customizing double click

customizing double click

[Rajneesh Hegde]

hi,
In LaTeX mode (AUCTeX), I want double-click to have the usual
selection effect when the click is on a word-constituent character,
but otherwise do a forward-search (i.e. invoke the dvi viewer). I
wrote the following function for doing the latter:

(defun my-LaTeX-forward-search (event)
  "Set point to the position of the mouse pointer and then call the
function TeX-view from AucTeX."
  (interactive "e")
  (if (and (numberp (posn-point (event-start event)))
	     (looking-at "\\W"))
             (TeX-view)))

Then I bind as follows:
(define-key LaTeX-mode-map [double-down-mouse-1] 'my-LaTeX-forward-search)

The problem is that on double-clicking on a word-constituent
character, the double-down event runs the above function (which, as
expected, does nothing) , but the subsequent double-click event
doesn't have the usual effect of selecting the word.

On the other hand, if I bind my function to [double-mouse-1], it
doesn't even get invoked, although the binding is successful. What am
I missing? Thanks,

Rajneesh.

P.S. I'm using GNU Emacs 22.0.50.2 (i386-mingw-nt5.1.2600) (from
crasseux.com) on a WinXP Home machine (the mouse is a Synaptics
touchpad.) The same problem happens with precompiled Emacs 21.3.

Re: customizing double click

[Eli Zaretskii]

> Date: Fri, 12 Aug 2005 20:11:32 -0400
> From: Rajneesh Hegde <emsink1@gmail.com>
> 
> Then I bind as follows:
> (define-key LaTeX-mode-map [double-down-mouse-1] 'my-LaTeX-forward-search)
> 
> The problem is that on double-clicking on a word-constituent
> character, the double-down event runs the above function (which, as
> expected, does nothing) , but the subsequent double-click event
> doesn't have the usual effect of selecting the word.
> 
> On the other hand, if I bind my function to [double-mouse-1], it
> doesn't even get invoked, although the binding is successful. What am
> I missing? Thanks,

Does the following excerpt from the ELisp manual help you understand
the issue?

       Before the double-click or double-drag event, Emacs generates a
    "double-down" event when the user presses the button down for the
    second time.  Its event type contains `double-down' instead of just
    `down'.  If a double-down event has no binding, Emacs looks for an
    alternate binding as if the event were an ordinary button-down event.
    If it finds no binding that way either, the double-down event is
    ignored.

       To summarize, when you click a button and then press it again right
    away, Emacs generates a down event and a click event for the first
    click, a double-down event when you press the button again, and finally
    either a double-click or a double-drag event.

Re: customizing double click

[Rajneesh Hegde]

> Does the following excerpt from the ELisp manual help you understand
> the issue?

yeah, I think I understand that part, but can't figure out why my
customizing isn't working. When I rebind [double-down-mouse-1] to my
function, it gets executed on a double click (from the double-down
event) but the subsequent double-mouse-1 (click) event doesn't have
its usual selection effect. It seems that event does get generated,
though, because a debugging message I put in my function dimmediately
isappears from the echo area (presumably because of the double-mouse-1
event).

However, what's more puzzling is that when I rebind 
[double-mouse-1] to my function, the double-down event should run
mouse-drag-region (as it gets demoted to a down-mouse-1 event) but
then the double-mouse (click) event should still run my function. But
it doesn't seem to, because debugging messages in the function don't
get printed. (I checked the *Messages* buffer.)

> 
>       Before the double-click or double-drag event, Emacs generates a
>    "double-down" event when the user presses the button down for the
>    second time.  Its event type contains `double-down' instead of just
>    `down'.  If a double-down event has no binding, Emacs looks for an
>    alternate binding as if the event were an ordinary button-down event.
>    If it finds no binding that way either, the double-down event is
>    ignored.
> 
>       To summarize, when you click a button and then press it again right
>    away, Emacs generates a down event and a click event for the first
>    click, a double-down event when you press the button again, and finally
>    either a double-click or a double-drag event.
> 
> 
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> Help-gnu-emacs mailing list
> Help-gnu-emacs@gnu.org
> http://lists.gnu.org/mailman/listinfo/help-gnu-emacs
>

Re: customizing double click

[Rajneesh Hegde]

> When I rebind [double-down-mouse-1] to my
> function, it gets executed on a double click (from the double-down
> event) but the subsequent double-mouse-1 (click) event doesn't have
> its usual selection effect.

ok, I've resolved this issue:
(defun my-LaTeX-forward-search (event)
 "Set point to the position of the mouse pointer and then call the
function TeX-view from AucTeX."
 (interactive "e")
 (if (and (numberp (posn-point (event-start event)))
            (looking-at "\\W"))
            (TeX-view)
      (mouse-drag-region event)))

i.e. if the click is on a word-constituent character, call
mouse-drag-region with this event (i.e. the double-down event). I'm
not sure why this should work though, as I didn't figure out the code
for mouse-drag-region.