Can't seem to get global screen position

[Coises]

More details: I've got my primary monitor on the right and a secondary monitor on the left. I simply cannot detect reliably what screen I'm running the app on or what global position the app has.

Is QDesktopWidget::primaryScreen() any use? The documentation is inconsistent: it says that property “holds the index of the screen that is configured to be the primary screen on the system”; but in the general description for QDesktopWidget it says, “For an application, the screen where the main widget resides is the primary screen. This is stored in the primaryScreen property.”

(Lord knows what the main widget is supposed to mean.)