Swizzle shader output and blend when using GL_RED to implement kAlpha_8_GrPixelConfig

GOLD_TRYBOT_URL= https://gold.skia.org/search2?unt=true&query=source_type%3Dgm&master=false&issue=1584473002

Review URL: https://codereview.chromium.org/1584473002

10 files changed, 139 insertions, 44 deletions

diff --git a/src/gpu/GrProgramDesc.h b/src/gpu/GrProgramDesc.h
index 13dd14935d..63e060ee62 100644
--- a/src/gpu/GrProgramDesc.h
+++ b/src/gpu/GrProgramDesc.h
@@ -70,15 +70,16 @@ public:
     }
 
     struct KeyHeader {
-        uint8_t                     fFragPosKey;   // set by GrGLShaderBuilder if there are
-                                                   // effects that read the fragment position.
-                                                   // Otherwise, 0.
+        // Set by GrGLShaderBuilder if there are effects that read the fragment position. Otherwise,
+        // 0.
+        uint8_t                     fFragPosKey;
+        // Set to uniquely idenitify any swizzling of the shader's output color(s).
+        uint8_t                     fOutputSwizzle;
         uint8_t                     fSnapVerticesToPixelCenters;
         int8_t                      fColorEffectCnt;
         int8_t                      fCoverageEffectCnt;
         uint8_t                     fIgnoresCoverage;
     };
-    GR_STATIC_ASSERT(sizeof(KeyHeader) == 5);
 
     int numColorEffects() const {
         return this->header().fColorEffectCnt;
diff --git a/src/gpu/GrSwizzle.h b/src/gpu/GrSwizzle.h
index 87ea9534b9..48748803dd 100644
--- a/src/gpu/GrSwizzle.h
+++ b/src/gpu/GrSwizzle.h
@@ -9,6 +9,7 @@
 #define GrSwizzle_DEFINED
 
 #include "GrTypes.h"
+#include "GrColor.h"
 
 /** Represents a rgba swizzle. It can be converted either into a string or a eight bit int.
     Currently there is no way to specify an arbitrary swizzle, just some static swizzles and an
@@ -17,11 +18,23 @@ class GrSwizzle {
 public:
     GrSwizzle() { *this = RGBA(); }
 
+    GrSwizzle(const GrSwizzle& that) { *this = that; }
+
     GrSwizzle& operator=(const GrSwizzle& that) {
         memcpy(this, &that, sizeof(GrSwizzle));
         return *this;
     }
 
+    /** Recreates a GrSwizzle from the output of asKey() */
+    void setFromKey(uint8_t key) {
+        fKey = key;
+        for (int i = 0; i < 4; ++i) {
+            fSwiz[i] = IdxToChar(key & 3);
+            key >>= 2;
+        }
+        SkASSERT(fSwiz[4] == 0);
+    }
+
     bool operator==(const GrSwizzle& that) const { return this->asUInt() == that.asUInt(); }
 
     bool operator!=(const GrSwizzle& that) const { return !(*this == that); }
@@ -32,6 +45,25 @@ public:
     /** 4 char null terminated string consisting only of chars 'r', 'g', 'b', 'a'. */
     const char* c_str() const { return fSwiz; }
 
+    /** Applies this swizzle to the input color and returns the swizzled color. */
+    GrColor applyTo(GrColor color) const {
+        int idx;
+        uint32_t key = fKey;
+        // Index of the input color that should be mapped to output r.
+        idx = (key & 3);
+        uint32_t outR = (color >> idx * 8)  & 0xFF;
+        key >>= 2;
+        idx = (key & 3);
+        uint32_t outG = (color >> idx * 8)  & 0xFF;
+        key >>= 2;
+        idx = (key & 3);
+        uint32_t outB = (color >> idx * 8)  & 0xFF;
+        key >>= 2;
+        idx = (key & 3);
+        uint32_t outA = (color >> idx * 8)  & 0xFF;
+        return GrColorPackRGBA(outR, outG, outB, outA);
+    }
+
     static const GrSwizzle& RGBA() {
         static GrSwizzle gRGBA("rgba");
         return gRGBA;
@@ -59,19 +91,31 @@ private:
     static int CharToIdx(char c) {
         switch (c) {
             case 'r':
-                return 0;
+                return (GrColor_SHIFT_R / 8);
             case 'g':
-                return 1;
+                return (GrColor_SHIFT_G / 8);
             case 'b':
-                return 2;
+                return (GrColor_SHIFT_B / 8);
             case 'a':
-                return 3;
+                return (GrColor_SHIFT_A / 8);
             default:
                 SkFAIL("Invalid swizzle char");
                 return 0;
         }
     }
 
