bug#23079: 25.0.92; Movement commands leave cursor in invisible line

[Stefan Monnier <monnier@IRO.UMontreal.CA>]

tags 23079 notabug
thanks

> I try to give a recipe resembling a bug in Magit concerning hidden lines
> and cursor movement.  In some buffer (emacs -Q) do

>   (insert "111" "\n222\n"
>           (propertize "333\n444\n\n" 'invisible t)
>           "555\n666\n")

> and move around with C-n, C-p.  Then the cursor will appear over the
> first "5" but point is actually located inside the invisible area.

That's normal: (get-pos-property <pos> 'invisible) returns nil in front
of "333" but t in front of "555", so point adjustment will try to move
point to right before "333" when we're in that invisible chunk.

IOW the position "right before 555" is actually considered as being
"inside the invisible area" whereas the position "right before 333" is
considered as being outside of it.

If you want point adjustment to move point to right before "555"
instead, you should change the stickiness of the `invisible' property so
as to change which boundary position is considered "inside" and which is
considered "outside".


        Stefan