424 lines
18 KiB
C++
424 lines
18 KiB
C++
/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
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/* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this
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* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
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/**
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* SurfaceCache is a service for caching temporary surfaces and decoded image
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* data in imagelib.
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*/
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#ifndef mozilla_image_SurfaceCache_h
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#define mozilla_image_SurfaceCache_h
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#include "mozilla/Maybe.h" // for Maybe
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#include "mozilla/MemoryReporting.h" // for MallocSizeOf
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#include "mozilla/HashFunctions.h" // for HashGeneric and AddToHash
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#include "gfx2DGlue.h"
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#include "gfxPoint.h" // for gfxSize
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#include "nsCOMPtr.h" // for already_AddRefed
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#include "mozilla/gfx/Point.h" // for mozilla::gfx::IntSize
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#include "mozilla/gfx/2D.h" // for SourceSurface
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#include "SurfaceFlags.h"
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#include "SVGImageContext.h" // for SVGImageContext
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namespace mozilla {
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namespace image {
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class Image;
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class imgFrame;
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class LookupResult;
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struct SurfaceMemoryCounter;
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/*
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* ImageKey contains the information we need to look up all cached surfaces for
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* a particular image.
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*/
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typedef Image* ImageKey;
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/*
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* SurfaceKey contains the information we need to look up a specific cached
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* surface. Together with an ImageKey, this uniquely identifies the surface.
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*
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* Callers should construct a SurfaceKey using the appropriate helper function
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* for their image type - either RasterSurfaceKey or VectorSurfaceKey.
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*/
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class SurfaceKey
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{
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typedef gfx::IntSize IntSize;
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public:
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bool operator==(const SurfaceKey& aOther) const
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{
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return aOther.mSize == mSize &&
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aOther.mSVGContext == mSVGContext &&
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aOther.mAnimationTime == mAnimationTime &&
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aOther.mFlags == mFlags;
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}
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uint32_t Hash() const
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{
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uint32_t hash = HashGeneric(mSize.width, mSize.height);
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hash = AddToHash(hash, mSVGContext.map(HashSIC).valueOr(0));
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hash = AddToHash(hash, mAnimationTime, uint32_t(mFlags));
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return hash;
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}
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IntSize Size() const { return mSize; }
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Maybe<SVGImageContext> SVGContext() const { return mSVGContext; }
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float AnimationTime() const { return mAnimationTime; }
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SurfaceFlags Flags() const { return mFlags; }
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private:
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SurfaceKey(const IntSize& aSize,
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const Maybe<SVGImageContext>& aSVGContext,
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const float aAnimationTime,
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const SurfaceFlags aFlags)
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: mSize(aSize)
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, mSVGContext(aSVGContext)
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, mAnimationTime(aAnimationTime)
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, mFlags(aFlags)
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{ }
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static uint32_t HashSIC(const SVGImageContext& aSIC) {
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return aSIC.Hash();
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}
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friend SurfaceKey RasterSurfaceKey(const IntSize&,
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SurfaceFlags,
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uint32_t);
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friend SurfaceKey VectorSurfaceKey(const IntSize&,
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const Maybe<SVGImageContext>&,
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float);
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IntSize mSize;
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Maybe<SVGImageContext> mSVGContext;
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float mAnimationTime;
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SurfaceFlags mFlags;
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};
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inline SurfaceKey
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RasterSurfaceKey(const gfx::IntSize& aSize,
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SurfaceFlags aFlags,
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uint32_t aFrameNum)
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{
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return SurfaceKey(aSize, Nothing(), float(aFrameNum), aFlags);
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}
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inline SurfaceKey
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VectorSurfaceKey(const gfx::IntSize& aSize,
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const Maybe<SVGImageContext>& aSVGContext,
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float aAnimationTime)
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{
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// We don't care about aFlags for VectorImage because none of the flags we
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// have right now influence VectorImage's rendering. If we add a new flag that
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// *does* affect how a VectorImage renders, we'll have to change this.
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return SurfaceKey(aSize, aSVGContext, aAnimationTime, DefaultSurfaceFlags());
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}
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enum class InsertOutcome : uint8_t {
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SUCCESS, // Success (but see Insert documentation).
