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