/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */ /* This Source Code Form is subject to the terms of the Mozilla Public * License, v. 2.0. If a copy of the MPL was not distributed with this * file, You can obtain one at http://mozilla.org/MPL/2.0/. */ /** * SurfaceCache is a service for caching temporary surfaces and decoded image * data in imagelib. */ #ifndef mozilla_image_SurfaceCache_h #define mozilla_image_SurfaceCache_h #include "mozilla/Maybe.h" // for Maybe #include "mozilla/NotNull.h" #include "mozilla/MemoryReporting.h" // for MallocSizeOf #include "mozilla/HashFunctions.h" // for HashGeneric and AddToHash #include "gfx2DGlue.h" #include "gfxPoint.h" // for gfxSize #include "nsCOMPtr.h" // for already_AddRefed #include "mozilla/gfx/Point.h" // for mozilla::gfx::IntSize #include "mozilla/gfx/2D.h" // for SourceSurface #include "PlaybackType.h" #include "SurfaceFlags.h" #include "SVGImageContext.h" // for SVGImageContext namespace mozilla { namespace image { class Image; class ISurfaceProvider; class LookupResult; class SurfaceCacheImpl; struct SurfaceMemoryCounter; /* * ImageKey contains the information we need to look up all SurfaceCache entries * for a particular image. */ typedef Image* ImageKey; /* * SurfaceKey contains the information we need to look up a specific * SurfaceCache entry. Together with an ImageKey, this uniquely identifies the * surface. * * Callers should construct a SurfaceKey using the appropriate helper function * for their image type - either RasterSurfaceKey or VectorSurfaceKey. */ class SurfaceKey { typedef gfx::IntSize IntSize; public: bool operator==(const SurfaceKey& aOther) const { return aOther.mSize == mSize && aOther.mSVGContext == mSVGContext && aOther.mPlayback == mPlayback && aOther.mFlags == mFlags; } uint32_t Hash() const { uint32_t hash = HashGeneric(mSize.width, mSize.height); hash = AddToHash(hash, mSVGContext.map(HashSIC).valueOr(0)); hash = AddToHash(hash, uint8_t(mPlayback), uint32_t(mFlags)); return hash; } const IntSize& Size() const { return mSize; } Maybe<SVGImageContext> SVGContext() const { return mSVGContext; } PlaybackType Playback() const { return mPlayback; } SurfaceFlags Flags() const { return mFlags; } private: SurfaceKey(const IntSize& aSize, const Maybe<SVGImageContext>& aSVGContext, PlaybackType aPlayback, SurfaceFlags aFlags) : mSize(aSize) , mSVGContext(aSVGContext) , mPlayback(aPlayback) , mFlags(aFlags) { } static uint32_t HashSIC(const SVGImageContext& aSIC) { return aSIC.Hash(); } friend SurfaceKey RasterSurfaceKey(const IntSize&, SurfaceFlags, PlaybackType); friend SurfaceKey VectorSurfaceKey(const IntSize&, const Maybe<SVGImageContext>&); IntSize mSize; Maybe<SVGImageContext> mSVGContext; PlaybackType mPlayback; SurfaceFlags mFlags; }; inline SurfaceKey RasterSurfaceKey(const gfx::IntSize& aSize, SurfaceFlags aFlags, PlaybackType aPlayback) { return SurfaceKey(aSize, Nothing(), aPlayback, aFlags); } inline SurfaceKey VectorSurfaceKey(const gfx::IntSize& aSize, const Maybe<SVGImageContext>& aSVGContext) { // We don't care about aFlags for VectorImage because none of the flags we // have right now influence VectorImage's rendering. If we add a new flag that // *does* affect how a VectorImage renders, we'll have to change this. // Similarly, we don't accept a PlaybackType parameter because we don't // currently cache frames of animated SVG images. return SurfaceKey(aSize, aSVGContext, PlaybackType::eStatic, DefaultSurfaceFlags()); } /** * AvailabilityState is used to track whether an ISurfaceProvider has a surface * available or is just a placeholder. * * To ensure that availability changes are atomic (and especially that internal * SurfaceCache code doesn't have to deal with asynchronous availability * changes), an ISurfaceProvider which starts as a placeholder can only reveal * the fact that it now has a surface available via a call to * SurfaceCache::SurfaceAvailable(). */ class AvailabilityState { public: static AvailabilityState StartAvailable() { return AvailabilityState(true); } static AvailabilityState StartAsPlaceholder() { return AvailabilityState(false); } bool IsAvailable() const { return mIsAvailable; } bool IsPlaceholder() const { return !mIsAvailable; } private: friend class SurfaceCacheImpl; explicit AvailabilityState(bool aIsAvailable) : mIsAvailable(aIsAvailable) { } void SetAvailable() { mIsAvailable = true; } bool mIsAvailable; }; enum class InsertOutcome : uint8_t { SUCCESS, // Success (but see Insert documentation). FAILURE, // Couldn't insert (e.g., for capacity reasons). FAILURE_ALREADY_PRESENT // A surface with the same key is already present. }; /** * SurfaceCache is an ImageLib-global service that allows caching of decoded * image surfaces, temporary surfaces (e.g. for caching rotated or clipped * versions of images), or dynamically generated surfaces (e.g. for animations). * SurfaceCache entries normally expire from the cache automatically if they go * too long without being accessed. * * Because SurfaceCache must support both normal surfaces and dynamically * generated surfaces, it does not actually hold surfaces directly. Instead, it * holds ISurfaceProvider objects which can provide access to a surface when * requested; SurfaceCache doesn't care