Add support for a maxLines property on Paragraph. (#3338)

Also fix 'ellipsis' overflow handling to work for multiline text.

Fixes https://github.com/flutter/flutter/issues/7271

lib/ui/text.dart

@@ -384,6 +384,7 @@ Int32List _encodeParagraphStyle(TextAlign textAlign,
                                 String fontFamily,
                                 double fontSize,
                                 double lineHeight,
+                                int maxLines,
                                 String ellipsis) {
   Int32List result = new Int32List(5);
   if (textAlign != null) {
@@ -414,10 +415,14 @@ Int32List _encodeParagraphStyle(TextAlign textAlign,
     result[0] |= 1 << 7;
     // Passed separately to native.
   }
-  if (ellipsis != null) {
+  if (maxLines != null) {
     result[0] |= 1 << 8;
     // Passed separately to native.
   }
+  if (ellipsis != null) {
+    result[0] |= 1 << 9;
+    // Passed separately to native.
+  }
   return result;
 }
 
@@ -441,6 +446,7 @@ class ParagraphStyle {
     String fontFamily,
     double fontSize,
     double lineHeight,
+    int maxLines,
     String ellipsis
   }) : _encoded = _encodeParagraphStyle(textAlign,
                                         fontWeight,
@@ -449,10 +455,12 @@ class ParagraphStyle {
                                         fontFamily,
                                         fontSize,
                                         lineHeight,
+                                        maxLines,
                                         ellipsis),
        _fontFamily = fontFamily,
        _fontSize = fontSize,
        _lineHeight = lineHeight,
+       _maxLines = maxLines,
        _ellipsis = ellipsis {
     assert(lineCount == null);
   }
@@ -461,6 +469,7 @@ class ParagraphStyle {
   final String _fontFamily;
   final double _fontSize;
   final double _lineHeight;
+  final int _maxLines;
   final String _ellipsis;
 
   bool operator ==(dynamic other) {
@@ -472,6 +481,7 @@ class ParagraphStyle {
     if ( _fontFamily != typedOther._fontFamily ||
         _fontSize != typedOther._fontSize ||
         _lineHeight != typedOther._lineHeight ||
+        _maxLines != typedOther._maxLines ||
         _ellipsis != typedOther._ellipsis)
      return false;
     for (int index = 0; index < _encoded.length; index += 1) {
@@ -481,7 +491,7 @@ class ParagraphStyle {
     return true;
   }
 
-  int get hashCode => hashValues(hashList(_encoded), _lineHeight);
+  int get hashCode => hashValues(hashList(_encoded), _lineHeight, _maxLines, _ellipsis);
 
   String toString() {
     return 'ParagraphStyle('
@@ -492,7 +502,8 @@ class ParagraphStyle {
              'fontFamily: ${  _encoded[0] & 0x20 == 0x20 ? _fontFamily                      : "unspecified"}, '
              'fontSize: ${    _encoded[0] & 0x40 == 0x40 ? _fontSize                        : "unspecified"}, '
              'lineHeight: ${  _encoded[0] & 0x80 == 0x80 ? "${_lineHeight}x"                : "unspecified"}, '
-             'ellipsis: ${    _encoded[0] & 0x100 == 0x100 ? "\"$_ellipsis\""                : "unspecified"}'
+             'maxLines: ${    _encoded[0] & 0x100 == 0x100 ? _maxLines                      : "unspecified"}, '
+             'ellipsis: ${    _encoded[0] & 0x200 == 0x200 ? "\"$_ellipsis\""               : "unspecified"}'
            ')';
   }
 }
@@ -716,8 +727,8 @@ abstract class Paragraph extends NativeFieldWrapperClass2 {
 class ParagraphBuilder extends NativeFieldWrapperClass2 {
   /// Creates a [ParagraphBuilder] object, which is used to create a
   /// [Paragraph].
-  ParagraphBuilder(ParagraphStyle style) { _constructor(style._encoded, style._fontFamily, style._fontSize, style._lineHeight, style._ellipsis); }
-  void _constructor(Int32List encoded, String fontFamily, double fontSize, double lineHeight, String ellipsis) native "ParagraphBuilder_constructor";
+  ParagraphBuilder(ParagraphStyle style) { _constructor(style._encoded, style._fontFamily, style._fontSize, style._lineHeight, style._maxLines, style._ellipsis); }
+  void _constructor(Int32List encoded, String fontFamily, double fontSize, double lineHeight, int maxLines, String ellipsis) native "ParagraphBuilder_constructor";
 
