Implement ellipsizing of text in the engine (#3056)

See https://github.com/flutter/flutter/issues/4478

lib/ui/text.dart

@@ -93,6 +93,15 @@ enum TextAlign {
   center
 }
 
+/// How to handle text that overflows its bounds
+enum TextOverflow {
+  /// Default
+  clip,
+
+  /// Render as a single line that is ellipsized if it is too wide to fit
+  ellipsis
+}
+
 /// A horizontal line used for aligning text
 enum TextBaseline {
   // The horizontal line used to align the bottom of glyphs for alphabetic characters
@@ -375,13 +384,16 @@ class TextStyle {
 //
 //  - Element 3: The enum index of the |fontStyle|.
 //
+//  - Element 4: The enum index of the |textOverflow|.
+//
 Int32List _encodeParagraphStyle(TextAlign textAlign,
                                 FontWeight fontWeight,
                                 FontStyle fontStyle,
+                                TextOverflow textOverflow,
                                 String fontFamily,
                                 double fontSize,
                                 double lineHeight) {
-  Int32List result = new Int32List(4);
+  Int32List result = new Int32List(5);
   if (textAlign != null) {
     result[0] |= 1 << 1;
     result[1] = textAlign.index;
@@ -394,16 +406,20 @@ Int32List _encodeParagraphStyle(TextAlign textAlign,
     result[0] |= 1 << 3;
     result[3] = fontStyle.index;
   }
-  if (fontFamily != null) {
+  if (textOverflow != null) {
     result[0] |= 1 << 4;
+    result[4] = textOverflow.index;
+  }
+  if (fontFamily != null) {
+    result[0] |= 1 << 5;
     // Passed separately to native.
   }
   if (fontSize != null) {
-    result[0] |= 1 << 5;
+    result[0] |= 1 << 6;
     // Passed separately to native.
   }
   if (lineHeight != null) {
-    result[0] |= 1 << 6;
+    result[0] |= 1 << 7;
     // Passed separately to native.
   }
   return result;
@@ -423,12 +439,14 @@ class ParagraphStyle {
     TextAlign textAlign,
     FontWeight fontWeight,
     FontStyle fontStyle,
+    TextOverflow textOverflow,
     String fontFamily,
     double fontSize,
     double lineHeight
   }) : _encoded = _encodeParagraphStyle(textAlign,
                                         fontWeight,
                                         fontStyle,
+                                        textOverflow,
                                         fontFamily,
                                         fontSize,
                                         lineHeight),
@@ -465,9 +483,10 @@ class ParagraphStyle {
              'textAlign: ${   _encoded[0] & 0x02 == 0x02 ? TextAlign.values[_encoded[1]]    : "unspecified"}, '
              'fontWeight: ${  _encoded[0] & 0x04 == 0x04 ? FontWeight.values[_encoded[2]]   : "unspecified"}, '
              'fontStyle: ${   _encoded[0] & 0x08 == 0x08 ? FontStyle.values[_encoded[3]]    : "unspecified"}, '
-             'fontFamily: ${  _encoded[0] & 0x10 == 0x10 ? _fontFamily                      : "unspecified"}, '
-             'fontSize: ${    _encoded[0] & 0x20 == 0x20 ? _fontSize                        : "unspecified"}, '
-             'lineHeight: ${  _encoded[0] & 0x40 == 0x40 ? "${_lineHeight}x"                : "unspecified"}'
+             'textOverflow: ${ _encoded[0] & 0x10 == 0x10 ? TextOverflow.values[_encoded[4]] : "unspecified"}, '
+             'fontFamily: ${  _encoded[0] & 0x20 == 0x20 ? _fontFamily                      : "unspecified"}, '
+             'fontSize: ${    _encoded[0] & 0x40 == 0x40 ? _fontSize                        : "unspecified"}, '
+             'lineHeight: ${  _encoded[0] & 0x80 == 0x80 ? "${_lineHeight}x"                : "unspecified"}'
            ')';
   }
 }

lib/ui/text/paragraph_builder.cc

@@ -95,13 +95,15 @@ const int tsHeightMask = 1 << tsHeightIndex;
 const int psTextAlignIndex = 1;
 const int psFontWeightIndex = 2;
 const int psFontStyleIndex = 3;
-const int psFontFamilyIndex = 4;
-const int psFontSizeIndex = 5;
-const int psLineHeightIndex = 6;
+const int psTextOverflowIndex = 4;
+const int psFontFamilyIndex = 5;
+const int psFontSizeIndex = 6;
+const int psLineHeightIndex = 7;
 
