Add helper functions to ensure we have sane tag lists

There should never be empty or duplicate tags on those lists.

Signed-off-by: Dirk Hohndel <dirk@hohndel.org>

dive.c

@@ -2089,6 +2089,30 @@ static void join_dive_computers(struct divecomputer *res, struct divecomputer *a
 	remove_redundant_dc(res, prefer_downloaded);
 }
 
+static bool tag_seen_before(struct tag_entry *start, struct tag_entry *before)
+{
+	while(start && start != before) {
+		if (same_string(start->tag->name, before->tag->name))
+			return true;
+		start = start->next;
+	}
+	return false;
+}
+
+/* remove duplicates and empty nodes */
+void taglist_cleanup(struct tag_entry **tag_list)
+{
+	struct tag_entry **tl = tag_list;
+	while (*tl) {
+		/* skip tags that are empty or that we have seen before */
+		if (same_string((*tl)->tag->name, "") || tag_seen_before(*tag_list, *tl)) {
+			*tl = (*tl)->next;
+			continue;
+		}
+		tl = &(*tl)->next;
+	}
+}
+
 int taglist_get_tagstring(struct tag_entry *tag_list, char *buffer, int len)
 {
 	int i = 0;

dive.h

@@ -197,6 +197,9 @@ struct divetag *taglist_add_tag(struct tag_entry **tag_list, const char *tag);
  */
 int taglist_get_tagstring(struct tag_entry *tag_list, char *buffer, int len);
 
+/* cleans up a list: removes empty tags and duplicates */
+void taglist_cleanup(struct tag_entry **tag_list);
+
 void taglist_init_global();
 void taglist_free(struct tag_entry *tag_list);
 

qt-ui/maintab.cpp

@@ -934,9 +934,9 @@ void MainTab::on_timeEdit_timeChanged(const QTime &time)
 void MainTab::saveTags()
 {
 	struct dive *cd = current_dive;
-	Q_FOREACH(const QString& tag, ui.tagWidget->getBlockStringList()){
+	Q_FOREACH (const QString& tag, ui.tagWidget->getBlockStringList())
 		taglist_add_tag(&displayed_dive.tag_list, tag.toUtf8().data());
-	}
+	taglist_cleanup(&displayed_dive.tag_list);
 	MODIFY_SELECTED_DIVES(
 		QString tag;
 		taglist_free(mydive->tag_list);