PopupMenu and ComboBox fire FocusLost while using their dropdowns

In Desktop applications, interacting with a PopupMenu or ComboBox dropdown can fire FocusLost while the user is still using that control. For PopupMenu, FocusLost can arrive before SelectionChanged; opening and cancelling the dropdown can also fire it without changing the selected value.

Moving between a control and its own dropdown should be treated as interaction within the same control. FocusLost should fire when keyboard focus genuinely leaves the complete control. Premature focus events can trigger application validation or commit logic while the user is still choosing a value. The selection/change event must continue to fire normally when the value changes.