Step towards variable length effect keys.

include/gpu/GrTBackendEffectFactory.h

 /*
  * Copyright 2012 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef GrTBackendEffectFactory_DEFINED
 #define GrTBackendEffectFactory_DEFINED
 
 #include "GrBackendEffectFactory.h"
 #include "GrDrawEffect.h"
 #include "gl/GrGLProgramEffects.h"
 
 /**
  * Implements GrBackendEffectFactory for a GrEffect subclass as a singleton.
  */
 template <typename EffectClass>
 class GrTBackendEffectFactory : public GrBackendEffectFactory {
 
 public:
     typedef typename EffectClass::GLEffect GLEffect;
 
     /** Returns a human-readable name that is accessible via GrEffect or
         GrGLEffect and is consistent between the two of them.
      */
     virtual const char* name() const SK_OVERRIDE { return EffectClass::Name(); }
 
-    /** Returns a value that identifies the GLSL shader code generated by
-        a GrEffect. This enables caching of generated shaders. Part of the
-        id identifies the GrEffect subclass. The remainder is based
-        on the aspects of the GrEffect object's configuration that affect
-        GLSL code generation. */
-    virtual EffectKey glEffectKey(const GrDrawEffect& drawEffect,
-                                  const GrGLCaps& caps) const SK_OVERRIDE {
+    /** Generates an effect's key. This enables caching of generated shaders. Part of the
+        id identifies the GrEffect subclass. The remainder is based on the aspects of the
+        GrEffect object's configuration that affect GLSL code generation. If this fails
+        then program generation should be aborted. Failure occurs if the effect uses more
+        transforms, attributes, or textures than the key has space for. */
+    virtual bool getGLEffectKey(const GrDrawEffect& drawEffect,
+                                const GrGLCaps& caps,
+                                GrEffectKeyBuilder* b) const SK_OVERRIDE {
         SkASSERT(kIllegalEffectClassID != fEffectClassID);
         EffectKey effectKey = GLEffect::GenKey(drawEffect, caps);
         EffectKey textureKey = GrGLProgramEffects::GenTextureKey(drawEffect, caps);
         EffectKey transformKey = GrGLProgramEffects::GenTransformKey(drawEffect);
         EffectKey attribKey = GrGLProgramEffects::GenAttribKey(drawEffect);

[jvanverth1, 2014/07/11 15:33:12]

It took me a while to figure out what this is doing (the comment "Failure
occurs..." above helped, but only as a guide). Maybe an additional comment?

-#ifdef SK_DEBUG
-        static const EffectKey kIllegalEffectKeyMask = (uint16_t) (~((1U << kEffectKeyBits) - 1));
-        SkASSERT(!(kIllegalEffectKeyMask & effectKey));
+        static const uint32_t kMetaKeyInvalidMask = ~((uint32_t) SK_MaxU16);
+        if ((textureKey | transformKey | attribKey | fEffectClassID) & kMetaKeyInvalidMask) {
+            return false;
+        }
 
-        static const EffectKey kIllegalTextureKeyMask = (uint16_t) (~((1U << kTextureKeyBits) - 1));
-        SkASSERT(!(kIllegalTextureKeyMask & textureKey));
-
-        static const EffectKey kIllegalTransformKeyMask = (uint16_t) (~((1U << kTransformKeyBits) - 1));
-        SkASSERT(!(kIllegalTransformKeyMask & transformKey));
-
-        static const EffectKey kIllegalAttribKeyMask = (uint16_t) (~((1U << kAttribKeyBits) - 1));
-        SkASSERT(!(kIllegalAttribKeyMask & textureKey));
-
-        static const EffectKey kIllegalClassIDMask = (uint16_t) (~((1U << kClassIDBits) - 1));
-        SkASSERT(!(kIllegalClassIDMask & fEffectClassID));
-#endif
-        return (fEffectClassID << (kEffectKeyBits+kTextureKeyBits+kTransformKeyBits+kAttribKeyBits)) |
-               (attribKey << (kEffectKeyBits+kTextureKeyBits+kTransformKeyBits)) |
-               (transformKey << (kEffectKeyBits+kTextureKeyBits)) |
-               (textureKey << kEffectKeyBits) |
-               (effectKey);
+        // effectKey must be first because it is what will be returned by
+        // GrGLProgramDesc::EffectKeyProvider and passed to the GrGLEffect as its key. 
+        b->add32(effectKey);
+        b->add32(textureKey << 16 | transformKey);
+        b->add32(fEffectClassID << 16 | attribKey);
+        return true;
     }
 
     /** Returns a new instance of the appropriate *GL* implementation class
         for the given GrEffect; caller is responsible for deleting
         the object. */
     virtual GrGLEffect* createGLInstance(const GrDrawEffect& drawEffect) const SK_OVERRIDE {
         return SkNEW_ARGS(GLEffect, (*this, drawEffect));
     }
 
     /** This class is a singleton. This function returns the single instance.
      */
     static const GrBackendEffectFactory& getInstance() {
         static SkAlignedSTStorage<1, GrTBackendEffectFactory> gInstanceMem;
         static const GrTBackendEffectFactory* gInstance;
         if (!gInstance) {
             gInstance = SkNEW_PLACEMENT(gInstanceMem.get(),
                                         GrTBackendEffectFactory);
         }
         return *gInstance;
     }
 
 protected:
     GrTBackendEffectFactory() {
         fEffectClassID = GenID();
     }
 };
 
 #endif