There is a bug https://bugs.kde.org/show_bug.cgi?id=340031 and videos showing the problem:
Initially I thought it is KDE konsole terminal bug but it doesn't seem to be the case.
I was able to reproduce it on two machines.
- Intel(R) HD Graphics 4600
- kde 4.14.2, xorg 1.16.2, kernel 3.18.0rc4
- I use kdm to log in
- I use this script
$ more /etc/X11/kdm/Xsetup
# Xsetup - run as root before the login dialog appears
/usr/bin/xrandr --dpi 141
/usr/bin/xrandr --output eDP1 --scale 0.6x0.6
to get 1920x1080 instead of native 3200x1800.
Note that dropping "/usr/bin/xrandr --dpi 141" from above makes the problem go away.
So I log in using kdm, twm starts, then I run xterm and run KDE "konsole" from it. In konsole vim /etc/passwd, then set cursorline and move cursors down and up, just like on videos.
- Intel(R) G41
- kde 4.14.2, xorg 1.16.1, kernel 3.17.2
- I use kdm to log in
- twm starts
- run xterm
- xrandr --dpi 80
- start KDE konsole
- under kde konsole: vim /etc/passwd; set cursorline; move up and down
I wasn't able to reproduce on friends laptop:
- Intel(R) HD Graphics 3000
- kde 4.14.2, xorg 1.16.2, kernel 3.17.2
- kde was running; xrandr --dpi XX (various XX values)
- konsole; vim ... ; set cursorline
Created attachment 109415 [details]
log from PC
- Liberation Mono 9, smooth fonts: ON, draw intense color in bold font: ON
and the problem is reproducible.
If I change font to:
- Terminus 9, smooth fonts: ON, draw intense color in bold font: ON
then the problem goes away.
Created attachment 109417 [details]
Terminus (size: 14), smooth fonts: OFF, draw intense colors in bold font: OFF - problem doesn't happen.
We tried to reproduce the problem by changing dpi and using Liberation Mono and the result was that cursorline was not being drawn at all!
Created attachment 109418 [details]
Liberation Mono 9, smooth fonts: ON, draw intense...: ON - problem is visible.
Switching to Terminus and the problem is gone.
Created attachment 109419 [details]
font used on my machine, from redhat liberation 1.07.4
On my laptop I use attached liberation mono font, from redhat liberation 1.07.4.
Created attachment 109420 [details]
font used on my machine, from redhat liberation 1.07.4, added as binary
Created attachment 109422 [details]
friend laptop and pc: liberation mono from redhat liberation: 2.00.1
Filename for above fonts: LiberationMono-Regular.ttf
Could this be generic xorg bug? Or konsole bug closely related to xorg/ddx settings?
Asking because now... reproduced on Radeon HD 6310. Using Liberation Mono font was enough to trigger.
Off the top of my head, I would think it is a font metrics bug (i.e. a bug in the ttf) or at least the processing of it by konsole+Qt. I will try to determine the misrendering and see if that is at least consistent with my theory.
Created attachment 109486 [details]
inconsoldata otf font where the problem is also visible (Inconsolata.otf)