Bug 23068

Description of problem:

The tooltip displaying under the top panel displays underneath (as expected), but with text starting to the right of the line of the right side of the applet icon or text.
By default, the (text mode) clock applet displays to the right, so if the date is not displayed in the panel (to give more space), it is no longer visible in the tooltip.  (Displaying almost entirely off screen.)
If the clock applet is moved to the left so the date shows in the clock applet tooltip, the tooltips of one or more applets still at the right are no longer visible.

Version-Release number of selected component (if applicable):
Same as panel.

How reproducible:
Move the mouse over any applet on or near the right of the top panel.

This may also affect the bottom panel, which I don't use.  Others may confirm.

Note that the tooltip might be controlled by another application, but I have no idea which.  To help determine this, I tested a few other applications (in alpha order).
Hope this helps.

Except for tooltips at the top controlled by the maté window manager (marco), this problerm also affects certain applications of maté (atril, caja, engrampa, eom, mate-color-select, mate-dictionary, pluma), as well as abiword, bluefish, gnome-calculator, libreoffice, rpmdrake, pavucontrol (pulseaudio), and sol (aisleriot).

However tooltips in the Maté window manager (marco, for example) can display to the right of a window, but do not display off screen if the same window is moved over to the right of the screen.
Also not affected are cherrytree, chromium, dia, diffpdf, diffuse, easyrpmbuilder, ekiga, gimp, gpicview, grip, hexchat, mate-control-center, meld, sudokuki, thunderbird and vlc.

(Many other applications not tested.)