How do I tell when the current buffer is the minibuffer?

How do I tell when the current buffer is the minibuffer?

[Alan Mackenzie]

Hello, Emacs.

My problem is as stated in the Subject: line.

Part of my program is being called from `signal_after_change' after
activity in the minibuffer.  However, in that program the buffer local
variables for the main buffer (not the minibuffer) are still in scope.

I need some way of distinguishing that we're in the minibuffer so as to
avoid corrupting the buffer local variables of the selected buffer.

I've tried "Fminibufferp (Qnil);", but this seems just to return nil,
even when the current buffer IS the minibuffer.

I've even tried reading the fine manual without finding anything useful.

Would somebody please tell me what I'm missing.

Thanks!

-- 
Alan Mackenzie (Nuremberg, Germany).

Re: How do I tell when the current buffer is the minibuffer?

[raman]

Alan Mackenzie <acm@muc.de> writes:

minibuffer-window-active-p perhaps 
> Hello, Emacs.
>
> My problem is as stated in the Subject: line.
>
> Part of my program is being called from `signal_after_change' after
> activity in the minibuffer.  However, in that program the buffer local
> variables for the main buffer (not the minibuffer) are still in scope.
>
> I need some way of distinguishing that we're in the minibuffer so as to
> avoid corrupting the buffer local variables of the selected buffer.
>
> I've tried "Fminibufferp (Qnil);", but this seems just to return nil,
> even when the current buffer IS the minibuffer.
>
> I've even tried reading the fine manual without finding anything useful.
>
> Would somebody please tell me what I'm missing.
>
> Thanks!

-- 

Re: How do I tell when the current buffer is the minibuffer?

[Andreas Schwab]

Alan Mackenzie <acm@muc.de> writes:

> Part of my program is being called from `signal_after_change' after
> activity in the minibuffer.  However, in that program the buffer local
> variables for the main buffer (not the minibuffer) are still in scope.

How can that happen?  A minibuffer is a buffer on its own, with its own
local variables.

Andreas.

-- 
Andreas Schwab, schwab@linux-m68k.org
GPG Key fingerprint = 58CA 54C7 6D53 942B 1756  01D3 44D5 214B 8276 4ED5
"And now for something completely different."

Re: How do I tell when the current buffer is the minibuffer?

[Alan Mackenzie]

Hello, Andreas.

On Sat, Mar 05, 2016 at 11:04:57PM +0100, Andreas Schwab wrote:
> Alan Mackenzie <acm@muc.de> writes:

> > Part of my program is being called from `signal_after_change' after
> > activity in the minibuffer.  However, in that program the buffer local
> > variables for the main buffer (not the minibuffer) are still in scope.

> How can that happen?  A minibuffer is a buffer on its own, with its own
> local variables.

What is happening is that the variable location (created in C) is being
shared by all buffers until a buffer local value is "primed" in a buffer
with a `setq' invocation.

How does one correctly create a buffer local variable in C?  What I have
at the moment is:

    DEFSYM (Qcomment_depth_hwm, "comment-depth-hwm");
    DEFVAR_LISP ("comment-depth-hwm", Vcomment_depth_hwm,
                 doc: /* Buffer position below which the `comment-depth' property is valid.  */);
    Vcomment_depth_hwm = make_number (1);
    Fmake_variable_buffer_local (Qcomment_depth_hwm);

This is clearly inadequate, of itself, to create a buffer local variable.

> Andreas.

> -- 
> Andreas Schwab, schwab@linux-m68k.org
> GPG Key fingerprint = 58CA 54C7 6D53 942B 1756  01D3 44D5 214B 8276 4ED5
> "And now for something completely different."

-- 
Alan Mackenzie (Nuremberg, Germany).

Re: How do I tell when the current buffer is the minibuffer?

[Andreas Schwab]

Alan Mackenzie <acm@muc.de> writes:

> How does one correctly create a buffer local variable in C?  What I have
> at the moment is:
>
>     DEFSYM (Qcomment_depth_hwm, "comment-depth-hwm");
>     DEFVAR_LISP ("comment-depth-hwm", Vcomment_depth_hwm,
>                  doc: /* Buffer position below which the `comment-depth' property is valid.  */);
>     Vcomment_depth_hwm = make_number (1);
>     Fmake_variable_buffer_local (Qcomment_depth_hwm);
>
> This is clearly inadequate, of itself, to create a buffer local variable.

In which way?

Andreas.

-- 
Andreas Schwab, schwab@linux-m68k.org
GPG Key fingerprint = 58CA 54C7 6D53 942B 1756  01D3 44D5 214B 8276 4ED5
"And now for something completely different."

Re: How do I tell when the current buffer is the minibuffer?

[Alan Mackenzie]

Hello, Andreas.