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FAILURE, // Couldn't insert (e.g., for capacity reasons).
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FAILURE_ALREADY_PRESENT // A surface with the same key is already present.
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};
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/**
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* SurfaceCache is an imagelib-global service that allows caching of temporary
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* surfaces. Surfaces normally expire from the cache automatically if they go
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* too long without being accessed.
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*
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* SurfaceCache does not hold surfaces directly; instead, it holds imgFrame
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* objects, which hold surfaces but also layer on additional features specific
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* to imagelib's needs like animation, padding support, and transparent support
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* for volatile buffers.
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*
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* Sometime it's useful to temporarily prevent surfaces from expiring from the
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* cache. This is most often because losing the data could harm the user
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* experience (for example, we often don't want to allow surfaces that are
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* currently visible to expire) or because it's not possible to rematerialize
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* the surface. SurfaceCache supports this through the use of image locking; see
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* the comments for Insert() and LockImage() for more details.
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*
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* Any image which stores surfaces in the SurfaceCache *must* ensure that it
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* calls RemoveImage() before it is destroyed. See the comments for
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* RemoveImage() for more details.
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*/
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struct SurfaceCache
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{
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typedef gfx::IntSize IntSize;
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/**
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* Initialize static data. Called during imagelib module initialization.
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*/
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static void Initialize();
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/**
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* Release static data. Called during imagelib module shutdown.
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*/
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static void Shutdown();
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/**
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* Look up the imgFrame containing a surface in the cache and returns a
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* drawable reference to that imgFrame.
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*
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* If the image associated with the surface is locked, then the surface will
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* be locked before it is returned.
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*
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* If the imgFrame was found in the cache, but had stored its surface in a
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* volatile buffer which was discarded by the OS, then it is automatically
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* removed from the cache and an empty LookupResult is returned. Note that
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* this will never happen to surfaces associated with a locked image; the
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* cache keeps a strong reference to such surfaces internally.
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*
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* @param aImageKey Key data identifying which image the surface belongs
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* to.
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*
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* @param aSurfaceKey Key data which uniquely identifies the requested
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* surface.
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*
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* @return a LookupResult, which will either contain a
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* DrawableFrameRef to the requested surface, or an
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* empty DrawableFrameRef if the surface was not found.
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*/
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static LookupResult Lookup(const ImageKey aImageKey,
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const SurfaceKey& aSurfaceKey);
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/**
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* Looks up the best matching surface in the cache and returns a drawable
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* reference to the imgFrame containing it.
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*
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* Returned surfaces may vary from the requested surface only in terms of
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* size.
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*
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* @param aImageKey Key data identifying which image the surface belongs
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* to.
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*
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* @param aSurfaceKey Key data which identifies the ideal surface to return.
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*
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* @return a LookupResult, which will either contain a
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* DrawableFrameRef to a surface similar to the
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* requested surface, or an empty DrawableFrameRef if
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* the surface was not found. Callers can use
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* LookupResult::IsExactMatch() to check whether the
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* returned surface exactly matches @aSurfaceKey.
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*/
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static LookupResult LookupBestMatch(const ImageKey aImageKey,
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const SurfaceKey& aSurfaceKey);
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/**
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* Insert a surface into the cache. If a surface with the same ImageKey and
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* SurfaceKey is already in the cache, Insert returns FAILURE_ALREADY_PRESENT.
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* If a matching placeholder is already present, the placeholder is removed.
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*
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* Surfaces will never expire as long as they remain locked, but if they
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* become unlocked, they can expire either because the SurfaceCache runs out
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* of capacity or because they've gone too long without being used. When it
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* is first inserted, a surface is locked if its associated image is locked.
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* When that image is later unlocked, the surface becomes unlocked too. To
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* become locked again at that point, two things must happen: the image must
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* become locked again (via LockImage()), and the surface must be touched
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* again (via one of the Lookup() functions).