   /// Applies the given style to the added text until [pop] is called.
   ///

lib/ui/text/paragraph_builder.cc

@@ -57,7 +57,8 @@ const int psFontStyleIndex = 3;
 const int psFontFamilyIndex = 5;
 const int psFontSizeIndex = 6;
 const int psLineHeightIndex = 7;
-const int psEllipsisIndex = 8;
+const int psMaxLinesIndex = 8;
+const int psEllipsisIndex = 9;
 
 const int psTextAlignMask = 1 << psTextAlignIndex;
 const int psFontWeightMask = 1 << psFontWeightIndex;
@@ -65,6 +66,7 @@ const int psFontStyleMask = 1 << psFontStyleIndex;
 const int psFontFamilyMask = 1 << psFontFamilyIndex;
 const int psFontSizeMask = 1 << psFontSizeIndex;
 const int psLineHeightMask = 1 << psLineHeightIndex;
+const int psMaxLinesMask = 1 << psMaxLinesIndex;
 const int psEllipsisMask = 1 << psEllipsisIndex;
 
 float getComputedSizeFromSpecifiedSize(float specifiedSize) {
@@ -100,6 +102,7 @@ PassRefPtr<RenderStyle> decodeParagraphStyle(
     const std::string& fontFamily,
     double fontSize,
     double lineHeight,
+    int maxLines,
     const std::string& ellipsis) {
   FTL_DCHECK(encoded.num_elements() == 5);
 
@@ -144,10 +147,11 @@ PassRefPtr<RenderStyle> decodeParagraphStyle(
   if (mask & psLineHeightMask)
     style->setLineHeight(Length(lineHeight * 100.0, Percent));
 
-  if (mask & psEllipsisMask) {
+  if (mask & psMaxLinesMask)
+    style->setMaxLines(maxLines);
+
+  if (mask & psEllipsisMask)
     style->setEllipsis(AtomicString::fromUTF8(ellipsis.c_str()));
-    style->setWordBreak(BreakAllWordBreak);
-  }
 
   return style.release();
 }
@@ -175,7 +179,7 @@ FOR_EACH_BINDING(DART_NATIVE_CALLBACK)
 
 void ParagraphBuilder::RegisterNatives(tonic::DartLibraryNatives* natives) {
   natives->Register(
-      {{"ParagraphBuilder_constructor", ParagraphBuilder_constructor, 6, true},
+      {{"ParagraphBuilder_constructor", ParagraphBuilder_constructor, 7, true},
        FOR_EACH_BINDING(DART_REGISTER_NATIVE)});
 }
 
@@ -184,20 +188,22 @@ ftl::RefPtr<ParagraphBuilder> ParagraphBuilder::create(
     const std::string& fontFamily,
     double fontSize,
     double lineHeight,
+    int maxLines,
     const std::string& ellipsis) {
   return ftl::MakeRefCounted<ParagraphBuilder>(
-      encoded, fontFamily, fontSize, lineHeight, ellipsis);
+      encoded, fontFamily, fontSize, lineHeight, maxLines, ellipsis);
 }
 
 ParagraphBuilder::ParagraphBuilder(tonic::Int32List& encoded,
                                    const std::string& fontFamily,
                                    double fontSize,
                                    double lineHeight,
+                                   int maxLines,
                                    const std::string& ellipsis) {
   createRenderView();
 
