On 20/01/2021 10:21, Christopher Miles wrote:
> 
> Thanks for your working. I will modify my mailcap config temporary until Org
> Mode fix this issue. You're right, this change might break some behavior of some
> users. I don't understand Emacs sub-process mechanism. Can't help on this
> problem. But I'm interested in this. I will take some time to study in. Anyway,
> thanks for your work.

Changes could be less intrusive, see another (untested) patch. However I 
am against shell where it is really necessary.

Personally, I am not comfortable with emacs subprocess functions as 
well. I just tried to avoid creation of a pseudoterminal that could make 
some harm to GUI application. I do not know if someone uses a handler 
that really require terminal features.

I have realized that :filter argument is not appropriate to arbitrary 
handler that could spam with various assert messages. Maybe :sentinel is 
better to report configuration problem to user when handler is called 
with inappropriate arguments.