Swizzle shader output and blend when using GL_RED to implement kAlpha_8_GrPixelConfig

src/gpu/gl/builders/GrGLProgramBuilder.cpp

 /*
  * Copyright 2014 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "GrGLProgramBuilder.h"
 
 #include "GrAutoLocaleSetter.h"
 #include "GrCoordTransform.h"
 #include "GrGLProgramBuilder.h"
+#include "GrSwizzle.h"
 #include "GrTexture.h"
 #include "SkRTConf.h"
 #include "SkTraceEvent.h"
 #include "gl/GrGLGpu.h"
 #include "gl/GrGLProgram.h"
 #include "gl/GrGLSLPrettyPrint.h"
 #include "gl/builders/GrGLShaderStringBuilder.h"
 #include "glsl/GrGLSLCaps.h"
 #include "glsl/GrGLSLFragmentProcessor.h"
 #include "glsl/GrGLSLGeometryProcessor.h"
@@ skipping 65 matching lines @@
 
     this->emitAndInstallProc(primProc, inputColor, inputCoverage);
 
     fFragmentProcessors.reset(new GrGLInstalledFragProcs);
     int numProcs = this->pipeline().numFragmentProcessors();
     this->emitAndInstallFragProcs(0, this->pipeline().numColorFragmentProcessors(), inputColor);
     this->emitAndInstallFragProcs(this->pipeline().numColorFragmentProcessors(), numProcs,
                                   inputCoverage);
     this->emitAndInstallXferProc(this->pipeline().getXferProcessor(), *inputColor, *inputCoverage,
                                  this->pipeline().ignoresCoverage());
+    this->emitFSOutputSwizzle(this->pipeline().getXferProcessor().hasSecondaryOutput());
     return true;
 }
 
 void GrGLProgramBuilder::emitAndInstallFragProcs(int procOffset,
                                                  int numProcs,
                                                  GrGLSLExpr4* inOut) {
     for (int i = procOffset; i < numProcs; ++i) {
         GrGLSLExpr4 output;
         const GrFragmentProcessor& fp = this->pipeline().getFragmentProcessor(i);
         this->emitAndInstallProc(fp, i, *inOut, &output);
@@ skipping 147 matching lines @@
                                        fFS.getSecondaryColorOutputName(),
                                        samplers);
     fXferProcessor->fGLProc->emitCode(args);
 
     // We have to check that effects and the code they emit are consistent, ie if an effect
     // asks for dst color, then the emit code needs to follow suit
     verify(xp);
     fFS.codeAppend("}");
 }
 
+void GrGLProgramBuilder::emitFSOutputSwizzle(bool hasSecondaryOutput) {
+    // Swizzle the fragment shader outputs if necessary.
+    GrSwizzle swizzle;
+    swizzle.setFromKey(this->desc().header().fOutputSwizzle);
+    if (swizzle != GrSwizzle::RGBA()) {
+        fFS.codeAppendf("%s = %s.%s;", fFS.getPrimaryColorOutputName(),
+                        fFS.getPrimaryColorOutputName(),
+                        swizzle.c_str());
+        if (hasSecondaryOutput) {
+            fFS.codeAppendf("%s = %s.%s;", fFS.getSecondaryColorOutputName(),
+                            fFS.getSecondaryColorOutputName(),
+                            swizzle.c_str());
+        }
+    }
+}
+
 void GrGLProgramBuilder::verify(const GrPrimitiveProcessor& gp) {
     SkASSERT(fFS.hasReadFragmentPosition() == gp.willReadFragmentPosition());
 }
 
 void GrGLProgramBuilder::verify(const GrXferProcessor& xp) {
     SkASSERT(fFS.hasReadDstColor() == xp.willReadDstColor());
 }
 
 void GrGLProgramBuilder::verify(const GrFragmentProcessor& fp) {
     SkASSERT(fFS.hasReadFragmentPosition() == fp.willReadFragmentPosition());
@@ skipping 203 matching lines @@
 }
 
 ///////////////////////////////////////////////////////////////////////////////////////////////////
 
 GrGLInstalledFragProcs::~GrGLInstalledFragProcs() {
     int numProcs = fProcs.count();
     for (int i = 0; i < numProcs; ++i) {
         delete fProcs[i];
     }
 }