On Sat, Mar 05, 2016 at 11:40:15PM +0100, Andreas Schwab wrote:
> Alan Mackenzie <acm@muc.de> writes:

> > How does one correctly create a buffer local variable in C?  What I have
> > at the moment is:

> >     DEFSYM (Qcomment_depth_hwm, "comment-depth-hwm");
> >     DEFVAR_LISP ("comment-depth-hwm", Vcomment_depth_hwm,
> >                  doc: /* Buffer position below which the `comment-depth' property is valid.  */);
> >     Vcomment_depth_hwm = make_number (1);
> >     Fmake_variable_buffer_local (Qcomment_depth_hwm);

> > This is clearly inadequate, of itself, to create a buffer local variable.

> In which way?

Until a `setq' (or the like) is done on the variable for a particular
buffer, C code reading/writing from Vcomment_depth_hwm reads and writes
the same piece of RAM that all other buffers do.

In the mean time, I've been looking around, and it might well be that
the correct way to create a buffer local variable in C is to use the
macro DEFVAR_PER_BUFFER in buffer.c.  It's doesn't seem documented
(outside of buffer.c), though.

> Andreas.

> -- 
> Andreas Schwab, schwab@linux-m68k.org
> GPG Key fingerprint = 58CA 54C7 6D53 942B 1756  01D3 44D5 214B 8276 4ED5
> "And now for something completely different."

-- 
Alan Mackenzie (Nuremberg, Germany).

Re: How do I tell when the current buffer is the minibuffer?

[Andreas Schwab]

Alan Mackenzie <acm@muc.de> writes:

> Hello, Andreas.
>
> On Sat, Mar 05, 2016 at 11:40:15PM +0100, Andreas Schwab wrote:
>> Alan Mackenzie <acm@muc.de> writes:
>
>> > How does one correctly create a buffer local variable in C?  What I have
>> > at the moment is:
>
>> >     DEFSYM (Qcomment_depth_hwm, "comment-depth-hwm");
>> >     DEFVAR_LISP ("comment-depth-hwm", Vcomment_depth_hwm,
>> >                  doc: /* Buffer position below which the `comment-depth' property is valid.  */);
>> >     Vcomment_depth_hwm = make_number (1);
>> >     Fmake_variable_buffer_local (Qcomment_depth_hwm);
>
>> > This is clearly inadequate, of itself, to create a buffer local variable.
>
>> In which way?
>
> Until a `setq' (or the like) is done on the variable for a particular
> buffer, C code reading/writing from Vcomment_depth_hwm reads and writes
> the same piece of RAM that all other buffers do.

That seems to work for deactivate-mark.

Andreas.

-- 
Andreas Schwab, schwab@linux-m68k.org
GPG Key fingerprint = 58CA 54C7 6D53 942B 1756  01D3 44D5 214B 8276 4ED5
"And now for something completely different."

Re: How do I tell when the current buffer is the minibuffer?

[Alan Mackenzie]

Hello again, Andreas.

On Sun, Mar 06, 2016 at 12:03:50AM +0100, Andreas Schwab wrote:
> Alan Mackenzie <acm@muc.de> writes:

> > On Sat, Mar 05, 2016 at 11:40:15PM +0100, Andreas Schwab wrote:
> >> Alan Mackenzie <acm@muc.de> writes:

> >> > How does one correctly create a buffer local variable in C?  What I have
> >> > at the moment is:

> >> >     DEFSYM (Qcomment_depth_hwm, "comment-depth-hwm");
> >> >     DEFVAR_LISP ("comment-depth-hwm", Vcomment_depth_hwm,
> >> >                  doc: /* Buffer position below which the `comment-depth' property is valid.  */);
> >> >     Vcomment_depth_hwm = make_number (1);
> >> >     Fmake_variable_buffer_local (Qcomment_depth_hwm);

> >> > This is clearly inadequate, of itself, to create a buffer local variable.

> >> In which way?

> > Until a `setq' (or the like) is done on the variable for a particular
> > buffer, C code reading/writing from Vcomment_depth_hwm reads and writes
> > the same piece of RAM that all other buffers do.

> That seems to work for deactivate-mark.

It's not working for comment-depth-hwm.

Perhaps somebody who understands this will chip in, here.  It could
really do with being in the Elisp manual.

> Andreas.

> -- 
> Andreas Schwab, schwab@linux-m68k.org
> GPG Key fingerprint = 58CA 54C7 6D53 942B 1756  01D3 44D5 214B 8276 4ED5
> "And now for something completely different."

-- 
Alan Mackenzie (Nuremberg, Germany).

Re: How do I tell when the current buffer is the minibuffer?

