Re: Undo mode

[Stefan Monnier]

>>> +(add-hook 'after-init-hook
>>> +          (lambda ()
>>> +            (add-hook 'delete-frame-functions
>>> +                      #'undelete-frame--handle-delete-frame -75)))
>> Why do we need to postpone it via `after-init-hook`?
> The problem is that during Emacs GUI startup, some temporary TTY frame
> is created and deleted.  Maybe this is a bug?

I think you're talking about the initial frame (which is actually not
a TTY frame either, it's the pseudo frame used for example during batch
processing, which sends messages to stdout/stderr and reads "minibuffer"
input from stdin).

It's kind of a pain to recognize in ELisp.  In C it's recognized by:

    #define FRAME_INITIAL_P(f) ((f)->output_method == output_initial)

But in ELisp, the only simple&convenient way I know is
(eq frame frame-initial-frame), but I'm not sure if that var is still
non-nil when that code is run.

I think it's better to add a specific workaround in
`undelete-frame--handle-delete-frame` such as:

    (unless (eq frame frame-initial-frame) ...)

And if that specific one doesn't work, we'll come up with
a different test.


        Stefan