GTK4 support

[orowith2os]

(coming from OpenTabletDriver/OpenTabletDriver#2574)
GTK4 was released a while ago and improves on GTK3 a lot, especially in the world of efficiency. Adding support for GTK4 would be appreciated.

Sidenote: maybe Libadwaita can be done too, but that might be harder to do, not sure.

https://docs.gtk.org/gtk4/migrating-3to4.html

[Miepee]

Eto uses GTKSharp, so that needs to get gtk4 support first. Not sure if it has.

EDIT: Apparently there already is an open issue: GtkSharp/GtkSharp#166

[hax0r31337]

What about migrate to Gir.Core to get Gtk4 & Libadwaita support instead of waiting for GtkSharp?
GtkSharp not seems to support Gtk4 anytime soon, the issue mentioned earlier is there for years and still not resolved.

[Miepee]

From the gir.core readme:

The code is under development and not ready for production use. There are nuget packages available. The API is subject to change as long as version 1.0 is not released.

[cyanfish]

FWIW the "not ready for production use" note has been removed from the Gir.Core readme.

[Miepee]

while that note is gone, I don't think it'd be that great of an idea for Eto to use Gir.Core due to them not having a 1.0 yet.

[cwensley]

Hey all, I did a barebones implementation of a Gir.Core based platform in #2879. Any takers to help fill this out? It will unfortunately be a lot of work as it's quite different from GtkSharp in its APIs.