I'm troubleshooting some issues to do with multiple monitors and HiDPI on Wayland. I've learnt from online resources that applications on XWayland may not handle this use-case as expected. So now I want to know which applications are using XWayland, and which aren't.

How can I tell if an application is using XWayland or not?

1 Answer

xlsclients

Running xlsclients in a terminal will list all the apps currently running which are using XWayland.

Use xeyes!

xeyes - a follow the mouse X demo

When you launch xeyes, it connects to the XWayland server and asks for the mouse position. If the mouse is currently over a window of an app that uses XWayland, XWayland knows the mouse position and can report it back to xeyes via the X11 protocol. But if the mouse is over a native Wayland client, XWayland can't get that — so the eyes will remain still even if you move your mouse.

xwininfo

Run xwininfo in a terminal window — when you hover over an xwayland window the mouse pointer will turn into a + sign. If you click the window it'll display some information and end, but it won't do anything with native Wayland windows.You can use Ctrl + C to end it.