With version 1.2.1 there are no more tooltips displayed. Version 1.1.2 worked fine.
Filed a bug in GNOME's bug tracker about this, maybe they can fix it in Gtk3:
The workaround is to set the update the update interval > 0.5s for now
Pushed this workaround in https://git.xfce.org/panel-plugins/xfce4-systemload-plugin/commit/?id=364956da514590ceac30c6443f1f421461bcdfa7
*** Bug 14746 has been marked as a duplicate of this bug. ***
The minimum might need to be bumped to 600 ms. 500 ms cuts a bit too close and doesn't work for me.
Using the tooltip.c example from , the tooltip appears if I use 500 ms on my desktop and 501 ms on my laptop. And even though 500 ms works with tooltip.c on my desktop, xfce4-systemload-plugin still needs a bump to 0.6 because 0.5 doesn't work.
Thank you very much!
It works very well with values greater than 0.5 s.
The problem is solved and I am happy to retrieve this useful feature!