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>

1 files changed, 12 insertions, 0 deletions

diff --git a/core/selection.cpp b/core/selection.cpp
index 48bb1a76f..d6267c78a 100644
--- a/core/selection.cpp
+++ b/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;