mmaug@yahoo.com

mmaug@yahoo.com

[Luc Teirlinck]

There appear to be several derived modes that do not yet properly
enclose the call to the parent mode in a delay-mode-hooks form.
Examples include sql-interactive-mode, inferior-emacs-lisp-mode and
inferior-lisp-mode.

Currently, we recommend to put the call to delay-mode-hooks around the
entire body, excluding the final call to run-mode-hooks.  That is what
define-derived-mode does.  It is strictly speaking the safest, just in
case anything else (except for the parent mode) should run a mode hook.
But that should really not happen.  So it should be sufficient to
enclose the call to the parent mode inside a delay-mode-hooks form,
which results in less deeply nested code.

I will take care of inferior-emacs-lisp-mode, inferior-lisp-mode and
any other modes I find (although I will leave sql-interactive-mode to
Michael), once I know how we want to handle them.  We could make them
all use define-derived-mode, but that has to be done carefully and has
the potential of introducing bugs.  Enclosing stuff in a
delay-mode-hooks form is routine, especially if it is only the parent
mode that needs to be enclosed.  This is important, as there may be
_many_ such modes.

So what do we do: insist on converting to define-derived-mode, using
delay-mode-hooks around the entire body except final call to
run-mode-hooks, or use delay-mode-hooks only around the call to the
parent mode?

If we decide on the latter, we could also make the following change to
modes.texi:

===File ~/modes.texi-diff===================================
*** modes.texi	23 May 2005 10:25:40 -0500	1.109
--- modes.texi	28 May 2005 14:06:53 -0500	
***************
*** 437,446 ****
  command (called the @dfn{parent mode}) and then alter some of its
  settings.  A mode that does this is called a @dfn{derived mode}.  The
  recommended way to define one is to use @code{define-derived-mode},
! but this is not required.  Such a mode should use
! @code{delay-mode-hooks} around its entire body (including the call to
! the parent mode command) @emph{except} for the final call to
! @code{run-mode-hooks}, which runs the derived mode's hook.  (Using
  @code{define-derived-mode} does this automatically.)  @xref{Derived
  Modes}, and @ref{Mode Hooks}.
  
--- 437,444 ----
  command (called the @dfn{parent mode}) and then alter some of its
  settings.  A mode that does this is called a @dfn{derived mode}.  The
  recommended way to define one is to use @code{define-derived-mode},
! but this is not required.  Such a mode should call the parent mode
! command inside a @code{delay-mode-hooks} form.  (Using
  @code{define-derived-mode} does this automatically.)  @xref{Derived
  Modes}, and @ref{Mode Hooks}.
  
============================================================

Re: mmaug@yahoo.com

[Richard Stallman]

    So it should be sufficient to
    enclose the call to the parent mode inside a delay-mode-hooks form,
    which results in less deeply nested code.

Yes, that is fine.

      command (called the @dfn{parent mode}) and then alter some of its
      settings.  A mode that does this is called a @dfn{derived mode}.  The
      recommended way to define one is to use @code{define-derived-mode},
    ! but this is not required.  Such a mode should call the parent mode
    ! command inside a @code{delay-mode-hooks} form.  (Using
      @code{define-derived-mode} does this automatically.)  @xref{Derived
      Modes}, and @ref{Mode Hooks}.

That change is ok too.

Re: mmaug@yahoo.com

[Stefan Monnier]

> Michael), once I know how we want to handle them.  We could make them
> all use define-derived-mode, but that has to be done carefully and has
> the potential of introducing bugs.  Enclosing stuff in a

If at all possible, please use define-derived-mode which results in
cleaner code and neatly hides those details.


        Stefan

Re: mmaug@yahoo.com

[Luc Teirlinck]

Stefan Monnier wrote:

   If at all possible, please use define-derived-mode which results in
   cleaner code and neatly hides those details.

The problem is that rewriting a mode to use define-derived-mode has to
be done carefully and takes time.  Otherwise, there is the risk of
introducing bugs.  On the other hand, enclosing the parent mode inside a
delay-mode-hooks is so completely routine and quick that it can be
done right after one notices the problem.  This is important, since
there may be a lot of these problems out there.  Rewriting the mode to
use define-derived-mode can always be done later when one has more
time and has no other, more urgent, things to do.

Sincerely,

Luc.

Re: mmaug@yahoo.com

[Stefan Monnier]

> Rewriting the mode to use define-derived-mode can always be done later
> when one has more time and has no other, more urgent, things to do.

When was the last time this happened to you?


        Stefan

Wrong subject (Re: mmaug@yahoo.com).

[Luc Teirlinck]

Sorry, I did not really mean to have this "Subject" field for this
thread.  That address was supposed to be a CC.  I must have messed
things up one way or the other.  I only noticed now.

Sincerely,

Luc.