GrContextOptions.h

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/*
 * 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 GrContextOptions_DEFINED
#define GrContextOptions_DEFINED
 
#include "include/core/SkData.h"
#include "include/core/SkString.h"
#include "include/core/SkTypes.h"
#include "include/gpu/GrDriverBugWorkarounds.h"
#include "include/gpu/GrTypes.h"
#include "include/gpu/ShaderErrorHandler.h"
#include "include/private/gpu/ganesh/GrTypesPriv.h"
 
#include <vector>
 
class SkExecutor;
 
struct SK_API GrContextOptions {
    enum class Enable {
        /** Forces an option to be disabled. */
        kNo,
        /** Forces an option to be enabled. */
        kYes,
        /**
         * Uses Skia's default behavior, which may use runtime properties (e.g. driver version).
         */
        kDefault
    };
 
    enum class ShaderCacheStrategy {
        kSkSL,
        kBackendSource,
        kBackendBinary,
    };
 
    /**
     * Abstract class which stores Skia data in a cache that persists between sessions. Currently,
     * Skia stores compiled shader binaries (only when glProgramBinary / glGetProgramBinary are
     * supported) when provided a persistent cache, but this may extend to other data in the future.
     */
    class SK_API PersistentCache {
    public:
        virtual ~PersistentCache() = default;
 
        /**
         * Returns the data for the key if it exists in the cache, otherwise returns null.
         */
        virtual sk_sp<SkData> load(const SkData& key) = 0;
 
        // Placeholder until all clients override the 3-parameter store(), then remove this, and
        // make that version pure virtual.
        virtual void store(const SkData& /*key*/, const SkData& /*data*/) { SkASSERT(false); }
 
        /**
         * Stores data in the cache, indexed by key. description provides a human-readable
         * version of the key.
         */
        virtual void store(const SkData& key, const SkData& data, const SkString& /*description*/) {
            this->store(key, data);
        }
 
    protected:
        PersistentCache() = default;
        PersistentCache(const PersistentCache&) = delete;
        PersistentCache& operator=(const PersistentCache&) = delete;
    };
 
    using ShaderErrorHandler = skgpu::ShaderErrorHandler;
 
    GrContextOptions() {}
 
    // Suppress prints for the GrContext.
    bool fSuppressPrints = false;
 
    /**
     * Controls whether we check for GL errors after functions that allocate resources (e.g.
     * glTexImage2D), at the end of a GPU submission, or checking framebuffer completeness. The
     * results of shader compilation and program linking are always checked, regardless of this
     * option. Ignored on backends other than GL.
     */
    Enable fSkipGLErrorChecks = Enable::kDefault;
 
    /** Overrides: These options override feature detection using backend API queries. These
        overrides can only reduce the feature set or limits, never increase them beyond the
        detected values. */
 
    int  fMaxTextureSizeOverride = SK_MaxS32;
 
    /** the threshold in bytes above which we will use a buffer mapping API to map vertex and index
        buffers to CPU memory in order to update them.  A value of -1 means the GrContext should
        deduce the optimal value for this platform. */
    int  fBufferMapThreshold = -1;
 
    /** Default minimum size to use when allocating buffers for uploading data to textures. The
        larger the value the more uploads can be packed into one buffer, but at the cost of
        more gpu memory allocated that may not be used. Uploads larger than the minimum will still
        work by allocating a dedicated buffer. */
    size_t fMinimumStagingBufferSize = 64 * 1024;
 
    /**
     * Executor to handle threaded work within Ganesh. If this is nullptr, then all work will be
     * done serially on the main thread. To have worker threads assist with various tasks, set this
     * to a valid SkExecutor instance. Currently, used for software path rendering, but may be used
     * for other tasks.
     */
    SkExecutor* fExecutor = nullptr;
 
    /** Construct mipmaps manually, via repeated downsampling draw-calls. This is used when
        the driver's implementation (glGenerateMipmap) contains bugs. This requires mipmap
        level control (ie desktop or ES3). */
    bool fDoManualMipmapping = false;
 
    /**
     * Disables the use of coverage counting shortcuts to render paths. Coverage counting can cause
     * artifacts along shared edges if care isn't taken to ensure both contours wind in the same
     * direction.
     */
    // FIXME: Once this is removed from Chrome and Android, rename to fEnable"".
    bool fDisableCoverageCountingPaths = true;
 
