bug#45837: 28.0.50; incorrect cursor position in visual-line-mode when word-wrap-by-category is t

[Eli Zaretskii]

> From: Liu Hui <liuhui1610@gmail.com>
> Date: Fri, 15 Jan 2021 15:28:33 +0800
> Cc: 45837@debbugs.gnu.org
> 
> I have tested the patch and found that the condition `(= (cdr (nth 2
> (posn-at-point))) orig-y)` was sometimes too strict. `posn-at-point`
> may give slightly different y positions for characters on the same
> line when different fonts were used (examples can be found in the
> HELLO file). If there are inline graphics (e.g. latex previews), the y
> position can also be different.

Hmm... you are right.  But that sounds like a bug in posn-at-point, I
will look into fixing it soon.

> My suggestion is `(< (abs (- (cdr (nth 2 (posn-at-point))) orig-y))
> X)`, where X could be, empirically, `(/ (line-pixel-height) 3)` or
> a customizable value.

I went with half the line height, thanks.

> The patch works well in other cases, thanks!

Thanks for testing, I've now installed the change on the master
branch.  I'm not yet closing the bug, because I want to see what can
be done about removing the tolerance in comparing values of
posn-at-point.