workaround for correct wayland positioning
Summary:
as showEvent is too soon, create the plasma surface on
:Expose event, and reposition the surface
Test Plan: krunner is correctly positioned with correct blur and shadows
Reviewers: Plasma, Plasma on Wayland, davidedmundson
Reviewed By: Plasma, davidedmundson
Subscribers: hein, davidedmundson, graesslin, plasma-devel
Tags: Plasma on Wayland
Differential Revision: https://phabricator.kde.org/D5748