Update feSpotLight to match spec

This change updates feSpotLight to match the spec via two changes:

1) specularExponent is ignored if the spotlight has no coneAngle (GPU
   bug only). This change updates the GPU path so that it matches the
   CPU path and the spec in this regard.

2) specularExponent is clamped to the 1-128 range. The spec does not
   specify a clamp for the specularExponent attribute of feSpotLight.
   Note that the spec *does* specify this clamp for the
   specularExponent attribute of feSpecularLighting. It looks like we
   incorrectly applied this to both specularExponent attributes.

   This change (along with a parallel change in Blink) allows us to pass
   the SVG filter effects conformance test here:
   http://www.w3.org/Graphics/SVG/Test/20110816/harness/htmlObject/filters-light-01-f.html

   Additionally, this brings our behavior in line with Safari and Edge’s
   behavior on this filter.

Two new cases were added to gm/lighting.cpp to catch these issues:
- The existing spotlight case exercised the path where our specular
  exponent was between 1-128 and had a limiting cone angle.
- The first new spotlight case exercises the path where our specular
  exponent is between 1-128 and we do not have a limiting cone angle.
- The second new spotlight case exercises the path where the specular
  exponent is not within the 1-128 range, to ensure that we don’t
  incorrectly clip to this range.

BUG=472849

Review URL: https://codereview.chromium.org/1403403003

1 files changed, 5 insertions, 13 deletions

diff --git a/src/effects/SkLightingImageFilter.cpp b/src/effects/SkLightingImageFilter.cpp
index 199bb4d684..f0f2c66d6f 100644
--- a/src/effects/SkLightingImageFilter.cpp
+++ b/src/effects/SkLightingImageFilter.cpp
@@ -682,7 +682,7 @@ class GrGLLight;
 
 class SkImageFilterLight : public SkRefCnt {
 public:
-    
+
 
     enum LightType {
         kDistant_LightType,
@@ -819,8 +819,8 @@ public:
         // Use X scale and Y scale on Z and average the result
         SkPoint locationZ = SkPoint::Make(fLocation.fZ, fLocation.fZ);
         matrix.mapVectors(&locationZ, 1);
-        SkPoint3 location = SkPoint3::Make(location2.fX, 
-                                           location2.fY, 
+        SkPoint3 location = SkPoint3::Make(location2.fX,
+                                           location2.fY,
                                            SkScalarAve(locationZ.fX, locationZ.fY));
         return new SkPointLight(location, color());
     }
@@ -854,7 +854,7 @@ public:
      : INHERITED(color),
        fLocation(location),
        fTarget(target),
-       fSpecularExponent(SkScalarPin(specularExponent, kSpecularExponentMin, kSpecularExponentMax))
+       fSpecularExponent(specularExponent)
     {
        fS = target - location;
        fast_normalize(&fS);
@@ -984,9 +984,6 @@ protected:
     }
 
 private:
-    static const SkScalar kSpecularExponentMin;
-    static const SkScalar kSpecularExponentMax;
-
     SkPoint3 fLocation;
     SkPoint3 fTarget;
     SkScalar fSpecularExponent;
@@ -998,11 +995,6 @@ private:
     typedef SkImageFilterLight INHERITED;
 };
 
-// According to the spec, the specular term should be in the range [1, 128] :
-// http://www.w3.org/TR/SVG/filters.html#feSpecularLightingSpecularExponentAttribute
-const SkScalar SkSpotLight::kSpecularExponentMin = 1.0f;
-const SkScalar SkSpotLight::kSpecularExponentMax = 128.0f;
-
 ///////////////////////////////////////////////////////////////////////////////
 
 void SkImageFilterLight::flattenLight(SkWriteBuffer& buffer) const {
@@ -1993,7 +1985,7 @@ void GrGLSpotLight::emitLightColor(GrGLFPBuilder* builder,
     lightColorBody.appendf("\t\treturn %s * scale * (cosAngle - %s) * %s;\n",
                            color, cosOuter, coneScale);
     lightColorBody.appendf("\t}\n");
-    lightColorBody.appendf("\treturn %s;\n", color);
+    lightColorBody.appendf("\treturn %s * scale;\n", color);
     GrGLFragmentBuilder* fsBuilder = builder->getFragmentShaderBuilder();
     fsBuilder->emitFunction(kVec3f_GrSLType,
                             "lightColor",