Add XferProcessor factory in GrPaint and GrDrawState.

include/core/SkXfermode.h

 
 /*
  * Copyright 2006 The Android Open Source Project
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 
 #ifndef SkXfermode_DEFINED
 #define SkXfermode_DEFINED
 
 #include "SkFlattenable.h"
 #include "SkColor.h"
 
 class GrFragmentProcessor;
 class GrTexture;
+class GrXPFactory;
 class SkString;
 
 /** \class SkXfermode
  *
  *  SkXfermode is the base class for objects that are called to implement custom
  *  "transfer-modes" in the drawing pipeline. The static function Create(Modes)
  *  can be called to return an instance of any of the predefined subclasses as
  *  specified in the Modes enum. When an SkXfermode is assigned to an SkPaint,
  *  then objects drawn with that paint have the xfermode applied.
  *
@@ skipping 163 matching lines @@
 
     /** A subclass may implement this factory function to work with the GPU backend. It is legal
         to call this with all params NULL to simply test the return value. 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. background specifies the
         texture to use as the background for compositing, and should be accessed in the effect's
         fragment shader. If NULL, the effect should request access to destination color
         (setWillReadDstColor()), and use that in the fragment shader (builder->dstColor()).
      */
+    // TODO: Once all custom xp's have been created the background parameter will be required here.
+    //       We will always use the XPFactory if there is no background texture and the fragment if
+    //       there is one.
     virtual bool asFragmentProcessor(GrFragmentProcessor**, GrTexture* background = NULL) const;
 
-    /** Returns true if the xfermode can be expressed as coeffs (src, dst), or as an effect
-        (effect). This helper calls the asCoeff() and asFragmentProcessor() virtuals. If the
-        xfermode is NULL, it is treated as kSrcOver_Mode. It is legal to call this with all params
-        NULL to simply test the return value.  effect, src, and dst must all be NULL or all
-        non-NULL.
+    /** A subclass may implement this factory function to work with the GPU backend. It is legal
+        to call this with xpf NULL to simply test the return value. If xpf is non-NULL then the
+        xfermode may optionally allocate a factory to return to the caller as *xpf. The caller
+        will install it and own a ref to it. Since the xfermode may or may not assign *xpf, the
+        caller should set *xpf to NULL beforehand. XP's cannot use a background texture since they
+        have no coord transforms.
      */
-    static bool asFragmentProcessorOrCoeff(SkXfermode*, GrFragmentProcessor**, Coeff* src,
-                                           Coeff* dst, GrTexture* background = NULL);
+    virtual bool asXPFactory(GrXPFactory** xpf) const;
+
+    /** Returns true if the xfermode can be expressed as an xfer processor factory (xpFactory),
+        or a fragment processor. This helper calls the asCoeff(), asXPFactory(),
+        and asFragmentProcessor() virtuals. If the xfermode is NULL, it is treated as kSrcOver_Mode.
+        It is legal to call this with all params NULL to simply test the return value.
+        fp, xpf, src, and dst must all be NULL or all non-NULL.
+     */
+    static bool AsFragmentProcessorOrXPFactory(SkXfermode*, GrFragmentProcessor**,
+                                               GrXPFactory**, Coeff* src, Coeff* dst);
 
     SK_TO_STRING_PUREVIRT()
     SK_DECLARE_FLATTENABLE_REGISTRAR_GROUP()
     SK_DEFINE_FLATTENABLE_TYPE(SkXfermode)
 
 protected:
     SkXfermode() {}
     /** The default implementation of xfer32/xfer16/xferA8 in turn call this
         method, 1 color at a time (upscaled to a SkPMColor). The default
         implmentation of this method just returns dst. If performance is
         important, your subclass should override xfer32/xfer16/xferA8 directly.
 
         This method will not be called directly by the client, so it need not
         be implemented if your subclass has overridden xfer32/xfer16/xferA8
     */
     virtual SkPMColor xferColor(SkPMColor src, SkPMColor dst) const;
 
 private:
     enum {
         kModeCount = kLastMode + 1
     };
 
     typedef SkFlattenable INHERITED;
 };
 
 #endif