Modifier state?

Modifier state?

[David Reitter]

Do we have a way to detect the modifier state from the Lisp level, or  
bind commands to modifier state changes?

I'd like to run a command whenever the user presses and releases the  
Meta (not ESC) key.  This would be on non-TTY sessions.

A lot of applications show additional info when you press Alt/Option  
(which is Meta for me); they even update the menus with alternative  
functions.  The user can even view a menu, press and hold Alt/Option  
and see the menu items change.

Thanks
- David

RE: Modifier state?

[Drew Adams]

> Do we have a way to detect the modifier state from the Lisp 
> level, or bind commands to modifier state changes?
> 
> I'd like to run a command whenever the user presses and releases the  
> Meta (not ESC) key.  This would be on non-TTY sessions.
> 
> A lot of applications show additional info when you press Alt/Option  
> (which is Meta for me); they even update the menus with alternative  
> functions.  The user can even view a menu, press and hold Alt/Option  
> and see the menu items change.

Someone else will perhaps correct this or provide more up-to-date info, but you
might take a look at function `event-modifiers'.

See the Elisp manual, nodes Keyboard Events and Classifying Events.

Re: Modifier state?

[Stefan Monnier]

> Do we have a way to detect the modifier state from the Lisp level, or bind
> commands to modifier state changes?

No.

I did some simple experiments with it, in order to get events like
<control> and <down-control> (which actually were <down-control> and
<C-control> because when the release event is received, the modifier
state is not yet cleared).  I did get it to work OK without too much
trouble (mostly I had to add some function-key-map entries to drop those
events when not bound, and I had to rework C-q so that it waits for
a "real" key press rather than stopping at the <down-control>), but
haven't investigated much further.


        Stefan

Re: Modifier state?

[David Reitter]

[-- Attachment #1: Type: text/plain, Size: 828 bytes --]

On 13 Feb 2009, at 20:43, Stefan Monnier wrote:

>> Do we have a way to detect the modifier state from the Lisp level,  
>> or bind
>> commands to modifier state changes?
>
> No.
>
> I did some simple experiments with it, in order to get events like
> <control> and <down-control> (which actually were <down-control> and
> <C-control> because when the release event is received, the modifier
> state is not yet cleared).  I did get it to work OK without too much
> trouble (mostly I had to add some function-key-map entries to drop  
> those
> events when not bound, and I had to rework C-q so that it waits for
> a "real" key press rather than stopping at the <down-control>), but
> haven't investigated much further.

And I guess there's a bit of port-specific work involved, too.
It would be excellent to have this post-23.1.

[-- Attachment #2: smime.p7s --]
[-- Type: application/pkcs7-signature, Size: 2193 bytes --]