src/gpu/ops/GrOp.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 GrOp_DEFINED
#define GrOp_DEFINED

#include "../private/SkAtomics.h"
#include "GrGpuResource.h"
#include "GrNonAtomicRef.h"
#include "GrTracing.h"
#include "GrXferProcessor.h"
#include "SkMatrix.h"
#include "SkRect.h"
#include "SkString.h"

#include <new>

class GrCaps;
class GrGpuCommandBuffer;
class GrOpFlushState;
class GrRenderTargetOpList;

/**
 * GrOp is the base class for all Ganesh deferred GPU operations. To facilitate reordering and to
 * minimize draw calls, Ganesh does not generate geometry inline with draw calls. Instead, it
 * captures the arguments to the draw and then generates the geometry when flushing. This gives GrOp
 * subclasses complete freedom to decide how/when to combine in order to produce fewer draw calls
 * and minimize state changes.
 *
 * Ops of the same subclass may be merged or chained using combineIfPossible. When two ops merge,
 * one takes on the union of the data and the other is left empty. The merged op becomes responsible
 * for drawing the data from both the original ops. When ops are chained each op maintains its own
 * data but they are linked in a list and the head op becomes responsible for executing the work for
 * the chain.
 *
 * The bounds of the op must contain all the vertices in device space *irrespective* of the clip.
 * The bounds are used in determining which clip elements must be applied and thus the bounds cannot
 * in turn depend upon the clip.
 */
#define GR_OP_SPEW 0
#if GR_OP_SPEW
    #define GrOP_SPEW(code) code
    #define GrOP_INFO(...) SkDebugf(__VA_ARGS__)
#else
    #define GrOP_SPEW(code)
    #define GrOP_INFO(...)
#endif

// Print out op information at flush time
#define GR_FLUSH_TIME_OP_SPEW 0

// A helper macro to generate a class static id
#define DEFINE_OP_CLASS_ID \
    static uint32_t ClassID() { \
        static uint32_t kClassID = GenOpClassID(); \
        return kClassID; \
    }

class GrOp : private SkNoncopyable {
public:
    virtual ~GrOp();

    virtual const char* name() const = 0;

    typedef std::function<void(GrSurfaceProxy*)> VisitProxyFunc;

    virtual void visitProxies(const VisitProxyFunc&) const {
        // This default implementation assumes the op has no proxies
    }

    enum class CombineResult {
        /**
         * The op that combineIfPossible was called on now represents its own work plus that of
         * the passed op. The passed op should be destroyed without being flushed. Currently it
         * is not legal to merge an op passed to combineIfPossible() the passed op is already in a
         * chain (though the op on which combineIfPossible() was called may be).
         */
        kMerged,
        /**
         * The caller *may* (but is not required) to chain these ops together. If they are chained
         * then prepare() and execute() will be called on the head op but not the other ops in the
         * chain. The head op will prepare and execute on behalf of all the ops in the chain.
         */
        kMayChain,
        /**
         * The ops cannot be combined.
         */
        kCannotCombine
    };

    CombineResult combineIfPossible(GrOp* that, const GrCaps& caps);

    const SkRect& bounds() const {
        SkASSERT(kUninitialized_BoundsFlag != fBoundsFlags);
        return fBounds;
    }

    void setClippedBounds(const SkRect& clippedBounds) {
        fBounds = clippedBounds;
        // The clipped bounds already incorporate any effect of the bounds flags.
        fBoundsFlags = 0;
    }

    bool hasAABloat() const {
        SkASSERT(fBoundsFlags != kUninitialized_BoundsFlag);
        return SkToBool(fBoundsFlags & kAABloat_BoundsFlag);
    }

    bool hasZeroArea() const {
        SkASSERT(fBoundsFlags != kUninitialized_BoundsFlag);
        return SkToBool(fBoundsFlags & kZeroArea_BoundsFlag);
    }

#ifdef SK_DEBUG
    // All GrOp-derived classes should be allocated in and deleted from a GrMemoryPool
    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);
    }
#endif

    /**
     * Helper for safely down-casting to a GrOp subclass
     */
    template <typename T> const T& cast() const {
        SkASSERT(T::ClassID() == this->classID());
        return *static_cast<const T*>(this);
    }

    template <typename T> T* cast() {
        SkASSERT(T::ClassID() == this->classID());
        return static_cast<T*>(this);
    }

    uint32_t classID() const { SkASSERT(kIllegalOpID != fClassID); return fClassID; }

    // We lazily initialize the uniqueID because currently the only user is GrAuditTrail
    uint32_t uniqueID() const {
        if (kIllegalOpID == fUniqueID) {
            fUniqueID = GenOpID();
        }
        return fUniqueID;
    }

    /**
     * Called prior to executing. The op should perform any resource creation or data transfers
     * necessary before execute() is called.
     */
    void prepare(GrOpFlushState* state) { this->onPrepare(state); }

    /** Issues the op's commands to GrGpu. */
    void execute(GrOpFlushState* state) {
        TRACE_EVENT0("skia", name());
        this->onExecute(state);
    }

    /** Used for spewing information about ops when debugging. */
    virtual SkString dumpInfo() const {
        SkString string;
        string.appendf("OpBounds: [L: %.2f, T: %.2f, R: %.2f, B: %.2f]\n",
                       fBounds.fLeft, fBounds.fTop, fBounds.fRight, fBounds.fBottom);
        return string;
    }

