key events handler return value to True to stop propagation

[fariza]

Fixing #6349

Right now only stopping the key press and key release event from propagating after callback.
I am in doubt about the other events, should be stopped also?

@tacaswell how does it work in Qt?

[tacaswell]

Qt does not have this notion of a 'callback' chain. Each signal can propagate to 0 or more slots, but they are, my understanding, all independently executed.

[QuLogic]

"stopping", not "stoping", but actually, just use "stop".

[dopplershift]

@tacaswell Qt's signals/slots mechanism is separate from its event handling (like keyboard events). Qt's event handling does have the notion of stopping the propagating of events.

[tacaswell]

@dopplershift 🐑 For reference http://doc.qt.io/qt-4.8/eventsandfilters.html

[tacaswell]

On a bit further reading, the notion of event propagation is handled by the method event in QObject which by default dispatches to a set of eventtypeEvent methods (all of which are void functions at the c++ layer) which we override. This 'accepts' the event and prevents propagation up to the parent widgets. We could re-enable that propagation by calling the default implementation of any of those methods, but as written of the Qt events are stopped by our handlers.

https://doc.qt.io/qt-4.8/qwidget.html#event

[fariza]

So with the changes in this PR we are at the same level that Qt

[tacaswell]

backported to 2.x as 9b39f3e