include/gpu/GrTextureProvider.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 GrTextureProvider_DEFINED
#define GrTextureProvider_DEFINED

#include "GrTexture.h"
#include "SkImageFilter.h"

class SK_API GrTextureProvider {
public:
    ///////////////////////////////////////////////////////////////////////////
    // Textures

    /**
     * Creates a new texture in the resource cache and returns it. The caller owns a
     * ref on the returned texture which must be balanced by a call to unref.
     *
     * @param desc      Description of the texture properties.
     * @param budgeted  Does the texture count against the resource cache budget?
     * @param srcData   Pointer to the pixel values (optional).
     * @param rowBytes  The number of bytes between rows of the texture. Zero
     *                  implies tightly packed rows. For compressed pixel configs, this
     *                  field is ignored.
     */
    GrTexture* createTexture(const GrSurfaceDesc& desc, bool budgeted, const void* srcData,
                             size_t rowBytes);

    /** Shortcut for creating a texture with no initial data to upload. */
    GrTexture* createTexture(const GrSurfaceDesc& desc, bool budgeted) {
        return this->createTexture(desc, budgeted, NULL, 0);
    }

    /** Assigns a unique key to the texture. The texture will be findable via this key using
        findTextureByUniqueKey(). If an existing texture has this key, it's key will be removed. */
    void assignUniqueKeyToTexture(const GrUniqueKey& key, GrTexture* texture) {
        this->assignUniqueKeyToResource(key, texture);
    }

    /** Finds a texture by unique key. If the texture is found it is ref'ed and returned. */
    GrTexture* findAndRefTextureByUniqueKey(const GrUniqueKey& key) {
        GrGpuResource* resource = this->findAndRefResourceByUniqueKey(key);
        if (resource) {
            GrTexture* texture = static_cast<GrSurface*>(resource)->asTexture();
            SkASSERT(texture);
            return texture;
        }
        return NULL;
    }

    /**
     * Determines whether a texture is associated with the unique key. If the texture is found it
     * will not be locked or returned. This call does not affect the priority of the resource for
     * deletion.
     */
    bool existsTextureWithUniqueKey(const GrUniqueKey& key) const {
        return this->existsResourceWithUniqueKey(key);
    }

    /**
     * Finds a texture that approximately matches the descriptor. Will be at least as large in width
     * and height as desc specifies. If desc specifies that the texture should be a render target
     * then result will be a render target. Format and sample count will always match the request.
     * The contents of the texture are undefined. The caller owns a ref on the returned texture and
     * must balance with a call to unref.
     */
    GrTexture* createApproxTexture(const GrSurfaceDesc&);

    enum SizeConstraint {
        kExact_SizeConstraint,
        kApprox_SizeConstraint,
    };

    GrTexture* createTexture(const GrSurfaceDesc& desc, SizeConstraint constraint) {
        switch (constraint) {
            case kExact_SizeConstraint:
                return this->createTexture(desc, true);
            case kApprox_SizeConstraint:
                return this->createApproxTexture(desc);
        }
        sk_throw();
        return nullptr;
    }

    static SizeConstraint FromImageFilter(SkImageFilter::SizeConstraint constraint) {
        if (SkImageFilter::kExact_SizeConstraint == constraint) {
            return kExact_SizeConstraint;
        } else {
            SkASSERT(SkImageFilter::kApprox_SizeConstraint == constraint);
            return kApprox_SizeConstraint;
        }
    }

    /** Legacy function that no longer should be used. */
    enum ScratchTexMatch {
        kExact_ScratchTexMatch,
        kApprox_ScratchTexMatch
    };
    GrTexture* refScratchTexture(const GrSurfaceDesc& desc, ScratchTexMatch match) {
        if (kApprox_ScratchTexMatch == match) {
            return this->createApproxTexture(desc);
        } else {
            return this->createTexture(desc, true);
        }
    }

    ///////////////////////////////////////////////////////////////////////////
    // Wrapped Backend Surfaces

    /**
     * Wraps an existing texture with a GrTexture object.
     *
     * OpenGL: if the object is a texture Gr may change its GL texture params
     *         when it is drawn.
     *
     * @return GrTexture object or NULL on failure.
     */
    GrTexture* wrapBackendTexture(const GrBackendTextureDesc& desc,
                                  GrWrapOwnership = kBorrow_GrWrapOwnership);

    /**
     * Wraps an existing render target with a GrRenderTarget object. It is
     * similar to wrapBackendTexture but can be used to draw into surfaces
     * that are not also textures (e.g. FBO 0 in OpenGL, or an MSAA buffer that
     * the client will resolve to a texture). Currently wrapped render targets
     * always use the kBorrow_GrWrapOwnership semantics.
     *
     * @return GrTexture object or NULL on failure.
     */
     GrRenderTarget* wrapBackendRenderTarget(const GrBackendRenderTargetDesc& desc);

protected:
    GrTextureProvider(GrGpu* gpu, GrResourceCache* cache) : fCache(cache), fGpu(gpu) {}

    /**
     * Assigns a unique key to a resource. If the key is associated with another resource that
     * association is removed and replaced by this resource.
     */
    void assignUniqueKeyToResource(const GrUniqueKey&, GrGpuResource*);

    /**
     * Finds a resource in the cache, based on the specified key. This is intended for use in
     * conjunction with addResourceToCache(). The return value will be NULL if not found. The
     * caller must balance with a call to unref().
     */
    GrGpuResource* findAndRefResourceByUniqueKey(const GrUniqueKey&);

    /**
     * Determines whether a resource is in the cache. If the resource is found it
     * will not be locked or returned. This call does not affect the priority of
     * the resource for deletion.
     */
    bool existsResourceWithUniqueKey(const GrUniqueKey& key) const;

    enum ScratchTextureFlags {
        kExact_ScratchTextureFlag           = 0x1,
        kNoPendingIO_ScratchTextureFlag     = 0x2, // (http://skbug.com/4156)
        kNoCreate_ScratchTextureFlag        = 0x4,
    };

    /** A common impl for GrTextureProvider and GrResourceProvider variants. */
    GrTexture* internalCreateApproxTexture(const GrSurfaceDesc& desc, uint32_t scratchTextureFlags);

    GrTexture* refScratchTexture(const GrSurfaceDesc&, uint32_t scratchTextureFlags);

    void abandon() {
        fCache = NULL;
        fGpu = NULL;
    }

    GrResourceCache* cache() { return fCache; }
    const GrResourceCache* cache() const { return fCache; }

    GrGpu* gpu() { return fGpu; }
    const GrGpu* gpu() const { return fGpu; }

    bool isAbandoned() const {
        SkASSERT(SkToBool(fGpu) == SkToBool(fCache));
        return !SkToBool(fCache);
    }

private:
    GrResourceCache* fCache;
    GrGpu* fGpu;
};

#endif