All our implementations of the popup windows have a logic that checks the screen of the owner of the popup. If the popup does not fit the bounds of the owner's screen we shift it to the correct screen.

For example, if the window cross two different monitors and JMenuItem is located on one screen, but the window itself is located on another screen(the biggest part of the window is on another screen), then we open the popup on the screen where the window is located, even if the menu item can be shown as-is since it is visible on another screen. The problem became worse if two screens have different DPI.