Re: Display problems with 'before-string in overlay

[Lennart Borgman (gmail)]

Lennart Borgman (gmail) wrote:
> Kim F. Storm wrote:
> > "Lennart Borgman (gmail)" <address@hidden> writes:
> >
> > > Yes, I looked at the code but decided it takes me too long time at the
> > > moment. Kim, is this easy for you?
> >
> > Changes to redisplay are NEVER easy ... 
> > I made a seemingly trivial change to fix one bug ... and two years
> > later someone finds a problem with it.
> >
> > IMO, this is not the time to try to fix that.
>
> Maybe not, but is not this more about positioning the cursor? The 
> characters are displayed correctly. Moving to char >= 2 works correctly. 
> But moving to char = 1 fails. Looks like it could be a corner case to 
> me, ie something that perhaps could be fixed without general impact.
>
> BTW I wonder if I did not complain about this two years ago too? But at 
> that time I worked against a different solution since I wanted to get 
> something that worked then. This time I think I need this change to get 
> things working.


I looked a bit at the code. (First time I used tags, quite nice.) Is it 
in set_point_both in intervals.c that the magic happens? It looks from 
that code like internally an intangible property is used in cases like this.

I therefore compared using 'before-string with using

  (put-text-property 1 (point) 'intangible t)

The cursor moves quite differently in those cases. Is there an 
intangible property missing internally on line endings in 
'before-string? (A wild guess of course, but the best I can do at the 
moment.)

BTW I also noticed that using 'before-string like I did here also 
influences undo intervals. Quite strange.