Mercurial > sdl-ios-xcode
view test/utf8.txt @ 4139:568c9b3c0167 SDL-1.2
* Added configure option --enable-screensaver, to allow enabling the screensaver by default.
* Use XResetScreenSaver() instead of disabling screensaver entirely.
Full discussion summary from Erik on the SDL mailing list:
Current behaviour
=================
SDL changes the user's display power management settings without
permission from the user and without telling the user.
The interface that it uses to do so is DPMSDisable/DPMSEnable, which
should only ever be used by configuration utilities like KControl, never
by normal application programs, let alone by the libraries that they
use. Using an interface that is not at all intended for what SDL tries
to achieve means that it will not work as it should. Firstly, the power
management is completely disabled during the whole lifetime of the SDL
program, not only when it should be. Secondly, it makes SDL
non-reentrant, meaning that things will break when multiple SDL programs
are clients of the same X server simultaneously. Thirdly, no cleanup
mechanism ensures that the setting is restored if the client does not do
that (for example if it crashes).
In addition to that, this interface is broken on xorg,
[http://bugs.freedesktop.org/show_bug.cgi?id=13962], so what SDL tries
to do does not work at all on that implementation of the X Window
System. (The reason that the DPMSEnable works in KControl is that it
calls DPMSSetTimeout immediately after,
[http://websvn.kde.org/tags/KDE/3.5.9/kdebase/kcontrol/energy/energy.cpp?annotate=774532#l343]).
The problems that the current behaviour causes
==============================================
1. Information leak. When the user is away, someone might see what the
user has on the display when the user counts on the screensaver
preventing this. This does not even require physical access to the
workstation, it is enough to see it from a distance.
2. Draining battery. An SDL program that runs on a laptop will quickly
drain the battery while the user is away. The system will soon shut down
and require recharging before being usable again, while it should in
fact have consumed very little energy if the user's settings would have
been obeyed.
3. Wasting energy. Even if battery issues are not considered, energy as
such is wasted.
4. Display wear. The display may be worn out.
The problems that the current behaviour tries to solve
======================================================
1. Preventing screensaver while playing movies.
Many SDL applications are media players. They have reasons to prevent
screensavers from being activated while a movie is being played. When a
user clicks on the play button it can be interpreted as saying "play
this movie, but do not turn off the display while playing it, because I
will watch it even though I do not interact with the system".
2. Preventing screensaver when some input bypasses X.
Sometimes SDL uses input from another source than the X server, so
that the X server is bypassed. This obviously breaks the screensaver
handling. SDL tries to work around that.
3. Preventing screensaver when all input bypasses X.
There is something called Direct Graphics Access mode, where a
program takes control of both the display and the input devices from the
X server. This obviously means that the X server can not handle the
screensaver alone, since screensaver handling depends on input handling.
SDL does not do what it should to help the X server to handle the
screensaver. Nor does SDL take care of screeensaver handling itself. SDL
simply disables the screensaver completely.
How the problems should be solved
=================================
The correct way for an application program to prevent the screensaver
under X is to call XResetScreenSaver. This was recently discovered and
implemented by the mplayer developers,
[http://svn.mplayerhq.hu/mplayer?view=rev&revision=25637]. SDL needs to
wrap this in an API call (SDL_ResetScreenSaver) and implement it for the
other video targets (if they do not have a corresponding call, SDL
should do what it takes on that particular target, for example sending
fake key events).
1. When a movie is played, the player should reset the screensaver when
the animation is advanced to a new frame. The same applies to anything
similar, like slideshows.
2. When the X server is handling input, it must handle all input
(keyboards, mice, gamepads, ...). This is necessary, not only to be able
to handle the screensaver, but also so that it can send the events to
the correct (the currently active) client. If there is an input device
that the X server can not handle for some reason (such as lack of Plug
and Play capability), the program that handles the device as a
workaround must simulate what would happen if the X server would have
handled the device, by calling XResetScreenSaver when input is received
from the device.
