Demo application attached to this bug report which demonstrates that QMainWindow
does not receive any enter/leave events. For QWidget classes enterEvent's are received when moving mouse either horizontally or vertically over the widget.
LeaveEvents are not triggered when moving mouse horizontally, only random vertical events are being fired.
This is an regression as it works in Qt 4.8.4.
Edit: When QGLWidget is in a QAbstractScrollArea, Enter or Leave events are not received at all.