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 "src/gpu/GrPipeline.h"
9#include "src/gpu/GrProcessor.h"
10#include "src/gpu/GrShaderCaps.h"
11#include "src/gpu/effects/GrDisableColorXP.h"
12#include "src/gpu/glsl/GrGLSLFragmentShaderBuilder.h"
13#include "src/gpu/glsl/GrGLSLProgramDataManager.h"
14#include "src/gpu/glsl/GrGLSLXferProcessor.h"
15
16/**
17 * This xfer processor disables color writing. Thus color and coverage and ignored and no blending
18 * occurs. This XP is usful for things like stenciling.
19 */
20class DisableColorXP : public GrXferProcessor {
21public:
22 DisableColorXP() : INHERITED(kDisableColorXP_ClassID) {}
23
24private:
25 const char* name() const override { return "Disable Color"; }
26 bool onIsEqual(const GrXferProcessor& xpBase) const override { return true; }
27 void onGetGLSLProcessorKey(const GrShaderCaps& caps, GrProcessorKeyBuilder* b) const override {
28 return; // No key.
29 }
30 void onGetBlendInfo(GrXferProcessor::BlendInfo* blendInfo) const override {
31 blendInfo->fWriteColor = false;
32 }
33 GrGLSLXferProcessor* createGLSLInstance() const override;
34
35 typedef GrXferProcessor INHERITED;
36};
37
38class GLDisableColorXP : public GrGLSLXferProcessor {
39private:
40 void emitOutputsForBlendState(const EmitArgs& args) override {
41 if (args.fShaderCaps->mustWriteToFragColor()) {
42 // This emit code should be empty. However, on the nexus 6 there is a driver bug where
43 // if you do not give gl_FragColor a value, the gl context is lost and we end up drawing
44 // nothing. So this fix just sets the gl_FragColor arbitrarily to 0.
45 // https://bugs.chromium.org/p/chromium/issues/detail?id=445377
46 GrGLSLXPFragmentBuilder* fragBuilder = args.fXPFragBuilder;
47 fragBuilder->codeAppendf("%s = half4(0);", args.fOutputPrimary);
48 }
49 }
50
51 void emitWriteSwizzle(GrGLSLXPFragmentBuilder*,
52 const GrSwizzle&,
53 const char*,
54 const char*) const override {
55 // Don't write any swizzling. This makes sure the final shader does not output a color.
56 return;
57 }
58
59 void onSetData(const GrGLSLProgramDataManager&, const GrXferProcessor&) override {}
60
61 typedef GrGLSLXferProcessor INHERITED;
62};
63
64GrGLSLXferProcessor* DisableColorXP::createGLSLInstance() const {
65 return new GLDisableColorXP();
66}
67
68sk_sp<const GrXferProcessor> GrDisableColorXPFactory::MakeXferProcessor() {
69 return sk_make_sp<DisableColorXP>();
70}
71
72GR_DEFINE_XP_FACTORY_TEST(GrDisableColorXPFactory);
73
74#if GR_TEST_UTILS
75const GrXPFactory* GrDisableColorXPFactory::TestGet(GrProcessorTestData*) {
76 return GrDisableColorXPFactory::Get();
77}
78#endif
79