src/gpu/GrRenderTargetProxy.h

/*
 * Copyright 2016 Google Inc.
 *
 * Use of this source code is governed by a BSD-style license that can be
 * found in the LICENSE file.
 */

#ifndef GrRenderTargetProxy_DEFINED
#define GrRenderTargetProxy_DEFINED

#include "include/private/GrTypesPriv.h"
#include "src/gpu/GrCaps.h"
#include "src/gpu/GrSurfaceProxy.h"
#include "src/gpu/GrSwizzle.h"

class GrResourceProvider;
class GrRenderTargetProxyPriv;

// This class delays the acquisition of RenderTargets until they are actually
// required
// Beware: the uniqueID of the RenderTargetProxy will usually be different than
// the uniqueID of the RenderTarget it represents!
class GrRenderTargetProxy : virtual public GrSurfaceProxy {
public:
    GrRenderTargetProxy* asRenderTargetProxy() override { return this; }
    const GrRenderTargetProxy* asRenderTargetProxy() const override { return this; }

    // Actually instantiate the backing rendertarget, if necessary.
    bool instantiate(GrResourceProvider*) override;

    bool canUseMixedSamples(const GrCaps& caps) const {
        return caps.mixedSamplesSupport() && !this->glRTFBOIDIs0() &&
               caps.internalMultisampleCount(this->backendFormat()) > 0 &&
               this->canChangeStencilAttachment();
    }

    /*
     * Indicate that a draw to this proxy requires stencil, and how many stencil samples it needs.
     * The number of stencil samples on this proxy will be equal to the largest sample count passed
     * to this method.
     */
    void setNeedsStencil(int8_t numStencilSamples) {
        SkASSERT(numStencilSamples >= fSampleCnt);
        fNumStencilSamples = SkTMax(numStencilSamples, fNumStencilSamples);
    }

    /**
     * Returns the number of stencil samples required by this proxy.
     * NOTE: Once instantiated, the actual render target may have more samples, but it is guaranteed
     * to have at least this many. (After a multisample stencil buffer has been attached to a render
     * target, we never "downgrade" it to one with fewer samples.)
     */
    int numStencilSamples() const { return fNumStencilSamples; }

    /**
     * Returns the number of samples/pixel in the color buffer (One if non-MSAA).
     */
    int numSamples() const { return fSampleCnt; }

    int maxWindowRectangles(const GrCaps& caps) const;

    const GrSwizzle& outputSwizzle() const { return fOutputSwizzle; }

    bool wrapsVkSecondaryCB() const { return fWrapsVkSecondaryCB == WrapsVkSecondaryCB::kYes; }

    // TODO: move this to a priv class!
    bool refsWrappedObjects() const;

    // Provides access to special purpose functions.
    GrRenderTargetProxyPriv rtPriv();
    const GrRenderTargetProxyPriv rtPriv() const;

protected:
    friend class GrProxyProvider;  // for ctors
    friend class GrRenderTargetProxyPriv;

    // Deferred version
    GrRenderTargetProxy(const GrCaps&, const GrBackendFormat&, const GrSurfaceDesc&,
                        int sampleCount, GrSurfaceOrigin, const GrSwizzle& textureSwizzle,
                        const GrSwizzle& outputSwizzle, SkBackingFit, SkBudgeted, GrProtected,
                        GrInternalSurfaceFlags);

    enum class WrapsVkSecondaryCB : bool { kNo = false, kYes = true };

    // Lazy-callback version
    // There are two main use cases for lazily-instantiated proxies:
    //   basic knowledge - width, height, config, samples, origin are known
    //   minimal knowledge - only config is known.
    //
    // The basic knowledge version is used for DDL where we know the type of proxy we are going to
    // use, but we don't have access to the GPU yet to instantiate it.
    //
    // The minimal knowledge version is used for CCPR where we are generating an atlas but we do not
    // know the final size until flush time.
    GrRenderTargetProxy(LazyInstantiateCallback&&, LazyInstantiationType lazyType,
                        const GrBackendFormat&, const GrSurfaceDesc&, int sampleCount,
                        GrSurfaceOrigin, const GrSwizzle& textureSwizzle,
                        const GrSwizzle& outputSwizzle, SkBackingFit, SkBudgeted, GrProtected,
                        GrInternalSurfaceFlags, WrapsVkSecondaryCB wrapsVkSecondaryCB);

    // Wrapped version
    GrRenderTargetProxy(sk_sp<GrSurface>, GrSurfaceOrigin, const GrSwizzle& textureSwizzle,
                        const GrSwizzle& outputSwizzle,
                        WrapsVkSecondaryCB wrapsVkSecondaryCB = WrapsVkSecondaryCB::kNo);

    sk_sp<GrSurface> createSurface(GrResourceProvider*) const override;

private:
    void setGLRTFBOIDIs0() {
        fSurfaceFlags |= GrInternalSurfaceFlags::kGLRTFBOIDIs0;
    }
    bool glRTFBOIDIs0() const {
        return fSurfaceFlags & GrInternalSurfaceFlags::kGLRTFBOIDIs0;
    }
    bool canChangeStencilAttachment() const;

    size_t onUninstantiatedGpuMemorySize() const override;
    SkDEBUGCODE(void onValidateSurface(const GrSurface*) override;)

    // WARNING: Be careful when adding or removing fields here. ASAN is likely to trigger warnings
    // when instantiating GrTextureRenderTargetProxy. The std::function in GrSurfaceProxy makes
    // each class in the diamond require 16 byte alignment. Clang appears to layout the fields for
    // each class to achieve the necessary alignment. However, ASAN checks the alignment of 'this'
    // in the constructors, and always looks for the full 16 byte alignment, even if the fields in
    // that particular class don't require it. Changing the size of this object can move the start
    // address of other types, leading to this problem.
    int8_t             fSampleCnt;
    int8_t             fNumStencilSamples = 0;
    WrapsVkSecondaryCB fWrapsVkSecondaryCB;
    GrSwizzle          fOutputSwizzle;
    // This is to fix issue in large comment above. Without the padding we end 6 bytes into a 16
    // byte range, so the GrTextureProxy ends up starting 8 byte aligned by not 16. We add the
    // padding here to get us right up to the 16 byte alignment (technically any padding of 3-10
    // bytes would work since it always goes up to 8 byte alignment, but we use 10 to more explicit
    // about what we're doing).
    char               fDummyPadding[10];

    typedef GrSurfaceProxy INHERITED;
};

#endif