mobile: remove DiveObjectHelper code

When editing a dive, a DiveObjectHelper of the unmodified dive
was created to compare the edited with the old values. Since
the DiveObjectHelper is used here only as a pointless wrapper
around the formatting functions, call these functions directly.

However, note that the code is in principle wrong since the
change to the mobile-models, which do not use the DiveObjectHelper.
The real fix would be to reload the data from the model to prevent
going out-of-sync with respect to the formatting routines!

Signed-off-by: Berthold Stoeger <bstoeger@mail.tuwien.ac.at>

core/string-format.cpp

@@ -250,3 +250,10 @@ QString formatDiveTime(const dive *d)
 	QDateTime localTime = timestampToDateTime(d->when);
 	return localTime.time().toString(prefs.time_format);
 }
+
+QString formatDiveDateTime(const dive *d)
+{
+	QDateTime localTime = timestampToDateTime(d->when);
+	return QStringLiteral("%1 %2").arg(localTime.date().toString(prefs.date_format_short),
+					   localTime.time().toString(prefs.time_format));
+}

core/string-format.h

@@ -24,5 +24,6 @@ QString formatDiveDuration(const dive *d);
 QString formatDiveGPS(const dive *d);
 QString formatDiveDate(const dive *d);
 QString formatDiveTime(const dive *d);
+QString formatDiveDateTime(const dive *d);
 
 #endif

core/subsurface-qt/diveobjecthelper.h

@@ -96,6 +96,4 @@ public:
 	QString waterType;
 };
 
-Q_DECLARE_METATYPE(DiveObjectHelper)
-
 #endif