Make GrGLConfigConversionEffect work for Imagination and some other GPUs.

src/gpu/gl/GrGLShaderBuilder.cpp

 /*
  * Copyright 2012 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "gl/GrGLShaderBuilder.h"
 #include "gl/GrGLProgram.h"
 #include "gl/GrGLUniformHandle.h"
@@ skipping 511 matching lines @@
         SkASSERT(NULL != effectStages[e] && NULL != effectStages[e]->getEffect());
         const GrEffectStage& stage = *effectStages[e];
 
         CodeStage::AutoStageRestore csar(&fCodeStage, &stage);
 
         if (inColor.isZeros()) {
             SkString inColorName;
 
             // Effects have no way to communicate zeros, they treat an empty string as ones.
             this->nameVariable(&inColorName, '\0', "input");
             this->fsCodeAppendf("\tvec4 %s = %s;\n", inColorName.c_str(), inColor.c_str());

[changjun.yang, 2014/06/10 11:41:16]

Sorry I am not quite familiar with the shader..
One possible way maybe overwrite this to "highp vec4" after the specific shader
being constructed? If so, could you please guide me more on how to implement
this overwrite?
Another way maybe pass a specific shader related "parameter" here to identify if
it is needed to switch to "highp vec4"? If so, what "parameter" would you
prefer?
Thanks a lot in advance!

[bsalomon, 2014/06/10 13:22:18]

Question: Is this the variable that needs to be highp to make the conversion
work? Or does it work to make a highp temporary var in
GrGLConfigConversionEffect::emitCode? Also, the GPU in question supports
integers, so perhaps we could write the effect using integer operations when
they are supported.

[changjun.yang, 2014/06/11 08:56:56]

Yes, it's the var that would make the conversion work if being made highp, but
not to make a temp var only in GrGLConfigConversionEffect::emitCode I think. I
may check the side effects to other shaders if we make this var to highp only
for specific IMG GPUs.

             inColor = inColorName;
         }
 
         // create var to hold stage result
         SkString outColorName;
         this->nameVariable(&outColorName, '\0', "output");
         this->fsCodeAppendf("\tvec4 %s;\n", outColorName.c_str());
         outColor = outColorName;
 
 
@@ skipping 143 matching lines @@
     // will immediately delete the shader object and free its memory even though it's
     // attached to a program, which then causes glLinkProgram to fail.
     GR_GL_CALL(gli, AttachShader(programId, shaderId));
 
     return shaderId;
 }
 
 bool GrGLShaderBuilder::compileAndAttachShaders(GrGLuint programId, SkTDArray<GrGLuint>* shaderIds) const {
     SkString fragShaderSrc(GrGetGLSLVersionDecl(this->ctxInfo()));
     fragShaderSrc.append(fFSExtensions);
-    append_default_precision_qualifier(kDefaultFragmentPrecision,
-                                       fGpu->glStandard(),
-                                       &fragShaderSrc);
+
+    if (kImagination_GrGLVendor == this->ctxInfo().vendor() &&
+        kPVRRogueHood_GrGLRenderer == this->ctxInfo().renderer())
+      append_default_precision_qualifier(GrGLShaderVar::kHigh_Precision,

[bsalomon, 2014/06/09 13:56:45]

Can you not just apply highp to the vars emitted by the config conversion
effect? Does this make any other shaders work better?

[changjun.yang, 2014/06/10 11:41:17]

Thanks! Pls see my comments above.

+                                         fGpu->glStandard(),
+                                         &fragShaderSrc);
+    else
+      append_default_precision_qualifier(kDefaultFragmentPrecision,
+                                         fGpu->glStandard(),
+                                         &fragShaderSrc);
+
     this->appendUniformDecls(kFragment_Visibility, &fragShaderSrc);
     this->appendDecls(fFSInputs, &fragShaderSrc);
     // We shouldn't have declared outputs on 1.10
     SkASSERT(k110_GrGLSLGeneration != fGpu->glslGeneration() || fFSOutputs.empty());
     this->appendDecls(fFSOutputs, &fragShaderSrc);
     fragShaderSrc.append(fFSFunctions);
     fragShaderSrc.append("void main() {\n");
     fragShaderSrc.append(fFSCode);
     fragShaderSrc.append("}\n");
 
@@ skipping 281 matching lines @@
 
     GrGLPathTexGenProgramEffectsBuilder pathTexGenEffectsBuilder(this,
                                                                  effectCnt);
     this->INHERITED::createAndEmitEffects(&pathTexGenEffectsBuilder,
                                           effectStages,
                                           effectKeys,
                                           effectCnt,
                                           inOutFSColor);
     return pathTexGenEffectsBuilder.finish();
 }