Convert date-time faithfully in QDateTimeEdit::setDateTime()

Previously, setDateTime() was documented to ignore the new date-time's
time-spec. It used the date and time (determined using that timespec)
with the QDateTimeEdit's configured spec. It is debatable whether that
really counts as ignoring its time-spec. All the same, that's what it
did. Fixing it is a behavior change. Added tests.

[ChangeLog][QtWidgets][QDateTimeEdit] QDateTimeEdit::setDateTime() now
converts the new datetime to the QDateTimeEdit's time-spec, rather
than combining its date and time (determined using the time spec it
came with) with the QDateTimeEdit's date and time.

Fixes: QTBUG-71181
Change-Id: Ibf0bd87723c3957ca00a2199d51d992032ef57ee
Reviewed-by: Paul Wicking <paul.wicking@qt.io>
Reviewed-by: Volker Hilsheimer <volker.hilsheimer@qt.io>
Reviewed-by: Konstantin Shegunov <kshegunov@gmail.com>

1 files changed, 1 insertions, 0 deletions

diff --git a/src/widgets/widgets/qdatetimeedit_p.h b/src/widgets/widgets/qdatetimeedit_p.h
index 392bb0c778..0a4433846f 100644
--- a/src/widgets/widgets/qdatetimeedit_p.h
+++ b/src/widgets/widgets/qdatetimeedit_p.h
@@ -109,6 +109,7 @@ public:
 
     void updateCache(const QVariant &val, const QString &str) const;
 
+    QDateTime convertTimeSpec(const QDateTime &datetime);
     void updateTimeSpec();
     QString valueToText(const QVariant &var) const { return textFromValue(var); }