There's logic in QMessageBox to resolve the default and escape button
if not set by the user. And the user may of course override these.
We now propagate the resulting buttons via the dialog helper, and
pick them up in the macOS native dialog backend. The only common
information we have between the standard buttons and custom buttons
is the button identifier, which for standard buttons is the enum
value, and for custom buttons is an auto generated identifier.
The same identifier is used when reporting the clicked button
from the native dialog helper.
Fixes: QTBUG-118308
Pick-to: 6.6 6.5
Change-Id: I5ca45604b51f0bbf74e56134d7b55bb8911f3563
Reviewed-by: Volker Hilsheimer <volker.hilsheimer@qt.io>
c5d9e4a7a7