Bug 35701

[dev aug 19] This is a regression, introduced I
think sometimes in the past week or so. I can see
it also in [dev aug 11] but I don't remember it
occurring in any previous dev builds. I am using
Linux with the Sawfish WM, NB in MDI mode.

When there are several tabs open in a mode, e.g.
editor, sometimes actions such as Next View
(Alt-Right) or Alt-Left or Ctrl-F4 are enabled,
and sometimes they are not. I can't establish any
exact pattern, but pressing Ctrl-Z or Ctrl-S or
some other kinds of keys (but not self-insert
typed keys, and not usually Backspace) in a
text/x-java buffer (but not text/plain?) seems to
trigger it. Suddenly the window system actions are
disabled (but e.g. Ctrl-S is not).

I created a toolbar, for testing purposes, with
FindAction, NextTabAction, and PreviousTabAction.
Of course if you are moving around in the editor
with >1 tab, they should all always be enabled.
But they aren't. Sometimes none of them are;
sometimes only Find is; sometimes only Next and
Previous are.

Find seems to be usually on, but sometimes when
switching Sawfish desktops back to NB it is not.
Switching to another tab and then back turns it on.

Next and Previous are always on after having
switched focus back to the NB main window, e.g.
after switching desktops. If all you do is scroll
up or down or otherwise move the cursor, and/or
switch tabs (Alt-Left and Alt-Right), they stay
on. But if you start working in a buffer - typing
something in it - they usually turn off. At that
point Alt-Left etc. just beep, as does Ctrl-F4.
You cannot switch buffers except with the mouse.
(If you do click on a new editor tab, the actions
turn on again.)

Best KB-accessible workaround seems to switch
virtual desktops away and back to NB, or to switch
focus to some other app and back to NB.

Marking P2 because this bug is extremely annoying
and interferes with everyday work. Also a recent
regression.