README
author Sam Lantinga <slouken@libsdl.org>
Thu, 02 Apr 2009 04:43:36 +0000
branchSDL-1.2
changeset 4167 a6f635e5eaa6
parent 3976 8582c6a5ca16
permissions -rw-r--r--
Fixed bug #611

From Tim Angus 2008-08-12 11:18:06

I'm one of the maintainers of ioquake3.org, an updated version of the
Quake 3 engine. Relatively recently, we moved ioq3 to use SDL as a
replacement for 95% of the platform specific code that was there. On the
whole it's doing a great job but unfortunately since the move we've been
getting complaints about the quality of the mouse input on the Windows
platform to the point where for many the game is unplayable. Put in
other terms, the current stable SDL 1.2 is basically not fit for purpose
if you need high quality mouse input as you do in a first person shooter.

Over the weekend I decided to pull my finger out and actually figure out
what's going on. There are basically two major problems. Firstly, when
using the "windib" driver, mouse input is gathered via the WM_MOUSEMOVE
message. Googling for this indicates that often this is known to result
in "spurious" and/or "missing" mouse movement events; this is the
primary cause of the poor mouse input. The second problem is that the
"directx" driver does not work at all in combination with OpenGL meaning
that you can't use DirectInput if your application also uses OpenGL. In
other words you're locked into using the "windib" driver and its poor
mouse input.

In order to address these problems I've done the following:

* Remove WM_MOUSEMOVE based motion event generation and replace with
calls to GetCursorPos which seems much more reliable. In order to
achieve this I've moved mouse motion out into a separate function that
is called once per DIB_PumpEvents.

* Remove the restriction on the "directx" driver being inoperable in
combination with OpenGL. There is a bug for this issues that I've
hijacked to a certain extent
(http://bugzilla.libsdl.org/show_bug.cgi?id=265). I'm the first to admit
I don't really understand why this restriction is there in the first
place. The commit message for the bug fix that introduced this
restriction (r581) isn't very elaborate and I couldn't see any other bug
tracking the issue. If anyone has more information on the bug that was
avoided by r581 it would be helpful as I/someone could then look into
addressing the problem without disabling the "directx" driver.

* I've also removed the restriction on not being allowed to use
DirectInput in windowed mode. I couldn't see any reason for this, at
least not from our perspective. I have my suspicions that it'll be
something like matching up the cursor with the mouse coordinates...

* I bumped up the DirectInput API used to version 7 in order to get
access to mouse buttons 4-7. I've had to inject a little bit of the DX7
headers into SDL there as the MinGW ones aren't up to date in this respect.
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                         Simple DirectMedia Layer
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                                  (SDL)
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                                Version 1.2
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---
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http://www.libsdl.org/
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This is the Simple DirectMedia Layer, a general API that provides low
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level access to audio, keyboard, mouse, joystick, 3D hardware via OpenGL,
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and 2D framebuffer across multiple platforms.
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The current version supports Linux, Windows CE/95/98/ME/XP/Vista, BeOS,
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MacOS Classic, Mac OS X, FreeBSD, NetBSD, OpenBSD, BSD/OS, Solaris, IRIX,
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and QNX.  The code contains support for Dreamcast, Atari, AIX, OSF/Tru64,
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RISC OS, SymbianOS, Nintendo DS, and OS/2, but these are not officially
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supported.
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SDL is written in C, but works with C++ natively, and has bindings to
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several other languages, including Ada, C#, Eiffel, Erlang, Euphoria,
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Guile, Haskell, Java, Lisp, Lua, ML, Objective C, Pascal, Perl, PHP,
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Pike, Pliant, Python, Ruby, and Smalltalk.
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This library is distributed under GNU LGPL version 2, which can be
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found in the file  "COPYING".  This license allows you to use SDL
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freely in commercial programs as long as you link with the dynamic
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library.
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The best way to learn how to use SDL is to check out the header files in
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the "include" subdirectory and the programs in the "test" subdirectory.
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The header files and test programs are well commented and always up to date.
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More documentation is available in HTML format in "docs/index.html", and
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a documentation wiki is available online at:
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	http://www.libsdl.org/cgi/docwiki.cgi
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The test programs in the "test" subdirectory are in the public domain.
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Frequently asked questions are answered online:
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	http://www.libsdl.org/faq.php
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If you need help with the library, or just want to discuss SDL related
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issues, you can join the developers mailing list:
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	http://www.libsdl.org/mailing-list.php
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Enjoy!
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	Sam Lantinga				(slouken@libsdl.org)
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