skia2/include/gpu/GrContext.h

/*
 * Copyright 2010 Google Inc.
 *
 * Use of this source code is governed by a BSD-style license that can be
 * found in the LICENSE file.
 */

#ifndef GrContext_DEFINED
#define GrContext_DEFINED

#include "GrCaps.h"
#include "GrClip.h"
#include "GrColor.h"
#include "GrPaint.h"
#include "GrRenderTarget.h"
#include "GrTextureProvider.h"
#include "SkMatrix.h"
#include "SkPathEffect.h"
#include "SkTypes.h"
#include "../private/GrAuditTrail.h"
#include "../private/GrSingleOwner.h"
#include "../private/SkMutex.h"

struct GrBatchAtlasConfig;
class GrBatchFontCache;
struct GrContextOptions;
class GrContextThreadSafeProxy;
class GrDrawingManager;
class GrDrawContext;
class GrFragmentProcessor;
class GrGpu;
class GrIndexBuffer;
class GrLayerCache;
class GrOvalRenderer;
class GrPath;
class GrPipelineBuilder;
class GrResourceEntry;
class GrResourceCache;
class GrResourceProvider;
class GrTestTarget;
class GrTextBlobCache;
class GrTextContext;
class GrTextureParams;
class GrVertexBuffer;
class GrSwizzle;
class SkTraceMemoryDump;

class SK_API GrContext : public SkRefCnt {
public:
    /**
     * Creates a GrContext for a backend context.
     */
    static GrContext* Create(GrBackend, GrBackendContext, const GrContextOptions& options);
    static GrContext* Create(GrBackend, GrBackendContext);

    /**
     * Only defined in test apps.
     */
    static GrContext* CreateMockContext();

    virtual ~GrContext();

    GrContextThreadSafeProxy* threadSafeProxy();

    /**
     * The GrContext normally assumes that no outsider is setting state
     * within the underlying 3D API's context/device/whatever. This call informs
     * the context that the state was modified and it should resend. Shouldn't
     * be called frequently for good performance.
     * The flag bits, state, is dpendent on which backend is used by the
     * context, either GL or D3D (possible in future).
     */
    void resetContext(uint32_t state = kAll_GrBackendState);

    /**
     * Callback function to allow classes to cleanup on GrContext destruction.
     * The 'info' field is filled in with the 'info' passed to addCleanUp.
     */
    typedef void (*PFCleanUpFunc)(const GrContext* context, void* info);

    /**
     * Add a function to be called from within GrContext's destructor.
     * This gives classes a chance to free resources held on a per context basis.
     * The 'info' parameter will be stored and passed to the callback function.
     */
    void addCleanUp(PFCleanUpFunc cleanUp, void* info) {
        CleanUpData* entry = fCleanUpData.push();

        entry->fFunc = cleanUp;
        entry->fInfo = info;
    }

    /**
     * Abandons all GPU resources and assumes the underlying backend 3D API context is not longer
     * usable. Call this if you have lost the associated GPU context, and thus internal texture,
     * buffer, etc. references/IDs are now invalid. Calling this ensures that the destructors of the
     * GrContext and any of its created resource objects will not make backend 3D API calls. Content
     * rendered but not previously flushed may be lost. After this function is called all subsequent
     * calls on the GrContext will fail or be no-ops.
     *
     * The typical use case for this function is that the underlying 3D context was lost and further
     * API calls may crash.
     */
    void abandonContext();

    /**
     * This is similar to abandonContext() however the underlying 3D context is not yet lost and
     * the GrContext will cleanup all allocated resources before returning. After returning it will
     * assume that the underlying context may no longer be valid.
     *
     * The typical use case for this function is that the client is going to destroy the 3D context
     * but can't guarantee that GrContext will be destroyed first (perhaps because it may be ref'ed
     * elsewhere by either the client or Skia objects).
     */
    void releaseResourcesAndAbandonContext();

