KDE/Debugging

Some loose, partially undocumented, but useful debugging methods found here and there in discussions, bug comments etc.

KDE4 ()

KDE5 (F24)

kwin_x11

https://community.kde.org/KWin/Debugging

export KWIN_USE_INTEL_SWAP_EVENT=0 # only affects intel IGPs 
export KWIN_EXPLICIT_SYNC=0 # most likely candidate on nvidia GPUs 
export KWIN_USE_BUFFER_AGE=0 # well, you tried, but hey ... ;-) 

kwin_x11 --replace &

xdotool lets you programatically (or manually) simulate keyboard input and mouse activity, move and resize windows, etc. It does this using X11's XTEST extension and other Xlib functions.

For example if screen is locked

xdotool key "XF86LogGrabInfo"

dumbs all device grabs into /var/log/Xorg.0.log file. It can be run from character based consoles by prefixing it with DISPLAY=:0

gam_server

Sometimes it helps to kill the gam_server process to release odd hangups or when applications wont start from panel buttons. Process can be safely killed, it gets respawned automatically, but running processes might not like it. Once killed, all pending start attempts are executed if the gam_server was the culprit. Sending a SIGUSR2 to running gam_server makes it dump its debugging information into /tmp/gamin_debug_*

kill -s SIGUSER $(pidof gam_server)

all gam_server bugs
most long lived bug deadlocks, leading to all KDE applications hanging

DBUS

DBUS can be followed using dbus-monitor, it can be lousy thou and hard to follow. Wireshark has dissector for dbus these days but it doesn't do that good job on it.

dbus-monitor

.xsession-errors

Users $HOME/.xsession-errors

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