Raspberry Pi Bookworm/Trixie Spurious App Input - WayVNC Problem?

[ISO8807]

I have been trying a fresh install of both Bookworm (Debian 12) and Trixie (Debian 13) on a Raspberry Pi 4. The WayVNC versions on these are respectively 0.9.1-1~bpo12+rpt4 and 0.9.1-1+rpt5.

I am using a VNC Viewer for Windows 11 on the same LAN as the Pi. Openbox/X11 (hence RealVNC Server) works OK on Bookworm/Trixie. But Wayland/Wayfire and Wayland/Labwc on Bookworm/Trxie (hence WayVNC) have a bizarre problem.

WayVNC works OK for an hour or two, then apps start getting spurious input. Specifically, endlessly repeating backslashes appear in app input fields when I click on them. It is as if I were holding down the backslash key. (I have once seen single quotes repeating instead of backslashes.)

Once this starts happening I can press any key to stop the input. However, it then happens again the next time I click on the input field. I have seen this problem with various types of apps: text editors, web browsers, Java apps, etc. Curiously, terminal emulators aren't affected. This might possibly be because I have "kb_repeat_rate = 0" in ~/.config/wayfire.ini, though that doesn't seem relevant.

Once this has started happening, the only fix to to disconnect the VNC Viewer and then reconnect it. Things then work for a while until the problem repeats. The problem happens with both RealVNC and UltraVNC Viewers on Windows, so I suspect it's a server-side problem

I don't think this is the oft-reported problem of lost or delayed packets causing repeated keystrokes. The repeated backslashes happen when I just click on an input field, but without touching the keyboard. The Pi and PC are also on the same LAN.

The fact that RealVNC Server with Bookworm/Trixie is free from this problem suggests the problem lies with WayVNC. It's not clear what diagnostic information would be possible or relevant.

Any inspirations? Thanks!

[any1]

Does this also happen with TigerVNC Viewer?

[ISO8807]

Many thanks for the suggestion. I delayed responding until I could conduct an extended evaluation. Indeed, this problem doesn't arise with TigerVNC Viewer. That allows me to use WayVNC without difficulties.

Of course, it raises the question of why TigerVNC works for me but RealVNC and UltraVNC hit this problem. Very mysterious.

[any1]

TigerVNC implements a couple of protocol extensions that make keyboard handling a bit more robust.

It seems unlikely that this is strictly time dependent. It would be helpful if you could try to better pinpoint what action triggers this.

[ISO8807]

That's interesting, though it was a mouse issue in my case rather than a keyboard issue.
I did try to find what triggered the problem behaviour but didn't find anything specific. About the only thing I noticed was that everything was normal for a few hours and then this problem repeatedly arose when clicking on an app input field.

The oddest thing for me was that terminal emulators (Gnome, Lx) didn't have this problem. When the problem arose I could switch between clicking on a terminal window (no input) and app windows (spurious backslashes). I don't know if terminal emulators react to mouse clicks in a different way from, say, web browsers (Firefox, Chromium) or Java apps (e.g. jEdit).

If it were a timing issue, I would expect it to happen at random and not continue once something went wrong. I did wonder if it was a memory issue (on the Pi) because some limit was reached, though I didn't spot anything obvious. All very mysterious and (I appreciate) hard to pin down.

[ISO8807]

Could it be a difference between which apps are using XWayland and which are using Wayland natively? I don't know which apps have been converted for Wayland.