3. When the X server is not handling the input, it depends on the
program that does to call XResetScreenSaver whenever an input event
occurs. Alternatively the program must handle the screensaver countdown
internally and call XActivateScreenSaver.
| author | Sam Lantinga <slouken@libsdl.org> |
|---|---|
| date | Fri, 29 Feb 2008 13:55:44 +0000 |
| parents | 4d711949cd9a |
| children |
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UTF-8 decoder capability and stress test ---------------------------------------- Markus Kuhn <http://www.cl.cam.ac.uk/~mgk25/> - 2003-02-19 This test file can help you examine, how your UTF-8 decoder handles various types of correct, malformed, or otherwise interesting UTF-8 sequences. This file is not meant to be a conformance test. It does not prescribes any particular outcome and therefore there is no way to "pass" or "fail" this test file, even though the texts suggests a preferable decoder behaviour at some places. The aim is instead to help you think about and test the behaviour of your UTF-8 on a systematic collection of unusual inputs. Experience so far suggests that most first-time authors of UTF-8 decoders find at least one serious problem in their decoder by using this file. The test lines below cover boundary conditions, malformed UTF-8 sequences as well as correctly encoded UTF-8 sequences of Unicode code points that should never occur in a correct UTF-8 file. According to ISO 10646-1:2000, sections D.7 and 2.3c, a device receiving UTF-8 shall interpret a "malformed sequence in the same way that it interprets a character that is outside the adopted subset" and "characters that are not within the adopted subset shall be indicated to the user" by a receiving device. A quite commonly used approach in UTF-8 decoders is to replace any malformed UTF-8 sequence by a replacement character (U+FFFD), which looks a bit like an inverted question mark, or a similar symbol. It might be a good idea to visually distinguish a malformed UTF-8 sequence from a correctly encoded Unicode character that is just not available in the current font but otherwise fully legal, even though ISO 10646-1 doesn't mandate this. In any case, just ignoring malformed sequences or unavailable characters does not conform to ISO 10646, will make debugging more difficult, and can lead to user confusion. Please check, whether a malformed UTF-8 sequence is (1) represented at all, (2) represented by exactly one single replacement character (or equivalent signal), and (3) the following quotation mark after an illegal UTF-8 sequence is correctly displayed, i.e. proper resynchronization takes place immageately after any malformed sequence. This file says "THE END" in the last line, so if you don't see that, your decoder crashed somehow before, which should always be cause for concern. All lines in this file are exactly 79 characters long (plus the line feed). In addition, all lines end with "|", except for the two test lines 2.1.1 and 2.2.1, which contain non-printable ASCII controls U+0000 and U+007F. If you display this file with a fixed-width font, these "|" characters should all line up in column 79 (right margin). This allows you to test quickly, whether your UTF-8 decoder finds the correct number of characters in every line, that is whether each malformed sequences is replaced by a single replacement character. Note that as an alternative to the notion of malformed sequence used here, it is also a perfectly acceptable (and in some situations even preferable) solution to represent each individual byte of a malformed sequence by a replacement character. If you follow this strategy in your decoder, then