/src/mozilla-central/image/FrameTimeout.h
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1 | | /* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- |
2 | | * |
3 | | * This Source Code Form is subject to the terms of the Mozilla Public |
4 | | * License, v. 2.0. If a copy of the MPL was not distributed with this |
5 | | * file, You can obtain one at http://mozilla.org/MPL/2.0/. */ |
6 | | |
7 | | #ifndef mozilla_image_FrameTimeout_h |
8 | | #define mozilla_image_FrameTimeout_h |
9 | | |
10 | | #include <stdint.h> |
11 | | #include "mozilla/Assertions.h" |
12 | | |
13 | | namespace mozilla { |
14 | | namespace image { |
15 | | |
16 | | /** |
17 | | * FrameTimeout wraps a frame timeout value (measured in milliseconds) after |
18 | | * first normalizing it. This normalization is necessary because some tools |
19 | | * generate incorrect frame timeout values which we nevertheless have to |
20 | | * support. For this reason, code that deals with frame timeouts should always |
21 | | * use a FrameTimeout value rather than the raw value from the image header. |
22 | | */ |
23 | | struct FrameTimeout |
24 | | { |
25 | | /** |
26 | | * @return a FrameTimeout of zero. This should be used only for math |
27 | | * involving FrameTimeout values. You can't obtain a zero FrameTimeout from |
28 | | * FromRawMilliseconds(). |
29 | | */ |
30 | 0 | static FrameTimeout Zero() { return FrameTimeout(0); } |
31 | | |
32 | | /// @return an infinite FrameTimeout. |
33 | 0 | static FrameTimeout Forever() { return FrameTimeout(-1); } |
34 | | |
35 | | /// @return a FrameTimeout obtained by normalizing a raw timeout value. |
36 | | static FrameTimeout FromRawMilliseconds(int32_t aRawMilliseconds) |
37 | 0 | { |
38 | 0 | // Normalize all infinite timeouts to the same value. |
39 | 0 | if (aRawMilliseconds < 0) { |
40 | 0 | return FrameTimeout::Forever(); |
41 | 0 | } |
42 | 0 | |
43 | 0 | // Very small timeout values are problematic for two reasons: we don't want |
44 | 0 | // to burn energy redrawing animated images extremely fast, and broken tools |
45 | 0 | // generate these values when they actually want a "default" value, so such |
46 | 0 | // images won't play back right without normalization. For some context, |
47 | 0 | // see bug 890743, bug 125137, bug 139677, and bug 207059. The historical |
48 | 0 | // behavior of IE and Opera was: |
49 | 0 | // IE 6/Win: |
50 | 0 | // 10 - 50ms is normalized to 100ms. |
51 | 0 | // >50ms is used unnormalized. |
52 | 0 | // Opera 7 final/Win: |
53 | 0 | // 10ms is normalized to 100ms. |
54 | 0 | // >10ms is used unnormalized. |
55 | 0 | if (aRawMilliseconds >= 0 && aRawMilliseconds <= 10 ) { |
56 | 0 | return FrameTimeout(100); |
57 | 0 | } |
58 | 0 | |
59 | 0 | // The provided timeout value is OK as-is. |
60 | 0 | return FrameTimeout(aRawMilliseconds); |
61 | 0 | } |
62 | | |
63 | | bool operator==(const FrameTimeout& aOther) const |
64 | 0 | { |
65 | 0 | return mTimeout == aOther.mTimeout; |
66 | 0 | } |
67 | | |
68 | 0 | bool operator!=(const FrameTimeout& aOther) const { return !(*this == aOther); } |
69 | | |
70 | | FrameTimeout operator+(const FrameTimeout& aOther) |
71 | 0 | { |
72 | 0 | if (*this == Forever() || aOther == Forever()) { |
73 | 0 | return Forever(); |
74 | 0 | } |
75 | 0 | |
76 | 0 | return FrameTimeout(mTimeout + aOther.mTimeout); |
77 | 0 | } |
78 | | |
79 | | FrameTimeout& operator+=(const FrameTimeout& aOther) |
80 | 0 | { |
81 | 0 | *this = *this + aOther; |
82 | 0 | return *this; |
83 | 0 | } |
84 | | |
85 | | /** |
86 | | * @return this FrameTimeout's value in milliseconds. Illegal to call on a |
87 | | * an infinite FrameTimeout value. |
88 | | */ |
89 | | uint32_t AsMilliseconds() const |
90 | 0 | { |
91 | 0 | if (*this == Forever()) { |
92 | 0 | MOZ_ASSERT_UNREACHABLE("Calling AsMilliseconds() on an infinite FrameTimeout"); |
93 | 0 | return 100; // Fail to something sane. |
94 | 0 | } |
95 | 0 |
|
96 | 0 | return uint32_t(mTimeout); |
97 | 0 | } |
98 | | |
99 | | /** |
100 | | * @return this FrameTimeout value encoded so that non-negative values |
101 | | * represent a timeout in milliseconds, and -1 represents an infinite |
102 | | * timeout. |
103 | | * |
104 | | * XXX(seth): This is a backwards compatibility hack that should be removed. |
105 | | */ |
106 | 0 | int32_t AsEncodedValueDeprecated() const { return mTimeout; } |
107 | | |
108 | | private: |
109 | | explicit FrameTimeout(int32_t aTimeout) |
110 | | : mTimeout(aTimeout) |
111 | 0 | { } |
112 | | |
113 | | int32_t mTimeout; |
114 | | }; |
115 | | |
116 | | } // namespace image |
117 | | } // namespace mozilla |
118 | | |
119 | | #endif // mozilla_image_FrameTimeout_h |