Wayland

Wayland is intended to be Article description::a simpler and modern replacement for X display server.

"Wayland is a protocol for a compositor to talk to its clients as well as a C library implementation of that protocol. The compositor can be a standalone display server running on Linux kernel modesetting and evdev input devices, an X application, or a wayland client itself. The clients can be traditional applications, X servers (rootless or fullscreen) or other display servers." Where possible, Wayland reuses existing drivers and infrastructure, such as the DRI drivers, the kernel side GEM scheduler and kernel mode setting.

Global
Several packages are aware of the global  USE flag.

GTK
Wayland is completely supported in GTK 3.22. Nevertheless, when porting application in general two issues must be considered:


 * Ensure that your application uses gtk+-3.0 for its pkg-config request.
 * All calls to the gdk_x11_ namespace and raw Xlib calls must be wrapped in build-time and run-time backend checks.

More details including plans and progress can be found on the GNOME wiki.

Qt
For Qt an additional package called is required. In the Qt Wiki it says: "QtWayland is a Qt 5 module that wraps the functionality of Wayland. QtWayland is separated into a client and server side. The client side is the wayland platform plugin, and provides a way to run Qt applications as Wayland clients. The server side is the QtCompositor API, and allows users to write their own Wayland compositors."

Porting Qt applications is much easier than GTK applications. More information on how to use QtWayland can be found at https://wiki.qt.io/Qtwayland and at https://wayland.freedesktop.org/qt5.html.

Applications
GTK 3.x and Qt support Wayland. Unfortunately most applications still require the X server. Several scenarios are possible to get them working:


 * Porting the application by rewriting the components with X.org dependencies such that they work also for wayland. Cf. Wayland-Ports. Other examples are mpv which is a video player based on MPlayer/mplayer2 or the minimalist web-client xombrero, midori and epiphany also have full support for wayland. GNOME and KDE are expected to be ported to it.
 * Xclients can be run on Wayland. Afterwards the required application can be run as usual on the Xclient. See X server running on wayland.
 * Xwayland is the third option which is running Wayland on the X server.

GTK
Sometimes it is necessary to start an X11 only application on Wayland. When the app uses the GTK toolkit, or when starting an X11 only app from Gnome 3, simply adjust the GDK_BACKEND environment variable as appropriate:

To check the current value:

To temporarily set the value to X11 and start the app, for this example starting the binary Tor browser:

External resources

 * https://wiki.archlinux.org/index.php/Wayland
 * https://manpages.ubuntu.com/manpages/cosmic/en/man1/weston.1.html
 * https://manpages.ubuntu.com/manpages/cosmic/en/man5/weston.ini.5.html
 * https://wiki.qt.io/Qtwayland
 * https://wiki.gnome.org/Initiatives/Wayland/GTK%2B
 * https://www.linux.com/news/what-why-and-how-wayland-and-weston-linux - A Linux.com article explaining Wayland (and Weston).