    /**
     * Disables distance field rendering for paths. Distance field computation can be expensive,
     * and yields no benefit if a path is not rendered multiple times with different transforms.
     */
    bool fDisableDistanceFieldPaths = false;
 
    /**
     * If true this allows path mask textures to be cached. This is only really useful if paths
     * are commonly rendered at the same scale and fractional translation.
     */
    bool fAllowPathMaskCaching = true;
 
    /**
     * If true, the GPU will not be used to perform YUV -> RGB conversion when generating
     * textures from codec-backed images.
     */
    bool fDisableGpuYUVConversion = false;
 
    /**
     * The maximum size of cache textures used for Skia's Glyph cache.
     */
    size_t fGlyphCacheTextureMaximumBytes = 2048 * 1024 * 4;
 
    /**
     * Below this threshold size in device space distance field fonts won't be used. Distance field
     * fonts don't support hinting which is more important at smaller sizes.
     */
    float fMinDistanceFieldFontSize = 18;
 
    /**
     * Above this threshold size in device space glyphs are drawn as individual paths.
     */
#if defined(SK_BUILD_FOR_ANDROID)
    float fGlyphsAsPathsFontSize = 384;
#elif defined(SK_BUILD_FOR_MAC)
    float fGlyphsAsPathsFontSize = 256;
#else
    float fGlyphsAsPathsFontSize = 324;
#endif
 
    /**
     * Can the glyph atlas use multiple textures. If allowed, the each texture's size is bound by
     * fGlypheCacheTextureMaximumBytes.
     */
    Enable fAllowMultipleGlyphCacheTextures = Enable::kDefault;
 
    /**
     * Bugs on certain drivers cause stencil buffers to leak. This flag causes Skia to avoid
     * allocating stencil buffers and use alternate rasterization paths, avoiding the leak.
     */
    bool fAvoidStencilBuffers = false;
 
    /**
     * Enables driver workaround to use draws instead of HW clears, e.g. glClear on the GL backend.
     */
    Enable fUseDrawInsteadOfClear = Enable::kDefault;
 
    /**
     * Allow Ganesh to more aggressively reorder operations to reduce the number of render passes.
     * Offscreen draws will be done upfront instead of interrupting the main render pass when
     * possible. May increase VRAM usage, but still observes the resource cache limit.
     * Enabled by default.
     */
    Enable fReduceOpsTaskSplitting = Enable::kDefault;
 
    /**
     * Some ES3 contexts report the ES2 external image extension, but not the ES3 version.
     * If support for external images is critical, enabling this option will cause Ganesh to limit
     * shaders to the ES2 shading language in that situation.
     */
    bool fPreferExternalImagesOverES3 = false;
 
    /**
     * Disables correctness workarounds that are enabled for particular GPUs, OSes, or drivers.
     * This does not affect code path choices that are made for perfomance reasons nor does it
     * override other GrContextOption settings.
     */
    bool fDisableDriverCorrectnessWorkarounds = false;
 
    /**
     * Maximum number of GPU programs or pipelines to keep active in the runtime cache.
     */
    int fRuntimeProgramCacheSize = 256;
 
    /**
     * Cache in which to store compiled shader binaries between runs.
     */
    PersistentCache* fPersistentCache = nullptr;
 
    /**
     * This affects the usage of the PersistentCache. We can cache SkSL, backend source (GLSL), or
     * backend binaries (GL program binaries). By default we cache binaries, but if the driver's
     * binary loading/storing is believed to have bugs, this can be limited to caching GLSL.
     * Caching GLSL strings still saves CPU work when a GL program is created.
     */
    ShaderCacheStrategy fShaderCacheStrategy = ShaderCacheStrategy::kBackendBinary;
 
    /**
     * If present, use this object to report shader compilation failures. If not, report failures
     * via SkDebugf and assert.
     */
    ShaderErrorHandler* fShaderErrorHandler = nullptr;
 
    /**
     * Specifies the number of samples Ganesh should use when performing internal draws with MSAA
     * (hardware capabilities permitting).
     *
     * If 0, Ganesh will disable internal code paths that use multisampling.
     */
    int  fInternalMultisampleCount = 4;
 
