Refactor how we store and use samplers in Ganesh

src/gpu/glsl/GrGLSLSampler.h

Index: src/gpu/glsl/GrGLSLSampler.h
diff --git a/src/gpu/glsl/GrGLSLSampler.h b/src/gpu/glsl/GrGLSLSampler.h
index 0fc67a9c937cd605ae45659f22b031e118ca76b0..694c03a40f5f14d31613439768faeba325da3ea2 100644
--- a/src/gpu/glsl/GrGLSLSampler.h
+++ b/src/gpu/glsl/GrGLSLSampler.h
@@ -9,27 +9,28 @@
 #define GrGLSLSampler_DEFINED
 
 #include "GrTypes.h"
-#include "SkTArray.h"
-#include "glsl/GrGLSLProgramDataManager.h"
+#include "GrTypesPriv.h"
+#include "SkString.h"
 
 class GrGLSLSampler {
 public:
-    typedef GrGLSLProgramDataManager::UniformHandle UniformHandle;
-    typedef SkTArray<GrGLSLSampler> SamplerArray;
-
-    GrGLSLSampler(UniformHandle uniform, GrPixelConfig config)
-        : fSamplerUniform(uniform)
+    explicit GrGLSLSampler(uint32_t visibility, GrPixelConfig config)
+        : fVisibility(visibility)
         , fConfig(config) {
         SkASSERT(kUnknown_GrPixelConfig != fConfig);
     }
 
+    uint32_t visibility() const { return fVisibility; }
     GrPixelConfig config() const { return fConfig; }
+    virtual GrSLType type() const = 0;
+
+    // Returns the string to be used for the sampler in glsl sample functions (texture, texture2D,
+    // etc.)
+    virtual const char* getSamplerFunctionName() const = 0;

[Chris Dalton, 2016/04/13 21:56:40]

This function is a bit problematic because there is nothing to return for
kSamplerBuffer. It appears to be used for doing a filtered, wrapped, mipmapped
sampling of a 2d image, which of course doesn't apply to a 1d texel array.

The functionality used to have a name more indicative of that, i.e.
GrGLSLGetTexture2DFunctionName. There it was easy enough to just assert on
GrSLTypeIs2DTextureType(). Maybe we could just change the name to make it clear
we are asking for the 2d texture sample name?

(Right now it is an error for kSamplerBuffer samplers to call
"appendTextureLookup" and they have to use "appendTexelFetch" instead.
appendTexelFetch can be used on any sampler.)

[egdaniel, 2016/04/13 23:44:45]

Okay so this function may just have been poorly named, mostly cause I wasn't
really sure what to call it. GrGLSLGetTexture2DFunctionName still exists. What
this functions returns for GL is the name of the variable for the sampler2D. In
vulkan, I may have a sampler2D variable or I could have a separate sampler and
texture. In the later case I need to "combine" the sampler and texture together
to make a sampler2D object. So the final functino call looks something like
"texture2D(sampler2D('samplerName', 'textureName'), ...);" This function would
return "sampler2D('samplerName', 'textureName')". Or in GL's case
"sampler2DName".

So maybe this should be something like getSampler2DName(), but this function
also works for sampler2DRect and such so I would prefer a name that was more
general, but still specific to what it's used for.

[egdaniel, 2016/04/13 23:51:43]

Also I just noticed I didn't upload the change that had the appendTexelFetch in
it. I'll have to see how the Vulkan variables are used for buffers, but I'm
thinking I may need a similar function to this for texelFetch to get the sampler
name. In GL it will probably just call directly the function above (aka just
gets the normal variable name). For vulkan I'll probably have to do some branch
of if it is a normal sampler (call function above) or do whatever vulkan does
for buffer samplers.

 
 private:
-    UniformHandle fSamplerUniform;
+    uint32_t      fVisibility;
     GrPixelConfig fConfig;
-
-    friend class GrGLSLShaderBuilder;
 };
 
 #endif