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 file,
michael@0:  * You can obtain one at http://mozilla.org/MPL/2.0/. */
michael@0: 
michael@0: #ifndef GFXCOWSURFACEWRAPPER
michael@0: #define GFXCOWSURFACEWRAPPER
michael@0: 
michael@0: #include "gfxImageSurface.h"
michael@0: #include "nsISupportsImpl.h"
michael@0: #include "nsAutoPtr.h"
michael@0: 
michael@0: 
michael@0: /**
michael@0:  * Provides an interface to implement a cross thread/process wrapper for a
michael@0:  * gfxImageSurface that has copy-on-write semantics.
michael@0:  *
michael@0:  * Only the owner thread can write to the surface and acquire
michael@0:  * read locks. Destroying a gfxReusableSurfaceWrapper releases
michael@0:  * a read lock.
michael@0:  *
michael@0:  * OMTC Usage:
michael@0:  * 1) Content creates a writable copy of this surface
michael@0:  *    wrapper which will be optimized to the same wrapper if there
michael@0:  *    are no readers.
michael@0:  * 2) The surface is sent from content to the compositor once
michael@0:  *    or potentially many times, each increasing a read lock.
michael@0:  * 3) When the compositor receives the surface, it adopts the
michael@0:  *    read lock.
michael@0:  * 4) Once the compositor has processed the surface and uploaded
michael@0:  *    the content, it then releases the read lock by dereferencing
michael@0:  *    its wrapper.
michael@0:  */
michael@0: class gfxReusableSurfaceWrapper {
michael@0:   NS_INLINE_DECL_THREADSAFE_REFCOUNTING(gfxReusableSurfaceWrapper)
michael@0: public:
michael@0: 
michael@0:   /**
michael@0:    * Returns a read-only pointer to the image data.
michael@0:    */
michael@0:   virtual const unsigned char* GetReadOnlyData() const = 0;
michael@0: 
michael@0:   /**
michael@0:    * Returns the image surface format.
michael@0:    */
michael@0:   virtual gfxImageFormat Format() = 0;
michael@0: 
michael@0:   /**
michael@0:    * Returns a writable copy of the image.
michael@0:    * If necessary this will copy the wrapper. If there are no contention
michael@0:    * the same wrapper will be returned. A ReadLock must be held when
michael@0:    * calling this function, and calling it will give up this lock.
michael@0:    */
michael@0:   virtual gfxReusableSurfaceWrapper* GetWritable(gfxImageSurface** aSurface) = 0;
michael@0: 
michael@0:   /**
michael@0:    * A read only lock count is recorded, any attempts to
michael@0:    * call GetWritable() while this count is greater than one will
michael@0:    * create a new surface/wrapper pair.
michael@0:    *
michael@0:    * When a surface's read count falls to zero, its memory will be
michael@0:    * deallocated. It is the responsibility of the user to make sure
michael@0:    * that all locks are matched with an equal number of unlocks.
michael@0:    */
michael@0:   virtual void ReadLock() = 0;
michael@0:   virtual void ReadUnlock() = 0;
michael@0: 
michael@0:   /**
michael@0:    * Types for each implementation of gfxReusableSurfaceWrapper.
michael@0:    */
michael@0:   enum Type {
michael@0:     TYPE_SHARED_IMAGE,
michael@0:     TYPE_IMAGE,
michael@0: 
michael@0:     TYPE_MAX
michael@0:   };
michael@0: 
michael@0:   /**
michael@0:    * Returns a unique ID for each implementation of gfxReusableSurfaceWrapper.
michael@0:    */
michael@0:   virtual Type GetType() = 0;
michael@0: 
michael@0: protected:
michael@0:   // Protected destructor, to discourage deletion outside of Release():
michael@0:   virtual ~gfxReusableSurfaceWrapper() {}
michael@0: 
michael@0:   NS_DECL_OWNINGTHREAD
michael@0: };
michael@0: 
michael@0: #endif // GFXCOWSURFACEWRAPPER