+    static /* constexpr */ char IToC(int idx) {
+        return (8*idx) == GrColor_SHIFT_R ? 'r' :
+               (8*idx) == GrColor_SHIFT_G ? 'g' :
+               (8*idx) == GrColor_SHIFT_B ? 'b' : 'a';
+    }
+
+    static char IdxToChar(int c) {
+        // Hopefully this array gets computed at compile time.
+        static const char gStr[4] = { IToC(0), IToC(1), IToC(2), IToC(3) };
+        return gStr[c];
+    }
+
     explicit GrSwizzle(const char* str) {
         SkASSERT(strlen(str) == 4);
         fSwiz[0] = str[0];
diff --git a/src/gpu/gl/GrGLCaps.cpp b/src/gpu/gl/GrGLCaps.cpp
index 5605babcec..678c62abb8 100644
--- a/src/gpu/gl/GrGLCaps.cpp
+++ b/src/gpu/gl/GrGLCaps.cpp
@@ -1548,6 +1548,19 @@ void GrGLCaps::initConfigTable(const GrGLContextInfo& ctxInfo, const GrGLInterfa
         }
     }
 
+    // Shader output swizzles will default to RGBA. When we've use GL_RED instead of GL_ALPHA to
+    // implement kAlpha_8_GrPixelConfig we need to swizzle the shader outputs so the alpha channel
+    // gets written to the single component.
+    if (this->textureRedSupport()) {
+        for (int i = 0; i < kGrPixelConfigCnt; ++i) {
+            GrPixelConfig config = static_cast<GrPixelConfig>(i);
+            if (GrPixelConfigIsAlphaOnly(config) &&
+                fConfigTable[i].fFormats.fBaseInternalFormat == GR_GL_RED) {
+                glslCaps->fConfigOutputSwizzle[i] = GrSwizzle::AAAA();
+            }
+        }
+    }
+
 #ifdef SK_DEBUG
     // Make sure we initialized everything.
     ConfigInfo defaultEntry;
diff --git a/src/gpu/gl/GrGLGpu.cpp b/src/gpu/gl/GrGLGpu.cpp
index b095e66ea3..8033ea60e5 100644
--- a/src/gpu/gl/GrGLGpu.cpp
+++ b/src/gpu/gl/GrGLGpu.cpp
@@ -1570,7 +1570,10 @@ bool GrGLGpu::flushGLState(const DrawArgs& args) {
     }
 
     if (blendInfo.fWriteColor) {
-        this->flushBlend(blendInfo);
+        // Swizzle the blend to match what the shader will output.
+        const GrSwizzle& swizzle = this->glCaps().glslCaps()->configOutputSwizzle(
+            args.fPipeline->getRenderTarget()->config());
+        this->flushBlend(blendInfo, swizzle);
     }
 
     SkSTArray<8, const GrTextureAccess*> textureAccesses;
@@ -1650,7 +1653,7 @@ void GrGLGpu::setupGeometry(const GrPrimitiveProcessor& primProc,
 void GrGLGpu::buildProgramDesc(GrProgramDesc* desc,
                                const GrPrimitiveProcessor& primProc,
                                const GrPipeline& pipeline) const {
-    if (!GrGLProgramDescBuilder::Build(desc, primProc, pipeline, this)) {
+    if (!GrGLProgramDescBuilder::Build(desc, primProc, pipeline, *this->glCaps().glslCaps())) {
         SkDEBUGFAIL("Failed to generate GL program descriptor");
     }
 }
@@ -2395,7 +2398,7 @@ void GrGLGpu::flushHWAAState(GrRenderTarget* rt, bool useHWAA) {
     }
 }
 
-void GrGLGpu::flushBlend(const GrXferProcessor::BlendInfo& blendInfo) {
+void GrGLGpu::flushBlend(const GrXferProcessor::BlendInfo& blendInfo, const GrSwizzle& swizzle) {
     // Any optimization to disable blending should have already been applied and
     // tweaked the equation to "add" or "subtract", and the coeffs to (1, 0).
 