[Eli Zaretskii]

> Date: Sat, 5 Mar 2016 23:20:43 +0000
> From: Alan Mackenzie <acm@muc.de>
> Cc: emacs-devel@gnu.org
> 
> On Sun, Mar 06, 2016 at 12:03:50AM +0100, Andreas Schwab wrote:
> > Alan Mackenzie <acm@muc.de> writes:
> 
> > > On Sat, Mar 05, 2016 at 11:40:15PM +0100, Andreas Schwab wrote:
> > >> Alan Mackenzie <acm@muc.de> writes:
> 
> > >> > How does one correctly create a buffer local variable in C?  What I have
> > >> > at the moment is:
> 
> > >> >     DEFSYM (Qcomment_depth_hwm, "comment-depth-hwm");
> > >> >     DEFVAR_LISP ("comment-depth-hwm", Vcomment_depth_hwm,
> > >> >                  doc: /* Buffer position below which the `comment-depth' property is valid.  */);
> > >> >     Vcomment_depth_hwm = make_number (1);
> > >> >     Fmake_variable_buffer_local (Qcomment_depth_hwm);
> 
> > >> > This is clearly inadequate, of itself, to create a buffer local variable.
> 
> > >> In which way?
> 
> > > Until a `setq' (or the like) is done on the variable for a particular
> > > buffer, C code reading/writing from Vcomment_depth_hwm reads and writes
> > > the same piece of RAM that all other buffers do.
> 
> > That seems to work for deactivate-mark.
> 
> It's not working for comment-depth-hwm.
> 
> Perhaps somebody who understands this will chip in, here.  It could
> really do with being in the Elisp manual.

Is there still a problem?  If so, please describe the details, because
I don't think I understand them well enough to try helping you.  (Yes,
I've read what you wrote, but your description was too general and
didn't include any code you tried to use, so I'm not sure what exactly
did you try and how.)

Re: How do I tell when the current buffer is the minibuffer?

[Alan Mackenzie]

Hello, Eli.

On Sun, Mar 06, 2016 at 07:44:25PM +0200, Eli Zaretskii wrote:
> > Date: Sat, 5 Mar 2016 23:20:43 +0000
> > From: Alan Mackenzie <acm@muc.de>
> > Cc: emacs-devel@gnu.org

> > On Sun, Mar 06, 2016 at 12:03:50AM +0100, Andreas Schwab wrote:
> > > Alan Mackenzie <acm@muc.de> writes:

> > > > On Sat, Mar 05, 2016 at 11:40:15PM +0100, Andreas Schwab wrote:
> > > >> Alan Mackenzie <acm@muc.de> writes:

> > > >> > How does one correctly create a buffer local variable in C?  What I have
> > > >> > at the moment is:

> > > >> >     DEFSYM (Qcomment_depth_hwm, "comment-depth-hwm");
> > > >> >     DEFVAR_LISP ("comment-depth-hwm", Vcomment_depth_hwm,
> > > >> >                  doc: /* Buffer position below which the `comment-depth' property is valid.  */);
> > > >> >     Vcomment_depth_hwm = make_number (1);
> > > >> >     Fmake_variable_buffer_local (Qcomment_depth_hwm);

> > > >> > This is clearly inadequate, of itself, to create a buffer local variable.

> > > >> In which way?

> > > > Until a `setq' (or the like) is done on the variable for a particular
> > > > buffer, C code reading/writing from Vcomment_depth_hwm reads and writes
> > > > the same piece of RAM that all other buffers do.

> > > That seems to work for deactivate-mark.

> > It's not working for comment-depth-hwm.

> > Perhaps somebody who understands this will chip in, here.  It could
> > really do with being in the Elisp manual.

> Is there still a problem?

No, I solved it by putting the variable into buffer.c, accessed via BVAR.
I'm still not sure if this is the canonical way to create a buffer local
variable accessed from C.

> If so, please describe the details, because I don't think I understand
> them well enough to try helping you.  (Yes, I've read what you wrote,
> but your description was too general and didn't include any code you
> tried to use, so I'm not sure what exactly did you try and how.)

The problem was assigning a value to Vcomment_depth_hwm in C didn't
create a buffer local copy of `comment-depth-hwm'.  Why should it?

I think the time it took me to find the solution is a problem.  A 2003
copy of the XEmacs internals manual was helpful.  ;-)

-- 
Alan Mackenzie (Nuremberg, Germany).

Re: How do I tell when the current buffer is the minibuffer?

[Stefan Monnier]

> Until a `setq' (or the like) is done on the variable for a particular
> buffer, C code reading/writing from Vcomment_depth_hwm reads and writes
> the same piece of RAM that all other buffers do.

If/when you write to the variable and intend it to be a buffer-local
change, you need to use Fset or Fmake_local_variable rather than just
using a C-level assignment.


        Stefan

Re: How do I tell when the current buffer is the minibuffer?

[Johan Bockgård]

Alan Mackenzie <acm@muc.de> writes:

> How does one correctly create a buffer local variable in C?  What I have
> at the moment is:
>
>     DEFSYM (Qcomment_depth_hwm, "comment-depth-hwm");
>     DEFVAR_LISP ("comment-depth-hwm", Vcomment_depth_hwm,
>                  doc: /* Buffer position below which the `comment-depth' property is valid.  */);
>     Vcomment_depth_hwm = make_number (1);
>     Fmake_variable_buffer_local (Qcomment_depth_hwm);
>
> This is clearly inadequate, of itself, to create a buffer local variable.

Yes:

    (make-variable-buffer-local VARIABLE)
    Make VARIABLE become buffer-local whenever it is set.

    (make-local-variable VARIABLE)
    Make VARIABLE have a separate value in the current buffer.

(Or DEFVAR_PER_BUFFER, as you said.)