How to check if the mouse has really left the QWidget?

Question

Consider a QWidget window, what event is triggered when the mouse has left this window?

The window has QLineEdit fields on it and they have completers (QCompleter) for input suggestions. The actual goal is to make such an (open) completer disappear when the mouse leaves the window. This is mostly because in some environments, moving the mouse over a different window may focus that other window, but keyboard events are still sent to the QLineEdit field (even though its parent window isn't focused anymore), which is confusing.

I could implement QWidget::leaveEvent(QEvent *event) (in the window), find the currently shown completer popup and hide it, that closes the popup. But ironically, leaveEvent() is also triggered when the mouse is moved over that popup - hiding it (making it impossible to click on an item in that popup). I guess that makes sense because the popup is a different QWidget, even though the popup is indirectly owned by the window.

So how do I check if the mouse has actually left the QWidget window?

Answer 1

Reimplement QWidget::leaveEvent(QEvent *event) in your derived class but start by checking that rect().contains(mapFromGlobal(QCursor::pos())) is true.

If not, return without doing anything. This should filter out all the events where the mouse is still over your widget.

Hope it helps!