RE: defcustom: changing from defvar - order of execution

["Drew Adams" <drew.adams@oracle.com>]

Oops - before someone gripes about users using defvar for variables that are
defined in libraries, let me change the initial user setup from this:

     (defvar foovar t)
     (load-library "foo")
     (foo-fn)

to this:

     (setq foovar t)
     (load-library "foo")
     (foo-fn)

I don't think it changes my overall question, in any case. Thanks. - Drew



    -----Original Message-----
    I'm unclear on the recommended way to change Lisp code from
    using defvar for user options to using defcustom. I guess I'm
    also unclear on just how defcustom and Customize work. I
    couldn't find an explanation of this in Info for Emacs or Emacs Lisp.

    Initial setup - library foo.el has this:

     (defvar foovar nil)
     (defun foo-fn () foovar)

    Initial setup - user has this in .emacs:

     (defvar foovar t)
     (load-library "foo")
     (foo-fn)

    When .emacs is loaded, (foo-fn) is executed, foovar is `t', so
    (foo-fn) returns `t'.


    Second setup - library foo.el has this:

     (defcustom foovar nil)
     (defun foo-fn () foovar)

    Second setup - user has this in .emacs, after customizing
    foovar to `t' with Customize:

     (load-library "foo")
     (foo-fn)
     ...
     (custom-set-variables '(foovar t)...)

    When .emacs is loaded, (foo-fn) is executed, foovar is (has
    default value) `nil', so (foo-fn) returns `nil'.

    That is, because (custom-set-variables...) is executed after
    (foo-fn), it has no effect during foo-fn's execution.

    What am I missing/confusing here? What is the proper way for
    library foo.el to move from using defvar to using defcustom?
    Also, what difference does it make, if any, whether a defcustom
    is executed at the top level or a lower level of a file.