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73 lines
2.1 KiB
C++
73 lines
2.1 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 "gfxASurface.h"
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#include "nsISupportsImpl.h"
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#include "nsAutoPtr.h"
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class gfxImageSurface;
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/**
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* Provides a cross thread wrapper for a gfxImageSurface
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* that has copy-on-write schemantics.
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*
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* Only the owner thread can write to the surface and aquire
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* read locks.
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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 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 time, each increasing a read lock.
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* 3) When the compositor has processed the surface and uploaded
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* the content it then releases the read lock.
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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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* Pass the gfxASurface to the wrapper.
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* The wrapper should hold the only strong reference
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* to the surface and its memebers.
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*/
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gfxReusableSurfaceWrapper(gfxImageSurface* aSurface);
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~gfxReusableSurfaceWrapper();
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const unsigned char* GetReadOnlyData() const {
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NS_ABORT_IF_FALSE(mReadCount > 0, "Should have read lock");
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return mSurfaceData;
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}
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const gfxASurface::gfxImageFormat& Format() { return mFormat; }
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/**
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* Get 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.
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*/
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gfxReusableSurfaceWrapper* GetWritable(gfxImageSurface** aSurface);
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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 positive will
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* create a new surface/wrapper pair.
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*/
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void ReadLock();
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void ReadUnlock();
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private:
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NS_DECL_OWNINGTHREAD
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nsRefPtr<gfxImageSurface> mSurface;
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const gfxASurface::gfxImageFormat mFormat;
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const unsigned char* mSurfaceData;
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PRInt32 mReadCount;
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};
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#endif // GFXCOWSURFACEWRAPPER
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