The calendar popup widget from the taskbar closes as soon as the mouse leaves the taskbar and the widget. This makes it unusable when trying to keep it up for a while (because needing to look it up while planning a meeting or event in another application). I vaguely remember that this already used to be an issue a while ago, but then was repaired. Recently it broke again.
Do you have 'Focus Follows Mouse' enabled? If yes - it's possibly related to https://bugs.kde.org/show_bug.cgi?id=363897
Marking as needs info
> Do you have 'Focus Follows Mouse' enabled? I have "Focus Follows Mouse - Mouse Precedence" (why can't I copy-paste this?) But it seems to happen on other settings as well (tried also "Focus Under Mouse", and "Focus Strictly Under Mouse")
You can pin the Calendar using the 'pin' icon in the corner.
Thanks for the info Alain. Can you please test and confirm if this issue is still occurring or if this bug report can be marked as resolved. I've set the bug status to "needsinfo" pending your response, please change back to "reported" or "resolved" when you respond, thanks.
The issue is still occurring (calendar collapses as soon as mouse enters another window). However Christophe Feck's workaround does work, thanks.
.
*** This bug has been marked as a duplicate of bug 336285 ***