Figure out missing display handle implementations

[madsmtm]

RawDisplayHandle documents that (emphasis mine):

Not all windowing systems have a separate display handle (or they haven’t been implemented yet) and their variants contain empty structs.

So... We should probably track, and follow up on the ones that haven't been implemented yet!

Checklist:

• UiKit - No display server (exposed to users, at least)
• AppKit - No display server (exposed to users, at least)
• Orbital - Unknown
• Xlib - Implemented
• Xcb - Implemented
• Wayland - Implemented
• Drm - Implemented
• Gbm - Implemented
• Windows - No display server (exposed to users, at least)
• Web - Doesn't use this concept
• Android - Unknown
• Haiku - Unknown

[notgull]

For Win32, there isn't really a concept of a display. Some structures are thread local, but overall there is very little context for the windows. Leaving it empty is probably the right choice. I am not familiar with WinRT.

Web stuff is generally contextualized by the window/document, which is often cached. But given that it can be derived from anywhere it might not be worth it.

I don't know other platforms well enough to comment on them.

[kchibisov]

Everything which is not implemented is not needed or doesn't exist as a concept. I remember discussing it with you on #matrix and I told that it's more about platforms having a concept of multiple display servers, so they need a way to distinguish between them, which is only an issue on platforms with the freedom to choose the display server.

[madsmtm]

I do remember too, I was just unsure if we were still missing something.

I guess I'll reword that section at some point then, and then close this issue.

[madsmtm]

The documentation, as far as I could find it, says that you're allowed to pass EGL_DEFAULT_DISPLAY (i.e. a null-ptr) on Wayland too? So why are we restricting that?

[madsmtm]

And it seems like HaikuOS just got the ability to pass a handle as well, although that doesn't really sound stable yet.

[kchibisov]

The documentation, as far as I could find it, says that you're allowed to pass EGL_DEFAULT_DISPLAY (i.e. a null-ptr) on Wayland too? So why are we restricting that?

you could try, but it'll fail.