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*
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* All of this means that a very particular procedure has to be followed for
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* surfaces which cannot be rematerialized. First, they must be inserted
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* *after* the image is locked with LockImage(); if you use the other order,
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* the surfaces might expire before LockImage() gets called or before the
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* surface is touched again by Lookup(). Second, the image they are associated
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* with must never be unlocked.
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*
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* If a surface cannot be rematerialized, it may be important to know whether
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* it was inserted into the cache successfully. Insert() returns FAILURE if it
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* failed to insert the surface, which could happen because of capacity
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* reasons, or because it was already freed by the OS. If the surface isn't
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* associated with a locked image, checking for SUCCESS or FAILURE is useless:
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* the surface might expire immediately after being inserted, even though
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* Insert() returned SUCCESS. Thus, many callers do not need to check the
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* result of Insert() at all.
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*
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* @param aTarget The new surface (wrapped in an imgFrame) to insert into
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* the cache.
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* @param aImageKey Key data identifying which image the surface belongs
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* to.
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* @param aSurfaceKey Key data which uniquely identifies the requested
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* surface.
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* @return SUCCESS if the surface was inserted successfully. (But see above
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* for more information about when you should check this.)
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* FAILURE if the surface could not be inserted, e.g. for capacity
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* reasons. (But see above for more information about when you
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* should check this.)
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* FAILURE_ALREADY_PRESENT if a surface with the same ImageKey and
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* SurfaceKey already exists in the cache.
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*/
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static InsertOutcome Insert(imgFrame* aSurface,
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const ImageKey aImageKey,
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const SurfaceKey& aSurfaceKey);
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/**
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* Insert a placeholder for a surface into the cache. If a surface with the
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* same ImageKey and SurfaceKey is already in the cache, InsertPlaceholder()
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* returns FAILURE_ALREADY_PRESENT.
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*
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* Placeholders exist to allow lazy allocation of surfaces. The Lookup*()
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* methods will report whether a placeholder for an exactly matching surface
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* existed by returning a MatchType of PENDING or SUBSTITUTE_BECAUSE_PENDING,
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* but they will never return a placeholder directly. (They couldn't, since
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* placeholders don't have an associated surface.)
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*
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* Once inserted, placeholders can be removed using RemoveSurface() or
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* RemoveImage(), just like a surface. They're automatically removed when a
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* real surface that matches the placeholder is inserted with Insert().
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*
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* @param aImageKey Key data identifying which image the placeholder
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* belongs to.
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* @param aSurfaceKey Key data which uniquely identifies the surface the
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* placeholder stands in for.
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* @return SUCCESS if the placeholder was inserted successfully.
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* FAILURE if the placeholder could not be inserted for some reason.
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* FAILURE_ALREADY_PRESENT if a surface with the same ImageKey and
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* SurfaceKey already exists in the cache.
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*/
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static InsertOutcome InsertPlaceholder(const ImageKey aImageKey,
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const SurfaceKey& aSurfaceKey);
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/**
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* Checks if a surface of a given size could possibly be stored in the cache.
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* If CanHold() returns false, Insert() will always fail to insert the
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* surface, but the inverse is not true: Insert() may take more information
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* into account than just image size when deciding whether to cache the
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* surface, so Insert() may still fail even if CanHold() returns true.
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*
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* Use CanHold() to avoid the need to create a temporary surface when we know
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* for sure the cache can't hold it.
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*
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* @param aSize The dimensions of a surface in pixels.
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* @param aBytesPerPixel How many bytes each pixel of the surface requires.
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* Defaults to 4, which is appropriate for RGBA or RGBX
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* images.
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*
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* @return false if the surface cache can't hold a surface of that size.
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*/
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static bool CanHold(const IntSize& aSize, uint32_t aBytesPerPixel = 4);
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static bool CanHold(size_t aSize);
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/**
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* Locks an image. Any of the image's surfaces which are either inserted or
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* accessed while the image is locked will not expire.
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*
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* Locking an image does not automatically lock that image's existing
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* surfaces. A call to LockImage() guarantees that surfaces which are inserted
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* afterward will not expire before the next call to UnlockImage() or
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* UnlockSurfaces() for that image. Surfaces that are accessed via Lookup() or
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* LookupBestMatch() after a LockImage() call will also not expire until the
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* next UnlockImage() or UnlockSurfaces() call for that image. Any other
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* surfaces owned by the image may expire at any time.