 const int psTextAlignMask = 1 << psTextAlignIndex;
 const int psFontWeightMask = 1 << psFontWeightIndex;
 const int psFontStyleMask = 1 << psFontStyleIndex;
+const int psTextOverflowMask = 1 << psTextOverflowIndex;
 const int psFontFamilyMask = 1 << psFontFamilyIndex;
 const int psFontSizeMask = 1 << psFontSizeIndex;
 const int psLineHeightMask = 1 << psLineHeightIndex;
@@ -241,7 +243,7 @@ ftl::RefPtr<Paragraph> ParagraphBuilder::build(tonic::Int32List& encoded,
                                                const std::string& fontFamily,
                                                double fontSize,
                                                double lineHeight) {
-  FTL_DCHECK(encoded.num_elements() == 4);
+  FTL_DCHECK(encoded.num_elements() == 5);
   int32_t mask = encoded[0];
 
   if (mask) {
@@ -282,6 +284,11 @@ ftl::RefPtr<Paragraph> ParagraphBuilder::build(tonic::Int32List& encoded,
     if (mask & psLineHeightMask)
       style->setLineHeight(Length(lineHeight * 100.0, Percent));
 
+    if (mask & psTextOverflowMask) {
+      style->setTextOverflow(
+          static_cast<TextOverflow>(encoded[psTextOverflowIndex]));
+    }
+
     m_renderParagraph->setStyle(style.release());
   }
 

sky/engine/core/rendering/BidiRun.h

@@ -41,6 +41,7 @@ struct BidiRun : BidiCharacterRun {
     {
         // Stored in base class to save space.
         m_hasHyphen = false;
+        m_hasAddedEllipsis = false;
     }
 
     BidiRun* next() { return static_cast<BidiRun*>(m_next); }

sky/engine/core/rendering/InlineBox.h

@@ -296,6 +296,7 @@ public:
             , m_hasEllipsisBoxOrHyphen(false)
             , m_dirOverride(false)
             , m_isText(false)
+            , m_hasAddedEllipsis(false)
             , m_determinedIfNextOnLineExists(false)
             , m_nextOnLineExists(false)
             , m_expansion(0)
@@ -326,6 +327,7 @@ public:
         // for InlineTextBox
         ADD_BOOLEAN_BITFIELD(dirOverride, DirOverride);
         ADD_BOOLEAN_BITFIELD(isText, IsText); // Whether or not this object represents text with a non-zero height. Includes non-image list markers, text boxes.
+        ADD_BOOLEAN_BITFIELD(hasAddedEllipsis, HasAddedEllipsis)
 
     private:
         mutable unsigned m_determinedIfNextOnLineExists : 1;
@@ -373,6 +375,8 @@ protected:
     void setCanHaveLeadingExpansion(bool canHaveLeadingExpansion) { m_bitfields.setHasSelectedChildrenOrCanHaveLeadingExpansion(canHaveLeadingExpansion); }
     signed expansion() { return m_bitfields.expansion(); }
     void setExpansion(signed expansion) { m_bitfields.setExpansion(expansion); }
+    bool hasAddedEllipsis() const { return m_bitfields.hasAddedEllipsis(); }
+    void setHasAddedEllipsis(bool hasAddedEllipsis) { m_bitfields.setHasAddedEllipsis(hasAddedEllipsis); }
 
     // For InlineFlowBox and InlineTextBox
     bool extracted() const { return m_bitfields.extracted(); }

sky/engine/core/rendering/InlineTextBox.cpp

@@ -450,9 +450,18 @@ void InlineTextBox::paint(PaintInfo& paintInfo, const LayoutPoint& paintOffset,
         string.narrow(m_start, length);
     maximumLength = renderer().textLength() - m_start;
 