about the details of how this is * accomplished. * * Sometime it's useful to temporarily prevent entries from expiring from the * cache. This is most often because losing the data could harm the user * experience (for example, we often don't want to allow surfaces that are * currently visible to expire) or because it's not possible to rematerialize * the surface. SurfaceCache supports this through the use of image locking; see * the comments for Insert() and LockImage() for more details. * * Any image which stores surfaces in the SurfaceCache *must* ensure that it * calls RemoveImage() before it is destroyed. See the comments for * RemoveImage() for more details. */ struct SurfaceCache { typedef gfx::IntSize IntSize; /** * Initialize static data. Called during imagelib module initialization. */ static void Initialize(); /** * Release static data. Called during imagelib module shutdown. */ static void Shutdown(); /** * Looks up the requested cache entry and returns a drawable reference to its * associated surface. * * If the image associated with the cache entry is locked, then the entry will * be locked before it is returned. * * If a matching ISurfaceProvider was found in the cache, but SurfaceCache * couldn't obtain a surface from it (e.g. because it had stored its surface * in a volatile buffer which was discarded by the OS) then it is * automatically removed from the cache and an empty LookupResult is returned. * Note that this will never happen to ISurfaceProviders associated with a * locked image; SurfaceCache tells such ISurfaceProviders to keep a strong * references to their data internally. * * @param aImageKey Key data identifying which image the cache entry * belongs to. * @param aSurfaceKey Key data which uniquely identifies the requested * cache entry. * @return a LookupResult which will contain a DrawableSurface * if the cache entry was found. */ static LookupResult Lookup(const ImageKey aImageKey, const SurfaceKey& aSurfaceKey); /** * Looks up the best matching cache entry and returns a drawable reference to * its associated surface. * * The result may vary from the requested cache entry only in terms of size. * * @param aImageKey Key data identifying which image the cache entry * belongs to. * @param aSurfaceKey Key data which uniquely identifies the requested * cache entry. * @return a LookupResult which will contain a DrawableSurface * if a cache entry similar to the one the caller * requested could be found. Callers can use * LookupResult::IsExactMatch() to check whether the * returned surface exactly matches @aSurfaceKey. */ static LookupResult LookupBestMatch(const ImageKey aImageKey, const SurfaceKey& aSurfaceKey); /** * Insert an ISurfaceProvider into the cache. If an entry with the same * ImageKey and SurfaceKey is already in the cache, Insert returns * FAILURE_ALREADY_PRESENT. If a matching placeholder is already present, it * is replaced. * * Cache entries will never expire as long as they remain locked, but if they * become unlocked, they can expire either because the SurfaceCache runs out * of capacity or because they've gone too long without being used. When it * is first inserted, a cache entry is locked if its associated image is * locked. When that image is later unlocked, the cache entry becomes * unlocked too. To become locked again at that point, two things must happen: * the image must become locked again (via LockImage()), and the cache entry * must be touched again (via one of the Lookup() functions). * * All of this means that a very particular procedure has to be followed for * cache entries which cannot be rematerialized. First, they must be inserted * *after* the image is locked with LockImage(); if you use the other order, * the cache entry might expire before LockImage() gets called or before the * entry is touched again by Lookup(). Second, the image they are associated * with must never be unlocked. * * If a cache entry cannot be rematerialized, it may be important to know * whether it was inserted into the cache successfully. Insert() returns * FAILURE if it failed to insert the cache entry, which could happen because * of capacity reasons, or because it was already freed by the OS. If the * cache entry isn't associated with a locked image, checking for SUCCESS or * FAILURE is useless: the entry might expire immediately after being * inserted, even though Insert() returned SUCCESS. Thus, many callers do not * need to check the result of Insert() at all. * * @param aProvider The new cache entry to insert into the cache. * @return SUCCESS if the cache entry was inserted successfully. (But see above * for more information about when you should check this.) * FAILURE if the cache entry could not be inserted, e.g. for capacity * reasons. (But see above for more information about when you * should check this.) * FAILURE_ALREADY_PRESENT if an entry with the same ImageKey and * SurfaceKey already exists in the cache. */ static InsertOutcome Insert(NotNull<ISurfaceProvider*> aProvider); /** * Mark the cache entry @aProvider as having an available surface. This turns * a placeholder cache entry into a normal cache entry. The cache entry * becomes locked if the associated image is locked; otherwise, it starts in * the