PiP protocol addition...!?

To have some XDG_something cross-toolkit variable being looked up in addition to QT_QPA_PLATFORM or GDK_BACKEND seems more a matter of coordination than a matter of implementation effort... and even if there are many toolkits, two of them are really "major" in terms of usage share, so having those two using a single agreed upon env variable could hopefully push most of the others to do the same...

This lack of coordination in minor details remains a pain point. The fact that differently to what we were used to with X11, basically every single toolkit and every single compositor can do as it wants way to often results in unpredictable results.

Things like xpra having a wayland client that is apparently unusable with plasma (because contextual menus disappear) but OK on gnome and the author honestly saying that this thing will remain unfixed as "wayland is too difficult". Or waypipe being hard to use because way to often rather than getting a window transferred to the client with waypipe, you get it to appear on the server with Xwayland. Or pinentry wrap scripts having trouble in interpreting the environment to know if it should prompt graphically or textually (so again you too easily when connecting remotely you end up with a pin entry dialog displayed graphically on the server rather than textually on the ssh session on the client).