Re: Selection threshold with mouse

[Eli Zaretskii <eliz@gnu.org>]

> From: Stefan Monnier <monnier@iro.umontreal.ca>
> Date: Mon, 21 Jul 2014 10:20:25 -0400
> 
> > Because the existing methods are glyph-granular, not pixel-granular.
> > When you tell them to stop at pixel coordinate X, they move one
> > "display element" (e.g., character or image) at a time,
> 
> But they need to keep track either of the "current pixel position" (to
> compare against X) or (equivalently) of "remaining pixels until X".
> So they should know the exact pixel position.

Like I said, you cannot rely on that:

      else if ((op & MOVE_TO_X) && it->current_x >= to_x)
	{                                       ^^^^
	  result = MOVE_X_REACHED;
	  break;
	}

IOW, the exact pixel position is not always what you want in the case
in point.  All you know it's not _before_ X.