selection: create global single_selected_trip() function

The DiveListView had a singleSelectedTrip function that
returns the selected trip if exactly one trip is selected.
This could be very slow if numerous non-trip items were
selected, because all the selection indices were back-
translated by the proxy model.

This could make selection changes very slow, because the
MainTab used said function to determine whether it should
show trip or dive data.. Indeed, with a 3500 dive test log,
when selecting all dives in tree mode, the updating of the
TabWidgets is sped up from 130 ms to 5 ms this commit.

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

core/selection.cpp

@@ -254,6 +254,18 @@ extern "C" void deselect_trip(struct dive_trip *trip)
 	}
 }
 
+extern "C" struct dive_trip *single_selected_trip()
+{
+	if (amount_trips_selected != 1)
+		return NULL;
+	for (int i = 0; i < trip_table.nr; ++i) {
+		if (trip_table.trips[i]->selected)
+			return trip_table.trips[i];
+	}
+	fprintf(stderr, "warning: found no selected trip even though one should be selected\n");
+	return NULL; // shouldn't happen
+}
+
 extern "C" void clear_selection(void)
 {
 	current_dive = nullptr;

core/selection.h

@@ -23,6 +23,7 @@ extern void select_newest_visible_dive();
 extern void select_single_dive(struct dive *d); // wrapper for setSelection() with a single dive. NULL clears the selection.
 extern void select_trip(struct dive_trip *trip);
 extern void deselect_trip(struct dive_trip *trip);
+extern struct dive_trip *single_selected_trip(); // returns trip if exactly one trip is selected, NULL otherwise.
 extern void clear_selection(void);
 
 #if DEBUG_SELECTION_TRACKING

desktop-widgets/divelistview.cpp

@@ -263,9 +263,8 @@ void DiveListView::rowsInserted(const QModelIndex &parent, int start, int end)
 // Shouldn't the core-layer call us?
 void DiveListView::tripChanged(dive_trip *trip, TripField)
 {
-	// First check if the trip is already selected (and only
+	// First check if the trip is already selected (and only this trip, as only then is it displayed).
-	// this trip, as only then is it displayed). Is so, then do nothing.
+	if (single_selected_trip() == trip)
-	if (singleSelectedTrip() == trip)
 		return;
 
 	unselectDives();
@@ -297,23 +296,6 @@ void DiveListView::unselectDives()
 	selectionModel()->clearSelection();
 }
 
-// This function returns a trip if there is one selected trip or NULL.
-// Returning all selected trips turned out to be too slow.
-dive_trip_t *DiveListView::singleSelectedTrip()
-{
-	dive_trip_t *res = nullptr;
-	for (const QModelIndex &index: selectionModel()->selectedRows()) {
-		if (index.parent().isValid())
-			continue;
-		if (dive_trip_t *trip = index.data(DiveTripModelBase::TRIP_ROLE).value<dive_trip *>()) {
-			if (res)
-				return nullptr; // More than one
-			res = trip;
-		}
-	}
-	return res;
-}
-
 bool DiveListView::eventFilter(QObject *, QEvent *event)
 {
 	if (event->type() != QEvent::KeyPress)

desktop-widgets/divelistview.h

@@ -25,7 +25,6 @@ public:
 	~DiveListView();
 	void setSortOrder(int i, Qt::SortOrder order); // Call to set sort order
 	void reload(); // Call to reload model data
-	dive_trip *singleSelectedTrip();
 	static QString lastUsedImageDir();
 	static void updateLastUsedImageDir(const QString &s);
 	void loadImages();

desktop-widgets/tab-widgets/maintab.cpp

@@ -365,7 +365,8 @@ void MainTab::updateDiveInfo()
 		// 2) the filter is reset, potentially erasing the current trip under our feet.
 		// TODO: Don't hard code tab location!
 		bool onDiveSiteTab = ui.tabWidget->currentIndex() == 6;
-		if ((currentTrip = MainWindow::instance()->diveList->singleSelectedTrip()) != nullptr) {
+		currentTrip = single_selected_trip();
+		if (currentTrip) {
 			// Remember the tab selected for last dive but only if we're not on the dive site tab
 			if (lastSelectedDive && !onDiveSiteTab)
 				lastTabSelectedDive = ui.tabWidget->currentIndex();
@@ -412,7 +413,6 @@ void MainTab::updateDiveInfo()
 			if (!lastSelectedDive && !onDiveSiteTab)
 				ui.tabWidget->setCurrentIndex(lastTabSelectedDive);
 			lastSelectedDive = true;
-			currentTrip = NULL;
 			// make all the fields visible writeable
 			ui.diveTripLocation->hide();
 			ui.location->show();