gecko-dev/gfx/thebes/gfxCachedTempSurface.h

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/* -*- Mode: C++; tab-width: 20; 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/. */
#ifndef GFX_CACHED_TEMP_SURFACE_H
#define GFX_CACHED_TEMP_SURFACE_H
#include "gfxASurface.h"
#include "nsExpirationTracker.h"
class gfxContext;
/**
* This class can be used to cache double-buffering back surfaces.
*
* Large resource allocations may have an overhead that can be avoided by
* caching. Caching also alows the system to use history in deciding whether
* to manage the surfaces in video or system memory.
*
* However, because we don't want to set aside megabytes of unused resources
* unncessarily, these surfaces are released on a timer.
*/
class THEBES_API gfxCachedTempSurface {
public:
/**
* Returns a context for a surface that can be efficiently copied to
* |aSimilarTo|.
*
* When |aContentType| has an alpha component, the surface will be cleared.
* For opaque surfaces, the initial surface contents are undefined.
* When |aContentType| differs in different invocations this is handled
* appropriately, creating a new surface if necessary.
*
* |aSimilarTo| should be of the same gfxSurfaceType in each invocation.
* Because the cached surface may have been created during a previous
* invocation, this will not be efficient if the new |aSimilarTo| has a
* different format.
*/
already_AddRefed<gfxContext> Get(gfxASurface::gfxContentType aContentType,
const gfxRect& aRect,
gfxASurface* aSimilarTo);
void Expire() { mSurface = nullptr; }
nsExpirationState* GetExpirationState() { return &mExpirationState; }
~gfxCachedTempSurface();
bool IsSurface(gfxASurface* aSurface) { return mSurface == aSurface; }
private:
nsRefPtr<gfxASurface> mSurface;
gfxIntSize mSize;
nsExpirationState mExpirationState;
#ifdef DEBUG
gfxASurface::gfxSurfaceType mType;
#endif
};
#endif /* GFX_CACHED_TEMP_SURFACE_H */