please ignore the "|" column. Here come the tests: | | 1 Some correct UTF-8 text | | (The codepoints for this test are: | U+03BA U+1F79 U+03C3 U+03BC U+03B5 --ryan.) | | You should see the Greek word 'kosme': "κόσμε" | | | 2 Boundary condition test cases | | 2.1 First possible sequence of a certain length | | (byte zero skipped...there's a null added at the end of the test. --ryan.) | | 2.1.2 2 bytes (U-00000080): "" | 2.1.3 3 bytes (U-00000800): "ࠀ" | 2.1.4 4 bytes (U-00010000): "𐀀" | | (5 and 6 byte sequences were made illegal in rfc3629. --ryan.) | 2.1.5 5 bytes (U-00200000): "" | 2.1.6 6 bytes (U-04000000): "" | | 2.2 Last possible sequence of a certain length | | 2.2.1 1 byte (U-0000007F): "" | 2.2.2 2 bytes (U-000007FF): "߿" | | (Section 5.3.2 below calls this illegal. --ryan.) | 2.2.3 3 bytes (U-0000FFFF): "" | | (5 and 6 bytes sequences, and 4 bytes sequences > 0x10FFFF were made illegal | in rfc3629, so these next three should be replaced with a invalid | character codepoint. --ryan.) | 2.2.4 4 bytes (U-001FFFFF): "" | 2.2.5 5 bytes (U-03FFFFFF): "" | 2.2.6 6 bytes (U-7FFFFFFF): "" | | 2.3 Other boundary conditions | | 2.3.1 U-0000D7FF = ed 9f bf = "" | 2.3.2 U-0000E000 = ee 80 80 = "" | 2.3.3 U-0000FFFD = ef bf bd = "�" | 2.3.4 U-0010FFFF = f4 8f bf bf = "" | | (This one is bogus in rfc3629. --ryan.) | 2.3.5 U-00110000 = f4 90 80 80 = "" | | 3 Malformed sequences | | 3.1 Unexpected continuation bytes | | Each unexpected continuation byte should be separately signalled as a | malformed sequence of its own. | | 3.1.1 First continuation byte 0x80: "" | 3.1.2 Last continuation byte 0xbf: "" | | 3.1.3 2 continuation bytes: "" | 3.1.4 3 continuation bytes: "" | 3.1.5 4 continuation bytes: "" | 3.1.6 5 continuation bytes: "" | 3.1.7 6 continuation bytes: "" | 3.1.8 7 continuation bytes: "" | | 3.1.9 Sequence of all 64 possible continuation bytes (0x80-0xbf): | | " | | | " | | 3.2 Lonely start characters | | 3.2.1 All 32 first bytes of 2-byte sequences (0xc0-0xdf), | each followed by a space character: | | " | " | | 3.2.2 All 16 first bytes of 3-byte sequences (0xe0-0xef), | each followed by a space character: | | " " | | 3.2.3 All 8 first bytes of 4-byte sequences (0xf0-0xf7), | each followed by a space character: | | " " | | 3.2.4 All 4 first bytes of 5-byte sequences (0xf8-0xfb), | each followed by a space character: | | " " | | 3.2.5 All 2 first bytes of 6-byte sequences (0xfc-0xfd), | each followed by a space character: | | " " | | 3.3 Sequences with last continuation byte missing | | All bytes of an incomplete sequence should be signalled as a single | malformed sequence, i.e., you should see only a single replacement | character in each of the next 10 tests. (Characters as in section 2) | | 3.3.1 2-byte sequence with last byte missing (U+0000): "" | 3.3.2 3-byte sequence with last byte missing (U+0000): "" | 3.3.3 4-byte sequence with last byte missing (U+0000): "" | 3.3.4 5-byte sequence with last byte missing (U+0000): "" | 3.3.5 6-byte sequence with last byte missing (U+0000): "" | 3.3.6 2-byte sequence with last byte missing (U-000007FF): "" | 3.3.7 3-byte sequence with last byte missing (U-0000FFFF): "" | 3.3.8 4-byte sequence with last byte missing (U-001FFFFF): "" | 3.3.9 5-byte sequence with last byte missing (U-03FFFFFF): "" | 3.3.10 6-byte sequence with last byte missing (U-7FFFFFFF): "" | | 3.4 Concatenation of incomplete sequences | | All the 10 sequences of 3.3 concatenated, you should see 10 malformed | sequences being signalled: | | "" | | 3.5 Impossible bytes | | The following two bytes cannot appear in a correct UTF-8 string | | 3.5.1 fe = "" | 3.5.2 ff = "" | 3.5.3 fe fe