panel in 18.04 does not register mouseover at top of screen properly

[nmaxx]

System: Ubuntu MATE 18.04 amd64
MATE Panel 1.20.1

GeForce GTX 750Ti, Nvidia drivers 390.48
Tried various screen resolutions like 640x480, 1920x1200, happens with all of them.

How to reproduce:
- have a panel layout with a panel containing the window list applet at the top
- start two applications that show up in the window list
- move mouse across the very top of the screen on top of the window button _not_ selected

=> window button flickers between mouseover highlight and unselected

- click while in "unselected" mode

=> nothing happens

Same problem when the panel at the top of the screen contains pinned applications or the dock applet. They also do not register mouseover properly.

This is a regression vs. 16.04 .

[Abu Sakib (selectiveduplicate)]

I can't seem to reproduce. Can you provide a screenshot?

[Alexander Browne (elcste)]

I can reproduce: in a new account, I moved the window applet to the top panel, then opened Caja and Firefox, and then moved the mouse along the top edge.

[Abu Sakib (selectiveduplicate)]

Everything's okay here!

[nmaxx (nmaxx)]

Updated the description - this isn't just affecting the window list but a general panel issue.

[nmaxx (nmaxx)]

issue is still present in 18.10

[nmaxx (nmaxx)]

tried a 19.04 daily build and the issue is present there also

[Quiddity (quiddity)]

This also affects the left-edge of the screen.
I made a video screencast of the panel-at-bottom, where mouseover/click isn't registering along the left side of the Start button. https://github.com/mate-desktop/mate-panel/issues/940#issuecomment-498050207

[nmaxx (nmaxx)]

A workaround has been posted here: https://ubuntu-mate.community/t/tip-to-fix-un-clickable-menu-and-show-desktop-buttons/19928

Edit your ~/.profile and add this line:
export GDK_CORE_DEVICE_EVENTS=1