Sticky option does not work

[rynchn]

It appears that the -s option does not make the window appear on all desktops (under kwin). E.g.,

kdocker -s kolourpaint

This might be because TrayItem::doSticky() sets _NET_WM_STATE_STICKY, which according to https://forum.kde.org/viewtopic.php?f=111&t=127128 has no effect on kwin; instead _NET_WM_DESKTOP should (also?) be set to 0xFFFFFFFF (according to xprop and https://specifications.freedesktop.org/wm-spec/wm-spec-latest.html#idm140200472635472).