Description:
Using 2 screens on Ubuntu (20.04 LTS).
When libreoffice (writer/calc/draw etc) main window is maximized on the right screen, menus and contextual menus opened near the left side of the screen will partly span over the second (left) screen, making them difficult to read when the screens are not physically joined. In other words, opened menus and contextual menus don't stay inside the main window.

Steps to Reproduce:
1.Use a display expanded on 2 screens
2.Maximize Calc on the right screen
3.Open the «File» menu or open a contextual menu on any cell in the A column

Actual Results:
Menu is spanned over the 2 screens, thus the menu is difficult to read.


Expected Results:
The menu should stay inside the main windows, on the right screen.


Reproducible: Always


User Profile Reset: Yes

Additional Info:
Problem is the same when libreoffice window is displayed fullscreen on the left screen and then opening contextual menus near the right side of the screen : menus will span over the 2 screens.
It seems that menus and contextual menus are displayed at the right side of the mouse when main window is on the left screen, and at the left side of the mouse when main window is on the right screen, but this policy is not relevant on display using more than 1 display.
Version : 6.4.7.2
Build ID : 1:6.4.7-0ubuntu0.20.04.8
Threads CPU : 8; OS : Linux 5.15; UI Render : par défaut; VCL: x11; 
Locale : fr-FR (fr_FR.UTF-8); Langue IHM : fr-FR
Calc: threaded