Bug#943367: light-locker shows only the cursor on a black screen after unlocking

[Andreas Stempfhuber <reportbug2025@afulinux.de>]

Hi,

xfwm4 user? Try the following and restart xfwm4:
xfconf-query -c xfwm4 -p /general/vblank_mode -s xpresent


Long description:

Issue can be sometimes reproduced by starting glxgears and locking the screen. 
After unlocking, the screen stays black with a visible and movable mouse 
cursor.

The issue isn't related to lightdm or light-locker. It also occurs with slim 
as display manager and with xscreensaver or xsecurelock/xss-lock.

It is related to the auto and glx vblank setting of the xfwm4 window manager 
which is unfortunately the default. Possibly in combination with (older) Intel 
graphics cards.

Workaround is to disable vblank or use xpresent which can be done with one of 
the following lines:

xfconf-query -c xfwm4 -p /general/vblank_mode -s xpresent
xfconf-query -c xfwm4 -p /general/vblank_mode -s off

xfwm4 must be restarted for the change to take effect.

It took me forever to figure that out.

Best regards,

Andreas