unlocked state. * * If the cache entry containing @aProvider has already been evicted from the * surface cache, this function has no effect. * * It's illegal to call this function if @aProvider is not a placeholder; by * definition, non-placeholder ISurfaceProviders should have a surface * available already. * * @param aProvider The cache entry that now has a surface available. */ static void SurfaceAvailable(NotNull<ISurfaceProvider*> aProvider); /** * Checks if a surface of a given size could possibly be stored in the cache. * If CanHold() returns false, Insert() will always fail to insert the * surface, but the inverse is not true: Insert() may take more information * into account than just image size when deciding whether to cache the * surface, so Insert() may still fail even if CanHold() returns true. * * Use CanHold() to avoid the need to create a temporary surface when we know * for sure the cache can't hold it. * * @param aSize The dimensions of a surface in pixels. * @param aBytesPerPixel How many bytes each pixel of the surface requires. * Defaults to 4, which is appropriate for RGBA or RGBX * images. * * @return false if the surface cache can't hold a surface of that size. */ static bool CanHold(const IntSize& aSize, uint32_t aBytesPerPixel = 4); static bool CanHold(size_t aSize); /** * Locks an image. Any of the image's cache entries which are either inserted * or accessed while the image is locked will not expire. * * Locking an image does not automatically lock that image's existing cache * entries. A call to LockImage() guarantees that entries which are inserted * afterward will not expire before the next call to UnlockImage() or * UnlockSurfaces() for that image. Cache entries that are accessed via * Lookup() or LookupBestMatch() after a LockImage() call will also not expire * until the next UnlockImage() or UnlockSurfaces() call for that image. Any * other cache entries owned by the image may expire at any time. * * All of an image's cache entries are removed by RemoveImage(), whether the * image is locked or not. * * It's safe to call LockImage() on an image that's already locked; this has * no effect. * * You must always unlock any image you lock. You may do this explicitly by * calling UnlockImage(), or implicitly by calling RemoveImage(). Since you're * required to call RemoveImage() when you destroy an image, this doesn't * impose any additional requirements, but it's preferable to call * UnlockImage() earlier if it's possible. * * @param aImageKey The image to lock. */ static void LockImage(const ImageKey aImageKey); /** * Unlocks an image, allowing any of its cache entries to expire at any time. * * It's OK to call UnlockImage() on an image that's already unlocked; this has * no effect. * * @param aImageKey The image to unlock. */ static void UnlockImage(const ImageKey aImageKey); /** * Unlocks the existing cache entries of an image, allowing them to expire at * any time. * * This does not unlock the image itself, so accessing the cache entries via * Lookup() or LookupBestMatch() will lock them again, and prevent them from * expiring. * * This is intended to be used in situations where it's no longer clear that * all of the cache entries owned by an image are needed. Calling * UnlockSurfaces() and then taking some action that will cause Lookup() to * touch any cache entries that are still useful will permit the remaining * entries to expire from the cache. * * If the image is unlocked, this has no effect. * * @param aImageKey The image which should have its existing cache entries * unlocked. */ static void UnlockEntries(const ImageKey aImageKey); /** * Removes all cache entries (including placeholders) associated with the * given image from the cache. If the image is locked, it is automatically * unlocked. * * This MUST be called, at a minimum, when an Image which could be storing * entries in the surface cache is destroyed. If another image were allocated * at the same address it could result in subtle, difficult-to-reproduce bugs. * * @param aImageKey The image which should be removed from the cache. */ static void RemoveImage(const ImageKey aImageKey); /** * Evicts all evictable entries from the cache. * * All entries are evictable except for entries associated with locked images. * Non-evictable entries can only be removed by RemoveImage(). */ static void DiscardAll(); /** * Collects an accounting of the surfaces contained in the SurfaceCache for * the given image, along with their size and various other metadata. * * This is intended for use with memory reporting. * * @param aImageKey The image to report memory usage for. * @param aCounters An array into which the report for each surface will * be written. * @param aMallocSizeOf A fallback malloc memory reporting function. */ static void CollectSizeOfSurfaces(const ImageKey aImageKey, nsTArray<SurfaceMemoryCounter>& aCounters, MallocSizeOf aMallocSizeOf); /** * @return maximum capacity of the SurfaceCache in bytes. This is only exposed * for use by tests; normal code should use CanHold() instead. */ static size_t MaximumCapacity(); private: virtual ~SurfaceCache() = 0; // Forbid instantiation. }; } // namespace image } // namespace mozilla #endif // mozilla_image_SurfaceCache_h