Normally I want ido to ignore all non-user buffers, i.e. all buffers which start with a *. I have achieved this using the following setting:
(setq ido-ignore-buffers '("\\` " "^\*"))
However, this poses a problem when working with a shell or an interpreter, e.g. ielm, where the interaction buffer is named *ielm*. Obviously adding all buffers to be ignored manually is not really an option because the list can get quite long with a lot of different emacs packages loaded. I know about C-a which disabled the ignore pattern from within ido, however, I don't want to hit C-a every time I switch to an ielm buffer.
My question is:
Is there some variable which allows to specify buffers which ido should not ignore (although they match the normal ignore list)? Or is there some other approach for solving this?
The list that the ido-ignore-buffers variable points to may contain not only regular expressions but also functions (any mix of them, actually). It's easy to provide a function to filter out all non-user buffers except *ielm*:
(defun ido-ignore-non-user-except-ielm (name)
"Ignore all non-user (a.k.a. *starred*) buffers except *ielm*."
(and (string-match "^\*" name)
(not (string= name "*ielm*"))))
(setq ido-ignore-buffers '("\\` " ido-ignore-non-user-except-ielm))
Here's an example of having multiple unignored buffer names:
(setq my-unignored-buffers '("*ielm*" "*scratch*" "*foo*" "*bar*"))
(defun my-ido-ignore-func (name)
"Ignore all non-user (a.k.a. *starred*) buffers except those listed in `my-unignored-buffers'."
(and (string-match "^\*" name)
(not (member name my-unignored-buffers))))
(setq ido-ignore-buffers '("\\` " my-ido-ignore-func))
An interesting example of using ignore functions can be found among comments in the ido.el source code (I've removed ;; at the beginning of each line):
(defun ido-ignore-c-mode (name)
"Ignore all c mode buffers -- example function for ido."
(with-current-buffer name
(derived-mode-p 'c-mode)))
Basically, once you've got buffer name, you can do any checking/ignoring you want.