Add interface to SkXfermode to return a GrEffect and blend coeffs.

Review URL: https://codereview.chromium.org/13097006

git-svn-id: http://skia.googlecode.com/svn/trunk@8412 2bbb7eff-a529-9590-31e7-b0007b416f81

include/core/SkXfermode.h

@@ -13,6 +13,8 @@
 #include "SkFlattenable.h"
 #include "SkColor.h"
 
+class GrContext;
+class GrEffectRef;
 class SkString;
 
 /** \class SkXfermode
@@ -74,7 +76,7 @@ public:
 
     /**
      *  The same as calling xfermode->asCoeff(..), except that this also checks
-     *  if the xfermode is NULL, and if so, treats its as kSrcOver_Mode.
+     *  if the xfermode is NULL, and if so, treats it as kSrcOver_Mode.
      */
     static bool AsCoeff(const SkXfermode*, Coeff* src, Coeff* dst);
 
@@ -136,7 +138,7 @@ public:
 
     /**
      *  The same as calling xfermode->asMode(mode), except that this also checks
-     *  if the xfermode is NULL, and if so, treats its as kSrcOver_Mode.
+     *  if the xfermode is NULL, and if so, treats it as kSrcOver_Mode.
      */
     static bool AsMode(const SkXfermode*, Mode* mode);
 
@@ -181,6 +183,22 @@ public:
         return AsMode(xfer, mode);
     }
 
+    /** A subclass may implement this factory function to work with the GPU backend. It is legal
+        to call this with all but the context param NULL to simply test the return value. effect,
+        src, and dst must all be NULL or all non-NULL. If effect is non-NULL then the xfermode may
+        optionally allocate an effect to return and the caller as *effect. The caller will install
+        it and own a ref to it. Since the xfermode may or may not assign *effect, the caller should
+        set *effect to NULL beforehand. If the function returns true then the src and dst coeffs
+        will be applied to the draw regardless of whether an effect was returned.
+     */
+    virtual bool asNewEffect(GrContext*, GrEffectRef** effect, Coeff* src, Coeff* dst) const;
+
+    /**
+     *  The same as calling xfermode->asNewEffect(...), except that this also checks if the xfermode
+     *  is NULL, and if so, treats it as kSrcOver_Mode.
+     */
+    static bool AsNewEffect(SkXfermode*, GrContext*, GrEffectRef** effect, Coeff* src, Coeff* dst);
+
     SkDEVCODE(virtual void toString(SkString* str) const = 0;)
     SK_DECLARE_FLATTENABLE_REGISTRAR_GROUP()
 protected:

src/core/SkXfermode.cpp

@@ -680,6 +680,22 @@ bool SkXfermode::asMode(Mode* mode) const {
     return false;
 }
 
+bool SkXfermode::asNewEffect(GrContext*, GrEffectRef**, Coeff*, Coeff*) const {
+    return false;
+}
+
+bool SkXfermode::AsNewEffect(SkXfermode* xfermode,
+                             GrContext* context,
+                             GrEffectRef** effect,
+                             Coeff* src,
+                             Coeff* dst) {
+    if (NULL == xfermode) {
+        return ModeAsCoeff(kSrcOver_Mode, src, dst);
+    } else {
+        return xfermode->asNewEffect(context, effect, src, dst);
+    }
+}
+
 SkPMColor SkXfermode::xferColor(SkPMColor src, SkPMColor dst) const{
     // no-op. subclasses should override this
     return dst;
@@ -958,6 +974,10 @@ public:
         return true;
     }
 
+    virtual bool asNewEffect(GrContext*, GrEffectRef**, Coeff* src, Coeff* dst) const SK_OVERRIDE {
+        return this->asCoeff(src, dst);
+    }
+
     SK_DEVELOPER_TO_STRING()
     SK_DECLARE_PUBLIC_FLATTENABLE_DESERIALIZATION_PROCS(SkProcCoeffXfermode)
 

src/gpu/SkGpuDevice.cpp

@@ -484,13 +484,15 @@ inline bool skPaint2GrPaintNoShader(SkGpuDevice* dev,
     SkXfermode::Coeff dm = SkXfermode::kISA_Coeff;
 
     SkXfermode* mode = skPaint.getXfermode();
-    if (mode) {
-        if (!mode->asCoeff(&sm, &dm)) {
-            //SkDEBUGCODE(SkDebugf("Unsupported xfer mode.\n");)
+    GrEffectRef* xferEffect;
+    if (SkXfermode::AsNewEffect(mode, dev->context(), &xferEffect, &sm, &dm)) {
+        // We're not ready for xfermode effects yet
+        GrAssert(NULL == xferEffect);
+    } else {
+        //SkDEBUGCODE(SkDebugf("Unsupported xfer mode.\n");)
 #if 0
-            return false;
+        return false;
 #endif
-        }
     }
     grPaint->setBlendFunc(sk_blend_to_grblend(sm), sk_blend_to_grblend(dm));