    ///////////////////////////////////////////////////////////////////////////
    // Resource Cache

    /**
     *  Return the current GPU resource cache limits.
     *
     *  @param maxResources If non-null, returns maximum number of resources that
     *                      can be held in the cache.
     *  @param maxResourceBytes If non-null, returns maximum number of bytes of
     *                          video memory that can be held in the cache.
     */
    void getResourceCacheLimits(int* maxResources, size_t* maxResourceBytes) const;

    /**
     *  Gets the current GPU resource cache usage.
     *
     *  @param resourceCount If non-null, returns the number of resources that are held in the
     *                       cache.
     *  @param maxResourceBytes If non-null, returns the total number of bytes of video memory held
     *                          in the cache.
     */
    void getResourceCacheUsage(int* resourceCount, size_t* resourceBytes) const;

    /**
     *  Specify the GPU resource cache limits. If the current cache exceeds either
     *  of these, it will be purged (LRU) to keep the cache within these limits.
     *
     *  @param maxResources The maximum number of resources that can be held in
     *                      the cache.
     *  @param maxResourceBytes The maximum number of bytes of video memory
     *                          that can be held in the cache.
     */
    void setResourceCacheLimits(int maxResources, size_t maxResourceBytes);

    GrTextureProvider* textureProvider() { return fTextureProvider; }
    const GrTextureProvider* textureProvider() const { return fTextureProvider; }

    /**
     * Frees GPU created by the context. Can be called to reduce GPU memory
     * pressure.
     */
    void freeGpuResources();

    /**
     * Purge all the unlocked resources from the cache.
     * This entry point is mainly meant for timing texture uploads
     * and is not defined in normal builds of Skia.
     */
    void purgeAllUnlockedResources();

    /** Access the context capabilities */
    const GrCaps* caps() const { return fCaps; }

    /**
     * Returns the recommended sample count for a render target when using this
     * context.
     *
     * @param  config the configuration of the render target.
     * @param  dpi the display density in dots per inch.
     *
     * @return sample count that should be perform well and have good enough
     *         rendering quality for the display. Alternatively returns 0 if
     *         MSAA is not supported or recommended to be used by default.
     */
    int getRecommendedSampleCount(GrPixelConfig config, SkScalar dpi) const;

    /**
     * Returns a helper object to orchestrate draws.
     * Callers assume the creation ref of the drawContext
     * NULL will be returned if the context has been abandoned.
     *
     * @param  rt           the render target receiving the draws
     * @param  surfaceProps the surface properties (mainly defines text drawing)
     *
     * @return a draw context
     */
    sk_sp<GrDrawContext> drawContext(sk_sp<GrRenderTarget> rt, const SkSurfaceProps* = nullptr);

    /**
     * Create both a GrRenderTarget and a matching GrDrawContext to wrap it.
     * We guarantee that "asTexture" will succeed for drawContexts created
     * via this entry point.
     */
    sk_sp<GrDrawContext> newDrawContext(SkBackingFit fit, 
                                        int width, int height,
                                        GrPixelConfig config,
                                        int sampleCnt = 0,
                                        GrSurfaceOrigin origin = kDefault_GrSurfaceOrigin,
                                        const SkSurfaceProps* surfaceProps = nullptr,
                                        SkBudgeted = SkBudgeted::kYes);

    ///////////////////////////////////////////////////////////////////////////
    // Misc.

