There are multiple ways to start a program, it turns out. LXDE - the window manager - supports auto-start of .desktop files places in either ~/.config/autostart or /etc/xdg/autostart - hooray!
http://wiki.lxde.org/en/Autostart
Except... though I can run a simple program as proof-of-concept in this way, when I try to run mine, it fails. I can't figure out why. The file
.xsession-errors.old
contains X server errors ("resource temporarily unavailable").
I am now using another mechanism - running the code from a shell script (this is necessary because I need to specify a working directory for the program). This uses the "autostart" file in /etc/xdg/lxsession/, and at least it works. Well kind of. I either have to "sleep 5" before running, or prefixing the run with an @ symbol which forces a retry if it fails. It looks a little like something my code is dependent on is not in place at the precise time the autostart mechanism finds it. I can find no way of ensuring startup order. This is plainly a crock of stinky stuff.