src/gpu/batches/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>
#include "GrNonAtomicRef.h"

#include "SkRect.h"

class GrCaps;

/**
 * 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.
 */
#define GR_BATCH_SPEW 0
#if GR_BATCH_SPEW
    #define GrBATCH_INFO(...) SkDebugf(__VA_ARGS__)
    #define GrBATCH_SPEW(code) code
#else
    #define GrBATCH_SPEW(code)
    #define GrBATCH_INFO(...)
#endif

class GrBatch : public GrNonAtomicRef {
public:
    GrBatch();
    ~GrBatch() override;

    virtual const char* name() const = 0;

    bool combineIfPossible(GrBatch* that, const GrCaps& caps) {
        if (this->classID() != that->classID()) {
            return false;
        }

        return this->onCombineIfPossible(that, caps);
    }

    const SkRect& bounds() const { return fBounds; }

    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(kIllegalBatchID != fClassID); return fClassID; }

#if GR_BATCH_SPEW
    uint32_t uniqueID() const { return fUniqueID; }
#endif
    SkDEBUGCODE(bool isUsed() const { return fUsed; })

protected:
    template <typename PROC_SUBCLASS> void initClassID() {
         static uint32_t kClassID = GenID(&gCurrBatchClassID);
         fClassID = kClassID;
    }

    // NOTE, compute some bounds, even if extremely conservative.  Do *NOT* setLargest on the bounds
    // rect because we outset it for dst copy textures
    void setBounds(const SkRect& newBounds) { fBounds = newBounds; }

    void joinBounds(const SkRect& otherBounds) {
        return fBounds.joinPossiblyEmptyRect(otherBounds);
    }

    SkRect                              fBounds;

private:
    virtual bool onCombineIfPossible(GrBatch*, const GrCaps& caps) = 0;

    static uint32_t GenID(int32_t* idCounter) {
        // 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(idCounter)) + 1;
        if (!id) {
            SkFAIL("This should never wrap as it should only be called once for each GrBatch "
                   "subclass.");
        }
        return id;
    }

    enum {
        kIllegalBatchID = 0,
    };

    uint32_t                            fClassID;
    SkDEBUGCODE(bool                    fUsed;)
#if GR_BATCH_SPEW
    uint32_t                            fUniqueID;
    static int32_t gCurrBatchUniqueID;
#endif
    static int32_t gCurrBatchClassID;
    typedef GrNonAtomicRef INHERITED;
};

#endif