HighDPI instructions for developpers

[Pierre-Yves Luyten <py luyten fr>]

Hi,

is there some wiki page to help devs with HighDPI support?
It is not that easy to follow-up current state in different libraries,
plus settings-daemon settings, and probably many other factors I do not
know yet.

I guess some "avoid these bad practices" / "recommandations" might be
useful too.

Moreover, many devs cannot test this themselves.

KR,
Pierre-Yves