Indeed, I too can reproduce these two behaviors and they are certainly
linked to each other.
I opened this ticket: GUACAMOLE-2289 [1]
Thank you for this report.
Best regards,
Corentin Soriano
On 2026-06-12 09:36, Antoine Besnier via user wrote:
Hi All,
Using guacamole client and server built from Github, I noticed since a
few weeks ago an undesirable behaviour during SSH sessions. I don't
think I saw a similar report in the user mailing list, nor in JIRA.
As English is not my first language, I hope I'll be clear in my
explanation.
Let's say I cat a long file, or ls a directory with many files (more
than one screen worth of lines), if I scroll up to select some of the
text (click/drag to select, right click to copy), the screen
immediately goes back to the current cursor positon / user prompt, at
the bottom of the screen.
This prevents me from selecting anything that is above one screen worth
of lines.
Attached are two video captures, one with 1.6.0, one with a build from
Github showing this behaviour.
Note that selecting anything within the current terminal lines works
fine.
Here's what is recorded in the logs (yes, it logs twice for each click)
:
guacd[299]: DEBUG: Ignoring unknown keysym: 0xFF7F
guacd[299]: DEBUG: Ignoring unknown keysym: 0xFF7F
Which makes no sense as 0xFF7F is supposed to be NumLock (which is
indeed not handled by terminal.c, and actually pressing NumLock will be
logged the same way)
The issue exists regardless of the browser (normal, it comes form
guacd), and is not reproducible with guacd built from source downloaded
from the official website.
I tried to diff the files in _src/terminal/_ between Github and the
official tar file, but there are too many changes, and I am not versed
enough in C to find what I was looking for.
I use Guacamole in a docker container, behind nginx reverse proxy (I
don't think it's relevant), and it used to work perfectly fine up until
a few weeks ago, as mentioned. Unfortunately, I did not notice when
exactly, as I thought it was a temporary quirk.
The build part in my Dockerfile is like so, if that makes any
difference:
# Install guacamole-server
&& cd /git && git clone https://github.com/apache/guacamole-server.git
--depth=1 -b main \
&& cd guacamole-server \
&& autoreconf -fi \
&& ./configure --enable-allow-freerdp-snapshots \
&& make -j$(getconf _NPROCESSORS_ONLN) \
&& make install \
&& cd .. \
&& rm -rf guacamole-server-${GUAC_VER}.tar.gz
guacamole-server-${GUAC_VER} \
&& ldconfig \
So, as a conclusion, I believe there are two things here:
- why is left click registered as 0xFF7F / NumLock, only when clicking
after scrolling up?
- why is the terminal reset to the bottom line when an unhandled
keypress is registered?
I hope I was as clear as possible, and I wish I knew more of C to be
more helpful...
Cheers
Antoine
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[1] https://issues.apache.org/jira/browse/GUACAMOLE-2289
