Preventing division by 0 in non-separable blend mode shaders.

src/core/SkXfermode.cpp

 
 /*
  * Copyright 2006 The Android Open Source Project
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 
 #include "SkXfermode.h"
@@ skipping 1082 matching lines @@
                 GrGLShaderVar("hueSat", kVec3f_GrSLType),
                 GrGLShaderVar("alpha", kFloat_GrSLType),
                 GrGLShaderVar("lumColor", kVec3f_GrSLType),
             };
             SkString setLumBody;
             setLumBody.printf("\tfloat diff = %s(lumColor - hueSat);\n", getFunction.c_str());
             setLumBody.append("\tvec3 outColor = hueSat + diff;\n");
             setLumBody.appendf("\tfloat outLum = %s(outColor);\n", getFunction.c_str());
             setLumBody.append("\tfloat minComp = min(min(outColor.r, outColor.g), outColor.b);\n"
                               "\tfloat maxComp = max(max(outColor.r, outColor.g), outColor.b);\n"
-                              "\tif (minComp < 0.0) {\n"
+                              "\tif (minComp < 0.0 && outLum != minComp) {\n"
                               "\t\toutColor = outLum + ((outColor - vec3(outLum, outLum, outLum)) * outLum) / (outLum - minComp);\n"
                               "\t}\n"
-                              "\tif (maxComp > alpha) {\n"
+                              "\tif (maxComp > alpha && maxComp != outLum) {\n"
                               "\t\toutColor = outLum + ((outColor - vec3(outLum, outLum, outLum)) * (alpha - outLum)) / (maxComp - outLum);\n"
                               "\t}\n"
                               "\treturn outColor;\n");
             fsBuilder->emitFunction(kVec3f_GrSLType,
                                     "set_luminance",
                                     SK_ARRAY_COUNT(setLumArgs), setLumArgs,
                                     setLumBody.c_str(),
                                     setLumFunction);
         }
 
@@ skipping 836 matching lines @@
         } else {
             proc16 = rec.fProc16_General;
         }
     }
     return proc16;
 }
 
 SK_DEFINE_FLATTENABLE_REGISTRAR_GROUP_START(SkXfermode)
     SK_DEFINE_FLATTENABLE_REGISTRAR_ENTRY(SkProcCoeffXfermode)
 SK_DEFINE_FLATTENABLE_REGISTRAR_GROUP_END