michael@0: /* -*- Mode: C++; tab-width: 20; indent-tabs-mode: nil; c-basic-offset: 2 -*-
michael@0:  * This Source Code Form is subject to the terms of the Mozilla Public
michael@0:  * License, v. 2.0. If a copy of the MPL was not distributed with this
michael@0:  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
michael@0: 
michael@0: #ifndef GFX_CACHED_TEMP_SURFACE_H
michael@0: #define GFX_CACHED_TEMP_SURFACE_H
michael@0: 
michael@0: #include "gfxASurface.h"
michael@0: #include "nsExpirationTracker.h"
michael@0: #include "nsSize.h"
michael@0: 
michael@0: class gfxContext;
michael@0: 
michael@0: /**
michael@0:  * This class can be used to cache double-buffering back surfaces.
michael@0:  *
michael@0:  * Large resource allocations may have an overhead that can be avoided by
michael@0:  * caching.  Caching also alows the system to use history in deciding whether
michael@0:  * to manage the surfaces in video or system memory.
michael@0:  *
michael@0:  * However, because we don't want to set aside megabytes of unused resources
michael@0:  * unncessarily, these surfaces are released on a timer.
michael@0:  */
michael@0: 
michael@0: class gfxCachedTempSurface {
michael@0: public:
michael@0:   /**
michael@0:    * Returns a context for a surface that can be efficiently copied to
michael@0:    * |aSimilarTo|.
michael@0:    *
michael@0:    * When |aContentType| has an alpha component, the surface will be cleared.
michael@0:    * For opaque surfaces, the initial surface contents are undefined.
michael@0:    * When |aContentType| differs in different invocations this is handled
michael@0:    * appropriately, creating a new surface if necessary.
michael@0:    * 
michael@0:    * Because the cached surface may have been created during a previous
michael@0:    * invocation, this will not be efficient if the new |aSimilarTo| has a
michael@0:    * different format, size, or gfxSurfaceType.
michael@0:    */
michael@0:   already_AddRefed<gfxContext> Get(gfxContentType aContentType,
michael@0:                                    const gfxRect& aRect,
michael@0:                                    gfxASurface* aSimilarTo);
michael@0: 
michael@0:   void Expire() { mSurface = nullptr; }
michael@0:   nsExpirationState* GetExpirationState() { return &mExpirationState; }
michael@0:   ~gfxCachedTempSurface();
michael@0: 
michael@0:   bool IsSurface(gfxASurface* aSurface) { return mSurface == aSurface; }
michael@0: 
michael@0: private:
michael@0:   nsRefPtr<gfxASurface> mSurface;
michael@0:   gfxIntSize mSize;
michael@0:   nsExpirationState mExpirationState;
michael@0:   gfxSurfaceType mType;
michael@0: };
michael@0: 
michael@0: #endif /* GFX_CACHED_TEMP_SURFACE_H */