Re: Point to Pixel

Re: Point to Pixel

[Stefan Monnier]

> I wanted this feature and couldn't find it... all I found were posts in
> lists also asking for the feature, with people denying it could be done
> in elisp. Well, that is not true! ;)

The problem with your code is that it doesn't correctly handle hidden text,
display properties (stretchable spaces, images, ...), proportional fonts,
faces that change the font size, line wrapping, ...

Emacs-CVS has a function that works correctly even in the face of the
above thingies.  It's called posn-at-point.


        Stefan

Re: Point to Pixel

[Patrick]

Yes, it's just a quick hack.

Anyone know where this posn-at-point is in the CVS tree? 

On 6/8/05, Stefan Monnier <monnier@iro.umontreal.ca> wrote:
> > I wanted this feature and couldn't find it... all I found were posts in
> > lists also asking for the feature, with people denying it could be done
> > in elisp. Well, that is not true! ;)
> 
> The problem with your code is that it doesn't correctly handle hidden text,
> display properties (stretchable spaces, images, ...), proportional fonts,
> faces that change the font size, line wrapping, ...
> 
> Emacs-CVS has a function that works correctly even in the face of the
> above thingies.  It's called posn-at-point.
> 
> 
>         Stefan
> _______________________________________________
> Help-gnu-emacs mailing list
> Help-gnu-emacs@gnu.org
> http://lists.gnu.org/mailman/listinfo/help-gnu-emacs
>

Re: Point to Pixel

[Stefan Monnier]

> Anyone know where this posn-at-point is in the CVS tree? 

Compile Emacs-CVS, then do C-h f posn-at-point, then middle-click on
the link (it's in the C source code).


        Stefan

Point to Pixel

[Patrick]

On windows gnu emacs (~21.3) this code will return the pixel-position
of the current point! (or at least, within a few pixels) Returns values
in form (x . y).

I wanted this feature and couldn't find it... all I found were posts in
lists also asking for the feature, with people denying it could be done
in elisp. Well, that is not true! ;)

I believe this should work in Xemacs and on other operating systems and
recent emacs versions.

I am currently using it to display an "intellisense"-like tooltip.
Which, on windows, gnu emacs has no tooltip, so I am executing a little
python app instead which handles the tooltip for me (via wx libraries).
Works very nice.


; helper func
(defun get-param-safe (s)
  "Sometimes frame-paramater returns values of (+ -4)"
  (let ((left (frame-parameter nil s)))
    (if (listp left) (cadr left) left)))


; this is it
(defun point-to-pixel ()
  "Converts the position of the current point to pixel
   coordinates relative to the screen (i.e. window manager)."
  (let ((left (car (window-edges)))
	(top (cadr (window-edges)))
	(point-left (- (point) (point-at-bol)))
	(point-top  (point)))
    (let ((x (+ (* (frame-char-width) left)  ; x =
		(* (frame-char-width) point-left)
		(get-param-safe 'left)))
	  (y (+ (* (frame-char-height)       ; y =
		   (+ top
		      (count-lines (window-start) (point))))
		(get-param-safe 'top))))
      (cons x y))))