Use "blur_sigma" instead of "blur_radius" in Shadow.

lib/ui/painting.dart

@@ -5010,7 +5010,7 @@ class Shadow {
   // See SkBlurMask::ConvertRadiusToSigma().
   // <https://github.com/google/skia/blob/bb5b77db51d2e149ee66db284903572a5aac09be/src/effects/SkBlurMask.cpp#L23>
   static double convertRadiusToSigma(double radius) {
-    return radius * 0.57735 + 0.5;
+    return radius > 0 ? radius * 0.57735 + 0.5 : 0;
   }
 
   /// The [blurRadius] in sigmas instead of logical pixels.
@@ -5147,8 +5147,9 @@ class Shadow {
         shadowsData.setFloat32(_kYOffset + shadowOffset,
           shadow.offset.dy, _kFakeHostEndian);
 
+        final double blurSigma = Shadow.convertRadiusToSigma(shadow.blurRadius);
         shadowsData.setFloat32(_kBlurOffset + shadowOffset,
-          shadow.blurRadius, _kFakeHostEndian);
+          blurSigma, _kFakeHostEndian);
       }
     }
 

lib/web_ui/lib/src/ui/painting.dart

@@ -614,7 +614,7 @@ class Shadow {
   // See SkBlurMask::ConvertRadiusToSigma().
   // <https://github.com/google/skia/blob/bb5b77db51d2e149ee66db284903572a5aac09be/src/effects/SkBlurMask.cpp#L23>
   static double convertRadiusToSigma(double radius) {
-    return radius * 0.57735 + 0.5;
+    return radius > 0 ? radius * 0.57735 + 0.5 : 0;
   }
 
   double get blurSigma => convertRadiusToSigma(blurRadius);

third_party/txt/src/skia/paragraph_builder_skia.cc

@@ -126,7 +126,7 @@ skt::TextStyle TxtToSkia(const TextStyle& txt) {
   for (const txt::TextShadow& txt_shadow : txt.text_shadows) {
     skt::TextShadow shadow;
     shadow.fOffset = txt_shadow.offset;
-    shadow.fBlurSigma = txt_shadow.blur_radius;
+    shadow.fBlurSigma = txt_shadow.blur_sigma;
     shadow.fColor = txt_shadow.color;
     skia.addShadow(shadow);
   }

third_party/txt/src/skia/paragraph_skia.cc

@@ -75,7 +75,7 @@ TextStyle SkiaToTxt(const skt::TextStyle& skia) {
   for (const skt::TextShadow& skia_shadow : skia.getShadows()) {
     txt::TextShadow shadow;
     shadow.offset = skia_shadow.fOffset;
-    shadow.blur_radius = skia_shadow.fBlurSigma;
+    shadow.blur_sigma = skia_shadow.fBlurSigma;
     shadow.color = skia_shadow.fColor;
     txt.text_shadows.emplace_back(shadow);
   }

third_party/txt/src/txt/paragraph_txt.cc

@@ -1650,9 +1650,9 @@ void ParagraphTxt::PaintShadow(SkCanvas* canvas,
 
     SkPaint paint;
     paint.setColor(text_shadow.color);
-    if (text_shadow.blur_radius != 0.0) {
+    if (text_shadow.blur_sigma > 0.5) {
       paint.setMaskFilter(SkMaskFilter::MakeBlur(
-          kNormal_SkBlurStyle, text_shadow.blur_radius, false));
+          kNormal_SkBlurStyle, text_shadow.blur_sigma, false));
     }
     canvas->drawTextBlob(record.text(), offset.x() + text_shadow.offset.x(),
                          offset.y() + text_shadow.offset.y(), paint);

third_party/txt/src/txt/text_shadow.cc

@@ -20,15 +20,15 @@
 namespace txt {
 
 TextShadow::TextShadow() {}
-TextShadow::TextShadow(SkColor color, SkPoint offset, double blur_radius)
-    : color(color), offset(offset), blur_radius(blur_radius) {}
+TextShadow::TextShadow(SkColor color, SkPoint offset, double blur_sigma)
+    : color(color), offset(offset), blur_sigma(blur_sigma) {}
 
 bool TextShadow::operator==(const TextShadow& other) const {
   if (color != other.color)
     return false;
   if (offset != other.offset)
     return false;
-  if (blur_radius != other.blur_radius)
+  if (blur_sigma != other.blur_sigma)
     return false;
 
   return true;
@@ -41,7 +41,7 @@ bool TextShadow::operator!=(const TextShadow& other) const {
 bool TextShadow::hasShadow() const {
   if (!offset.isZero())
     return true;
-  if (blur_radius != 0.0)
+  if (blur_sigma > 0.5)
     return true;
 
   return false;

third_party/txt/src/txt/text_shadow.h

@@ -26,11 +26,11 @@ class TextShadow {
  public:
   SkColor color = SK_ColorBLACK;
   SkPoint offset;
-  double blur_radius = 0.0;
+  double blur_sigma = 0.0;
 
   TextShadow();
 
-  TextShadow(SkColor color, SkPoint offset, double blur_radius);
+  TextShadow(SkColor color, SkPoint offset, double blur_sigma);
 
   bool operator==(const TextShadow& other) const;