   RefPtr<RenderStyle> paragraphStyle = decodeParagraphStyle(
-      m_renderView->style(), encoded, fontFamily, fontSize, lineHeight, ellipsis);
+      m_renderView->style(), encoded, fontFamily, fontSize, lineHeight, maxLines, ellipsis);
   encoded.Release();
 
   m_renderParagraph = new RenderParagraph();

lib/ui/text/paragraph_builder.h

@@ -25,6 +25,7 @@ class ParagraphBuilder : public ftl::RefCountedThreadSafe<ParagraphBuilder>,
                                               const std::string& fontFamily,
                                               double fontSize,
                                               double lineHeight,
+                                              int maxLines,
                                               const std::string& ellipsis);
 
   ~ParagraphBuilder() override;
@@ -48,6 +49,7 @@ class ParagraphBuilder : public ftl::RefCountedThreadSafe<ParagraphBuilder>,
                             const std::string& fontFamily,
                             double fontSize,
                             double lineHeight,
+                            int maxLines,
                             const std::string& ellipsis);
 
   void createRenderView();

sky/engine/core/rendering/RenderParagraph.cpp

@@ -23,7 +23,6 @@
 #include "flutter/sky/engine/wtf/Vector.h"
 #include "flutter/sky/engine/wtf/unicode/CharacterNames.h"
 
-
 namespace blink {
 
 using namespace WTF::Unicode;

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

@@ -62,6 +62,8 @@ InlineIterator BreakingContext::handleEndOfLine()
         } while (!m_lineBreak.atEnd() && isEmptyInline(m_lineBreak.object()));
     }
 
+    m_lineInfo.incrementLineIndex();
+
     return m_lineBreak;
 }
 

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

@@ -84,7 +84,6 @@ public:
 
     void increment();
 
-    void handleBR();
     void handleOutOfFlowPositioned(Vector<RenderBox*>& positionedObjects);
     void handleEmptyInline();
     void handleReplaced();
@@ -225,26 +224,6 @@ inline void BreakingContext::increment()
     m_atStart = false;
 }
 
-inline void BreakingContext::handleBR()
-{
-    if (m_width.fitsOnLine()) {
-        RenderObject* br = m_current.object();
-        m_lineBreak.moveToStartOf(br);
-        m_lineBreak.increment();
-
-        // A <br> always breaks a line, so don't let the line be collapsed
-        // away. Also, the space at the end of a line with a <br> does not
-        // get collapsed away. It only does this if the previous line broke
-        // cleanly. Otherwise the <br> has no effect on whether the line is
-        // empty or not.
-        if (m_startingNewParagraph)
-            m_lineInfo.setEmpty(false, m_block, &m_width);
-        m_trailingObjects.clear();
-        m_lineInfo.setPreviousLineBrokeCleanly(true);
-    }
-    m_atEnd = true;
-}
-
 inline LayoutUnit borderPaddingMarginStart(RenderInline* child)
 {
     return child->marginStart() + child->paddingStart() + child->borderStart();
@@ -467,12 +446,16 @@ inline bool BreakingContext::handleText(WordMeasurements& wordMeasurements, bool
 
     float hyphenWidth = 0;
 
-    bool ellipsizeMode = !m_blockStyle->ellipsis().isEmpty();
+    bool ellipsizeMode = false;
     float ellipsisWidth = 0;
     unsigned ellipsisBreakOffset = 0;
-    if (ellipsizeMode) {
-        ASSERT(breakAll);
-        ellipsisWidth = measureEllipsisWidth(renderText, font, m_blockStyle->ellipsis().string());
+    if (m_lineInfo.lineIndex() == m_blockStyle->maxLines() - 1 ||
+        m_blockStyle->maxLines() == INT_MAX) {
+        ellipsizeMode = !m_blockStyle->ellipsis().isEmpty();
+        if (ellipsizeMode) {
+            ellipsisWidth = measureEllipsisWidth(renderText, font, m_blockStyle->ellipsis().string());
+            breakAll = true;
+        }
     }
 
     if (m_renderTextInfo.m_text != renderText) {
@@ -629,6 +612,7 @@ inline bool BreakingContext::handleText(WordMeasurements& wordMeasurements, bool
                 m_lineBreak.moveTo(m_current.object(), m_current.offset(), m_current.nextBreakablePosition());
                 m_lineBreak.increment();
                 m_lineInfo.setPreviousLineBrokeCleanly(true);
+                m_lineInfo.incrementLineIndex(); // caller only calls this if we return false
                 return true;
             }
 

