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

2 files changed, 85 insertions, 58 deletions

diff --git a/include/gpu/GrBackendEffectFactory.h b/include/gpu/GrBackendEffectFactory.h
index 32f14f2746..ef9e436401 100644
--- a/include/gpu/GrBackendEffectFactory.h
+++ b/include/gpu/GrBackendEffectFactory.h
@@ -14,22 +14,12 @@
 #include "SkTypes.h"
 #include "SkTArray.h"
 
-/** Given a GrEffect of a particular type, creates the corresponding graphics-backend-specific
-    effect object. Also tracks equivalence of shaders generated via a key. Each factory instance
-    is assigned a generation ID at construction. The ID of the return of GrEffect::getFactory()
-    is used as a type identifier. Thus a GrEffect subclass must return a singleton from
-    getFactory(). GrEffect subclasses should use the derived class GrTBackendEffectFactory that is
-    templated on the GrEffect subclass as their factory object. It requires that the GrEffect
-    subclass has a nested class (or typedef) GLEffect which is its GL implementation and a subclass
-    of GrGLEffect.
- */
-
 class GrGLEffect;
 class GrGLCaps;
 class GrDrawEffect;
 
 /**
- * Used by effects to build their keys. It incorpates each per-effect key into a larger shader key.
+ * Used by effects to build their keys. It incorporates each per-effect key into a larger shader key.
  */
 class GrEffectKeyBuilder {
 public:
@@ -42,6 +32,14 @@ public:
         fData->push_back_n(4, reinterpret_cast<uint8_t*>(&v));
     }
 
+    /** Inserts count uint32_ts into the key. The returned pointer is only valid until the next
+        add*() call. */
+    uint32_t* SK_WARN_UNUSED_RESULT add32n(int count) {
+        SkASSERT(count > 0);
+        fCount += count;
+        return reinterpret_cast<uint32_t*>(fData->push_back_n(4 * count));
+    }
+
     size_t size() const { return sizeof(uint32_t) * fCount; }
 
 private:
@@ -49,43 +47,74 @@ private:
     int fCount;                     // number of uint32_ts added to fData by the effect.
 };
 
+/**
+ * Given a GrEffect of a particular type, creates the corresponding graphics-backend-specific
+ * effect object. It also tracks equivalence of shaders generated via a key. The factory for an
+ * effect is accessed via GrEffect::getFactory(). Each factory instance is assigned an ID at
+ * construction. The ID of GrEffect::getFactory() is used as a type identifier. Thus, a GrEffect
+ * subclass must always return the same object from getFactory() and that factory object must be
+ * unique to the GrEffect subclass (and unique from any further derived subclasses).
+ *
+ * Rather than subclassing this class themselves, it is recommended that GrEffect authors use 
+ * the templated subclass GrTBackendEffectFactory by writing their getFactory() method as:
+ *
+ * const GrBackendEffectFactory& MyEffect::getFactory() const {
+ *     return GrTBackendEffectFactory<MyEffect>::getInstance();
+ * }
+ *
+ * Using GrTBackendEffectFactory places a few constraints on the effect. See that class's comments.
+ */
 class GrBackendEffectFactory : SkNoncopyable {
 public:
     typedef uint32_t EffectKey;
 
-    virtual bool getGLEffectKey(const GrDrawEffect&, const GrGLCaps&, GrEffectKeyBuilder*) const = 0;
+    /** 
+     * Generates an effect's key. The key is based on the aspects of the GrEffect object's
+     * configuration that affect GLSL code generation. Two GrEffect instances that would cause
+     * this->createGLInstance()->emitCode() to produce different code must produce different keys.
+     */
+    virtual void getGLEffectKey(const GrDrawEffect&, const GrGLCaps&, GrEffectKeyBuilder*) const = 0;
+
+    /**
+     * Creates a GrGLEffect instance that is used both to generate code for the GrEffect in a GLSL
+     * program and to manage updating uniforms for the program when it is used.
+     */
     virtual GrGLEffect* createGLInstance(const GrDrawEffect&) const = 0;
 
-    bool operator ==(const GrBackendEffectFactory& b) const {
-        return fEffectClassID == b.fEffectClassID;
-    }
-    bool operator !=(const GrBackendEffectFactory& b) const {
-        return !(*this == b);
-    }
-
+    /**
+     * Produces a human-reable name for the effect.
+     */
     virtual const char* name() const = 0;
 
+    /**
+     * A unique value for every instance of this factory. It is automatically incorporated into the
+     * effect's key. This allows keys generated by getGLEffectKey() to only be unique within a
+     * GrEffect subclass and not necessarily across subclasses.
+     */
+    uint32_t effectClassID() const { return fEffectClassID; }
+
 protected:
+    GrBackendEffectFactory() : fEffectClassID(GenID()) {}
+    virtual ~GrBackendEffectFactory() {}
+
+private:
     enum {
         kIllegalEffectClassID = 0,
     };
 
-    GrBackendEffectFactory() {
-        fEffectClassID = kIllegalEffectClassID;
-    }
-    virtual ~GrBackendEffectFactory() {}
-
-    static int32_t GenID() {
+    static uint32_t GenID() {
         // fCurrEffectClassID has been initialized to kIllegalEffectClassID. The
         // atomic inc returns the old value not the incremented value. So we add
         // 1 to the returned value.
-        int32_t id = sk_atomic_inc(&fCurrEffectClassID) + 1;
+        uint32_t id = static_cast<uint32_t>(sk_atomic_inc(&fCurrEffectClassID)) + 1;
+        if (!id) {
+            SkFAIL("This should never wrap as it should only be called once for each GrEffect "
+                   "subclass.");
+        }
         return id;
     }
 
-    int32_t fEffectClassID;
-
-private:
+    const uint32_t fEffectClassID;
     static int32_t fCurrEffectClassID;
 };
 
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