Draw no stroke for an empty or missing /C, as Acrobat does

core/fpdfdoc/cpdf_appearancegenerator_common.cpp

@@ -519,6 +519,22 @@ ByteString GetColorStringWithDefault(const CPDF_Array* color_array,
   return GenerateColorAP(default_color, operation);
 }
 
+// The stroke colour operator for /C, or none when /C names no colour: left
+// out, or the empty array ISO 32000 defines as "no colour; transparent".
+// Acrobat draws neither with a stroke, so the shape keeps only its fill.
+std::optional<ByteString> GetStrokeColorString(const CPDF_Dictionary* dict) {
+  RetainPtr<const CPDF_Array> color_array =
+      dict->GetArrayFor(pdfium::annotation::kC);
+  if (!color_array) {
+    return std::nullopt;
+  }
+  const CFX_Color color = fpdfdoc::CFXColorFromArray(*color_array);
+  if (color.nColorType == CFX_Color::Type::kTransparent) {
+    return std::nullopt;
+  }
+  return GenerateColorAP(color, PaintOperation::kStroke);
+}
+
 float GetBorderWidth(const CPDF_Dictionary* dict) {
   RetainPtr<const CPDF_Dictionary> border_style_dict = dict->GetDictFor("BS");
   if (border_style_dict) {

core/fpdfdoc/cpdf_appearancegenerator_internal.h

@@ -157,6 +157,7 @@ ByteString GenerateBorderAP(const CFX_FloatRect& rect,
 ByteString GetColorStringWithDefault(const CPDF_Array* color_array,
                                      const CFX_Color& default_color,
                                      PaintOperation operation);
+std::optional<ByteString> GetStrokeColorString(const CPDF_Dictionary* dict);
 float GetBorderWidth(const CPDF_Dictionary* dict);
 ByteString GetDashPatternString(const CPDF_Dictionary* dict);
 ByteString GetPaintOperatorString(bool is_stroke_rect, bool is_fill_rect);
@@ -260,13 +261,25 @@ bool GenerateStrikeOutAP(APGenerationTarget* target,
 
 // cpdf_appearancegenerator_shapes.cpp
 ByteString ReadLineEndingToken(const CPDF_Array* le, size_t idx);
+// `stroked` false fills a closed ending without outlining it: a line with no
+// stroke colour keeps only its filled endings.
 void EmitArrowPath(fxcrt::ostringstream& out,
                    float stroke_w,
                    ArrowStyle style,
-                   bool do_fill);
-void EmitCirclePath(fxcrt::ostringstream& out, float stroke_w, bool filled);
-void EmitSquarePath(fxcrt::ostringstream& out, float stroke_w, bool filled);
-void EmitDiamondPath(fxcrt::ostringstream& out, float stroke_w, bool filled);
+                   bool do_fill,
+                   bool stroked = true);
+void EmitCirclePath(fxcrt::ostringstream& out,
+                    float stroke_w,
+                    bool filled,
+                    bool stroked = true);
+void EmitSquarePath(fxcrt::ostringstream& out,
+                    float stroke_w,
+                    bool filled,
+                    bool stroked = true);
+void EmitDiamondPath(fxcrt::ostringstream& out,
+                     float stroke_w,
+                     bool filled,
+                     bool stroked = true);
 void EmitButtOrSlashPath(fxcrt::ostringstream& out,
                          float stroke_w,
                          float len_factor);