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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     static GrXferProcessor* Create() { return new DisableColorXP; }
     22 
     23     ~DisableColorXP() override {};
     24 
     25     const char* name() const override { return "Disable Color"; }
     26 
     27     GrGLSLXferProcessor* createGLSLInstance() const override;
     28 
     29 private:
     30     DisableColorXP();
     31 
     32     GrXferProcessor::OptFlags onGetOptimizations(const GrPipelineOptimizations& optimizations,
     33                                                  bool doesStencilWrite,
     34                                                  GrColor* color,
     35                                                  const GrCaps& caps) const override {
     36         return GrXferProcessor::kIgnoreColor_OptFlag | GrXferProcessor::kIgnoreCoverage_OptFlag;
     37     }
     38 
     39     void onGetGLSLProcessorKey(const GrGLSLCaps& caps, GrProcessorKeyBuilder* b) const override;
     40 
     41     void onGetBlendInfo(GrXferProcessor::BlendInfo* blendInfo) const override;
     42 
     43     bool onIsEqual(const GrXferProcessor& xpBase) const override {
     44         return true;
     45     }
     46 
     47     typedef GrXferProcessor INHERITED;
     48 };
     49 
     50 ///////////////////////////////////////////////////////////////////////////////
     51 
     52 class GLDisableColorXP : public GrGLSLXferProcessor {
     53 public:
     54     GLDisableColorXP(const GrProcessor&) {}
     55 
     56     ~GLDisableColorXP() override {}
     57 
     58     static void GenKey(const GrProcessor&, const GrGLSLCaps&, GrProcessorKeyBuilder*) {}
     59 
     60 private:
     61     void emitOutputsForBlendState(const EmitArgs& args) override {
     62         // This emit code should be empty. However, on the nexus 6 there is a driver bug where if
     63         // you do not give gl_FragColor a value, the gl context is lost and we end up drawing
     64         // nothing. So this fix just sets the gl_FragColor arbitrarily to 0.
     65         GrGLSLXPFragmentBuilder* fragBuilder = args.fXPFragBuilder;
     66         fragBuilder->codeAppendf("%s = vec4(0);", args.fOutputPrimary);
     67     }
     68 
     69     void onSetData(const GrGLSLProgramDataManager&, const GrXferProcessor&) override {}
     70 
     71     typedef GrGLSLXferProcessor INHERITED;
     72 };
     73 
     74 ///////////////////////////////////////////////////////////////////////////////
     75 
     76 DisableColorXP::DisableColorXP() {
     77     this->initClassID<DisableColorXP>();
     78 }
     79 
     80 void DisableColorXP::onGetGLSLProcessorKey(const GrGLSLCaps& caps, GrProcessorKeyBuilder* b) const {
     81     GLDisableColorXP::GenKey(*this, caps, b);
     82 }
     83 
     84 GrGLSLXferProcessor* DisableColorXP::createGLSLInstance() const { return new GLDisableColorXP(*this); }
     85 
     86 void DisableColorXP::onGetBlendInfo(GrXferProcessor::BlendInfo* blendInfo) const {
     87     blendInfo->fWriteColor = false;
     88 }
     89 
     90 ///////////////////////////////////////////////////////////////////////////////
     91 
     92 GrDisableColorXPFactory::GrDisableColorXPFactory() {
     93     this->initClassID<GrDisableColorXPFactory>();
     94 }
     95 
     96 GrXferProcessor*
     97 GrDisableColorXPFactory::onCreateXferProcessor(const GrCaps& caps,
     98                                                const GrPipelineOptimizations& optimizations,
     99                                                bool hasMixedSamples,
    100                                                const DstTexture* dst) const {
    101     SkASSERT(!optimizations.fOverrides.fUsePLSDstRead);
    102     return DisableColorXP::Create();
    103 }
    104 
    105 GR_DEFINE_XP_FACTORY_TEST(GrDisableColorXPFactory);
    106 
    107 const GrXPFactory* GrDisableColorXPFactory::TestCreate(GrProcessorTestData*) {
    108     return GrDisableColorXPFactory::Create();
    109 }
    110 
    111