[Impeller] libImpeller: Allow setting ellipses. (#169610)

chinmaygarde · web-flow · commit 09c7f4fa5bdb · 2025-05-29T19:39:20.000Z
Fixes flutter/flutter#168750 <img width="1136" alt="Screenshot 2025-05-28 at 11 41 24 AM" src="https://github.com/user-attachments/assets/d421783b-9e04-46e1-aa0c-236c3f546e11" />
diff --git a/engine/src/flutter/impeller/toolkit/interop/impeller.cc b/engine/src/flutter/impeller/toolkit/interop/impeller.cc
@@ -1159,6 +1159,12 @@ void ImpellerParagraphStyleSetLocale(ImpellerParagraphStyle paragraph_style,
   GetPeer(paragraph_style)->SetLocale(ReadString(locale));
 }
 
+IMPELLER_EXTERN_C
+void ImpellerParagraphStyleSetEllipsis(ImpellerParagraphStyle paragraph_style,
+                                       const char* ellipsis) {
+  GetPeer(paragraph_style)->SetEllipsis(ReadString(ellipsis));
+}
+
 IMPELLER_EXTERN_C
 void ImpellerDisplayListBuilderDrawParagraph(ImpellerDisplayListBuilder builder,
                                              ImpellerParagraph paragraph,
diff --git a/engine/src/flutter/impeller/toolkit/interop/impeller.h b/engine/src/flutter/impeller/toolkit/interop/impeller.h
@@ -2472,6 +2472,18 @@ void ImpellerParagraphStyleSetLocale(
     ImpellerParagraphStyle IMPELLER_NONNULL paragraph_style,
     const char* IMPELLER_NONNULL locale);
 
+//------------------------------------------------------------------------------
+/// @brief      Set the UTF-8 string to use as the ellipsis. Pass `nullptr` to
+///             clear the setting to default.
+///
+/// @param[in]  paragraph_style  The paragraph style.
+/// @param[in]  data             The ellipsis string UTF-8 data, or null.
+///
+IMPELLER_EXPORT
+void ImpellerParagraphStyleSetEllipsis(
+    ImpellerParagraphStyle IMPELLER_NONNULL paragraph_style,
+    const char* IMPELLER_NULLABLE ellipsis);
+
 //------------------------------------------------------------------------------
 // Paragraph Builder
 //------------------------------------------------------------------------------
diff --git a/engine/src/flutter/impeller/toolkit/interop/impeller.hpp b/engine/src/flutter/impeller/toolkit/interop/impeller.hpp
@@ -168,6 +168,7 @@ struct Proc {
   PROC(ImpellerParagraphStyleRelease)                             \
   PROC(ImpellerParagraphStyleRetain)                              \
   PROC(ImpellerParagraphStyleSetBackground)                       \
+  PROC(ImpellerParagraphStyleSetEllipsis)                         \
   PROC(ImpellerParagraphStyleSetFontFamily)                       \
   PROC(ImpellerParagraphStyleSetFontSize)                         \
   PROC(ImpellerParagraphStyleSetFontStyle)                        \
@@ -1088,6 +1089,14 @@ class ParagraphStyle
     return *this;
   }
 
+  //----------------------------------------------------------------------------
+  /// @see      ImpellerParagraphStyleSetEllipsis
+  ///
+  ParagraphStyle& SetEllipsis(const char* ellipsis) {
+    gGlobalProcTable.ImpellerParagraphStyleSetEllipsis(Get(), ellipsis);
+    return *this;
+  }
+
   //----------------------------------------------------------------------------
   /// @see      ImpellerParagraphStyleSetMaxLines
   ///
diff --git a/engine/src/flutter/impeller/toolkit/interop/impeller_unittests.cc b/engine/src/flutter/impeller/toolkit/interop/impeller_unittests.cc
@@ -631,4 +631,29 @@ TEST_P(InteropPlaygroundTest, CanGetPathBounds) {
   ASSERT_EQ(bounds.height, 100);
 }
 
+TEST_P(InteropPlaygroundTest, CanControlEllipses) {
+  hpp::TypographyContext context;
+  auto style = hpp::ParagraphStyle{};
+  style.SetFontSize(50);
+  style.SetForeground(hpp::Paint{}.SetColor({.red = 1.0, .alpha = 1.0}));
+  const auto text = std::string{"The quick brown fox jumped over the lazy dog"};
+  style.SetEllipsis("🐶");
+  auto para1 =
+      hpp::ParagraphBuilder{context}.PushStyle(style).AddText(text).Build(250);
+  style.SetForeground(hpp::Paint{}.SetColor({.green = 1.0, .alpha = 1.0}));
+  style.SetEllipsis(nullptr);
+  auto para2 =
+      hpp::ParagraphBuilder{context}.PushStyle(style).AddText(text).Build(250);
+  auto dl = hpp::DisplayListBuilder{}
+                .DrawParagraph(para1, {100, 100})
+                .DrawParagraph(para2, {100, 200})
+                .Build();
+  ASSERT_TRUE(
+      OpenPlaygroundHere([&](const auto& context, const auto& surface) -> bool {
+        hpp::Surface window(surface.GetC());
+        window.Draw(dl);
+        return true;
+      }));
+}
+
 }  // namespace impeller::interop::testing
diff --git a/engine/src/flutter/impeller/toolkit/interop/paragraph_style.cc b/engine/src/flutter/impeller/toolkit/interop/paragraph_style.cc
@@ -4,6 +4,8 @@
 
 #include "impeller/toolkit/interop/paragraph_style.h"
 
+#include "flutter/fml/string_conversion.h"
+
 namespace impeller::interop {
 
 ParagraphStyle::ParagraphStyle() = default;
@@ -84,4 +86,12 @@ void ParagraphStyle::SetTextDecoration(
   decoration_ = decoration;
 }
 
+void ParagraphStyle::SetEllipsis(const std::string& string) {
+  if (string.empty()) {
+    style_.ellipsis = {};
+    return;
+  }
+  style_.ellipsis = fml::Utf8ToUtf16(string);
+}
+
 }  // namespace impeller::interop
diff --git a/engine/src/flutter/impeller/toolkit/interop/paragraph_style.h b/engine/src/flutter/impeller/toolkit/interop/paragraph_style.h
@@ -48,6 +48,8 @@ class ParagraphStyle final
 
   void SetLocale(std::string locale);
 
+  void SetEllipsis(const std::string& string);
+
   txt::TextStyle CreateTextStyle() const;
 
   const txt::ParagraphStyle& GetParagraphStyle() const;
