author Sam Lantinga <>
Thu, 02 Apr 2009 04:43:36 +0000
changeset 4167 a6f635e5eaa6
parent 1187 19d8949b4584
permissions -rw-r--r--
Fixed bug #611

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

I'm one of the maintainers of, 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
( 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.
     1 ==============================================================================
     2 Using the Simple DirectMedia Layer with OpenBSD/wscons
     3 ==============================================================================
     5 The wscons SDL driver can be used to run SDL programs on OpenBSD
     6 without running X.  So far, the driver only runs on the Sharp Zaurus,
     7 but the driver is written to be easily extended for other machines.
     8 The main missing pieces are blitting routines for anything but 16 bit
     9 displays, and keycode maps for other keyboards.  Also, there is no
    10 support for hardware palettes.
    12 There is currently no mouse support.
    14 To compile SDL with support for wscons, use the
    15 "--enable-video-wscons" option when running configure.  I used the
    16 following command line:
    18 ./configure --disable-oss --disable-ltdl --enable-pthread-sem \
    19 	    --disable-esd --disable-arts --disable-video-aalib  \
    20 	    --enable-openbsdaudio --enable-video-wscons \
    21 	    --prefix=/usr/local --sysconfdir=/etc
    24 Setting the console device to use
    25 =================================
    27 When starting an SDL program on a wscons console, the driver uses the
    28 current virtual terminal (usually /dev/ttyC0).  To force the driver to
    29 use a specific terminal device, set the environment variable
    32 bash$ SDL_WSCONSDEV=/dev/ttyC1 ./some-sdl-program
    34 This is especially useful when starting an SDL program from a remote
    35 login prompt (which is great for development).  If you do this, and
    36 want to use keyboard input, you should avoid having some other program
    37 reading from the used virtual console (i.e., do not have a getty
    38 running).
    41 Rotating the display
    42 ====================
    44 The display can be rotated by the wscons SDL driver.  This is useful
    45 for the Sharp Zaurus, since the display hardware is wired so that it
    46 is correctly rotated only when the display is folded into "PDA mode."
    47 When using the Zaurus in "normal," or "keyboard" mode, the hardware
    48 screen is rotated 90 degrees anti-clockwise.
    50 To let the wscons SDL driver rotate the screen, set the environment
    51 variable SDL_VIDEO_WSCONS_ROTATION to "CW", "CCW", or "UD", for
    52 clockwise, counter clockwise, and upside-down rotation respectively.
    53 "CW" makes the screen appear correct on a Sharp Zaurus SL-C3100.
    55 When using rotation in the driver, a "shadow" frame buffer is used to
    56 hold the intermediary display, before blitting it to the actual
    57 hardware frame buffer.  This slows down performance a bit.
    59 For completeness, the rotation "NONE" can be specified to use a shadow
    60 frame buffer without actually rotating.  Unsetting
    61 SDL_VIDEO_WSCONS_ROTATION, or setting it to '' turns off the shadow
    62 frame buffer for maximum performance.
    65 Running MAME
    66 ============
    68 Since my main motivation for writing the driver was playing MAME on
    69 the Zaurus, I'll give a few hints:
    71 XMame compiles just fine under OpenBSD.
    73 I'm not sure this is strictly necessary, but set
    75 MY_CPU = arm
    77 in makefile.unix, and
    81 in src/unix/unix.max
    83 to be sure.
    85 The latest XMame (0.101 at this writing) is a very large program.
    86 Either tinker with the make files to compile a version without support
    87 for all drivers, or, get an older version of XMame.  My recommendation
    88 would be 0.37b16.
    90 When running MAME, DO NOT SET SDL_VIDEO_WSCONS_ROTATION!  Performace
    91 is MUCH better without this, and it is COMPLETELY UNNECESSARY, since
    92 MAME can rotate the picture itself while drawing, and does so MUCH
    93 FASTER.
    95 Use the Xmame command line option "-ror" to rotate the picture to the
    96 right.
    99 Acknowledgments
   100 ===============
   102 I studied the wsfb driver for XFree86/Xorg quite a bit before writing
   103 this, so there ought to be some similarities.
   106 --
   107 Staffan Ulfberg <>