Re: Selection threshold with mouse

[Eli Zaretskii <eliz@gnu.org>]

> From: Stefan Monnier <monnier@iro.umontreal.ca>
> Date: Sat, 19 Jul 2014 21:22:28 -0400
> 
> > Is it possible to change the sweet spot?
> 
> Of course, it's possible, but Emacs currently does not provide
> this option.  You'd have to change some of the C code for that.
> Patches welcome.

We don't currently have a method to find the character to the left of
some screen coordinates (except some silly iteration that each time
sheds 1 pixel from the coordinates).  So it is not really easy to find
the character that is to the left of the given screen coordinates in a
way that will work with bidirectional display.

We could perhaps _approximate_ that by subtracting some fixed fraction
of the width of the character to the right of the mouse, but that
might mean some strange effects when the characters on the two sides
of the mouse pointer differ in size.  Maybe that's acceptable.  If
not, changing the current code that determines buffer position from
mouse coordinates would need a complete redesign (in a way I cannot
yet imagine) to support the required feature.

And yes, patches welcome.