From 929f29a5c1bffa7f7c1b5a376351d0762b8ac561 Mon Sep 17 00:00:00 2001
From: bsalomon <bsalomon@google.com>
Date: Thu, 17 Jul 2014 07:55:11 -0700
Subject: Makes GrGLProgramDesc's key store the lengths as well as offsets of
 the effect keys.

Makes it possible to use GrBackendEffectFactories other than GrTBEF by moving meta-key generation out of GrTBEF.

Cleans up docs around GrBackendEffectFactory.

Committed: https://skia.googlesource.com/skia/+/c0ea398aff8254e31152cbb94c9ab6150428e252

R=robertphillips@google.com, jvanverth@google.com

Author: bsalomon@google.com

Review URL: https://codereview.chromium.org/379113004
---
 include/gpu/GrTBackendEffectFactory.h | 56 +++++++++++++++++------------------
 1 file changed, 27 insertions(+), 29 deletions(-)

(limited to 'include/gpu/GrTBackendEffectFactory.h')

diff --git a/include/gpu/GrTBackendEffectFactory.h b/include/gpu/GrTBackendEffectFactory.h
index cd4c0a49e9..251e8c7768 100644
--- a/include/gpu/GrTBackendEffectFactory.h
+++ b/include/gpu/GrTBackendEffectFactory.h
@@ -13,7 +13,26 @@
 #include "gl/GrGLProgramEffects.h"
 
 /**
- * Implements GrBackendEffectFactory for a GrEffect subclass as a singleton.
+ * Implements GrBackendEffectFactory for a GrEffect subclass as a singleton. This can be used by
+ * most GrEffect subclasses to implement the GrEffect::getFactory() method:
+ *
+ * const GrBackendEffectFactory& MyEffect::getFactory() const {
+ *     return GrTBackendEffectFactory<MyEffect>::getInstance();
+ * }
+ *
+ * Using this class requires that the GrEffect subclass always produces the same GrGLEffect
+ * subclass. Additionally, It adds the following requirements to the GrEffect and GrGLEffect
+ * subclasses:
+ *
+ * 1. The GrGLEffect used by GrEffect subclass MyEffect must be named or typedef'ed to
+ *    MyEffect::GLEffect.
+ * 2. MyEffect::GLEffect must have a static function:
+ *      EffectKey GenKey(const GrDrawEffect, const GrGLCaps&)
+ *    which generates a key that maps 1 to 1 with code variations emitted by
+ *    MyEffect::GLEffect::emitCode().
+ * 3. MyEffect must have a static function:
+ *      const char* Name()
+ *    which returns a human-readable name for the effect.
  */
 template <typename EffectClass>
 class GrTBackendEffectFactory : public GrBackendEffectFactory {
@@ -21,35 +40,17 @@ 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.
-     */
+    /** Returns a human-readable name for the effect. Implemented using GLEffect::Name as described
+     *  in this class's comment. */
     virtual const char* name() const SK_OVERRIDE { return EffectClass::Name(); }
 
-    /** 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,
+
+    /** Implemented using GLEffect::GenKey as described in this class's comment. */
+    virtual void 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);
-        static const uint32_t kMetaKeyInvalidMask = ~((uint32_t) SK_MaxU16);
-        if ((textureKey | transformKey | attribKey | fEffectClassID) & kMetaKeyInvalidMask) {
-            return false;
-        }
-
-        // 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
@@ -59,8 +60,7 @@ public:
         return SkNEW_ARGS(GLEffect, (*this, drawEffect));
     }
 
-    /** This class is a singleton. This function returns the single instance.
-     */
+    /** This class is a singleton. This function returns the single instance. */
     static const GrBackendEffectFactory& getInstance() {
         static SkAlignedSTStorage<1, GrTBackendEffectFactory> gInstanceMem;
         static const GrTBackendEffectFactory* gInstance;
@@ -72,9 +72,7 @@ public:
     }
 
 protected:
-    GrTBackendEffectFactory() {
-        fEffectClassID = GenID();
-    }
+    GrTBackendEffectFactory() {}
 };
 
 #endif
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