Sharing PATH across login mechanisms with modification support

Question

I'm running Xubuntu 14.10, currently using lightdm. Let's examine two process trees:

init───lightdm───lightdm───upstart───xfce4-terminal───bash

and:

init───lightdm───lightdm───upstart───emacs─┬─{dconf worker}
                                           ├─{gdbus}
                                           └─{gmain}

My issue is that I am setting PATH in .bashrc, which given that emacs is started by upstart (using the keyboard shortcut), makes it not have the same PATH value. (I know I should move that to .bash_profile or so, but that won't fix the issue and it's fine given that I usually login in one way only, through X / lightdm.)

Consider these three cases:

• Terminal on vty1 -> bash - path is initialized by bash (.bash_profile)
• X -> emacs - path is initialized by lightdm (.xinitrc)
• X -> xfce4-terminal -> bash - path is initialized by lightdm (.xinitrc), then modified by bash (.bash_profile)

First - is the above correct or are there other things happening? Or better yet - should I be using the above to initialize or some other files / mechanisms?

If the above is correct, I assume putting PATH in a script, then calling from both .bash_profile and .xinitrc would be the best way to sync up all these environments, correct?

Are there hooks that provide a way to reset the PATH of lightdm? I'd like to avoid logging in and out when changing PATH if possible.