There were no problem with selection 16.04.3 version. But starting from 16.08.2 or maybe even earlier selection by mouse is really sluggish. Often mouse scroll suffers too but if I scroll with slider, it works fine. I'm not sure but probably long lines are most affected. It does not depend on any other package in my system. Just emerging 16.04.3 is enough to fix this problem on my Gentoo system.
Perhaps bug #367882?
I don't know. links underlining is disabled for me already but it's still sluggish. For example xfce4-terminal is very fast on the me output
I cannot reproduce this behavior with Konsole 18.08.2. Selecting text works practically instantly for me. Do you still experience this bug with a newer version of Konsole?
Just tried print a bunch of huge links and then select them. Works fast enough with 17.12.3. I guess it was fixed. PS do you know if kscreen developers are still alive? it's terribly broken on resume from sleep with some monitors.
Thanks for your fast response. There is still some activity in the KScreen repository (see https://phabricator.kde.org/source/kscreen/), so maybe a developer will have a chance to look at your issue. I am sadly not familiar enough with the KScreen source, so I cannot help you any further.