Added function CreateFrom2Procs() in new namespace GrXfermodeFragmentProcessor

include/core/SkComposeShader.h

Index: include/core/SkComposeShader.h
diff --git a/include/core/SkComposeShader.h b/include/core/SkComposeShader.h
index 41be197eb7769f766a77da2ddb866a9b2df43346..13163dcdf2df7aecd8424496de85af353f363264 100644
--- a/include/core/SkComposeShader.h
+++ b/include/core/SkComposeShader.h
@@ -88,4 +88,35 @@ private:
     typedef SkShader INHERITED;
 };
 
+#if SK_SUPPORT_GPU

[bsalomon, 2015/09/08 15:10:57]

I don't think we should be exposing this object via this header file (or really
any header file).

Can you GrComposeEffect to GrXfermodeFragmentProcessor.cpp? Also, can you remove
the word "effect". It's use in older processors is legacy we want to drop. Maybe
GrComposeTwoFragmentProcessor or something like that.

[wangyix, 2015/09/09 17:32:35]

GrComposeEffect::onCreateGLInstance() needs GrGLComposeEffect's class
definition. How should I expose GrGLComposeEffect to it can be used in
GrXfermodeFragmentProcessor.cpp?    

[bsalomon, 2015/09/09 17:34:56]

move it there too?

[wangyix, 2015/09/09 17:41:08]

Is it weird to have GL-specific stuff in GrXfermodeFragmentProcessor.cpp?

+
+#include "SkString.h"

[tomhudson, 2015/09/02 20:02:36]

Move the #includes to the top, please.

[egdaniel, 2015/09/02 20:12:44]

So I'm not sure what our official style is, but it very common in our code for
these "SkEffect" classes which have GPU implementations in them surrounded by
#if SK_SUPPORT_GPU to have the includes needed only by the gpu down with the
code.

But I'm just saying what is done in practice, not necessarily what our style is.

+#include "../gpu/GrFragmentProcessor.h"
+
+/////////////////////////////////////////////////////////////////////
+
+class GrComposeEffect : public GrFragmentProcessor {
+public:
+    GrComposeEffect(const GrFragmentProcessor* fpA, const GrFragmentProcessor* fpB,
+                    SkXfermode::Mode mode);
+    const char* name() const override { return "ComposeShader"; }
+    void onGetGLProcessorKey(const GrGLSLCaps& caps, GrProcessorKeyBuilder* b) const override;
+
+    SkXfermode::Mode getMode() const { return fMode; }
+
+protected:
+    bool onIsEqual(const GrFragmentProcessor&) const override;
+    void onComputeInvariantOutput(GrInvariantOutput* inout) const override;
+
+private:
+    GrGLFragmentProcessor* onCreateGLInstance() const override;
+
+    SkXfermode::Mode fMode;
+
+    GR_DECLARE_FRAGMENT_PROCESSOR_TEST;
+
+    typedef GrFragmentProcessor INHERITED;
+};
+#endif
+
 #endif