[text shaping] Add shaping-boundary/start/end/in-between bits to line run and display box

alanbaradlay · alanbaradlay · commit 13855c61b93f · 2025-09-16T07:04:05.000-07:00
https://bugs.webkit.org/show_bug.cgi?id=298830 Reviewed by Antti Koivisto. This is in preparation for adding text shaping support. Line builder will set these bits on runs and TextBoxPainter will consult the display box if it needs special type of painting. * Source/WebCore/layout/formattingContexts/inline/InlineLine.cpp: (WebCore::Layout::Line::appendText): (WebCore::Layout::Line::Run::Run): (WebCore::Layout::Line::Run::expand): * Source/WebCore/layout/formattingContexts/inline/InlineLine.h: (WebCore::Layout::Line::Run::isShapingBoundaryStart const): (WebCore::Layout::Line::Run::isShapingBoundaryEnd const): (WebCore::Layout::Line::Run::isBetweenShapingBoundaries const): (WebCore::Layout::Line::Run::isShapingBoundary const): * Source/WebCore/layout/formattingContexts/inline/InlineLineBuilder.cpp: (WebCore::Layout::LineBuilder::commitCanidateContent): * Source/WebCore/layout/formattingContexts/inline/display/InlineDisplayBox.h: (WebCore::InlineDisplay::Box::Text::isAtShapingBoundaryStart const): (WebCore::InlineDisplay::Box::Text::isAtShapingBoundaryEnd const): (WebCore::InlineDisplay::Box::Text::isBetweenShapingBoundaries const): (WebCore::InlineDisplay::Box::Text::Text): * Source/WebCore/layout/formattingContexts/inline/display/InlineDisplayContentBuilder.cpp: (WebCore::Layout::InlineDisplayContentBuilder::appendTextDisplayBox): Canonical link: https://commits.webkit.org/300028@main
diff --git a/Source/WebCore/layout/formattingContexts/inline/InlineLine.cpp b/Source/WebCore/layout/formattingContexts/inline/InlineLine.cpp
@@ -334,7 +334,7 @@ void Line::appendInlineBoxEnd(const InlineItem& inlineItem, const RenderStyle& s
     }
 }
 
-void Line::appendText(const InlineTextItem& inlineTextItem, const RenderStyle& style, InlineLayoutUnit logicalWidth)
+void Line::appendText(const InlineTextItem& inlineTextItem, const RenderStyle& style, InlineLayoutUnit logicalWidth, std::optional<Line::ShapingBoundary> shapingBoundary)
 {
     auto willCollapseCompletely = [&] {
         if (inlineTextItem.isEmpty()) {
@@ -387,6 +387,8 @@ void Line::appendText(const InlineTextItem& inlineTextItem, const RenderStyle& s
             // We may end up with mismatching computed widths and misplaced glyphs at paint time -unless we keep dedicated runs with explicit positions.
             return true;
         }
+        if (shapingBoundary || lastRun.isShapingBoundary())
+            return true;
         return false;
     }();
     auto oldContentLogicalWidth = contentLogicalWidth();
@@ -399,7 +401,7 @@ void Line::appendText(const InlineTextItem& inlineTextItem, const RenderStyle& s
                 return -TextUtil::hangablePunctuationStartWidth(inlineTextItem, style);
             return lastRunLogicalRight() + (inlineTextItem.isWordSeparator() ? style.fontCascade().wordSpacing() : 0.0f);
         }();
-        m_runs.append({ inlineTextItem, style, runLogicalLeft, logicalWidth });
+        m_runs.append({ inlineTextItem, style, runLogicalLeft, logicalWidth, { }, shapingBoundary });
         // Note that the _content_ logical right may be larger than the _run_ logical right.
         contentLogicalRight = runLogicalLeft + logicalWidth;
     } else {
@@ -786,13 +788,14 @@ Line::Run::Run(const InlineSoftLineBreakItem& softLineBreakItem, const RenderSty
 {
 }
 
-Line::Run::Run(const InlineTextItem& inlineTextItem, const RenderStyle& style, InlineLayoutUnit logicalLeft, InlineLayoutUnit logicalWidth, InlineLayoutUnit textSpacingAdjustment)
+Line::Run::Run(const InlineTextItem& inlineTextItem, const RenderStyle& style, InlineLayoutUnit logicalLeft, InlineLayoutUnit logicalWidth, InlineLayoutUnit textSpacingAdjustment, std::optional<Line::ShapingBoundary> shapingBoundary)
     : m_type(inlineTextItem.isWordSeparator() ? Type::WordSeparator : inlineTextItem.isQuirkNonBreakingSpace() ? Type::NonBreakingSpace : Type::Text)
     , m_layoutBox(&inlineTextItem.layoutBox())
     , m_style(style)
     , m_logicalLeft(logicalLeft)
     , m_logicalWidth(logicalWidth)
     , m_bidiLevel(inlineTextItem.bidiLevel())
+    , m_shapingBoundary(shapingBoundary)
     , m_textSpacingAdjustment(textSpacingAdjustment)
 {
     auto length = inlineTextItem.length();
@@ -811,6 +814,7 @@ void Line::Run::expand(const InlineTextItem& inlineTextItem, InlineLayoutUnit lo
     ASSERT(isText() && inlineTextItem.isText());
     ASSERT(m_layoutBox == &inlineTextItem.layoutBox());
     ASSERT(m_bidiLevel == inlineTextItem.bidiLevel());
+    ASSERT(!m_shapingBoundary || *m_shapingBoundary != ShapingBoundary::End);
 
