In the Mutter window manager code, developed as part of the GNOME 3.34 development cycle, , allowing you to automate the launch of XWayland when you try to run an application based on the X11 protocol in a graphical environment based on the Wayland protocol. The difference from the behavior of GNOME 3.32 and earlier releases is that, until now, the XWayland component ran continuously and required explicit pre-launch (started when the GNOME session was initialized), but will now run dynamically when the components are needed to ensure X11 compatibility. GNOME 3.34 is scheduled for release on September 11, 2019.
Recall that to ensure the execution of ordinary X11 applications in a Wayland-based environment, the DDX component is used. (Device-Dependent X) which as part of the core X.Org codebase. XWayland is similar in organization to Xwin and Xquartz for Win32 and OS X platforms, and includes components for running X.Org Server on top of Wayland. The change made to Mutter will allow the X server to run only when necessary, which will have a positive impact on resource consumption on systems that do not use X11 applications in the Wayland environment (an X server process usually takes up more than a hundred megabytes of RAM).
Source: opennet.ru