrailingExpansion;
881     return expansionBehavior;
882 }
883
884 static void justifyRuns(const LineState& line, Layout::RunVector& runs, unsigned firstRunIndex)
885 {
886     ASSERT(runs.size());
887     auto widthToDistribute = line.availableWidth() - line.width();
888     if (widthToDistribute <= 0)
889         return;
890
891     auto lastRunIndex = runs.size() - 1;
892     ASSERT(firstRunIndex <= lastRunIndex);
893     Vector<std::pair<unsigned, ExpansionBehavior>> expansionOpportunityList;
894     unsigned expansionOpportunityCountOnThisLine = 0;
895     auto isAfterExpansion = true;
896     for (auto i = firstRunIndex; i <= lastRunIndex; ++i) {
897         const auto& run = runs.at(i);
898         unsigned opportunityCountInRun = 0;
899         std::tie(opportunityCountInRun, isAfterExpansion) = line.expansionOpportunityCount(run.start, run.end);
900         expansionOpportunityList.append(std::make_pair(opportunityCountInRun, expansionBehavior(isAfterExpansion, i == lastRunIndex)));
901         expansionOpportunityCountOnThisLine += opportunityCountInRun;
902     }
903     if (!expansionOpportunityCountOnThisLine)
904         return;
905
906     ASSERT(expansionOpportunityList.size() == lastRunIndex - firstRunIndex + 1);
907     auto expansion = widthToDistribute / expansionOpportunityCountOnThisLine;
908     float accumulatedExpansion = 0;
909     for (auto i = firstRunIndex; i <= lastRunIndex; ++i) {
910         auto& run = runs.at(i);
911         unsigned opportunityCountInRun;
912         std::tie(opportunityCountInRun, run.expansionBehavior) = expansionOpportunityList.at(i - firstRunIndex);
913         run.expansion = opportunityCountInRun * expansion;
914         run.logicalLeft += accumulatedExpansion;
915         run.logicalRight += (accumulatedExpansion + run.expansion);
916         accumulatedExpansion += run.expansion;
917     }
918 }
919
920 static TextAlignMode textAlignForLine(const TextFragmentIterator::Style& style, bool lastLine)
921 {
922     // Fallback to TextAlignMode::Left (START) alignment for non-collapsable content and for the last line before a forced break or the end of the block.
923     auto textAlign = style.textAlign;
924     if (textAlign == TextAlignMode::Justify && (!style.collapseWhitespace || lastLine))
925         textAlign = TextAlignMode::Left;
926     return textAlign;
927 }
928
929 static void closeLineEndingAndAdjustRuns(LineState& line, Layout::RunVector& runs, Optional<unsigned> lastRunIndexOfPreviousLine, unsigned& lineCount,
930     const TextFragmentIterator& textFragmentIterator, bool lastLineInFlow)
931 {
932     if (!runs.size() || (lastRunIndexOfPreviousLine && runs.size() - 1 == lastRunIndexOfPreviousLine.value()))
933         return;
934     removeTrailingWhitespace(line, runs, textFragmentIterator);
935     if (!runs.size())
936         return;
937     // Adjust runs' position by taking line's alignment into account.
938     const auto& style = textFragmentIterator.style();
939     auto firstRunIndex = lastRunIndexOfPreviousLine ? lastRunIndexOfPreviousLine.value() + 1 : 0;
940     auto lineLogicalLeft = line.logicalLeftOffset();
941     auto textAlign = textAlignForLine(style, lastLineInFlow || (line.lastFragment().isValid() && line.lastFragment().type() == TextFragmentIterator::TextFragment::HardLineBreak));
942     if (textAlign == TextAlignMode::Justify)
943         justifyRuns(line, runs, firstRunIndex);
944     else
945         lineLogicalLeft = computeLineLeft(textAlign, line.availableWidth(), line.width(), line.logicalLeftOffset());
946     for (auto i = firstRunIndex; i < runs.size(); ++i) {
947         runs[i].logicalLeft += lineLogicalLeft;
948         runs[i].logicalRight += lineLogicalLeft;
949     }
950     runs.last().isEndOfLine = true;
951     ++lineCount;
952 }
953
954 static void createTextRuns(Layout::RunVector& runs, RenderBlockFlow& flow, unsigned& lineCount)
955 {
956     LayoutUnit borderAndPaddingBefore = flow.borderAndPaddingBefore();
957     LayoutUnit lineHeight = lineHeightFromFlow(flow);
958     LineState line;
959     unsigned numberOfPrecedingLinesWithHyphen = 0;
960     bool isEndOfContent = false;
961     TextFragmentIterator textFragmentIterator = TextFragmentIterator(flow);
962     Optional<unsigned> lastRunIndexOfPreviousLine;
963     do {
964         flow.setLogicalHeight(lineHeight * lineCount + borderAndPaddingBefore);
965         LineState previousLine = line;
966         line = LineState();
967         updateLineConstrains(flow, line, previousLine, numberOfPrecedingLinesWithHyphen, textFragmentIterator.style(), !lineCount);
968         isEndOfContent = createLineRuns(line, previousLine, runs, textFragmentIterator);
969         closeLineEndingAndAdjustRuns(line, runs, lastRunIndexOfPreviousLine, lineCount, textFragmentIterator, isEndOfContent);
970         if (runs.size())
971             lastRunIndexOfPreviousLine = runs.size() - 1;
972     } while (!isEndOfContent);
973 }
974
975 Ref<Layout> create(RenderBlockFlow& flow)
976 {
977     unsigned lineCount = 0;
978     Layout::RunVector runs;
979     createTextRuns(runs, flow, lineCount);
980     return Layout::create(runs, lineCount, flow);
981 }
982
983 Ref<Layout> Layout::create(const RunVector& runVector, unsigned lineCount, const RenderBlockFlow& blockFlow)
984 {
985     void* slot = WTF::fastMalloc(sizeof(Layout) + sizeof(Run) * runVector.size());
986     return adoptRef(*new (NotNull, slot) Layout(runVector, lineCount, blockFlow));
987 }
988
989 Layout::Layout(const RunVector& runVector, unsigned lineCount, const RenderBlockFlow& blockFlow)
990     : m_lineCount(lineCount)
991     , m_runCount(runVector.size())
992     , m_blockFlowRenderer(blockFlow)
993 {
994     memcpy(m_runs, runVector.data(), m_runCount * sizeof(Run));
995 }
996
997 const RunResolver& Layout::runResolver() const
998 {
999     if (!m_runResolver)
1000         m_runResolver = makeUnique<RunResolver>(m_blockFlowRenderer, *this);
1001     return *m_runResolver;
1002 }
1003
1004 Layout::~Layout()
1005 {
1006     simpleLineLayoutWillBeDeleted(*this);
1007 }
1008
1009 }
1010 }