[Wayland-bugs] [Bug 719989] Prefer the wayland backend over the x11 one

[gtk+ (bugzilla.gnome.org)]

https://bugzilla.gnome.org/show_bug.cgi?id=719989
  gtk+ | wayland | unspecified

--- Comment #3 from Emilio Pozuelo Monfort <pochu27 at gmail.com> 2013-12-09 12:28:22 UTC ---
(In reply to comment #0)
> Right now, gdk tries the x11 backend first, and only if that fails, it tries
> the wayland backend.
> 
> There are two situations with different consequences depending on whether gdk
> tries x11 or wayland first:
> 
> If you're under X11, you want the x11 used. Having the x11 backend tried first
> means the x11 backend will be chosen. If the order was changed and wayland was
> tried first, it would normally fail and x11 would be chosen, which is good.
> However if you were running wayland on a different tty, or if you're running,
> say, weston as a window through its x11 backend, and you open a gtk+
> application, the wayland backend will be chosen and it'll use the wayland
> backend, which would make it appear in the other tty or in the weston window,
> which is confusing.

With the attached patches, the x11 backend is chosen when launching apps from
within x11 because the wayland backend initialization now fails as
WAYLAND_BACKEND isn't set. This is desired and similar to what happens if you
try to run an app without DISPLAY set.

> On the other hand, let's say you're running weston or gnome-shell-wayland. x11
> is preferred over wayland (status quo). If you don't have XWayland, the x11
> backend fails and you get the wayland backend, which is all good. But if you
> have XWayland, the x11 backend is going to work and will be preferred over the
> wayland backend, making apps that could run natively run through XWayland. If
> the wayland backend was preferred over x11, apps would run natively with the
> wayland backend. Those gtk+ apps that really need the x11 backend would just
> need to specify this with gdk_set_allowed_backends("x11").

With the attached patches, the wayland backend is preferred over the x11 one
unless the app explicitly says that it needs the x11 backend.

> I suppose that until wayland becomes more relevant for gtk+ we don't want the
> order changed, but eventually (particularly when gnome-shell-wayland becomes
> the recommended way to run gnome-shell and not just a beta product) we will
> need to change the ordering to favor the wayland backend over the x11 one.

So with the above patches, I think our behaviour is correct in all cases and we
can proceed with this now.

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