Only update tags in the selected dives if they were changed

If current_dive and displayed_dive still have the same tags then we
shouldn't touch the tags of other selected dives.

Fixes #826

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

dive.c

@@ -2618,6 +2618,24 @@ bool taglist_contains(struct tag_entry *tag_list, const char *tag)
 	return false;
 }
 
+// check if all tags in subtl are included in supertl (so subtl is a subset of supertl)
+static bool taglist_contains_all(struct tag_entry *subtl, struct tag_entry *supertl)
+{
+	while (subtl) {
+		if (!taglist_contains(supertl, subtl->tag->name))
+			return false;
+		subtl = subtl->next;
+	}
+	return true;
+
+}
+
+// if tl1 is both a subset and superset of tl2 they must be the same
+bool taglist_equal(struct tag_entry *tl1, struct tag_entry *tl2)
+{
+	return taglist_contains_all(tl1, tl2) && taglist_contains_all(tl2, tl1);
+}
+
 // count the dives where the tag list contains the given tag
 int count_dives_with_tag(const char *tag)
 {

dive.h

@@ -238,6 +238,7 @@ void taglist_init_global();
 void taglist_free(struct tag_entry *tag_list);
 
 bool taglist_contains(struct tag_entry *tag_list, const char *tag);
+bool taglist_equal(struct tag_entry *tl1, struct tag_entry *tl2);
 int count_dives_with_tag(const char *tag);
 int count_dives_with_person(const char *person);
 int count_dives_with_location(const char *location);

qt-ui/maintab.cpp

@@ -1099,6 +1099,9 @@ void MainTab::saveTags()
 	Q_FOREACH (const QString& tag, ui.tagWidget->getBlockStringList())
 		taglist_add_tag(&displayed_dive.tag_list, tag.toUtf8().data());
 	taglist_cleanup(&displayed_dive.tag_list);
+	// we need to check if the tags were changed before just overwriting them
+	if (taglist_equal(displayed_dive.tag_list, cd->tag_list))
+		return;
 	MODIFY_SELECTED_DIVES(
 		QString tag;
 		taglist_free(mydive->tag_list);