Re: user-load-path (was: Re: Emacs 21 NEWS file (was Re: [OT?] Gnu Emacs is dying?)(fwd))

[Dave Love]

>>>>> "PA" == Per Abrahamsen <abraham@dina.kvl.dk> writes:

 PA> [ FUT: gnu.emacs.bug ]
 PA> Kai.Grossjohann@CS.Uni-Dortmund.DE (Kai Großjohann) writes:

 >> On 18 Jun 2001, Per Abrahamsen wrote:
 >> 
 >>> "Mark A. Flacy" <flacy@nortelnetworks.com> writes:
 >>> 
 >>>> It would be very nice to allow for a user-settable component to the
 >>>> load path that *could* be customized.

I'm not sure I understand, and may be confused by the bizarre
Subject:.  `load-path' in Emacs 20 has a canonical `defcustom', if
that's the issue.  This was a mistake and was removed for Emacs 21, so
`load-path' won't be customizable.

 PA> However, customize wants to "own" the variables it touches.  It
 PA> is not big on sharing.  I.e. no other Lisp code should change the
 PA> variable reserved for customize.  This includes calls to
 PA> 'add-to-list' in various init files.

But Custom can tell how the standard value of a variable has been
munged.

[I have some sense of déjà vu about this.]

 PA> Of course, all code that _reads_ 'load-path' will need to be
 PA> inspected, and likely changed.  Luckily, most user code only
 PA> write the variable.

I don't think it's acceptable or necessary for a Custom interface to
require uses of such a variable to be changed, if that's the idea.
[An example of load-path user code: if I want to override the normal
image search path in Emacs 21, I push a directory onto a `let'-bound
`load-path'.]

There should be a standard method for augmenting customized
{a,p,}lists.  `load-path' isn't the only variable of this type.  I
implemented a couple of approaches when I undid the `load-path'
customization.  One involved a specific `load-path-additions' user
option with suitable :set and :get methods.  The other was a new
Custom widget to address the general problem, keeping track of the
standard value.