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      1 /*
      2  * Copyright 2014 Google Inc.
      3  *
      4  * Use of this source code is governed by a BSD-style license that can be
      5  * found in the LICENSE file.
      6  */
      7 
      8 #include "effects/GrDisableColorXP.h"
      9 #include "GrPipeline.h"
     10 #include "GrProcessor.h"
     11 #include "glsl/GrGLSLFragmentShaderBuilder.h"
     12 #include "glsl/GrGLSLProgramDataManager.h"
     13 #include "glsl/GrGLSLXferProcessor.h"
     14 
     15 /**
     16  * This xfer processor disables color writing. Thus color and coverage and ignored and no blending
     17  * occurs. This XP is usful for things like stenciling.
     18  */
     19 class DisableColorXP : public GrXferProcessor {
     20 public:
     21     DisableColorXP()
     22     : INHERITED(kDisableColorXP_ClassID) {}
     23 
     24     const char* name() const override { return "Disable Color"; }
     25 
     26     GrGLSLXferProcessor* createGLSLInstance() const override;
     27 
     28 private:
     29 
     30     void onGetGLSLProcessorKey(const GrShaderCaps& caps, GrProcessorKeyBuilder* b) const override;
     31 
     32     void onGetBlendInfo(GrXferProcessor::BlendInfo* blendInfo) const override;
     33 
     34     bool onIsEqual(const GrXferProcessor& xpBase) const override {
     35         return true;
     36     }
     37 
     38     typedef GrXferProcessor INHERITED;
     39 };
     40 
     41 ///////////////////////////////////////////////////////////////////////////////
     42 
     43 class GLDisableColorXP : public GrGLSLXferProcessor {
     44 public:
     45     GLDisableColorXP(const GrProcessor&) {}
     46 
     47     ~GLDisableColorXP() override {}
     48 
     49     static void GenKey(const GrProcessor&, const GrShaderCaps&, GrProcessorKeyBuilder*) {}
     50 
     51 private:
     52     void emitOutputsForBlendState(const EmitArgs& args) override {
     53         // This emit code should be empty. However, on the nexus 6 there is a driver bug where if
     54         // you do not give gl_FragColor a value, the gl context is lost and we end up drawing
     55         // nothing. So this fix just sets the gl_FragColor arbitrarily to 0.
     56         GrGLSLXPFragmentBuilder* fragBuilder = args.fXPFragBuilder;
     57         fragBuilder->codeAppendf("%s = half4(0);", args.fOutputPrimary);
     58     }
     59 
     60     void onSetData(const GrGLSLProgramDataManager&, const GrXferProcessor&) override {}
     61 
     62     typedef GrGLSLXferProcessor INHERITED;
     63 };
     64 
     65 ///////////////////////////////////////////////////////////////////////////////
     66 
     67 void DisableColorXP::onGetGLSLProcessorKey(const GrShaderCaps& caps, GrProcessorKeyBuilder* b) const {
     68     GLDisableColorXP::GenKey(*this, caps, b);
     69 }
     70 
     71 GrGLSLXferProcessor* DisableColorXP::createGLSLInstance() const { return new GLDisableColorXP(*this); }
     72 
     73 void DisableColorXP::onGetBlendInfo(GrXferProcessor::BlendInfo* blendInfo) const {
     74     blendInfo->fWriteColor = false;
     75 }
     76 
     77 ///////////////////////////////////////////////////////////////////////////////
     78 sk_sp<const GrXferProcessor> GrDisableColorXPFactory::makeXferProcessor(
     79         const GrProcessorAnalysisColor&,
     80         GrProcessorAnalysisCoverage,
     81         bool hasMixedSamples,
     82         const GrCaps& caps) const {
     83     return sk_sp<const GrXferProcessor>(new DisableColorXP);
     84 }
     85 
     86 GR_DEFINE_XP_FACTORY_TEST(GrDisableColorXPFactory);
     87 
     88 #if GR_TEST_UTILS
     89 const GrXPFactory* GrDisableColorXPFactory::TestGet(GrProcessorTestData*) {
     90     return GrDisableColorXPFactory::Get();
     91 }
     92 #endif
     93