Revert "Revert "Removing ref counting from GrXPFactory.""

This reverts commit 003312a211e65f35e402d6fe80a32e23d4c94ac4.

Change-Id: Ib41065e5c356d1dd99e70fa10611ac6756c2b79d
Reviewed-on: https://skia-review.googlesource.com/6803
Reviewed-by: Brian Salomon <bsalomon@google.com>
Commit-Queue: Brian Salomon <bsalomon@google.com>

1 files changed, 20 insertions, 44 deletions

diff --git a/include/gpu/GrXferProcessor.h b/include/gpu/GrXferProcessor.h
index e97c0b92c7..17cd2c7bf3 100644
--- a/include/gpu/GrXferProcessor.h
+++ b/include/gpu/GrXferProcessor.h
@@ -289,8 +289,22 @@ GR_MAKE_BITFIELD_OPS(GrXferProcessor::OptFlags);
  * Before the XP is created, the XPF is able to answer queries about what functionality the XPs it
  * creates will have. For example, can it create an XP that supports RGB coverage or will the XP
  * blend with the destination color.
+ *
+ * GrXPFactories are intended to be static immutable objects. We pass them around as raw pointers
+ * and expect the pointers to always be valid and for the factories to be reusable and thread safe.
+ * Equality is tested for using pointer comparison. GrXPFactory destructors must be no-ops.
  */
-class GrXPFactory : public SkRefCnt {
+
+// In order to construct GrXPFactory subclass instances as constexpr the subclass, and therefore
+// GrXPFactory, must be a literal type. One requirement is having a trivial destructor. This is ok
+// since these objects have no need for destructors. However, GCC and clang throw a warning when a
+// class has virtual functions and a non-virtual destructor. We suppress that warning here and
+// for the subclasses.
+#if defined(__GNUC__) || defined(__clang)
+#pragma GCC diagnostic push
+#pragma GCC diagnostic ignored "-Wnon-virtual-dtor"
+#endif
+class GrXPFactory {
 public:
     typedef GrXferProcessor::DstTexture DstTexture;
     GrXferProcessor* createXferProcessor(const GrPipelineAnalysis&,
@@ -317,29 +331,8 @@ public:
 
     bool willNeedDstTexture(const GrCaps& caps, const GrPipelineAnalysis&) const;
 
-    bool isEqual(const GrXPFactory& that) const {
-        if (this->classID() != that.classID()) {
-            return false;
-        }
-        return this->onIsEqual(that);
-    }
-
-    /**
-      * Helper for down-casting to a GrXPFactory subclass
-      */
-    template <typename T> const T& cast() const { return *static_cast<const T*>(this); }
-
-    uint32_t classID() const { SkASSERT(kIllegalXPFClassID != fClassID); return fClassID; }
-
 protected:
-    GrXPFactory() : fClassID(kIllegalXPFClassID) {}
-
-    template <typename XPF_SUBCLASS> void initClassID() {
-         static uint32_t kClassID = GenClassID();
-         fClassID = kClassID;
-    }
-
-    uint32_t fClassID;
+    constexpr GrXPFactory() {}
 
 private:
     virtual GrXferProcessor* onCreateXferProcessor(const GrCaps& caps,
@@ -347,34 +340,17 @@ private:
                                                    bool hasMixedSamples,
                                                    const DstTexture*) const = 0;
 
-    virtual bool onIsEqual(const GrXPFactory&) const = 0;
-
     bool willReadDstColor(const GrCaps&, const GrPipelineAnalysis&) const;
+
     /**
      *  Returns true if the XP generated by this factory will explicitly read dst in the fragment
      *  shader.
      */
     virtual bool onWillReadDstColor(const GrCaps&, const GrPipelineAnalysis&) const = 0;
-
-    static uint32_t GenClassID() {
-        // fCurrXPFactoryID has been initialized to kIllegalXPFactoryID. The
-        // atomic inc returns the old value not the incremented value. So we add
-        // 1 to the returned value.
-        uint32_t id = static_cast<uint32_t>(sk_atomic_inc(&gCurrXPFClassID)) + 1;
-        if (!id) {
-            SkFAIL("This should never wrap as it should only be called once for each GrXPFactory "
-                   "subclass.");
-        }
-        return id;
-    }
-
-    enum {
-        kIllegalXPFClassID = 0,
-    };
-    static int32_t gCurrXPFClassID;
-
-    typedef GrProgramElement INHERITED;
 };
+#if defined(__GNUC__) || defined(__clang)
+#pragma GCC diagnostic pop
+#endif
 
 #endif