    /**
     * A helper for iterating over an op chain in a range for loop that also downcasts to a GrOp
     * subclass. E.g.:
     *     for (MyOpSubClass& op : ChainRange<MyOpSubClass>(this)) {
     *         // ...
     *     }
     */
    template <typename OpSubclass> class ChainRange {
    private:
        class Iter {
        public:
            explicit Iter(const GrOp* head) : fCurr(head) {}
            inline Iter& operator++() { return *this = Iter(fCurr->nextInChain()); }
            const OpSubclass& operator*() const { return fCurr->cast<OpSubclass>(); }
            bool operator!=(const Iter& that) const { return fCurr != that.fCurr; }

        private:
            const GrOp* fCurr;
        };
        const GrOp* fHead;

    public:
        explicit ChainRange(const GrOp* head) : fHead(head) {}
        Iter begin() { return Iter(fHead); }
        Iter end() { return Iter(nullptr); }
    };

    void setNextInChain(GrOp*);
    /** Returns true if this is the head of a chain (including a length 1 chain). */
    bool isChainHead() const { return !fChainHead || (fChainHead == this); }
    /** Gets the head op of the chain. */
    const GrOp* chainHead() const { return fChainHead ? fChainHead : this; }
    /** Returns true if this is the tail of a chain (including a length 1 chain). */
    bool isChainTail() const { return !fNextInChain; }
    /** Returns true if this is part of chain with length > 1. */
    bool isChained() const { return SkToBool(fChainHead); }
    /** The next op in the chain. */
    const GrOp* nextInChain() const { return fNextInChain; }

protected:
    GrOp(uint32_t classID);

    /**
     * Indicates that the op will produce geometry that extends beyond its bounds for the
     * purpose of ensuring that the fragment shader runs on partially covered pixels for
     * non-MSAA antialiasing.
     */
    enum class HasAABloat : bool {
        kNo = false,
        kYes = true
    };
    /**
     * Indicates that the geometry represented by the op has zero area (e.g. it is hairline or
     * points).
     */
    enum class IsZeroArea : bool {
        kNo = false,
        kYes = true
    };

    void setBounds(const SkRect& newBounds, HasAABloat aabloat, IsZeroArea zeroArea) {
        fBounds = newBounds;
        this->setBoundsFlags(aabloat, zeroArea);
    }
    void setTransformedBounds(const SkRect& srcBounds, const SkMatrix& m,
                              HasAABloat aabloat, IsZeroArea zeroArea) {
        m.mapRect(&fBounds, srcBounds);
        this->setBoundsFlags(aabloat, zeroArea);
    }
    void makeFullScreen(GrSurfaceProxy* proxy) {
        this->setBounds(SkRect::MakeIWH(proxy->width(), proxy->height()),
                        HasAABloat::kNo, IsZeroArea::kNo);
    }

    void joinBounds(const GrOp& that) {
        if (that.hasAABloat()) {
            fBoundsFlags |= kAABloat_BoundsFlag;
        }
        if (that.hasZeroArea()) {
            fBoundsFlags |= kZeroArea_BoundsFlag;
        }
        return fBounds.joinPossiblyEmptyRect(that.fBounds);
    }

    void replaceBounds(const GrOp& that) {
        fBounds = that.fBounds;
        fBoundsFlags = that.fBoundsFlags;
    }

    static uint32_t GenOpClassID() { return GenID(&gCurrOpClassID); }

private:
    virtual CombineResult onCombineIfPossible(GrOp*, const GrCaps&) {
        return CombineResult::kCannotCombine;
    }

    virtual void onPrepare(GrOpFlushState*) = 0;
    virtual void onExecute(GrOpFlushState*) = 0;

    static uint32_t GenID(int32_t* idCounter) {
        // 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) {
            SK_ABORT("This should never wrap as it should only be called once for each GrOp "
                   "subclass.");
        }
        return id;
    }

    void setBoundsFlags(HasAABloat aabloat, IsZeroArea zeroArea) {
        fBoundsFlags = 0;
        fBoundsFlags |= (HasAABloat::kYes == aabloat) ? kAABloat_BoundsFlag : 0;
        fBoundsFlags |= (IsZeroArea ::kYes == zeroArea) ? kZeroArea_BoundsFlag : 0;
    }

    enum {
        kIllegalOpID = 0,
    };

    enum BoundsFlags {
        kAABloat_BoundsFlag                     = 0x1,
        kZeroArea_BoundsFlag                    = 0x2,
        SkDEBUGCODE(kUninitialized_BoundsFlag   = 0x4)
    };

    GrOp*                               fNextInChain = nullptr;
    GrOp*                               fChainHead = nullptr;    // null if this is not in a chain.
    const uint16_t                      fClassID;
    uint16_t                            fBoundsFlags;

    static uint32_t GenOpID() { return GenID(&gCurrOpUniqueID); }
    mutable uint32_t                    fUniqueID = SK_InvalidUniqueID;
    SkRect                              fBounds;

    static int32_t                      gCurrOpUniqueID;
    static int32_t                      gCurrOpClassID;
};

#endif