Bug 5269 - Easily running out of keycodes when dynamically allocating Xvnc keysyms
Summary: Easily running out of keycodes when dynamically allocating Xvnc keysyms
Status: NEW
Alias: None
Product: ThinLinc
Classification: Unclassified
Component: VNC (show other bugs)
Version: 4.2.0
Hardware: PC Unknown
: P2 Normal
Target Milestone: MediumPrio
Assignee: Bugzilla mail exporter
URL:
Keywords:
Depends on:
Blocks: keyboard 7540
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Reported: 2014-09-24 13:27 CEST by Peter Åstrand
Modified: 2023-04-26 10:51 CEST (History)
2 users (show)

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Description Peter Åstrand cendio 2014-09-24 13:27:35 CEST 
When an "unknown" keysym is recieved by Xvnc, it will dynamically allocate one from the "xmodmap table". Unfortunately there's only room for 255 keycodes. Our default table nowadays includes many multimedia keys etc, so there's only 29 free positions. If the client uses more keysyms than this (consider cyrillic clients for example), we will run out of free positions. The effect is that no (new) symbols can be entered. 

I guess it's difficult to find a real solution for this, but we could perhaps tweak the allocation somewhat, for example consider removing rarely used keysyms to make room for new ones.
Comment 1 Pierre Ossman cendio 2018-05-02 12:57:41 CEST 
An administrator can mitigate this problem by configuring the default keyboard layout to the layout users are actually using (we have "us" layout by default).

A user can also work around the issue by manually setting the keyboard layout inside the session (using setxkbmap or some GUI).
Comment 3 Pierre Ossman cendio 2020-08-17 10:25:42 CEST 
This command can be run to see how much free space a layout has:

> xmodmap -pke | grep '=$' | wc -l
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