     m_logicalWidth += logicalWidth;
     auto whitespaceType = trailingWhitespaceType(inlineTextItem);
diff --git a/Source/WebCore/layout/formattingContexts/inline/InlineLine.h b/Source/WebCore/layout/formattingContexts/inline/InlineLine.h
@@ -49,7 +49,7 @@ class Line {
     void initialize(const Vector<InlineItem, 1>& lineSpanningInlineBoxes, bool isFirstFormattedLine);
 
     enum class ShapingBoundary : uint8_t { Start, Middle, End };
-    void appendText(const InlineTextItem&, const RenderStyle&, InlineLayoutUnit logicalWidth);
+    void appendText(const InlineTextItem&, const RenderStyle&, InlineLayoutUnit logicalWidth, std::optional<ShapingBoundary>);
     void appendTextFast(const InlineTextItem&, const RenderStyle&, InlineLayoutUnit logicalWidth); // Reserved for TextOnlySimpleLineBuilder
     void appendAtomicInlineBox(const InlineItem&, const RenderStyle&, InlineLayoutUnit marginBoxLogicalWidth);
     void appendInlineBoxStart(const InlineItem&, const RenderStyle&, InlineLayoutUnit logicalWidth, InlineLayoutUnit textSpacingAdjustment);
@@ -149,10 +149,15 @@ class Line {
 
         UBiDiLevel bidiLevel() const { return m_bidiLevel; }
 
+        bool isShapingBoundaryStart() const { return isShapingBoundary() && *m_shapingBoundary == Line::ShapingBoundary::Start; }
+        bool isShapingBoundaryEnd() const { return isShapingBoundary() && *m_shapingBoundary == Line::ShapingBoundary::End; }
+        bool isBetweenShapingBoundaries() const { return isShapingBoundary() && *m_shapingBoundary == Line::ShapingBoundary::Middle; }
+        bool isShapingBoundary() const { return m_shapingBoundary.has_value(); }
+
         // FIXME: Maybe add create functions intead?
         Run(const InlineItem&, const RenderStyle&, InlineLayoutUnit logicalLeft);
         Run(const InlineItem& lineSpanningInlineBoxItem, InlineLayoutUnit logicalLeft, InlineLayoutUnit logicalWidth, InlineLayoutUnit textSpacingAdjustment = 0.f);
-        Run(const InlineTextItem&, const RenderStyle&, InlineLayoutUnit logicalLeft, InlineLayoutUnit logicalWidth, InlineLayoutUnit textSpacingAdjustment = 0.f);
+        Run(const InlineTextItem&, const RenderStyle&, InlineLayoutUnit logicalLeft, InlineLayoutUnit logicalWidth, InlineLayoutUnit textSpacingAdjustment = 0.f, std::optional<Line::ShapingBoundary> = std::nullopt);
 
     private:
         friend class Line;
@@ -201,6 +206,7 @@ class Line {
         std::optional<TrailingWhitespace> m_trailingWhitespace { };
         std::optional<size_t> m_lastNonWhitespaceContentStart { };
         std::optional<Text> m_textContent;
+        std::optional<Line::ShapingBoundary> m_shapingBoundary;
         InlineLayoutUnit m_textSpacingAdjustment { 0 };
     };
     using RunList = Vector<Run, 10>;
diff --git a/Source/WebCore/layout/formattingContexts/inline/InlineLineBuilder.cpp b/Source/WebCore/layout/formattingContexts/inline/InlineLineBuilder.cpp
@@ -1243,7 +1243,7 @@ void LineBuilder::commitCanidateContent(const LineCandidate& lineCandidate, std:
             m_line.setContentNeedsBidiReordering();
 
         if (auto* inlineTextItem = dynamicDowncast<InlineTextItem>(inlineItem)) {
-            m_line.appendText(*inlineTextItem, run.style, run.contentWidth());
+            m_line.appendText(*inlineTextItem, run.style, run.contentWidth(), { });
             return;
         }
 
