[solved] tigervnc holds back on last screen update

[jamapii]

Hello

I have one box, where tigervnc 1.12.0-r7 almost always does not display the last character typed in an xterm (just for example). It does display it when the next character is typed (but then again holds back on the new last character). It also displays things after a mouse event or movement.

The viewer is from tigervnc 1.10, in KDE plasma 5.25.4, Xorg

I tested

• konsole instead of xterm. It does not depend on the choice of application, it is a specific vncserver/specific box thing.
  
• moving the mouse outside the vnc viewer, typing, then shading (rollup) and unshading the viewer. This does NOT make the last character appear, but moving the mouse on the titlebar does.
  
• other vncserver instances on the same box, same problem
  
• vnc instances on 2 other boxes, NO problem
  
• using a viewer in another box inside a working vnc server, NO problem
  
• an ipad viewer, NO problem
  

So it might be a vnc server/vnc viewer/KDE plasma compositor interaction.

It reminds me of a situation from an old Ubuntu default installation, maybe 14.4, where almost always, on all terminals, the last typed character was delayed by 2 seconds. I wrote about it somewhere, and I can not believe I'm the only one who sees it, but nobody else was bothered by it.

Could anyone ever track these things down? What packages are involved, or what else? What must be changed?

thanks

edit: ok, let's call it solved, but the root cause is not known.

[jamapii]

After update to tigervnc 1.12 on the viewer side, it seems to work again.

This tigervnc 1.10 viewer never had any other specific problem AFAIK.

As if the tigervnc things negotiate some extra channel, and there was a hiccup with this specific combination.