Lost mouse events on hidden windows on Xfce4 (Server) and Gnome (Client)

[kimberli]

A strange thing I recently encountered that I’m not sure what the cause is is that sometimes (randomly or because I activated a shortcut key combination of some program), the mouse navigation function has lost control.
Although I can still move the cursor across the screen normally, it seems that the (default) mouse cursor position is delayed/frozen, stuck somewhere, or even in the window of the screen on some applications.

When I move the mouse cursor to the 2nd application on the taskbar and click on it, the result is the 4th application on the taskbar (and it seems impossible to left-click to open the 2nd application then; the only way is using the key combination to switch windows from the keyboard).

Or when I switch the window from the Browser (here I use Firefox) to a messaging application (Beeper), I cannot scroll the page with the mouse or interact on the message screen; when I try to do that, it strangely affects the Firefox window (which is sunk below Beeper’s window), similar to other applications.

I think there is a problem with the window manager or mouse events, but I don’t know how to diagnose it??

Strangely enough, it also affects the client (Ubuntu Gnome 22.04), following similar mouse navigation.
At first, I thought the cause was the client side, or worse, a physical hardware error, but when trying to connect to the Xfce4 host from Android, the error was still the same.

Sometimes it disappears and then suddenly comes back in a mysterious way.

Can you give me suggestions on what to do to diagnose and debug this case?

[Britgirl]

Is there an application maybe grabbing the cursor. You could try installing xdotool and run the command xdotool key XF86Ungrab when the problem occurs, to verify if the cursor works correctly. If it does work correctly, it means another application is grabbing the cursor.

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