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*
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* Regardless of locking, any of an image's surfaces may be removed using
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* RemoveSurface(), and all of an image's surfaces are removed by
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* RemoveImage(), whether the image is locked or not.
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*
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* It's safe to call LockImage() on an image that's already locked; this has
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* no effect.
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*
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* You must always unlock any image you lock. You may do this explicitly by
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* calling UnlockImage(), or implicitly by calling RemoveImage(). Since you're
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* required to call RemoveImage() when you destroy an image, this doesn't
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* impose any additional requirements, but it's preferable to call
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* UnlockImage() earlier if it's possible.
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*
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* @param aImageKey The image to lock.
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*/
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static void LockImage(const ImageKey aImageKey);
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/**
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* Unlocks an image, allowing any of its surfaces to expire at any time.
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*
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* It's OK to call UnlockImage() on an image that's already unlocked; this has
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* no effect.
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*
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* @param aImageKey The image to unlock.
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*/
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static void UnlockImage(const ImageKey aImageKey);
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/**
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* Unlocks the existing surfaces of an image, allowing them to expire at any
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* time.
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*
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* This does not unlock the image itself, so accessing the surfaces via
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* Lookup() or LookupBestMatch() will lock them again, and prevent them from
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* expiring.
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*
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* This is intended to be used in situations where it's no longer clear that
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* all of the surfaces owned by an image are needed. Calling UnlockSurfaces()
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* and then taking some action that will cause Lookup() to touch any surfaces
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* that are still useful will permit the remaining surfaces to expire from the
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* cache.
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*
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* If the image is unlocked, this has no effect.
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*
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* @param aImageKey The image which should have its existing surfaces
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* unlocked.
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*/
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static void UnlockSurfaces(const ImageKey aImageKey);
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/**
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* Removes a surface or placeholder from the cache, if it's present. If it's
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* not present, RemoveSurface() has no effect.
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*
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* Use this function to remove individual surfaces that have become invalid.
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* Prefer RemoveImage() or DiscardAll() when they're applicable, as they have
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* much better performance than calling this function repeatedly.
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*
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* @param aImageKey Key data identifying which image the surface belongs
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to.
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* @param aSurfaceKey Key data which uniquely identifies the requested
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surface.
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*/
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static void RemoveSurface(const ImageKey aImageKey,
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const SurfaceKey& aSurfaceKey);
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/**
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* Removes all cached surfaces and placeholders associated with the given
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* image from the cache. If the image is locked, it is automatically
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* unlocked.
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*
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* This MUST be called, at a minimum, when an Image which could be storing
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* surfaces in the surface cache is destroyed. If another image were allocated
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* at the same address it could result in subtle, difficult-to-reproduce bugs.
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*
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* @param aImageKey The image which should be removed from the cache.
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*/
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static void RemoveImage(const ImageKey aImageKey);
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/**
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* Evicts all evictable surfaces from the cache.
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*
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* All surfaces are evictable except for surfaces associated with locked
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* images. Non-evictable surfaces can only be removed by RemoveSurface() or
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* RemoveImage().
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*/
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static void DiscardAll();
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/**
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* Collects an accounting of the surfaces contained in the SurfaceCache for
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* the given image, along with their size and various other metadata.
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*
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* This is intended for use with memory reporting.
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*
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* @param aImageKey The image to report memory usage for.
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* @param aCounters An array into which the report for each surface will
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* be written.
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* @param aMallocSizeOf A fallback malloc memory reporting function.
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*/
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static void CollectSizeOfSurfaces(const ImageKey aImageKey,
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nsTArray<SurfaceMemoryCounter>& aCounters,
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MallocSizeOf aMallocSizeOf);
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private:
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virtual ~SurfaceCache() = 0; // Forbid instantiation.
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};
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} // namespace image
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} // namespace mozilla
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#endif // mozilla_image_SurfaceCache_h
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