Filter: add reference counting for dive-site mode

The dive-site-edit and dive-site-table tabs both put the filter
into a special dive-site mode. When switching between both, it
could happen that the one got its show befor the other got
its hide event.

Thus, the first would start dive-site filtering and the second
stop it. Now the app was not in filter mode even though it should.

To solve this problem, add reference counting for the filter's
dive-site mode. In both tabs call the enter/exit functions
on show/hide. In the dive-site-table tab, when the selection
changes, use a set function that doesn't modify the reference count.

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

desktop-widgets/tab-widgets/TabDiveSite.cpp

@@ -83,7 +83,7 @@ void TabDiveSite::on_filterText_textChanged(const QString &text)
 	model.setFilter(text);
 }
 
-void TabDiveSite::updateFilter()
+QVector<dive_site *> TabDiveSite::selectedDiveSites()
 {
 	const QModelIndexList indexes = ui.diveSites->view()->selectionModel()->selectedIndexes();
 	QVector<dive_site *> sites;
@@ -92,7 +92,12 @@ void TabDiveSite::updateFilter()
 		struct dive_site *ds = model.getDiveSite(idx);
 		sites.append(ds);
 	}
-	MultiFilterSortModel::instance()->startFilterDiveSites(sites);
+	return sites;
+}
+
+void TabDiveSite::updateFilter()
+{
+	MultiFilterSortModel::instance()->setFilterDiveSite(selectedDiveSites());
 }
 
 void TabDiveSite::selectionChanged(const QItemSelection &, const QItemSelection &)
@@ -104,7 +109,7 @@ void TabDiveSite::showEvent(QShowEvent *)
 {
 	// If the user switches to the dive site tab and there was already a selection,
 	// filter on that selection.
-	updateFilter();
+	MultiFilterSortModel::instance()->startFilterDiveSites(selectedDiveSites());
 }
 
 void TabDiveSite::hideEvent(QHideEvent *)

desktop-widgets/tab-widgets/TabDiveSite.h

@@ -22,6 +22,7 @@ private slots:
 private:
 	Ui::TabDiveSite ui;
 	DiveSiteSortedModel model;
+	QVector<dive_site *> selectedDiveSites();
 	void updateFilter();
 	void hideEvent(QHideEvent *) override;
 	void showEvent(QShowEvent *) override;

qt-models/filtermodels.cpp

@@ -105,7 +105,8 @@ MultiFilterSortModel *MultiFilterSortModel::instance()
 }
 
 MultiFilterSortModel::MultiFilterSortModel(QObject *parent) : QSortFilterProxyModel(parent),
-	divesDisplayed(0)
+	divesDisplayed(0),
+	diveSiteRefCount(0)
 {
 	setFilterKeyColumn(-1); // filter all columns
 	setFilterCaseSensitivity(Qt::CaseInsensitive);
@@ -269,15 +270,24 @@ void MultiFilterSortModel::clearFilter()
 void MultiFilterSortModel::startFilterDiveSites(QVector<dive_site *> ds)
 {
 	dive_sites = ds;
+	++diveSiteRefCount;
 	myInvalidate();
 }
 
 void MultiFilterSortModel::stopFilterDiveSites()
 {
+	if (--diveSiteRefCount > 0)
+		return;
 	dive_sites.clear();
 	myInvalidate();
 }
 
+void MultiFilterSortModel::setFilterDiveSite(QVector<dive_site *> ds)
+{
+	dive_sites = ds;
+	myInvalidate();
+}
+
 const QVector<dive_site *> &MultiFilterSortModel::filteredDiveSites() const
 {
 	return dive_sites;

qt-models/filtermodels.h

@@ -70,6 +70,7 @@ slots:
 	void myInvalidate();
 	void clearFilter();
 	void startFilterDiveSites(QVector<dive_site *> ds);
+	void setFilterDiveSite(QVector<dive_site *> ds);
 	void stopFilterDiveSites();
 	void filterChanged(const QModelIndex &from, const QModelIndex &to, const QVector<int> &roles);
 	void resetModel(DiveTripModelBase::Layout layout);
@@ -86,6 +87,14 @@ private:
 	QVector<dive_site *> dive_sites;
 	void countsChanged();
 	FilterData filterData;
+
+	// We use ref-counting for the dive site mode. The reason is that when switching
+	// between two tabs that both need dive site mode, the following course of
+	// events may happen:
+	//	1) The new tab appears -> enter dive site mode.
+	//	2) The old tab gets its hide() signal -> exit dive site mode.
+	// The filter is now not in dive site mode, even if it should
+	int diveSiteRefCount;
 };
 
 #endif