Start hooking shaders into SkRasterPipelineBlitter.

Here first just the simplest, constant-color shaders.

BUG=skia:

GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=4743

Change-Id: I92c6523660e21a1e2aa353524570230282ba5dfe
Reviewed-on: https://skia-review.googlesource.com/4743
Reviewed-by: Brian Osman <brianosman@google.com>
Commit-Queue: Mike Klein <mtklein@chromium.org>

1 files changed, 15 insertions, 1 deletions

diff --git a/include/core/SkShader.h b/include/core/SkShader.h
index 5e21c28331..48e84192ab 100644
--- a/include/core/SkShader.h
+++ b/include/core/SkShader.h
@@ -18,9 +18,11 @@
 
 class SkColorFilter;
 class SkColorSpace;
+class SkFallbackAlloc;
 class SkImage;
 class SkPath;
 class SkPicture;
+class SkRasterPipeline;
 class GrContext;
 class GrFragmentProcessor;
 
@@ -98,6 +100,12 @@ public:
     virtual bool isOpaque() const { return false; }
 
     /**
+     *  Returns true if the shader is guaranteed to produce only a single color.
+     *  Subclasses can override this to allow loop-hoisting optimization.
+     */
+    virtual bool isConstant() const { return false; }
+
+    /**
      *  ContextRec acts as a parameter bundle for creating Contexts.
      */
     struct ContextRec {
@@ -399,7 +407,7 @@ public:
 
     //////////////////////////////////////////////////////////////////////////
     //  Factory methods for stock shaders
-    
+
     /**
      *  Call this to create a new "empty" shader, that will not draw anything.
      */
@@ -467,6 +475,8 @@ public:
     SK_DEFINE_FLATTENABLE_TYPE(SkShader)
     SK_DECLARE_FLATTENABLE_REGISTRAR_GROUP()
 
+    bool appendStages(SkRasterPipeline*, SkColorSpace*, SkFallbackAlloc*) const;
+
 protected:
     void flatten(SkWriteBuffer&) const override;
 
@@ -498,6 +508,10 @@ protected:
         return nullptr;
     }
 
+    virtual bool onAppendStages(SkRasterPipeline*, SkColorSpace*, SkFallbackAlloc*) const {
+        return false;
+    }
+
 private:
     // This is essentially const, but not officially so it can be modified in
     // constructors.