worley@compass.UUCP (Dale Worley) (01/11/89)
People who do extensive customizations in their .emacs files have
noticed that if a function is defined in an autoload file it is
necessary to first load the file before overriding the definition. A
new "load-hooks" feature is now available that avoids this. The
program can declare an operation (e.g., a defun) to be done
immediately after a particular file is loaded. The way this is done
is through a variable, load-hooks:
Documentation:
A list of hooks to be run after files are loaded.
It has the form ((filename form form ...) (filename form form ...) ...).
After one of the files is loaded, its forms are executed.
An error in the hooks does not undo the load.
Each filename is a string which must be exactly the same as the first
argument to load. This is not a problem in practice, since
(require 'foo) calls (load "foo" ...) and (autoload 'foo-fun "foo" ...)
calls (load "foo" ...).
To use the load-hooks feature, include the following two functions in
your .emacs:
(defun add-load-hook (file form)
"Add a load hook for FILE which is FORM. FORM is added to load-hooks after
all load-hooks for FILE which are presently there."
(let ((a (assoc file load-hooks)))
(if (null a)
(setq load-hooks (cons (list file form) load-hooks))
(nconc a (cons form nil)))))
(defun read-load-hook (file)
"Read the next input form and add it as a load hook for FILE.
If a call to read-load-hook is in a file that is being loaded, the next lisp
expression after it will be read as the load hook."
(add-load-hook file (read)))
One can now say (add-load-hook "fff" 'xxx) to cause the code xxx to be
executed immediately after the file fff is loaded. Don't forget the '
before the code -- otherwise it will be executed when your .emacs file
is read! Usually, this code is a defun that overides some defun in
the file. For example,
(add-load-hook "lpr"
'(defun print-region-1 ...))
will override the definition of print-region-1 in the file lpr.
The one problem with this form is that it plays hob with the
indentation. To avoid this in your .emacs file, you can use the
alternate form
(read-load-hook "lpr")
(defun print-region-1 ...)
The code of read-load-hook reads the lisp expression that follows it
(without executing it) and saves it as a load hook for the given file.
The changes to Emacs (18.52) are simple:
*** lread.c.old Tue Jan 10 13:34:34 1989
--- lread.c Tue Jan 10 14:42:53 1989
***************
*** 166,171 ****
--- 166,172 ----
void readevalloop ();
static Lisp_Object load_unwind ();
+ Lisp_Object Vload_hooks;
DEFUN ("load", Fload, Sload, 1, 4, 0,
"Execute a file of Lisp code named FILE.\n\
***************
*** 186,191 ****
--- 187,193 ----
register Lisp_Object lispstream;
register FILE **ptr;
int count = specpdl_ptr - specpdl;
+ Lisp_Object temp;
struct gcpro gcpro1;
CHECK_STRING (str, 0);
***************
*** 223,228 ****
--- 225,237 ----
load_in_progress++;
readevalloop (Qget_file_char, stream, Feval, 0);
unbind_to (count);
+ /* added code to implement load-hooks */
+ temp = Fassoc (str, Vload_hooks);
+ if (!NULL (temp))
+ {
+ Fprogn (Fcdr (temp));
+ }
+ /* end of added code */
UNGCPRO;
if (!noninteractive && NULL (nomessage))
***************
*** 1296,1301 ****
--- 1305,1321 ----
DEFVAR_BOOL ("load-in-progress", &load_in_progress,
"Non-nil iff inside of load.");
+
+ DEFVAR_LISP ("load-hooks", &Vload_hooks,
+ "A list of hooks to be run after files are loaded.\n\
+ It has the form ((filename form form ...) (filename form form ...) ...).\n\
+ After one of the files is loaded, its forms are executed.\n\
+ An error in the hooks does not undo the load.\n\
+ Each filename is a string which must be exactly the same as the first\n\
+ argument to load. This is not a problem in practice, since\n\
+ (require 'foo) calls (load \"foo\" ...) and (autoload 'foo-fun \"foo\" ...)\n\
+ calls (load \"foo\" ...).");
+ Vload_hooks = Qnil;
Qstandard_input = intern ("standard-input");
staticpro (&Qstandard_input);
Dale
--
Dale Worley, Compass, Inc. compass!worley@think.com
Seen in a technical journal: "You'll always offend someone when you deal with
a large group of people. There's always someone that can't stand Bambi."