@@ -2448,15 +2451,16 @@ void GrGLGpu::flushBlend(const GrXferProcessor::BlendInfo& blendInfo) {
         fHWBlendState.fDstCoeff = dstCoeff;
     }
 
-    GrColor blendConst = blendInfo.fBlendConstant;
-    if ((BlendCoeffReferencesConstant(srcCoeff) ||
-         BlendCoeffReferencesConstant(dstCoeff)) &&
-        (!fHWBlendState.fConstColorValid || fHWBlendState.fConstColor != blendConst)) {
-        GrGLfloat c[4];
-        GrColorToRGBAFloat(blendConst, c);
-        GL_CALL(BlendColor(c[0], c[1], c[2], c[3]));
-        fHWBlendState.fConstColor = blendConst;
-        fHWBlendState.fConstColorValid = true;
+    if ((BlendCoeffReferencesConstant(srcCoeff) || BlendCoeffReferencesConstant(dstCoeff))) {
+        GrColor blendConst = blendInfo.fBlendConstant;
+        blendConst = swizzle.applyTo(blendConst);
+        if (!fHWBlendState.fConstColorValid || fHWBlendState.fConstColor != blendConst) {
+            GrGLfloat c[4];
+            GrColorToRGBAFloat(blendConst, c);
+            GL_CALL(BlendColor(c[0], c[1], c[2], c[3]));
+            fHWBlendState.fConstColor = blendConst;
+            fHWBlendState.fConstColorValid = true;
+        }
     }
 }
 
@@ -2840,6 +2844,12 @@ bool GrGLGpu::onCopySurface(GrSurface* dst,
                             GrSurface* src,
                             const SkIRect& srcRect,
                             const SkIPoint& dstPoint) {
+    // None of our copy methods can handle a swizzle. TODO: Make copySurfaceAsDraw handle the
+    // swizzle.
+    if (this->glCaps().glslCaps()->configOutputSwizzle(src->config()) !=
+        this->glCaps().glslCaps()->configOutputSwizzle(dst->config())) {
+        return false;
+    }
     if (src->asTexture() && dst->asRenderTarget()) {
         this->copySurfaceAsDraw(dst, src, srcRect, dstPoint);
         return true;
@@ -3064,6 +3074,9 @@ void GrGLGpu::createWireRectProgram() {
 }
 
 void GrGLGpu::drawDebugWireRect(GrRenderTarget* rt, const SkIRect& rect, GrColor color) {
+    // TODO: This should swizzle the output to match dst's config, though it is a debugging
+    // visualization.
+
     this->handleDirtyContext();
     if (!fWireRectProgram.fProgram) {
         this->createWireRectProgram();
@@ -3114,7 +3127,7 @@ void GrGLGpu::drawDebugWireRect(GrRenderTarget* rt, const SkIRect& rect, GrColor
 
     GrXferProcessor::BlendInfo blendInfo;
     blendInfo.reset();
-    this->flushBlend(blendInfo);
+    this->flushBlend(blendInfo, GrSwizzle::RGBA());
     this->flushColorWrite(true);
     this->flushDrawFace(GrPipelineBuilder::kBoth_DrawFace);
     this->flushHWAAState(glRT, false);
@@ -3185,7 +3198,7 @@ void GrGLGpu::copySurfaceAsDraw(GrSurface* dst,
 
     GrXferProcessor::BlendInfo blendInfo;
     blendInfo.reset();
-    this->flushBlend(blendInfo);
+    this->flushBlend(blendInfo, GrSwizzle::RGBA());
     this->flushColorWrite(true);
     this->flushDrawFace(GrPipelineBuilder::kBoth_DrawFace);
     this->flushHWAAState(dstRT, false);
diff --git a/src/gpu/gl/GrGLGpu.h b/src/gpu/gl/GrGLGpu.h
index 532a864f07..cdd8a38c66 100644
--- a/src/gpu/gl/GrGLGpu.h
+++ b/src/gpu/gl/GrGLGpu.h
@@ -26,6 +26,7 @@
 
 class GrPipeline;
 class GrNonInstancedVertices;
+class GrSwizzle;
 
 #ifdef SK_DEVELOPER
 #define PROGRAM_CACHE_STATS
@@ -199,8 +200,7 @@ private:
                        const GrNonInstancedVertices& vertices,
                        size_t* indexOffsetInBytes);
 
-    // Subclasses should call this to flush the blend state.
-    void flushBlend(const GrXferProcessor::BlendInfo& blendInfo);
+    void flushBlend(const GrXferProcessor::BlendInfo& blendInfo, const GrSwizzle&);
 
     bool hasExtension(const char* ext) const { return fGLContext->hasExtension(ext); }
 
diff --git a/src/gpu/gl/GrGLProgramDesc.cpp b/src/gpu/gl/GrGLProgramDesc.cpp
index 45e01e7c84..4c95e2b532 100644
--- a/src/gpu/gl/GrGLProgramDesc.cpp
+++ b/src/gpu/gl/GrGLProgramDesc.cpp
@@ -46,7 +46,7 @@ static void add_texture_key(GrProcessorKeyBuilder* b, const GrProcessor& proc,
  * function because it is hairy, though FPs do not have attribs, and GPs do not have transforms
  */
 static bool gen_meta_key(const GrProcessor& proc,
-                         const GrGLCaps& caps,
+                         const GrGLSLCaps& glslCaps,
                          uint32_t transformKey,
                          GrProcessorKeyBuilder* b) {
     size_t processorKeySize = b->size();
@@ -58,7 +58,7 @@ static bool gen_meta_key(const GrProcessor& proc,
         return false;
     }
 
