Add GLSL support for texelFetch

src/gpu/glsl/GrGLSLShaderBuilder.h

 /*
  * Copyright 2014 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef GrGLSLShaderBuilder_DEFINED
 #define GrGLSLShaderBuilder_DEFINED
 
@@ skipping 16 matching lines @@
 
     /** Appends a 2D texture sample with projection if necessary. coordType must either be Vec2f or
         Vec3f. The latter is interpreted as projective texture coords. The vec length and swizzle
         order of the result depends on the GrTextureAccess associated with the GrGLSLSampler.
         */
     void appendTextureLookup(SkString* out,
                              const GrGLSLSampler&,
                              const char* coordName,
                              GrSLType coordType = kVec2f_GrSLType) const;
 
-    /** Version of above that appends the result to the fragment shader code instead.*/
+    /** Version of above that appends the result to the shader code instead.*/
     void appendTextureLookup(const GrGLSLSampler&,
                              const char* coordName,
                              GrSLType coordType = kVec2f_GrSLType);
 
 
     /** Does the work of appendTextureLookup and modulates the result by modulation. The result is
         always a vec4. modulation and the swizzle specified by GrGLSLSampler must both be
         vec4 or float. If modulation is "" or nullptr it this function acts as though
         appendTextureLookup were called. */
     void appendTextureLookupAndModulate(const char* modulation,
                                         const GrGLSLSampler&,
                                         const char* coordName,
                                         GrSLType coordType = kVec2f_GrSLType);
 
+    /** Fetches an unfiltered texel from a sampler at integer coordinates. coordExpr must match the
+        dimensionality of the sampler and must be within the sampler's range. coordExpr is emitted
+        exactly once, so expressions like "idx++" are acceptable. */
+    void appendTexelFetch(SkString* out, const GrGLSLSampler&, const char* coordExpr) const;
+
+    /** Version of above that appends the result to the shader code instead.*/
+    void appendTexelFetch(const GrGLSLSampler&, const char* coordExpr);
+
     /**
     * Adds a #define directive to the top of the shader.
     */
     void define(const char* macro, const char* replacement) {
         this->definitions().appendf("#define %s %s\n", macro, replacement);
     }
 
     void define(const char* macro, int replacement) {
         this->definitions().appendf("#define %s %i\n", macro, replacement);
     }
@@ skipping 106 matching lines @@
      * A low level function to build default layout qualifiers.
      *
      *   e.g. layout(param1, param2, ...) out;
      *
      * GLSL allows default layout qualifiers for in, out, and uniform.
      */
     void addLayoutQualifier(const char* param, InterfaceQualifier);
 
     void compileAndAppendLayoutQualifiers();
 
+    /* Appends any swizzling we may need to get from some backend internal format to the format used
+     * in GrPixelConfig. If this is implemented by the GrGpu object, then swizzle will be rgba. For
+     * shader prettiness we omit the swizzle rather than appending ".rgba".
+     */
+    void appendTextureSwizzle(SkString* out, GrPixelConfig) const;
+
     void nextStage() {
         fShaderStrings.push_back();
         fCompilerStrings.push_back(this->code().c_str());
         fCompilerStringLengths.push_back((int)this->code().size());
         fCodeIndex++;
     }
 
     SkString& versionDecl() { return fShaderStrings[kVersionDecl]; }
     SkString& extensions() { return fShaderStrings[kExtensions]; }
     SkString& definitions() { return fShaderStrings[kDefinitions]; }
@@ skipping 37 matching lines @@
     int fCodeIndex;
     bool fFinalized;
 
     friend class GrGLSLProgramBuilder;
     friend class GrGLProgramBuilder;
     friend class GrGLSLVaryingHandler; // to access noperspective interpolation feature.
     friend class GrGLPathProgramBuilder; // to access fInputs.
     friend class GrVkPipelineStateBuilder;
 };
 #endif