annotate README @ 4384:6800e2560310 SDL-1.2

Fixed bugs #882 and 865, re-opening bug #634 Ronald Lamprecht to SDL Hi, Sam Lantinga wrote: The problem with that fix is that it breaks IME events again. Maybe we can handle keyboard events differently to prevent this issue? Spending an hour reading MSDN, analysing SDL and another hour testing the reality on XP I am really wondering how patch r4990 could have ever worked in any situation. It's main effect is to break the unicode translation and causing spurious activation events! Why does TranslateMessage(&msg) nothing useful? Simply because it does not affect "msg" at all! All keyboard events are dispatched without the slightest change (see MSDN). TranslateMessage() just appends additional WM_CHAR, WM_DEADCHAR, WM_SYSCHAR, WM_SYSDEADCHAR event messages to the queue. But I could not find any SDL event handling routine that catches these events and transforms them to proper SDL keyevents while eliminating the corresponding WM_KEYDOWN, etc. events. Thus any IME input like the '@' generated by "Alt + 6(Numpad) + 4(Numpad)" is simply lost. But the situation is even worse! Up to r4990 the TranslateKey()/ToUnicode() calls did evaluate dead keys and did deliver proper key events for subsequent key strokes like '´' + 'e' resulting in 'é'. ToUnicode() needs proper key state informations to be able to handle these substitutions. But unfortunatly TranslateMessage() needs the same state information and eats it up while generating the WM_CHAR messages :-( Thus the current 1.2.14 breakes the partial IME support of previous releases, too. The key state race condition between ToUnicode() and TranslateMessage() requires to avoid any ToUnicode() usage for receiving proper WM_CHAR, etc. messages generated by TranslateMessage(). (Yes - the '@' and 'é' appear as WM_CHAR messages when unicode is switched off). The spurious SDL activation events are *not* caused by additional WM_ACTIVATE Windows messages! Besides DIB_HandleMessage() SDL_PrivateAppActive() is called by another source which I am not yet aware of - any hints? Thus I do strongly recommend the deletion of the TranslateMessage(&msg) call as a quick fix. A proper support of unicode and IME requires a clean SDL keyboard input concept first. Which SDL keyboards events should be transmitted to the app when the user presses '´' + 'e' ? Within the current unicode handling the first key stroke is hidden. Even though ToUnicode() delivers the proper key SDL does ignore it in TranslateKey(). Just the composed key event is transmitted to the app. That is what you expect for text input, but the app can no longer use keys like '^' as a key button because it will never receive a key event for it! With a given concept it seems to be necessary to regenerate SDL key events out of the WM_CHAR, etc. events and to drop all related direct WM_KEYDOWN, etc. events while the remaining basic WM_KEYDOWN, etc. events would still have to result in SDL key events. Anyway the source of the spurious WM_ACTIVATE should be located to avoid future trouble. Greets, Ronald
author Sam Lantinga <slouken@libsdl.org>
date Tue, 17 Nov 2009 04:59:13 +0000
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2 Simple DirectMedia Layer
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4 (SDL)
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6 Version 1.2
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8 ---
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9 http://www.libsdl.org/
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11 This is the Simple DirectMedia Layer, a general API that provides low
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12 level access to audio, keyboard, mouse, joystick, 3D hardware via OpenGL,
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13 and 2D framebuffer across multiple platforms.
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15 The current version supports Linux, Windows CE/95/98/ME/XP/Vista, BeOS,
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16 MacOS Classic, Mac OS X, FreeBSD, NetBSD, OpenBSD, BSD/OS, Solaris, IRIX,
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17 and QNX. The code contains support for Dreamcast, Atari, AIX, OSF/Tru64,
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18 RISC OS, SymbianOS, Nintendo DS, and OS/2, but these are not officially
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19 supported.
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21 SDL is written in C, but works with C++ natively, and has bindings to
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22 several other languages, including Ada, C#, Eiffel, Erlang, Euphoria,
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23 Guile, Haskell, Java, Lisp, Lua, ML, Objective C, Pascal, Perl, PHP,
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24 Pike, Pliant, Python, Ruby, and Smalltalk.
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26 This library is distributed under GNU LGPL version 2, which can be
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27 found in the file "COPYING". This license allows you to use SDL
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28 freely in commercial programs as long as you link with the dynamic
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29 library.
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31 The best way to learn how to use SDL is to check out the header files in
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32 the "include" subdirectory and the programs in the "test" subdirectory.
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33 The header files and test programs are well commented and always up to date.
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34 More documentation is available in HTML format in "docs/index.html", and
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35 a documentation wiki is available online at:
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36 http://www.libsdl.org/cgi/docwiki.cgi
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38 The test programs in the "test" subdirectory are in the public domain.
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40 Frequently asked questions are answered online:
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41 http://www.libsdl.org/faq.php
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43 If you need help with the library, or just want to discuss SDL related
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44 issues, you can join the developers mailing list:
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45 http://www.libsdl.org/mailing-list.php
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47 Enjoy!
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48 Sam Lantinga (slouken@libsdl.org)
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