This is because the greeter is implemented as a modal window, I guess.

this was working at one point, i'll see if i can figure out why it stopped working.

so this broke in the process moving from a branch to master.

Created attachment 196833 [details] [review]
main: Let SWITCH_PANELS keybinding through at login screen

Users depend on being able to switch focus between the panel
and the login screen using ctrl-alt-tab.

Because the login screen has no overview, we were short circuiting
some code that needs to get run to support ctrl-alt-tab.

This commit changes the short-circuit code to only run for user
sessions.

Created attachment 196834 [details] [review]
ctrlAltTab: don't allow more than one popup

In a normal user session you can't have more than one
popup, because the popup is modal and we don't allow
the popup to show up when there are other modals.

In a GDM session, however, the login dialog is modal, and
we want a popup, so we don't have that same check.

This commit changes the ctrlAltTab manager code to not
allow multiple popups.

I accidentally dropped the first patch when changing the code to use a dummy overview instead of conditionalizing the overview.  I accidentally dropped (a form of) the second patch when cleaning up the branch before posting to bugzilla.

Comment on attachment 196833 [details] [review]
main: Let SWITCH_PANELS keybinding through at login screen

blah. ok

Attachment 196833 [details] pushed as 2e48dbf - main: Let SWITCH_PANELS keybinding through at login screen
Attachment 196834 [details] pushed as 2b2a8b4 - ctrlAltTab: don't allow more than one popup