SkLS accepts nullptr for pointer args, handles alpha accurately, has new GM

src/gpu/GrFragmentProcessor.cpp

 /*
 * Copyright 2015 Google Inc.
 *
 * Use of this source code is governed by a BSD-style license that can be
 * found in the LICENSE file.
 */
 
 #include "GrFragmentProcessor.h"
 #include "GrCoordTransform.h"
 #include "GrInvariantOutput.h"
@@ skipping 125 matching lines @@
 
 sk_sp<GrFragmentProcessor> GrFragmentProcessor::MulOutputByInputAlpha(
     sk_sp<GrFragmentProcessor> fp) {
     if (!fp) {
         return nullptr;
     }
     return GrXfermodeFragmentProcessor::MakeFromDstProcessor(std::move(fp),
                                                              SkXfermode::kDstIn_Mode);
 }
 
+sk_sp<GrFragmentProcessor> GrFragmentProcessor::PremulInput(sk_sp<GrFragmentProcessor> fp) {
+
+    class PremulInputFragmentProcessor : public GrFragmentProcessor {
+    public:
+        PremulInputFragmentProcessor() {
+            this->initClassID<PremulInputFragmentProcessor>();
+        }
+
+        const char* name() const override { return "PremultiplyInput"; }
+
+    private:
+        GrGLSLFragmentProcessor* onCreateGLSLInstance() const override {
+            class GLFP : public GrGLSLFragmentProcessor {
+            public:
+                void emitCode(EmitArgs& args) override {
+                    GrGLSLFPFragmentBuilder* fragBuilder = args.fFragBuilder;
+
+                    fragBuilder->codeAppendf("%s = %s;", args.fOutputColor, args.fInputColor);
+                    fragBuilder->codeAppendf("%s.rgb *= %s.a;", args.fOutputColor, args.fInputColor);

[egdaniel, 2016/07/14 03:22:47]

100 chars

[dvonbeck, 2016/07/14 14:30:33]

This was fixed in patch set 6

+                }
+            };
+            return new GLFP;
+        }
+
+        void onGetGLSLProcessorKey(const GrGLSLCaps&, GrProcessorKeyBuilder*) const override {}
+
+        bool onIsEqual(const GrFragmentProcessor&) const override { return true; }
+
+        void onComputeInvariantOutput(GrInvariantOutput* inout) const override {
+            inout->mulByUnknownFourComponents();

[egdaniel, 2016/07/14 03:22:47]

This doesn't seem right. I feel like it should be able to tell some info if some
of the values are known. For example if we know the alpha is opaque then we
should do nothing to the inout. Knowing that the color stays opaque can
definitely be useful to us in our optimizations later on.

[dvonbeck, 2016/07/14 14:30:33]

Adding appropriate invariant option in separate CL.

+        }
+    };
+    if (!fp) {
+        return nullptr;
+    }
+    sk_sp<GrFragmentProcessor> fpPipeline[] = { sk_make_sp<PremulInputFragmentProcessor>(), fp};
+    return GrFragmentProcessor::RunInSeries(fpPipeline, 2);
+}
+
 sk_sp<GrFragmentProcessor> GrFragmentProcessor::MulOutputByInputUnpremulColor(
     sk_sp<GrFragmentProcessor> fp) {
 
     class PremulFragmentProcessor : public GrFragmentProcessor {
     public:
         PremulFragmentProcessor(sk_sp<GrFragmentProcessor> processor) {
             this->initClassID<PremulFragmentProcessor>();
             this->registerChildProcessor(processor);
         }
 
@@ skipping 214 matching lines @@
     } else {
         series += firstIdx;
         cnt -= firstIdx;
     }
 
     if (1 == cnt) {
         return series[0];
     }
     return sk_sp<GrFragmentProcessor>(new SeriesFragmentProcessor(series, cnt));
 }