Dive list: cache shown flag in model (quick-fix for undo-crash)

We have a very fundamental problem with data-duplication in
core and qt-models. In a particular case, this led to an easily
reproducible crash:
1) An undo command moved the last dive of a trip to another.
2) When an undo-command removed the last dive of
   a trip to a different trip, the dive was removed from the
   trip in the core. Then, the model was updated.
3) That lead at first to a rearrangement of the trips, because
   the trip with the added dive is moved before the trip with
   the removed dive.
4) In such a case, the filter-model checks the visibility of
   the trip.
5) Since the trip with the removed dive has no dives in the core,
   visibility was determined as false.
6) From this point on the mappings of the QSortFilterProxyModel
   were messed up. Accesses led to crashes. It is unclear
   whether this is a Qt bug or only a QOI issue.

As a quick-fix, cache the visibility flag of trips directly
in the Qt-models. Don't set the visibility directly in the
core, but go via the Qt-models. Thus, a more clear layering
is achieved.

In the long run, we can hopefully get rid of the data-duplication
in the models.

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

1 files changed, 5 insertions, 0 deletions

diff --git a/qt-models/divetripmodel.h b/qt-models/divetripmodel.h
index 236dbb1d2..592234917 100644
--- a/qt-models/divetripmodel.h
+++ b/qt-models/divetripmodel.h
@@ -52,6 +52,7 @@ public:
 		DIVE_ROLE,
 		TRIP_ROLE,
 		DIVE_IDX,
+		SHOWN_ROLE,
 		SELECTED_ROLE
 	};
 	enum Layout {
@@ -74,6 +75,7 @@ public:
 	DiveTripModelBase(QObject *parent = 0);
 	int columnCount(const QModelIndex&) const;
 	virtual void filterFinished() = 0;
+	virtual bool setShown(const QModelIndex &idx, bool shown) = 0;
 
 	// Used for sorting. This is a bit of a layering violation, as sorting should be performed
 	// by the higher-up QSortFilterProxyModel, but it makes things so much easier!
@@ -126,6 +128,7 @@ private:
 	bool lessThan(const QModelIndex &i1, const QModelIndex &i2) const override;
 	void changeDiveSelection(dive_trip *trip, const QVector<dive *> &dives, bool select) override;
 	dive *diveOrNull(const QModelIndex &index) const override;
+	bool setShown(const QModelIndex &idx, bool shown);
 
 	// The tree model has two levels. At the top level, we have either trips or dives
 	// that do not belong to trips. Such a top-level item is represented by the "Item"
@@ -138,6 +141,7 @@ private:
 	struct Item {
 		dive_or_trip		d_or_t;
 		std::vector<dive *>	dives;			// std::vector<> instead of QVector for insert() with three iterators
+		bool			shown;
 		Item(dive_trip *t, const QVector<dive *> &dives);
 		Item(dive_trip *t, dive *d);			// Initialize a trip with one dive
 		Item(dive *d);					// Initialize a top-level dive
@@ -187,6 +191,7 @@ private:
 	bool lessThan(const QModelIndex &i1, const QModelIndex &i2) const override;
 	void changeDiveSelection(dive_trip *trip, const QVector<dive *> &dives, bool select) override;
 	dive *diveOrNull(const QModelIndex &index) const override;
+	bool setShown(const QModelIndex &idx, bool shown);
 
 	std::vector<dive *> items;				// TODO: access core data directly
 };