+    StringBuilder charactersWithEllipsis;
+    if (hasAddedEllipsis()) {
+      charactersWithEllipsis.reserveCapacity(string.length() + 1);
+      charactersWithEllipsis.append(string);
+      charactersWithEllipsis.append(WTF::Unicode::horizontalEllipsis);
+      string = charactersWithEllipsis.toString().createView();
+      maximumLength = string.length();
+    }
+
     StringBuilder charactersWithHyphen;
     TextRun textRun = constructTextRun(styleToUse, font, string, maximumLength, hasHyphen() ? &charactersWithHyphen : 0);
-    if (hasHyphen())
+    if (hasHyphen() || hasAddedEllipsis())
         length = textRun.length();
 
     int sPos = 0;

sky/engine/core/rendering/InlineTextBox.h

@@ -76,6 +76,7 @@ public:
 
     using InlineBox::hasHyphen;
     using InlineBox::setHasHyphen;
+    using InlineBox::setHasAddedEllipsis;
     using InlineBox::canHaveLeadingExpansion;
     using InlineBox::setCanHaveLeadingExpansion;
 

sky/engine/core/rendering/RenderParagraph.cpp

@@ -515,6 +515,8 @@ RootInlineBox* RenderParagraph::constructLine(BidiRunList<BidiRun>& bidiRuns, co
             text->setDirOverride(r->dirOverride());
             if (r->m_hasHyphen)
                 text->setHasHyphen(true);
+            if (r->m_hasAddedEllipsis)
+                text->setHasAddedEllipsis(true);
         }
     }
 
@@ -909,6 +911,8 @@ void RenderParagraph::layoutRunsAndFloatsInRange(LineLayoutState& layoutState,
 
             if (bidiRuns.runCount() && lineBreaker.lineWasHyphenated())
                 bidiRuns.logicallyLastRun()->m_hasHyphen = true;
+            if (bidiRuns.runCount() && lineBreaker.lineWasEllipsized())
+                bidiRuns.logicallyLastRun()->m_hasAddedEllipsis = true;
 
             // Now that the runs have been ordered, we create the line boxes.
             // At the same time we figure out where border/padding/margin should be applied for
@@ -928,6 +932,12 @@ void RenderParagraph::layoutRunsAndFloatsInRange(LineLayoutState& layoutState,
 
         lineMidpointState.reset();
         resolver.setPosition(endOfLine, numberOfIsolateAncestors(endOfLine));
+
+        // Limit ellipsized text to a single line.
+        if (lineBreaker.lineWasEllipsized()) {
+            resolver.setPosition(InlineIterator(resolver.position().root(), 0, 0), 0);
+            break;
+        }
     }
 }
 

sky/engine/core/rendering/line/BreakingContextInlineHeaders.h

@@ -88,7 +88,7 @@ public:
     void handleOutOfFlowPositioned(Vector<RenderBox*>& positionedObjects);
     void handleEmptyInline();
     void handleReplaced();
-    bool handleText(WordMeasurements&, bool& hyphenated);
+    bool handleText(WordMeasurements&, bool& hyphenated, bool& ellipsized);
     void commitAndUpdateLineBreakIfNeeded();
     InlineIterator handleEndOfLine();
 
@@ -409,6 +409,13 @@ inline float measureHyphenWidth(RenderText* renderer, const Font& font, TextDire
         style->hyphenString().string(), style, style->direction()));
 }
 
+inline float measureEllipsisWidth(RenderText* renderer, const Font& font)
+{
+    RenderStyle* style = renderer->style();
+    return font.width(constructTextRun(renderer, font,
+        String(&WTF::Unicode::horizontalEllipsis, 1), style, style->direction()));
+}
+
 ALWAYS_INLINE TextDirection textDirectionFromUnicode(WTF::Unicode::Direction direction)
 {
     return direction == WTF::Unicode::RightToLeft
@@ -428,7 +435,7 @@ ALWAYS_INLINE float textWidth(RenderText* text, unsigned from, unsigned len, con
     return font.width(run, fallbackFonts, &glyphOverflow);
 }
 
-inline bool BreakingContext::handleText(WordMeasurements& wordMeasurements, bool& hyphenated)
+inline bool BreakingContext::handleText(WordMeasurements& wordMeasurements, bool& hyphenated, bool& ellipsized)
 {
     if (!m_current.offset())
         m_appliedStartWidth = false;
@@ -458,8 +465,17 @@ inline bool BreakingContext::handleText(WordMeasurements& wordMeasurements, bool
     bool breakWords = m_currentStyle->breakWords() && ((m_autoWrap && !m_width.committedWidth()) || m_currWS == PRE);
     bool midWordBreak = false;
     bool breakAll = m_currentStyle->wordBreak() == BreakAllWordBreak && m_autoWrap;
+
     float hyphenWidth = 0;
 
