Desktop: fix crash on dive site tab

An interesting crash:

1) On the dive site tab select a dive site such that only one
   trip is shown.
2) Unselect all dives.
3) Press CTRL-A while the dive list has focus.
4) This will select a trip.
5) In MainTab::updateDiveInfo() this will switch to the previous
   tab active when in trip mode.
6) This will reset the filter.
7) This will reset the currentTrip field which we just set.
8) Since we just set the currentTrip field, we don't expect
   it to change and reference a null pointer.

To fix, don't switch tabs when on the dive site tab. This also
improves user experience as there seems to be no reason to switch
away from the dive site tab.

Currently the index of the dive site tab is hard-coded - this
should be changed!

Fixes #2077

Reported-by: Doug Junkins <junkins@foghead.com>
Signed-off-by: Berthold Stoeger <bstoeger@mail.tuwien.ac.at>

1 files changed, 15 insertions, 9 deletions

diff --git a/desktop-widgets/tab-widgets/maintab.cpp b/desktop-widgets/tab-widgets/maintab.cpp
index 17ff289e8..412ec899b 100644
--- a/desktop-widgets/tab-widgets/maintab.cpp
+++ b/desktop-widgets/tab-widgets/maintab.cpp
@@ -431,19 +431,25 @@ void MainTab::updateDiveInfo()
 		widget->updateData();
 
 	if (current_dive) {
+		// If we're on the dive-site tab, we don't want to switch tab when entering / exiting
+		// trip mode. The reason is that
+		// 1) this disrupts the user-experience and
+		// 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 (MainWindow::instance() && MainWindow::instance()->diveList->selectedTrips().count() == 1) {
-			// Remember the tab selected for last dive
-			if (lastSelectedDive)
+			currentTrip = MainWindow::instance()->diveList->selectedTrips().front();
+			// 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();
 			ui.tabWidget->setTabText(0, tr("Trip notes"));
 			ui.tabWidget->setTabEnabled(1, false);
 			ui.tabWidget->setTabEnabled(2, false);
 			ui.tabWidget->setTabEnabled(5, false);
-			// Recover the tab selected for last dive trip
-			if (lastSelectedDive)
+			// Recover the tab selected for last dive trip but only if we're not on the dive site tab
+			if (lastSelectedDive && !onDiveSiteTab)
 				ui.tabWidget->setCurrentIndex(lastTabSelectedDiveTrip);
 			lastSelectedDive = false;
-			currentTrip = *MainWindow::instance()->diveList->selectedTrips().begin();
 			// only use trip relevant fields
 			ui.divemaster->setVisible(false);
 			ui.DivemasterLabel->setVisible(false);
@@ -482,8 +488,8 @@ void MainTab::updateDiveInfo()
 			ui.duration->setVisible(false);
 			ui.durationLabel->setVisible(false);
 		} else {
-			// Remember the tab selected for last dive trip
-			if (!lastSelectedDive)
+			// Remember the tab selected for last dive trip but only if we're not on the dive site tab
+			if (!lastSelectedDive && !onDiveSiteTab)
 				lastTabSelectedDiveTrip = ui.tabWidget->currentIndex();
 			ui.tabWidget->setTabText(0, tr("Notes"));
 			ui.tabWidget->setTabEnabled(1, true);
@@ -491,8 +497,8 @@ void MainTab::updateDiveInfo()
 			ui.tabWidget->setTabEnabled(3, true);
 			ui.tabWidget->setTabEnabled(4, true);
 			ui.tabWidget->setTabEnabled(5, true);
-			// Recover the tab selected for last dive
-			if (!lastSelectedDive)
+			// Recover the tab selected for last dive but only if we're not on the dive site tab
+			if (!lastSelectedDive && !onDiveSiteTab)
 				ui.tabWidget->setCurrentIndex(lastTabSelectedDive);
 			lastSelectedDive = true;
 			currentTrip = NULL;