Non-modal or window modal dialogs are shown at show(), via AppKit APIs
that are non-blocking. If we want to block execution at this point, we
need to spin our own event loop. The runModal API of NSSavePanel is not
meant to be used for blocking execution for already shown dialogs, but
is reserved for application modal dialogs.
This means we no longer trip over AppKit's understanding of what state
the dialog is in, which would result in the dialog not reporting back
any files. It also allows us to remove the guard for closing dialogs
twice.
We now also correctly close and end the application modal session if
the dialog is closed programmatically using Qt APIs.
Task-number: QTBUG-89959
Fixes: QTBUG-85547
Pick-to: 6.0 5.15
Change-Id: Ida3dc404417789d4823822ecfbf0935591c23878
Reviewed-by: Morten Johan Sørvig <morten.sorvig@qt.io>
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