Auto enable minor modes in fundamental-mode

Question

By design, the fundamental-mode is bare bones as other major modes are supposed to derive from this one.

From the info page (elisp) Major Modes, we have:

This is the major mode command for Fundamental mode. Unlike other mode commands, it does not run any mode hooks (*note Major Mode Conventions::), since you are not supposed to customize this mode.

For that reason,

• We do not have a fundamental-mode-hook.
• Also my-minor-mode does not get enabled ONLY in this major mode buffers inspite of having (global-my-minor-mode 1) in my config.

Below would work but only if I manually typed M-x fundamental-mode:

(add-hook 'after-change-major-mode-hook #'my-minor-mode)

It does not help in the below case where a fundamental-mode buffer (*abcd*) is created by default:

(with-current-buffer (get-buffer-create "*abcd*")
  (insert "Hello world"))

Why I want to enable a minor mode in fundamental-mode?

I like to keep my custom key bindings in my minor mode map. I have this minor mode enabled globally (but it does not get enabled only in fundamental-mode buffers).

Here's a use case that made this ask this question here. On doing M-x esup (esup package), it creates an *esup-log* buffer with fundamental-mode as its major mode. But each time I need to enable my minor mode manually in it to use my convenient bindings.

I'd like to enable my-minor-mode in a truly global fashion, fundamental-mode or not.

Update 1:

Here is my minor mode definition: modi-mode.

Update 2:

Based on @npostavs' comment, I reviewed what's different between my minor mode modi-mode and override-global-mode in use-package/bind-key.el. And it turns out that the init value of my mode is nil and that of override-global-mode is t.

If I change the init value of my mode to t, it too gets enabled in the fundamental-mode buffers! But the act of (global-modi-mode 1) does not end with the same result. Is that odd? Probably a bug?

Answer 1

The only way I can get a minor mode enabled by default in fundamental-mode buffers is to set the init value of that minor mode to t.

(define-minor-mode my-minor-mode
 "My minor mode"
 :init-value t)

Note that simply toggling ON a globalized minor mode (see C-h i g (elisp) Defining Minor Modes) with init value nil does not do the same thing. In this case, a fundamental-mode buffer will be created with this minor mode disabled.

---

The above, of course, will work only if you control the minor mode source. For all other minor modes that come with different packages, if you'd like to enable a minor mode by default in fundamental-mode buffers, you would need to do

(setq-default the-minor-mode t)

Answer 2

Do not use fundamental-mode -- at least not interactively. You rarely want to be in fundamental-mode. There is almost always something better.

The whole point of fundamental-mode is to not have the usual major-mode handling (hooks etc.). You can think of fundamental-mode as kind of like an abstract class.

If some package puts you in a buffer that is in fundamental-mode then do what you need to do to prevent this -- use some other mode for it.

Consider customizing major-mode so that it defaults to something other than fundamental-mode. (I use indented-text-mode.)

---

Formerly there was default-major-mode for this, which I think was a bit clearer, but they decided to deprecate that (it still works, of course).

default-major-mode is a variable defined in `C source code`.
Its value is indented-text-mode

  This variable is obsolete since 23.2;
  use `major-mode' instead.

Documentation:
Value of `major-mode` for new buffers.

Answer 3

The function get-buffer-create is defined in buffer.c, and at the very end of that function it calls the buffer-list-update-hook. Such a hook could be used to run a custom function, but certain conditions may need to be added to prevent the custom function from firing at inopportune moments whenever that hook is called by other functions.