    /**
     * Flags that affect flush() behavior.
     */
    enum FlushBits {
        /**
         * A client may reach a point where it has partially rendered a frame
         * through a GrContext that it knows the user will never see. This flag
         * causes the flush to skip submission of deferred content to the 3D API
         * during the flush.
         */
        kDiscard_FlushBit                    = 0x2,
    };

    /**
     * Call to ensure all drawing to the context has been issued to the
     * underlying 3D API.
     * @param flagsBitfield     flags that control the flushing behavior. See
     *                          FlushBits.
     */
    void flush(int flagsBitfield = 0);

    void flushIfNecessary() {
        if (fFlushToReduceCacheSize || this->caps()->immediateFlush()) {
            this->flush();
        }
    }

   /**
    * These flags can be used with the read/write pixels functions below.
    */
    enum PixelOpsFlags {
        /** The GrContext will not be flushed before the surface read or write. This means that
            the read or write may occur before previous draws have executed. */
        kDontFlush_PixelOpsFlag = 0x1,
        /** Any surface writes should be flushed to the backend 3D API after the surface operation
            is complete */
        kFlushWrites_PixelOp = 0x2,
        /** The src for write or dst read is unpremultiplied. This is only respected if both the
            config src and dst configs are an RGBA/BGRA 8888 format. */
        kUnpremul_PixelOpsFlag  = 0x4,
    };

    /**
     * Reads a rectangle of pixels from a surface.
     * @param surface       the surface to read from.
     * @param left          left edge of the rectangle to read (inclusive)
     * @param top           top edge of the rectangle to read (inclusive)
     * @param width         width of rectangle to read in pixels.
     * @param height        height of rectangle to read in pixels.
     * @param config        the pixel config of the destination buffer
     * @param buffer        memory to read the rectangle into.
     * @param rowBytes      number of bytes bewtween consecutive rows. Zero means rows are tightly
     *                      packed.
     * @param pixelOpsFlags see PixelOpsFlags enum above.
     *
     * @return true if the read succeeded, false if not. The read can fail because of an unsupported
     *         pixel configs
     */
    bool readSurfacePixels(GrSurface* surface,
                           int left, int top, int width, int height,
                           GrPixelConfig config, void* buffer,
                           size_t rowBytes = 0,
                           uint32_t pixelOpsFlags = 0);

    /**
     * Writes a rectangle of pixels to a surface.
     * @param surface       the surface to write to.
     * @param left          left edge of the rectangle to write (inclusive)
     * @param top           top edge of the rectangle to write (inclusive)
     * @param width         width of rectangle to write in pixels.
     * @param height        height of rectangle to write in pixels.
     * @param config        the pixel config of the source buffer
     * @param buffer        memory to read pixels from
     * @param rowBytes      number of bytes between consecutive rows. Zero
     *                      means rows are tightly packed.
     * @param pixelOpsFlags see PixelOpsFlags enum above.
     * @return true if the write succeeded, false if not. The write can fail because of an
     *         unsupported combination of surface and src configs.
     */
    bool writeSurfacePixels(GrSurface* surface,
                            int left, int top, int width, int height,
                            GrPixelConfig config, const void* buffer,
                            size_t rowBytes,
                            uint32_t pixelOpsFlags = 0);

    /**
     * Copies contents of src to dst, while applying a gamma curve. Fails if the two surfaces
     * are not identically sized.
     * @param dst           the surface to copy to.
     * @param src           the texture to copy from.
     * @param gamma         the gamma value to apply.
     */
    bool applyGamma(GrRenderTarget* dst, GrTexture* src, SkScalar gamma);

    /**
     * Copies a rectangle of texels from src to dst.
     * @param dst           the surface to copy to.
     * @param src           the surface to copy from.
     * @param srcRect       the rectangle of the src that should be copied.
     * @param dstPoint      the translation applied when writing the srcRect's pixels to the dst.
     */
    bool copySurface(GrSurface* dst,
                     GrSurface* src,
                     const SkIRect& srcRect,
                     const SkIPoint& dstPoint);

    /** Helper that copies the whole surface but fails when the two surfaces are not identically
        sized. */
    bool copySurface(GrSurface* dst, GrSurface* src) {
        return this->copySurface(dst, src, SkIRect::MakeWH(dst->width(), dst->height()),
                                 SkIPoint::Make(0,0));
    }

    /**
     * After this returns any pending writes to the surface will have been issued to the backend 3D API.
     */
    void flushSurfaceWrites(GrSurface* surface);