    /**
     * In Skia's vulkan backend a single GrContext submit equates to the submission of a single
     * primary command buffer to the VkQueue. This value specifies how many vulkan secondary command
     * buffers we will cache for reuse on a given primary command buffer. A single submit may use
     * more than this many secondary command buffers, but after the primary command buffer is
     * finished on the GPU it will only hold on to this many secondary command buffers for reuse.
     *
     * A value of -1 means we will pick a limit value internally.
     */
    int fMaxCachedVulkanSecondaryCommandBuffers = -1;
 
    /**
     * If true, the caps will never support mipmaps.
     */
    bool fSuppressMipmapSupport = false;
 
    /**
     * If true, the TessellationPathRenderer will not be used for path rendering.
     * If false, will fallback to any driver workarounds, if set.
     */
    bool fDisableTessellationPathRenderer = false;
 
    /**
     * If true, and if supported, enables hardware tessellation in the caps.
     * DEPRECATED: This value is ignored; experimental hardware tessellation is always disabled.
     */
    bool fEnableExperimentalHardwareTessellation = false;
 
    /**
     * If true, then add 1 pixel padding to all glyph masks in the atlas to support bi-lerp
     * rendering of all glyphs. This must be set to true to use Slugs.
     */
    bool fSupportBilerpFromGlyphAtlas = false;
 
    /**
     * Uses a reduced variety of shaders. May perform less optimally in steady state but can reduce
     * jank due to shader compilations.
     */
    bool fReducedShaderVariations = false;
 
    /**
     * If true, then allow to enable MSAA on new Intel GPUs.
     */
    bool fAllowMSAAOnNewIntel = false;
 
    /**
     * Currently on ARM Android we disable the use of GL TexStorage because of memory regressions.
     * However, some clients may still want to use TexStorage. For example, TexStorage support is
     * required for creating protected textures.
     *
     * This flag has no impact on non GL backends.
     */
    bool fAlwaysUseTexStorageWhenAvailable = false;
 
    /**
     * Optional callback that can be passed into the GrDirectContext which will be called when the
     * GrDirectContext is about to be destroyed. When this call is made, it will be safe for the
     * client to delete the GPU backend context that is backing the GrDirectContext. The
     * GrDirectContextDestroyedContext will be passed back to the client in the callback.
     */
    GrDirectContextDestroyedContext fContextDeleteContext = nullptr;
    GrDirectContextDestroyedProc fContextDeleteProc = nullptr;
 
#if defined(GR_TEST_UTILS)
    /**
     * Private options that are only meant for testing within Skia's tools.
     */
 
    /**
     * Testing-only mode to exercise allocation failures in the flush-time callback objects.
     * For now it only simulates allocation failure during the preFlush callback.
     */
    bool fFailFlushTimeCallbacks = false;
 
    /**
     * Prevents use of dual source blending, to test that all xfer modes work correctly without it.
     */
    bool fSuppressDualSourceBlending = false;
 
    /**
     * Prevents the use of non-coefficient-based blend equations, for testing dst reads, barriers,
     * and in-shader blending.
     */
    bool fSuppressAdvancedBlendEquations = false;
 
    /**
     * Prevents the use of framebuffer fetches, for testing dst reads and texture barriers.
     */
    bool fSuppressFramebufferFetch = false;
 
    /**
     * If true, then all paths are processed as if "setIsVolatile" had been called.
     */
    bool fAllPathsVolatile = false;
 
    /**
     * Render everything in wireframe
     */
    bool fWireframeMode = false;
 
    /**
     * Enforces clearing of all textures when they're created.
     */
    bool fClearAllTextures = false;
 
    /**
     * Randomly generate a (false) GL_OUT_OF_MEMORY error
     */
    bool fRandomGLOOM = false;
 
    /**
     * Force off support for write/transfer pixels row bytes in caps.
     */
    bool fDisallowWriteAndTransferPixelRowBytes = false;
 
    /**
     * Include or exclude specific GPU path renderers.
     */
    GpuPathRenderers fGpuPathRenderers = GpuPathRenderers::kDefault;
 
    /**
     * Specify the GPU resource cache limit. Equivalent to calling `setResourceCacheLimit` on the
     * context at construction time.
     *
     * A value of -1 means use the default limit value.
     */
    int fResourceCacheLimitOverride = -1;
 
    /**
     * Maximum width and height of internal texture atlases.
     */
    int  fMaxTextureAtlasSize = 2048;
#endif
 
    GrDriverBugWorkarounds fDriverBugWorkarounds;
};
 
#endif