Code:
bash-3.1$ firefox --help
Usage: /usr/lib64/firefox-3.6/firefox-bin [ options ... ] [URL]
where options include:
X11 options
--display=DISPLAY X display to use
--sync Make X calls synchronous
--no-xshm Don't use X shared memory extension
--xim-preedit=STYLE
--xim-status=STYLE
--g-fatal-warnings Make all warnings fatal
Firefox options
-h or -help Print this message.
-v or -version Print Firefox version.
-P <profile> Start with <profile>.
-migration Start with migration wizard.
-ProfileManager Start with ProfileManager.
-no-remote Open new instance, not a new window in running instance.
-UILocale <locale> Start with <locale> resources as UI Locale.
-safe-mode Disables extensions and themes for this session.
-jsconsole Open the Error console.
-browser Open a browser window.
-private Enable private browsing mode.
-setDefaultBrowser Set this app as the default browser.
Usage: firefox [-flags] [<url>]
Since it hadn't been posted, I thought it might be handy to show what arguments FF accepts when run from commandline. I for one had either not known about, or forgotten about, the
--display argument, but I suspect (it *should*) act the same as giving "DISPLAY=<blah.blah> firefox .." however: "display" is not synonymous with "screen" -- as I think has been evinced earlier, DISPLAY=:0.0 and DISPLAY=:0.1 both refer to the same DISPLAY, but not to the same SCREEN.
I believe (and am not an expert on this) that the Window Manager can play an important role in how/where a given app gets placed when it starts, *provided* that enough of the following are true and cooperating:
1) the WM can properly identify the NAME of the app;
2) the app correctly supplies its NAME to the WM
3) the WM can do "smart" or "programmed" placement of apps/instances.
4) the app can be made to give itself a new name for a new instance.
5) the DISPLAY.SCREEN argument is both accepted by the app, passed to the WM, and honored by the WM.
I note that the OP seems to be using GNOME, so what I write next will probably be interpreted slightly differently by GNOME than it has for me:
For myself, historically, I used KDE and XFCE mostly, and this window/screen functionality tended to work much of the time, for the majority of apps. Currently, I've switched to
i3 Window Manager, and the functionality of placing windows/apps usually works (though this WM is very new and is WIP) but the WM has problems particularly with Firefox windows and child-windows, because as I mentioned earlier, Firefox does not adhere properly to the EWM standards defining parent & child window naming (i.e. some windows are not even named until they are already rendered to the screen, making it too late for the WM to place them where you want them; and, mozilla/firefox uses almost as many different names as they do windows, and the scheme seems inconsistent, making it sometimes able to place *some* FF windows where you want, but not others).
Maybe not much help in that rambling, but I hope maybe it's interesting at the very least
Sasha