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

@@ -36,6 +36,7 @@ public:
         , m_isEmpty(true)
         , m_previousLineBrokeCleanly(true)
         , m_runsFromLeadingWhitespace(0)
+        , m_lineIndex(0)
     { }
 
     bool isFirstLine() const { return m_isFirstLine; }
@@ -53,6 +54,9 @@ public:
         m_isEmpty = empty;
     }
 
+    void incrementLineIndex() { ++m_lineIndex; }
+    int lineIndex() const { return m_lineIndex; }
+
     void setPreviousLineBrokeCleanly(bool previousLineBrokeCleanly) { m_previousLineBrokeCleanly = previousLineBrokeCleanly; }
 
 private:
@@ -61,6 +65,7 @@ private:
     bool m_isEmpty;
     bool m_previousLineBrokeCleanly;
     unsigned m_runsFromLeadingWhitespace;
+    int m_lineIndex;
 };
 
 }

sky/engine/core/rendering/style/RenderStyle.h

@@ -645,6 +645,7 @@ public:
 
     // Flutter property getters
     const AtomicString& ellipsis() const { return rareNonInheritedData->m_ellipsis; }
+    int maxLines() const { return rareNonInheritedData->m_maxLines; }
 
 // attribute setter methods
 
@@ -905,6 +906,7 @@ public:
 
     // Flutter property setters
     void setEllipsis(const AtomicString& e) { SET_VAR(rareNonInheritedData, m_ellipsis, e); }
+    void setMaxLines(int m) { SET_VAR(rareNonInheritedData, m_maxLines, m); }
 
     static ClipPathOperation* initialClipPath() { return 0; }
 

sky/engine/core/rendering/style/StyleRareNonInheritedData.cpp

@@ -40,6 +40,7 @@ StyleRareNonInheritedData::StyleRareNonInheritedData()
     , m_textDecorationColor(StyleColor::currentColor())
     , m_order(RenderStyle::initialOrder())
     , m_objectPosition(RenderStyle::initialObjectPosition())
+    , m_maxLines(INT_MAX)
     , m_transformStyle3D(RenderStyle::initialTransformStyle3D())
     , m_alignContent(RenderStyle::initialAlignContent())
     , m_alignItems(RenderStyle::initialAlignItems())
@@ -79,6 +80,7 @@ StyleRareNonInheritedData::StyleRareNonInheritedData(const StyleRareNonInherited
     , m_textDecorationColor(o.m_textDecorationColor)
     , m_order(o.m_order)
     , m_objectPosition(o.m_objectPosition)
+    , m_maxLines(o.m_maxLines)
     , m_transformStyle3D(o.m_transformStyle3D)
     , m_alignContent(o.m_alignContent)
     , m_alignItems(o.m_alignItems)
@@ -122,6 +124,7 @@ bool StyleRareNonInheritedData::operator==(const StyleRareNonInheritedData& o) c
         && m_textDecorationColor == o.m_textDecorationColor
         && m_order == o.m_order
         && m_objectPosition == o.m_objectPosition
+        && m_maxLines == o.m_maxLines
         && m_transformStyle3D == o.m_transformStyle3D
         && m_alignContent == o.m_alignContent
         && m_alignItems == o.m_alignItems

sky/engine/core/rendering/style/StyleRareNonInheritedData.h

@@ -88,6 +88,7 @@ public:
     LengthPoint m_objectPosition;
 
     AtomicString m_ellipsis;
+    int m_maxLines;
 
     unsigned m_transformStyle3D : 1; // ETransformStyle3D