ff ff = "" | | 4 Overlong sequences | | The following sequences are not malformed according to the letter of | the Unicode 2.0 standard. However, they are longer then necessary and | a correct UTF-8 encoder is not allowed to produce them. A "safe UTF-8 | decoder" should reject them just like malformed sequences for two | reasons: (1) It helps to debug applications if overlong sequences are | not treated as valid representations of characters, because this helps | to spot problems more quickly. (2) Overlong sequences provide | alternative representations of characters, that could maliciously be | used to bypass filters that check only for ASCII characters. For | instance, a 2-byte encoded line feed (LF) would not be caught by a | line counter that counts only 0x0a bytes, but it would still be | processed as a line feed by an unsafe UTF-8 decoder later in the | pipeline. From a security point of view, ASCII compatibility of UTF-8 | sequences means also, that ASCII characters are *only* allowed to be | represented by ASCII bytes in the range 0x00-0x7f. To ensure this | aspect of ASCII compatibility, use only "safe UTF-8 decoders" that | reject overlong UTF-8 sequences for which a shorter encoding exists. | | 4.1 Examples of an overlong ASCII character | | With a safe UTF-8 decoder, all of the following five overlong | representations of the ASCII character slash ("/") should be rejected | like a malformed UTF-8 sequence, for instance by substituting it with | a replacement character. If you see a slash below, you do not have a | safe UTF-8 decoder! | | 4.1.1 U+002F = c0 af = "" | 4.1.2 U+002F = e0 80 af = "" | 4.1.3 U+002F = f0 80 80 af = "" | 4.1.4 U+002F = f8 80 80 80 af = "" | 4.1.5 U+002F = fc 80 80 80 80 af = "" | | 4.2 Maximum overlong sequences | | Below you see the highest Unicode value that is still resulting in an | overlong sequence if represented with the given number of bytes. This | is a boundary test for safe UTF-8 decoders. All five characters should | be rejected like malformed UTF-8 sequences. | | 4.2.1 U-0000007F = c1 bf = "" | 4.2.2 U-000007FF = e0 9f bf = "" | 4.2.3 U-0000FFFF = f0 8f bf bf = "" | 4.2.4 U-001FFFFF = f8 87 bf bf bf = "" | 4.2.5 U-03FFFFFF = fc 83 bf bf bf bf = "" | | 4.3 Overlong representation of the NUL character | | The following five sequences should also be rejected like malformed | UTF-8 sequences and should not be treated like the ASCII NUL | character. | | 4.3.1 U+0000 = c0 80 = "" | 4.3.2 U+0000 = e0 80 80 = "" | 4.3.3 U+0000 = f0 80 80 80 = "" | 4.3.4 U+0000 = f8 80 80 80 80 = "" | 4.3.5 U+0000 = fc 80 80 80 80 80 = "" | | 5 Illegal code positions | | The following UTF-8 sequences should be rejected like malformed | sequences, because they never represent valid ISO 10646 characters and | a UTF-8 decoder that accepts them might introduce security problems | comparable to overlong UTF-8 sequences. | | 5.1 Single UTF-16 surrogates | | 5.1.1 U+D800 = ed a0 80 = "" | 5.1.2 U+DB7F = ed ad bf = "" | 5.1.3 U+DB80 = ed ae 80 = "" | 5.1.4 U+DBFF = ed af bf = "" | 5.1.5 U+DC00 = ed b0 80 = "" | 5.1.6 U+DF80 = ed be 80 = "" | 5.1.7 U+DFFF = ed bf bf = "" | | 5.2 Paired UTF-16 surrogates | | 5.2.1 U+D800 U+DC00 = ed a0 80 ed b0 80 = "" | 5.2.2 U+D800 U+DFFF = ed a0 80 ed bf bf = "" | 5.2.3 U+DB7F U+DC00 = ed ad bf ed b0 80 = "" | 5.2.4 U+DB7F U+DFFF = ed ad bf ed bf bf = "" | 5.2.5 U+DB80 U+DC00 = ed ae 80 ed b0 80 = "" | 5.2.6 U+DB80 U+DFFF = ed ae 80 ed bf bf = "" | 5.2.7 U+DBFF U+DC00 = ed af bf ed b0 80 = "" | 5.2.8 U+DBFF U+DFFF = ed af bf ed bf bf = "" | | 5.3 Other illegal code positions | | 5.3.1 U+FFFE = ef bf be = "" | 5.3.2 U+FFFF = ef bf bf = "" | | THE END |