    /**
     * Finalizes all pending reads and writes to the surface and also performs an MSAA resolve
     * if necessary.
     *
     * It is not necessary to call this before reading the render target via Skia/GrContext.
     * GrContext will detect when it must perform a resolve before reading pixels back from the
     * surface or using it as a texture.
     */
    void prepareSurfaceForExternalIO(GrSurface*);

    /**
     * An ID associated with this context, guaranteed to be unique.
     */
    uint32_t uniqueID() { return fUniqueID; }

    ///////////////////////////////////////////////////////////////////////////
    // Functions intended for internal use only.
    GrGpu* getGpu() { return fGpu; }
    const GrGpu* getGpu() const { return fGpu; }
    GrBatchFontCache* getBatchFontCache() { return fBatchFontCache; }
    GrLayerCache* getLayerCache() { return fLayerCache.get(); }
    GrTextBlobCache* getTextBlobCache() { return fTextBlobCache; }
    bool abandoned() const;
    GrResourceProvider* resourceProvider() { return fResourceProvider; }
    const GrResourceProvider* resourceProvider() const { return fResourceProvider; }
    GrResourceCache* getResourceCache() { return fResourceCache; }

    // Called by tests that draw directly to the context via GrDrawContext
    void getTestTarget(GrTestTarget*, sk_sp<GrDrawContext>);

    /** Reset GPU stats */
    void resetGpuStats() const ;

    /** Prints cache stats to the string if GR_CACHE_STATS == 1. */
    void dumpCacheStats(SkString*) const;
    void dumpCacheStatsKeyValuePairs(SkTArray<SkString>* keys, SkTArray<double>* values) const;
    void printCacheStats() const;

    /** Prints GPU stats to the string if GR_GPU_STATS == 1. */
    void dumpGpuStats(SkString*) const;
    void dumpGpuStatsKeyValuePairs(SkTArray<SkString>* keys, SkTArray<double>* values) const;
    void printGpuStats() const;

    /** Specify the TextBlob cache limit. If the current cache exceeds this limit it will purge.
        this is for testing only */
    void setTextBlobCacheLimit_ForTesting(size_t bytes);

    /** Specify the sizes of the GrAtlasTextContext atlases.  The configs pointer below should be
        to an array of 3 entries */
    void setTextContextAtlasSizes_ForTesting(const GrBatchAtlasConfig* configs);

    /** Enumerates all cached GPU resources and dumps their memory to traceMemoryDump. */
    void dumpMemoryStatistics(SkTraceMemoryDump* traceMemoryDump) const;

    /** Get pointer to atlas texture for given mask format */
    GrTexture* getFontAtlasTexture(GrMaskFormat format);

    GrAuditTrail* getAuditTrail() { return &fAuditTrail; }

    /** This is only useful for debug purposes */
    SkDEBUGCODE(GrSingleOwner* debugSingleOwner() const { return &fSingleOwner; } )

private:
    GrGpu*                                  fGpu;
    const GrCaps*                           fCaps;
    GrResourceCache*                        fResourceCache;
    // this union exists because the inheritance of GrTextureProvider->GrResourceProvider
    // is in a private header.
    union {
        GrResourceProvider*                 fResourceProvider;
        GrTextureProvider*                  fTextureProvider;
    };

    SkAutoTUnref<GrContextThreadSafeProxy>  fThreadSafeProxy;

    GrBatchFontCache*                       fBatchFontCache;
    SkAutoTDelete<GrLayerCache>             fLayerCache;
    SkAutoTDelete<GrTextBlobCache>          fTextBlobCache;

