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