Re: Inspecting behaviour of `make-overlay', is this expected?

[Marcin Borkowski <mbork@mbork.pl>]

On 2022-12-24, at 09:36, Eli Zaretskii <eliz@gnu.org> wrote:

>> Date: Sat, 24 Dec 2022 10:52:47 +0300
>> From: Jean Louis <bugs@gnu.support>
>> 
>> XXXXXXXXXX
>> ^
>> | position 0 in buffer
>> 
>> (setq my-overlay (make-overlay 0 10))
>> (get-buffer-window (overlay-buffer my-overlay))
>> (overlay-put my-overlay 'display "Hello") then I get:
>> 
>> HelloX 
>> 
>> instead of "Hello"
>> 
>> Is this normal behavior?
>
> Yes.  The 10 part says that the overlay _ends_ before position 10.
> This is standard Emacs behavior with text properties and overlays: END
> means the first character NOT affected by the property/overlay.

Somewhat related: https://fhur.me/posts/always-use-closed-open-intervals
(not my piece, just found it on the internet; also I do not want to
imply the OP doesn't know/understand that - but I consider this short
article interesting & worthwhile also for others reading this).

Best,

-- 
Marcin Borkowski
http://mbork.pl