Hi,
I’m trying to get two fullscreen SDL (1.2.13) apps to run on separate X screens (:0.0 and :0.1) of the same machine. For testing I’m using the attached sdltest.cpp, which uses OpenGL to draw its stuff. The behaviour that I’m seeing is that when I start one sdltest on the first screen (using DISPLAY=:0.0) followed by the second sdltest on the second screen (DISPLAY=:0.1) they both run fine. But, when I start up the first process, ctrl-Z it to go to sleep and then start the second process this latter one will not run. Attaching to it with gdb shows it to wait in SDL_SetVideoMode:
(gdb) bt
#0 0x00007f2ae07d6bb0 in nanosleep () from /lib/libc.so.6
#1 0x00007f2ae1815fe4 in SDL_Delay () from /usr/lib/libSDL-1.2.so.0
#2 0x00007f2ae17feb1f in ?? () from /usr/lib/libSDL-1.2.so.0
#3 0x00007f2ae17fec54 in ?? () from /usr/lib/libSDL-1.2.so.0
#4 0x00007f2ae17ed147 in ?? () from /usr/lib/libSDL-1.2.so.0
#5 0x00007f2ae17ee989 in SDL_SetVideoMode () from /usr/lib/libSDL-1.2.so.0
#6 0x00000000004015d5 in main ()
If I then awake the first process again the second process will continue and both start to run fine. You may wonder why I care about this situation, but we’re working on a networked display app where multiple display processes will need to synchronize at startup before starting to draw. This waiting on SDL_SetVideoMode() in one process when the other process is started up but waiting (on data from a socket) is causing us headaches and I simply do not understand why two unrelated SDL apps would interfere with each other like this. Can somebody explain why this is happening? Or even, better how to avoid it?
Thanks,
Paul
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