GrBatchPrototype

src/gpu/GrBatch.h

+/*
+ * Copyright 2015 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#ifndef GrBatch_DEFINED
+#define GrBatch_DEFINED
+
+#include <new>
+// TODO remove this header when we move entirely to batch
+#include "GrGeometryProcessor.h"
+#include "SkRefCnt.h"
+#include "SkThread.h"
+#include "SkTypes.h"
+
+class GrBatchTarget;
+class GrGpu;
+class GrIndexBufferAllocPool;
+class GrInitInvariantOutput;
+class GrOptDrawState;
+class GrVertexBufferAllocPool;
+
+/*
+ * GrBatch is the base class for all Ganesh deferred geometry generators.  To facilitate
+ * reorderable batching, Ganesh does not generate geometry inline with draw calls.  Instead, it
+ * captures the arguments to the draw and then generates the geometry on demand.  This gives GrBatch
+ * subclasses complete freedom to decide how / what they can batch.
+ *
+ * Batches are created when GrContext processes a draw call. Batches of the same  subclass may be
+ * merged using combineIfPossible. When two batches merge, one takes on the union of the data
+ * and the other is left empty. The merged batch becomes responsible for drawing the data from both
+ * the original batches.
+ *
+ * If there are any possible optimizations which might require knowing more about the full state of
+ * the draw, ie whether or not the GrBatch is allowed to tweak alpha for coverage, then this
+ * information will be communicated to the GrBatch prior to geometry generation.
+ */
+
+struct GrBatchOpt {
+  bool fCanTweakAlphaForCoverage;
+};
+
+class GrBatch : public SkRefCnt {
+public:
+    SK_DECLARE_INST_COUNT(GrBatch)
+    GrBatch() { SkDEBUGCODE(fUsed = false;) }
+    virtual ~GrBatch() {}
+    virtual const char* name() const = 0;
+    virtual void getInvariantOutputColor(GrInitInvariantOutput* out,
+                                         const GrBatchOpt&) const = 0;
+    virtual void getInvariantOutputCoverage(GrInitInvariantOutput* out,
+                                            const GrBatchOpt&) const = 0;
+
+    virtual void initBatchOpt(const GrBatchOpt&) = 0;

[bsalomon, 2015/01/22 16:00:59]

The virtuals that the client overrides could use some documentation.

+    virtual void initBatchTracker(const GrGeometryProcessor::InitBT& init) = 0;
+
+    bool combineIfPossible(GrBatch* that) {
+        if (this->classID() != that->classID()) {
+            return false;
+        }
+
+        return onCombineIfPossible(that);
+    }
+
+    virtual bool onCombineIfPossible(GrBatch*) = 0;
+
+    virtual void generateGeometry(GrBatchTarget*, const GrOptDrawState*) = 0;
+
+    void* operator new(size_t size);
+    void operator delete(void* target);
+
+    void* operator new(size_t size, void* placement) {
+        return ::operator new(size, placement);
+    }
+    void operator delete(void* target, void* placement) {
+        ::operator delete(target, placement);
+    }
+
+    /**
+      * Helper for down-casting to a GrBatch subclass
+      */
+    template <typename T> const T& cast() const { return *static_cast<const T*>(this); }
+    template <typename T> T* cast() { return static_cast<T*>(this); }
+
+    uint32_t classID() const { SkASSERT(kIllegalBatchClassID != fClassID); return fClassID; }
+
+    // TODO no GrPrimitiveProcessors yet read fragment position
+    bool willReadFragmentPosition() const { return false; }
+
+    SkDEBUGCODE(bool isUsed() const { return fUsed; })
+
+protected:
+    template <typename PROC_SUBCLASS> void initClassID() {
+         static uint32_t kClassID = GenClassID();
+         fClassID = kClassID;
+    }
+
+    uint32_t fClassID;
+
+private:
+    static uint32_t GenClassID() {
+        // fCurrProcessorClassID has been initialized to kIllegalProcessorClassID. 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(&gCurrBatchClassID)) + 1;
+        if (!id) {
+            SkFAIL("This should never wrap as it should only be called once for each GrBatch "
+                   "subclass.");
+        }
+        return id;
+    }
+
+    enum {
+        kIllegalBatchClassID = 0,
+    };
+    static int32_t gCurrBatchClassID;
+
+    SkDEBUGCODE(bool fUsed;)
+
+    typedef SkRefCnt INHERITED;
+};
+
+#endif