Put back the 0.5 bias in the shader. Only adjust the radii for the geometry, not the radii constants.

After working through this with Jim, this is more mathematically correct, and also accounts for the inner radius.

BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search2?unt=true&query=source_type%3Dgm&master=false&issue=1692683003

Review URL: https://codereview.chromium.org/1692683003

1 files changed, 5 insertions, 5 deletions

diff --git a/src/gpu/GrOvalRenderer.cpp b/src/gpu/GrOvalRenderer.cpp
index bc85f94228..5779f8ac4c 100644
--- a/src/gpu/GrOvalRenderer.cpp
+++ b/src/gpu/GrOvalRenderer.cpp
@@ -297,7 +297,7 @@ public:
             // avoid calling inversesqrt on zero.
             fragBuilder->codeAppend("grad_dot = max(grad_dot, 1.0e-4);");
             fragBuilder->codeAppend("float invlen = inversesqrt(grad_dot);");
-            fragBuilder->codeAppend("float edgeAlpha = clamp(-test*invlen, 0.0, 1.0);");
+            fragBuilder->codeAppend("float edgeAlpha = clamp(0.5-test*invlen, 0.0, 1.0);");
 
             // for inner curve
             if (ee.isStroked()) {
@@ -1081,8 +1081,8 @@ static GrDrawBatch* create_ellipse_batch(GrColor color,
     // We've extended the outer x radius out half a pixel to antialias.
     // This will also expand the rect so all the pixels will be captured.
     // TODO: Consider if we should use sqrt(2)/2 instead
-    xRadius += SK_ScalarHalf;
-    yRadius += SK_ScalarHalf;
+    SkScalar geoXRadius = xRadius + SK_ScalarHalf;
+    SkScalar geoYRadius = yRadius + SK_ScalarHalf;
 
     EllipseBatch::Geometry geometry;
     geometry.fViewMatrix = viewMatrix;
@@ -1092,8 +1092,8 @@ static GrDrawBatch* create_ellipse_batch(GrColor color,
     geometry.fInnerXRadius = innerXRadius;
     geometry.fInnerYRadius = innerYRadius;
     geometry.fStroke = isStrokeOnly && innerXRadius > 0 && innerYRadius > 0;
-    geometry.fDevBounds = SkRect::MakeLTRB(center.fX - xRadius, center.fY - yRadius,
-                                           center.fX + xRadius, center.fY + yRadius);
+    geometry.fDevBounds = SkRect::MakeLTRB(center.fX - geoXRadius, center.fY - geoYRadius,
+                                           center.fX + geoXRadius, center.fY + geoYRadius);
 
     return EllipseBatch::Create(geometry);
 }