Yes, xterms apparently have character codes for showing bitmaps. Wonder how long until the Linux framebuffer console gets those as well...
Interesting. How long has this been part of xterm? Is it standard, or is it Linux-specific? Is it documented anywhere?
It's part of X. Your xterm sets environment variables for WINDOWID, DISPLAY, and XAUTHORITY, and that's enough for an app to figure out how to connect to your display and which window to scribble on.
If you don't have WINDOWID set, you can fool it. Try this:
unset WINDOWID
sleep 5; w3m <some site>
..then switch focus to another window like your graphical web browser.
Ah. :-( Now if it was something neater, such as an escape code meaning "the following N bytes are a X by Y bitmap in encoding Z; draw it in such and such cells", that'd be pretty cool (and portable).
It'd be almost like the BBC Micro's extended control codes.
Actually, it does it by poking around in X and drawing over your window without its permission.