+    bool ellipsizeMode = m_blockStyle->textOverflow() == TextOverflowEllipsis;
+    float ellipsisWidth = 0;
+    unsigned ellipsisBreakOffset = 0;
+    if (ellipsizeMode) {
+        ellipsisWidth = measureEllipsisWidth(renderText, font);
+        breakAll = true;
+    }
+
     if (m_renderTextInfo.m_text != renderText) {
         m_renderTextInfo.m_text = renderText;
         m_renderTextInfo.m_font = &font;
@@ -496,7 +512,14 @@ inline bool BreakingContext::handleText(WordMeasurements& wordMeasurements, bool
             wrapW += charWidth;
             bool midWordBreakIsBeforeSurrogatePair = U16_IS_LEAD(c) && m_current.offset() + 1 < renderText->textLength() && U16_IS_TRAIL((*renderText)[m_current.offset() + 1]);
             charWidth = textWidth(renderText, m_current.offset(), midWordBreakIsBeforeSurrogatePair ? 2 : 1, font, m_width.committedWidth() + wrapW, isFixedPitch, m_collapseWhiteSpace);
-            midWordBreak = m_width.committedWidth() + wrapW + charWidth > m_width.availableWidth();
+
+            float midWordWidth = m_width.committedWidth() + wrapW + charWidth;
+            midWordBreak = midWordWidth > m_width.availableWidth();
+
+            // Check whether there is enough space to fit this character plus an ellipsis.
+            if (ellipsizeMode && midWordWidth + ellipsisWidth <= m_width.availableWidth()) {
+                ellipsisBreakOffset = m_current.offset();
+            }
         }
 
         int nextBreakablePosition = m_current.nextBreakablePosition();
@@ -584,6 +607,13 @@ inline bool BreakingContext::handleText(WordMeasurements& wordMeasurements, bool
                             wordMeasurement.width = charWidth;
                         }
                     }
+
+                    if (ellipsizeMode) {
+                        // Break the line at the position where an ellipsis would fit.
+                        m_lineBreak.moveTo(m_current.object(), ellipsisBreakOffset, m_current.nextBreakablePosition());
+                        ellipsized = true;
+                    }
+
                     // Didn't fit. Jump to the end unless there's still an opportunity to collapse whitespace.
                     if (m_ignoringSpaces || !m_collapseWhiteSpace || !m_currentCharacterIsSpace || !previousCharacterIsSpace) {
                         m_atEnd = true;

sky/engine/core/rendering/line/LineBreaker.cpp

@@ -45,6 +45,7 @@ void LineBreaker::reset()
 {
     m_positionedObjects.clear();
     m_hyphenated = false;
+    m_ellipsized = false;
 }
 
 InlineIterator LineBreaker::nextLineBreak(InlineBidiResolver& resolver, LineInfo& lineInfo,
@@ -75,7 +76,7 @@ InlineIterator LineBreaker::nextLineBreak(InlineBidiResolver& resolver, LineInfo
         } else if (context.currentObject()->isReplaced()) {
             context.handleReplaced();
         } else if (context.currentObject()->isText()) {
-            if (context.handleText(wordMeasurements, m_hyphenated)) {
+            if (context.handleText(wordMeasurements, m_hyphenated, m_ellipsized)) {
                 // We've hit a hard text line break. Our line break iterator is updated, so go ahead and early return.
                 return context.lineBreak();
             }

sky/engine/core/rendering/line/LineBreaker.h

@@ -46,6 +46,7 @@ public:
         FloatingObject* lastFloatFromPreviousLine, WordMeasurements&);
 
     bool lineWasHyphenated() { return m_hyphenated; }
+    bool lineWasEllipsized() { return m_ellipsized; }
     const Vector<RenderBox*>& positionedObjects() { return m_positionedObjects; }
 private:
     void reset();
@@ -54,6 +55,7 @@ private:
 
     RenderParagraph* m_block;
     bool m_hyphenated;
+    bool m_ellipsized;
     Vector<RenderBox*> m_positionedObjects;
 };
 

sky/engine/platform/text/BidiCharacterRun.h

@@ -69,6 +69,7 @@ struct BidiCharacterRun {
     // Do not add anything apart from bitfields until after m_next. See https://bugs.webkit.org/show_bug.cgi?id=100173
     bool m_override : 1;
     bool m_hasHyphen : 1; // Used by BidiRun subclass which is a layering violation but enables us to save 8 bytes per object on 64-bit.
+    bool m_hasAddedEllipsis : 1;
     unsigned char m_level;
     BidiCharacterRun* m_next;
     int m_start;