gfx/thebes/gfxReusableSurfaceWrapper.h@97036ab72558 (annotated)
gfx/thebes/gfxReusableSurfaceWrapper.h
Tue, 06 Jan 2015 21:39:09 +0100
- author
- Michael Schloh von Bennewitz <michael@schloh.com>
- date
- Tue, 06 Jan 2015 21:39:09 +0100
- branch
- TOR_BUG_9701
- changeset 8
- 97036ab72558
- permissions
- -rw-r--r--
Conditionally force memory storage according to privacy.thirdparty.isolate;
This solves Tor bug #9701, complying with disk avoidance documented in
https://www.torproject.org/projects/torbrowser/design/#disk-avoidance.
| michael@0 | 1 | /* This Source Code Form is subject to the terms of the Mozilla Public |
| michael@0 | 2 | * License, v. 2.0. If a copy of the MPL was not distributed with this file, |
| michael@0 | 3 | * You can obtain one at http://mozilla.org/MPL/2.0/. */ |
| michael@0 | 4 | |
| michael@0 | 5 | #ifndef GFXCOWSURFACEWRAPPER |
| michael@0 | 6 | #define GFXCOWSURFACEWRAPPER |
| michael@0 | 7 | |
| michael@0 | 8 | #include "gfxImageSurface.h" |
| michael@0 | 9 | #include "nsISupportsImpl.h" |
| michael@0 | 10 | #include "nsAutoPtr.h" |
| michael@0 | 11 | |
| michael@0 | 12 | |
| michael@0 | 13 | /** |
| michael@0 | 14 | * Provides an interface to implement a cross thread/process wrapper for a |
| michael@0 | 15 | * gfxImageSurface that has copy-on-write semantics. |
| michael@0 | 16 | * |
| michael@0 | 17 | * Only the owner thread can write to the surface and acquire |
| michael@0 | 18 | * read locks. Destroying a gfxReusableSurfaceWrapper releases |
| michael@0 | 19 | * a read lock. |
| michael@0 | 20 | * |
| michael@0 | 21 | * OMTC Usage: |
| michael@0 | 22 | * 1) Content creates a writable copy of this surface |
| michael@0 | 23 | * wrapper which will be optimized to the same wrapper if there |
| michael@0 | 24 | * are no readers. |
| michael@0 | 25 | * 2) The surface is sent from content to the compositor once |
| michael@0 | 26 | * or potentially many times, each increasing a read lock. |
| michael@0 | 27 | * 3) When the compositor receives the surface, it adopts the |
| michael@0 | 28 | * read lock. |
| michael@0 | 29 | * 4) Once the compositor has processed the surface and uploaded |
| michael@0 | 30 | * the content, it then releases the read lock by dereferencing |
| michael@0 | 31 | * its wrapper. |
| michael@0 | 32 | */ |
| michael@0 | 33 | class gfxReusableSurfaceWrapper { |
| michael@0 | 34 | NS_INLINE_DECL_THREADSAFE_REFCOUNTING(gfxReusableSurfaceWrapper) |
| michael@0 | 35 | public: |
| michael@0 | 36 | |
| michael@0 | 37 | /** |
| michael@0 | 38 | * Returns a read-only pointer to the image data. |
| michael@0 | 39 | */ |
| michael@0 | 40 | virtual const unsigned char* GetReadOnlyData() const = 0; |
| michael@0 | 41 | |
| michael@0 | 42 | /** |
| michael@0 | 43 | * Returns the image surface format. |
| michael@0 | 44 | */ |
| michael@0 | 45 | virtual gfxImageFormat Format() = 0; |
| michael@0 | 46 | |
| michael@0 | 47 | /** |
| michael@0 | 48 | * Returns a writable copy of the image. |
| michael@0 | 49 | * If necessary this will copy the wrapper. If there are no contention |
| michael@0 | 50 | * the same wrapper will be returned. A ReadLock must be held when |
| michael@0 | 51 | * calling this function, and calling it will give up this lock. |
| michael@0 | 52 | */ |
| michael@0 | 53 | virtual gfxReusableSurfaceWrapper* GetWritable(gfxImageSurface** aSurface) = 0; |
| michael@0 | 54 | |
| michael@0 | 55 | /** |
| michael@0 | 56 | * A read only lock count is recorded, any attempts to |
| michael@0 | 57 | * call GetWritable() while this count is greater than one will |
| michael@0 | 58 | * create a new surface/wrapper pair. |
| michael@0 | 59 | * |
| michael@0 | 60 | * When a surface's read count falls to zero, its memory will be |
| michael@0 | 61 | * deallocated. It is the responsibility of the user to make sure |
| michael@0 | 62 | * that all locks are matched with an equal number of unlocks. |
| michael@0 | 63 | */ |
| michael@0 | 64 | virtual void ReadLock() = 0; |
| michael@0 | 65 | virtual void ReadUnlock() = 0; |
| michael@0 | 66 | |
| michael@0 | 67 | /** |
| michael@0 | 68 | * Types for each implementation of gfxReusableSurfaceWrapper. |
| michael@0 | 69 | */ |
| michael@0 | 70 | enum Type { |
| michael@0 | 71 | TYPE_SHARED_IMAGE, |
| michael@0 | 72 | TYPE_IMAGE, |
| michael@0 | 73 | |
| michael@0 | 74 | TYPE_MAX |
| michael@0 | 75 | }; |
| michael@0 | 76 | |
| michael@0 | 77 | /** |
| michael@0 | 78 | * Returns a unique ID for each implementation of gfxReusableSurfaceWrapper. |
| michael@0 | 79 | */ |
| michael@0 | 80 | virtual Type GetType() = 0; |
| michael@0 | 81 | |
| michael@0 | 82 | protected: |
| michael@0 | 83 | // Protected destructor, to discourage deletion outside of Release(): |
| michael@0 | 84 | virtual ~gfxReusableSurfaceWrapper() {} |
| michael@0 | 85 | |
| michael@0 | 86 | NS_DECL_OWNINGTHREAD |
| michael@0 | 87 | }; |
| michael@0 | 88 | |
| michael@0 | 89 | #endif // GFXCOWSURFACEWRAPPER |