@@ -1297,7 +1297,7 @@ void LineBuilder::commitCanidateContent(const LineCandidate& lineCandidate, std:
             // Create and commit partial trailing item.
             if (auto* trailingInlineTextItem = dynamicDowncast<InlineTextItem>(runs[trailingRunIndex].inlineItem)) {
                 auto partialTrailingTextItem = trailingInlineTextItem->left(partialRun->length);
-                m_line.appendText(partialTrailingTextItem, trailingInlineTextItem->style(), partialRun->logicalWidth);
+                m_line.appendText(partialTrailingTextItem, trailingInlineTextItem->style(), partialRun->logicalWidth, { });
                 if (trailingInlineTextItem->bidiLevel() != UBIDI_DEFAULT_LTR)
                     m_line.setContentNeedsBidiReordering();
             } else
diff --git a/Source/WebCore/layout/formattingContexts/inline/display/InlineDisplayBox.h b/Source/WebCore/layout/formattingContexts/inline/display/InlineDisplayBox.h
@@ -42,13 +42,17 @@ struct Box {
     struct Text {
     public:
         Text() = default;
-        Text(size_t position, size_t length, const String& originalContent, String adjustedContentToRender = String(), bool hasHyphen = false);
+        enum ShapingBoundary : uint8_t { Start, Inside, End, NotApplicable };
+        Text(size_t position, size_t length, const String& originalContent, String adjustedContentToRender = String(), bool hasHyphen = false, ShapingBoundary = ShapingBoundary::NotApplicable);
 
         size_t start() const { return m_start; }
         size_t end() const { return start() + length(); }
         size_t length() const { return m_length; }
         StringView originalContent() const { return StringView(m_originalContent).substring(m_start, m_length); }
         StringView renderedContent() const { return m_adjustedContentToRender.isNull() ? originalContent() : m_adjustedContentToRender; }
+        bool isAtShapingBoundaryStart() const { return m_shapingBoundary == ShapingBoundary::Start; }
+        bool isAtShapingBoundaryEnd() const { return m_shapingBoundary == ShapingBoundary::End; }
+        bool isBetweenShapingBoundaries() const { return m_shapingBoundary == ShapingBoundary::Inside; }
         bool hasHyphen() const { return m_hasHyphen; }
         std::optional<size_t> partiallyVisibleContentLength() const;
         void setPartiallyVisibleContentLength(size_t truncatedLength);
@@ -61,6 +65,7 @@ struct Box {
 
         unsigned m_start { 0 };
         unsigned m_length { 0 };
+        ShapingBoundary m_shapingBoundary { ShapingBoundary::NotApplicable };
         unsigned m_partiallyVisibleContentLength : 30 { };
         bool m_hasPartiallyVisibleContentLength : 1 { false };
         bool m_hasHyphen : 1 { false };
@@ -212,11 +217,12 @@ inline Box::~Box()
         removeBoxFromGlyphDisplayListCache(*this);
 }
 
-inline Box::Text::Text(size_t start, size_t length, const String& originalContent, String adjustedContentToRender, bool hasHyphen)
+inline Box::Text::Text(size_t start, size_t length, const String& originalContent, String adjustedContentToRender, bool hasHyphen, ShapingBoundary shapingBoundary)
     : m_originalContent(originalContent)
     , m_adjustedContentToRender(adjustedContentToRender)
     , m_start(start)
     , m_length(length)
+    , m_shapingBoundary(shapingBoundary)
     , m_hasHyphen(hasHyphen)
 {
 }
diff --git a/Source/WebCore/layout/formattingContexts/inline/display/InlineDisplayContentBuilder.cpp b/Source/WebCore/layout/formattingContexts/inline/display/InlineDisplayContentBuilder.cpp
@@ -235,6 +235,15 @@ void InlineDisplayContentBuilder::appendTextDisplayBox(const Line::Run& lineRun,
     auto adjustedContentToRender = [&] {
         return text->needsHyphen ? makeString(StringView(content).substring(text->start, text->length), style.hyphenString()) : String();
     };
+    auto shapingBoundary = [&] {
+        if (lineRun.isShapingBoundaryStart())
+            return InlineDisplay::Box::Text::ShapingBoundary::Start;
+        if (lineRun.isShapingBoundaryEnd())
+            return InlineDisplay::Box::Text::ShapingBoundary::End;
+        if (lineRun.isBetweenShapingBoundaries())
+            return InlineDisplay::Box::Text::ShapingBoundary::Inside;
+        return InlineDisplay::Box::Text::ShapingBoundary::NotApplicable;
+    };
     boxes.append({ lineIndex()
         , lineRun.isWordSeparator() ? InlineDisplay::Box::Type::WordSeparator : InlineDisplay::Box::Type::Text
         , inlineTextBox
@@ -243,7 +252,7 @@ void InlineDisplayContentBuilder::appendTextDisplayBox(const Line::Run& lineRun,
         , inkOverflow
         , isFirstFormattedLine()
         , lineRun.expansion()
-        , InlineDisplay::Box::Text { text->start, text->length, content, adjustedContentToRender(), text->needsHyphen }
+        , InlineDisplay::Box::Text { text->start, text->length, content, adjustedContentToRender(), text->needsHyphen, shapingBoundary() }
         , isContentful
         , isLineFullyTruncatedInBlockDirection()
     });