-    add_texture_key(b, proc, *caps.glslCaps());
+    add_texture_key(b, proc, glslCaps);
 
     uint32_t* key = b->add32n(2);
     key[0] = (classID << 16) | SkToU32(processorKeySize);
@@ -68,25 +68,24 @@ static bool gen_meta_key(const GrProcessor& proc,
 
 static bool gen_frag_proc_and_meta_keys(const GrPrimitiveProcessor& primProc,
                                         const GrFragmentProcessor& fp,
-                                        const GrGLCaps& caps,
+                                        const GrGLSLCaps& glslCaps,
                                         GrProcessorKeyBuilder* b) {
     for (int i = 0; i < fp.numChildProcessors(); ++i) {
-        if (!gen_frag_proc_and_meta_keys(primProc, fp.childProcessor(i), caps, b)) {
+        if (!gen_frag_proc_and_meta_keys(primProc, fp.childProcessor(i), glslCaps, b)) {
             return false;
         }
     }
 
-    fp.getGLSLProcessorKey(*caps.glslCaps(), b);
+    fp.getGLSLProcessorKey(glslCaps, b);
 
-    //**** use glslCaps here?
-    return gen_meta_key(fp, caps, primProc.getTransformKey(fp.coordTransforms(),
-                                                           fp.numTransformsExclChildren()), b);
+    return gen_meta_key(fp, glslCaps, primProc.getTransformKey(fp.coordTransforms(),
+                                                               fp.numTransformsExclChildren()), b);
 }
 
 bool GrGLProgramDescBuilder::Build(GrProgramDesc* desc,
                                    const GrPrimitiveProcessor& primProc,
                                    const GrPipeline& pipeline,
-                                   const GrGLGpu* gpu) {
+                                   const GrGLSLCaps& glslCaps) {
     // The descriptor is used as a cache key. Thus when a field of the
     // descriptor will not affect program generation (because of the attribute
     // bindings in use or other descriptor field settings) it should be set
@@ -101,25 +100,23 @@ bool GrGLProgramDescBuilder::Build(GrProgramDesc* desc,
 
     GrProcessorKeyBuilder b(&glDesc->key());
 
-    primProc.getGLSLProcessorKey(*gpu->glCaps().glslCaps(), &b);
-    //**** use glslCaps here?
-    if (!gen_meta_key(primProc, gpu->glCaps(), 0, &b)) {
+    primProc.getGLSLProcessorKey(glslCaps, &b);
+    if (!gen_meta_key(primProc, glslCaps, 0, &b)) {
         glDesc->key().reset();
         return false;
     }
 
     for (int i = 0; i < pipeline.numFragmentProcessors(); ++i) {
         const GrFragmentProcessor& fp = pipeline.getFragmentProcessor(i);
-        if (!gen_frag_proc_and_meta_keys(primProc, fp, gpu->glCaps(), &b)) {
+        if (!gen_frag_proc_and_meta_keys(primProc, fp, glslCaps, &b)) {
             glDesc->key().reset();
             return false;
         }
     }
 
     const GrXferProcessor& xp = pipeline.getXferProcessor();
-    xp.getGLSLProcessorKey(*gpu->glCaps().glslCaps(), &b);
-    //**** use glslCaps here?
-    if (!gen_meta_key(xp, gpu->glCaps(), 0, &b)) {
+    xp.getGLSLProcessorKey(glslCaps, &b);
+    if (!gen_meta_key(xp, glslCaps, 0, &b)) {
         glDesc->key().reset();
         return false;
     }
@@ -139,6 +136,9 @@ bool GrGLProgramDescBuilder::Build(GrProgramDesc* desc,
         header->fFragPosKey = 0;
     }
 
