[gtk] add wayland support on linux

[feliwir]

Fixes #51038

• Changes comply with the maintainer guide.
• SHA512s are updated for each updated download.
• The "supports" clause reflects platforms that may be fixed by this new version, or no changes were necessary.
• Any fixed CI baseline and CI feature baseline entries are removed from that file, or no entries needed to be changed.
• All patch files in the port are applied and succeed.
• The version database is fixed by rerunning ./vcpkg x-add-version --all and committing the result.
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[feliwir]

@microsoft-github-policy-service agree

[feliwir]

apparently the wayland version by the wayland distro in the CI is too old. What should be the fix here?

[AenBleidd]

Why this should be always enabled by default? It is still possible to build GTK with X11 backend, and thus this port should give a possibility to do that, and not just hardcode Wayland for Linux

[feliwir]

Well, currently x11 is also hardcoded for linux. When enabling wayland that does not disable x11, it just enables both backends. So on a X11 desktop GTK would pick the x11 backend, on a wayland desktop the wayland backend (currently it quits there).

Ideally we'd want VCPKG features for the backend selection, but in general this port currently lacks any proper feature support. E.g. vulkan, opengl etc. should also be selectable.
To me it seemed like this is out of scope of this PR

[AenBleidd]

By this change you will force all applications to build (or install) Wayland even if they don't use it, so this is a breaking change. Also can you confirm that with Wayland backend application will switch to X11 when there is not Wayland support and what is more important will not require installing anything additional?

[feliwir]

I can confirm this since i've used Gtk (without VCPKG) for years. The automatic backend selection is the default behaviour unless explicitly set: https://docs.gtk.org/gtk4/running.html#gdk_backend

This port not having features forces a lot of restrictions. My distro has no X11 support, still this port forces me to build & compile the x11 backend.

If majority wants me to pull this out as a feature I'll do so, but then the other backends should be "optional" aswell

[AenBleidd]

And in this port you explicitly wet it to use Wayland. I do know that on Wayland X11 applications can run because Wayland provides a special mediator library.
I'm not sure this will work other way around when you build an application setting a Wayland backend that ill fall back to X11 if Wayland is not present.
To clarify: I'm ok to have Wayland a defaul backend, but there should be a possibility to configure this port to use some other backend.

If majority wants me to pull this out as a feature I'll do so, but then the other backends should be "optional" aswell

This is basically up to maintainers to decide.
However, the only 'other' backend is broadway, since macos is MacOs specific, and win32 is Windows specific.

[AenBleidd]

I double checked the documentation. This is true, but still this adds a hard dependency on Wayland libraries during the build, and this might be not desired. I do see that the backend options should be configurable (for Linux) with the X11 set as a default.

@vicroms, @BillyONeal, it would be nice if you could take a look at this.

[feliwir]

I think that the default should be that all available backends are compiled in.
The Gtk version we currently build with this port is a "crippled" version of the default Gtk. Preferably the built binaries should have similar / more features than the Gtk shipped with the OS / distro.

See this quote of a Gtk maintainer: gtk-rs/gtk4-rs#1963 (comment)

I think we should try to become a solid choice for Gtk users and that the Gtk team actually approves our effort / port being used

[AenBleidd]

This "default' means that all the port users that were previously build it with x11 libraries only will need to build it now with wayland as well.
Personally I prefer to have a choice which libraries I would like to build and don't blow up my build pipeline with unneded dependencies (don't forget, that not all people build ports with the system libraries included, some prefer to have a pure static builds (and vcpkg by default builds static libraries for Linux unless *-dynamic port is selected)) with the controlled dependencies, not just with everything that comes with the distro).
This is a little bit more complicated that you think since there are a lot of users of vcpkg with very different scenarious, and as a package manager it should give a choice to the users and not just promote some particular way of building a library.

[feliwir]

I agree with you that features would be sweet, the question is just if this is in scope of this PR.
To have all Gtk build options represented as features would require us to add more than 10+ features probably (e.g. the renderer choice etc.)

[AenBleidd]

You don't need to do anything in one PR. You can start with backend options and add other features later.
I mean, if you do this change now, it will be visible immediately (ok, for the majority of users after the next monthly release), and at that point it will be too late to improve something since the only option will be the rollback.
Regarding the other features, if would be nice to have them if they are required.