    // Set by OverbudgetCB() to request that GrContext flush before exiting a draw.
    bool                                    fFlushToReduceCacheSize;
    bool                                    fDidTestPMConversions;
    int                                     fPMToUPMConversion;
    int                                     fUPMToPMConversion;
    // The sw backend may call GrContext::readSurfacePixels on multiple threads
    // We may transfer the responsibilty for using a mutex to the sw backend
    // when there are fewer code paths that lead to a readSurfacePixels call
    // from the sw backend. readSurfacePixels is reentrant in one case - when performing
    // the PM conversions test. To handle this we do the PM conversions test outside
    // of fReadPixelsMutex and use a separate mutex to guard it. When it re-enters
    // readSurfacePixels it will grab fReadPixelsMutex and release it before the outer
    // readSurfacePixels proceeds to grab it.
    // TODO: Stop pretending to make GrContext thread-safe for sw rasterization and provide
    // a mechanism to make a SkPicture safe for multithreaded sw rasterization.
    SkMutex                                 fReadPixelsMutex;
    SkMutex                                 fTestPMConversionsMutex;

    // In debug builds we guard against improper thread handling
    // This guard is passed to the GrDrawingManager and, from there to all the
    // GrDrawContexts.  It is also passed to the GrTextureProvider and SkGpuDevice.
    mutable GrSingleOwner                   fSingleOwner;

    struct CleanUpData {
        PFCleanUpFunc fFunc;
        void*         fInfo;
    };

    SkTDArray<CleanUpData>                  fCleanUpData;

    const uint32_t                          fUniqueID;

    SkAutoTDelete<GrDrawingManager>         fDrawingManager;

    GrAuditTrail                            fAuditTrail;

    // TODO: have the CMM use drawContexts and rm this friending
    friend class GrClipMaskManager; // the CMM is friended just so it can call 'drawingManager'
    friend class GrDrawingManager;  // for access to drawingManager for ProgramUnitTest
    GrDrawingManager* drawingManager() { return fDrawingManager; }

    GrContext(); // init must be called after the constructor.
    bool init(GrBackend, GrBackendContext, const GrContextOptions& options);

    void initMockContext();
    void initCommon(const GrContextOptions&);

    /**
     * These functions create premul <-> unpremul effects if it is possible to generate a pair
     * of effects that make a readToUPM->writeToPM->readToUPM cycle invariant. Otherwise, they
     * return NULL. They also can perform a swizzle as part of the draw.
     */
    const GrFragmentProcessor* createPMToUPMEffect(GrTexture*, const GrSwizzle&,
                                                   const SkMatrix&) const;
    const GrFragmentProcessor* createUPMToPMEffect(GrTexture*, const GrSwizzle&,
                                                   const SkMatrix&) const;
    /** Called before either of the above two functions to determine the appropriate fragment
        processors for conversions. This must be called by readSurfacePixels before a mutex is
        taken, since testingvPM conversions itself will call readSurfacePixels */
    void testPMConversionsIfNecessary(uint32_t flags);
    /** Returns true if we've already determined that createPMtoUPMEffect and createUPMToPMEffect
        will fail. In such cases fall back to SW conversion. */
    bool didFailPMUPMConversionTest() const;

    /**
     *  This callback allows the resource cache to callback into the GrContext
     *  when the cache is still over budget after a purge.
     */
    static void OverBudgetCB(void* data);

    /**
     * A callback similar to the above for use by the TextBlobCache
     * TODO move textblob draw calls below context so we can use the call above.
     */
    static void TextBlobCacheOverBudgetCB(void* data);

    typedef SkRefCnt INHERITED;
};

/**
 * Can be used to perform actions related to the generating GrContext in a thread safe manner. The
 * proxy does not access the 3D API (e.g. OpenGL) that backs the generating GrContext.
 */
class GrContextThreadSafeProxy : public SkRefCnt {
private:
    GrContextThreadSafeProxy(const GrCaps* caps, uint32_t uniqueID)
        : fCaps(SkRef(caps))
        , fContextUniqueID(uniqueID) {}

    SkAutoTUnref<const GrCaps>  fCaps;
    uint32_t                    fContextUniqueID;

    friend class GrContext;
    friend class SkImage;

    typedef SkRefCnt INHERITED;
};

#endif