+    header->fOutputSwizzle =
+        glslCaps.configOutputSwizzle(pipeline.getRenderTarget()->config()).asKey();
+
     if (pipeline.ignoresCoverage()) {
         header->fIgnoresCoverage = 1;
     } else {
diff --git a/src/gpu/gl/GrGLProgramDesc.h b/src/gpu/gl/GrGLProgramDesc.h
index 7ce79ecae9..0ebf6a228e 100644
--- a/src/gpu/gl/GrGLProgramDesc.h
+++ b/src/gpu/gl/GrGLProgramDesc.h
@@ -52,14 +52,13 @@ public:
      *                        general draw information, as well as the specific color, geometry,
      *                        and coverage stages which will be used to generate the GL Program for
      *                        this optstate.
-     * @param GrGLGpu  A GL Gpu, the caps and Gpu object are used to output processor specific
-     *                 parts of the descriptor.
+     * @param GrGLSLCaps     Capabilities of the GLSL backend.
      * @param GrProgramDesc  The built and finalized descriptor
      **/
     static bool Build(GrProgramDesc*,
                       const GrPrimitiveProcessor&,
                       const GrPipeline&,
-                      const GrGLGpu*);
+                      const GrGLSLCaps&);
 };
 
 #endif
diff --git a/src/gpu/gl/builders/GrGLProgramBuilder.cpp b/src/gpu/gl/builders/GrGLProgramBuilder.cpp
index 97fcce59b7..4360f7858d 100644
--- a/src/gpu/gl/builders/GrGLProgramBuilder.cpp
+++ b/src/gpu/gl/builders/GrGLProgramBuilder.cpp
@@ -10,6 +10,7 @@
 #include "GrAutoLocaleSetter.h"
 #include "GrCoordTransform.h"
 #include "GrGLProgramBuilder.h"
+#include "GrSwizzle.h"
 #include "GrTexture.h"
 #include "SkRTConf.h"
 #include "SkTraceEvent.h"
@@ -95,6 +96,7 @@ bool GrGLProgramBuilder::emitAndInstallProcs(GrGLSLExpr4* inputColor, GrGLSLExpr
                                   inputCoverage);
     this->emitAndInstallXferProc(this->pipeline().getXferProcessor(), *inputColor, *inputCoverage,
                                  this->pipeline().ignoresCoverage());
+    this->emitFSOutputSwizzle(this->pipeline().getXferProcessor().hasSecondaryOutput());
     return true;
 }
 
@@ -262,6 +264,22 @@ void GrGLProgramBuilder::emitAndInstallXferProc(const GrXferProcessor& 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());
 }
diff --git a/src/gpu/gl/builders/GrGLProgramBuilder.h b/src/gpu/gl/builders/GrGLProgramBuilder.h
index cbec5a9863..70cfad5633 100644
--- a/src/gpu/gl/builders/GrGLProgramBuilder.h
+++ b/src/gpu/gl/builders/GrGLProgramBuilder.h
@@ -92,6 +92,7 @@ private:
                                 const GrGLSLExpr4& colorIn,
                                 const GrGLSLExpr4& coverageIn,
                                 bool ignoresCoverage);
+    void emitFSOutputSwizzle(bool hasSecondaryOutput);
 
     void verify(const GrPrimitiveProcessor&);
     void verify(const GrXferProcessor&);
diff --git a/src/gpu/glsl/GrGLSLCaps.h b/src/gpu/glsl/GrGLSLCaps.h
index eba9602e5a..136bef466c 100755
--- a/src/gpu/glsl/GrGLSLCaps.h
+++ b/src/gpu/glsl/GrGLSLCaps.h
@@ -108,12 +108,17 @@ public:
     /**
      * Given a texture's config, this determines what swizzle must be appended to accesses to the
      * texture in generated shader code. Swizzling may be implemented in texture parameters or a
-     * sampler rather than in the shader. In this case the shader swizzle will always be "rgba".
+     * sampler rather than in the shader. In this case the returned swizzle will always be "rgba".
      */
     const GrSwizzle& configTextureSwizzle(GrPixelConfig config) const {
         return fConfigTextureSwizzle[config];
     }
 
+    /** Swizzle that should occur on the fragment shader outputs for a given config. */
+    const GrSwizzle& configOutputSwizzle(GrPixelConfig config) const {
+        return fConfigOutputSwizzle[config];
+    }
+
     GrGLSLGeneration generation() const { return fGLSLGeneration; }
 
     /**
@@ -150,6 +155,7 @@ private:
     AdvBlendEqInteraction fAdvBlendEqInteraction;
 
     GrSwizzle fConfigTextureSwizzle[kGrPixelConfigCnt];
+    GrSwizzle fConfigOutputSwizzle[kGrPixelConfigCnt];
 
     friend class GrGLCaps;  // For initialization.