Re: `delete-frame-hook' isn't defined

[Richard Stallman]

    However, `delete-frame-hook' isn't presently defined as a variable.
    `delete-frame' does run the hook if you define it.

    Should it be defined?

Yes, nowadays we may as well give it a defvar.

                           One possible problem is that tooltips are
    frames that are deleted when they disappear.  Users may not expect the
    hook to be run then.

Hmm.  Perhaps it should not be run for tooltip frames.
Can you find a clean way to distinguish tooltip frames?

    Also, should it be renamed to `delete-frame-functions' because it is
    an abnormal hook ?

Yes, definitely.  It was a mistake to give it the name
delete-frame-hook.