From e5a3e6a845e105566dd6def263cd2d7326155d42 Mon Sep 17 00:00:00 2001
From: James R <justsomejames2@gmail.com>
Date: Sat, 5 Dec 2020 01:14:52 -0800
Subject: [PATCH] Fix removing a tag unsetting the bit array even if more
 elements with that tag exist

---
 src/lua_taglib.c |  2 +-
 src/taglist.c    | 28 +++++++++++++++++++++++-----
 src/taglist.h    |  1 +
 3 files changed, 25 insertions(+), 6 deletions(-)

diff --git a/src/lua_taglib.c b/src/lua_taglib.c
index 73f033312..07646af87 100644
--- a/src/lua_taglib.c
+++ b/src/lua_taglib.c
@@ -145,7 +145,7 @@ static int lib_numTaggroupElements(lua_State *L)
 	else
 	{
 		const taggroup_t ** garray = lua_touserdata(L, up_garray);
-		lua_pushnumber(L, garray[tag] ? garray[tag]->count : 0);
+		lua_pushnumber(L, Taggroup_Count(garray[tag]));
 	}
 	return 1;
 }
diff --git a/src/taglist.c b/src/taglist.c
index cfd9cbb9c..a759f4d02 100644
--- a/src/taglist.c
+++ b/src/taglist.c
@@ -110,6 +110,12 @@ size_t Taggroup_Find (const taggroup_t *group, const size_t id)
 	return -1;
 }
 
+/// group->count, but also checks for NULL
+size_t Taggroup_Count (const taggroup_t *group)
+{
+	return group ? group->count : 0;
+}
+
 /// Iterate thru elements in a global taggroup.
 INT32 Taggroup_Iterate
 (		taggroup_t *garray[],
@@ -153,9 +159,10 @@ void Taggroup_Add (taggroup_t *garray[], const mtag_t tag, size_t id)
 		return;
 
 	if (! in_bit_array(tags_available, tag))
+	{
 		num_tags++;
-
-	set_bit_array(tags_available, tag);
+		set_bit_array(tags_available, tag);
+	}
 
 	// Create group if empty.
 	if (!group)
@@ -182,6 +189,16 @@ void Taggroup_Add (taggroup_t *garray[], const mtag_t tag, size_t id)
 	group->elements[i] = id;
 }
 
+static size_t total_elements_with_tag (const mtag_t tag)
+{
+	return
+		(
+				Taggroup_Count(tags_sectors[tag]) +
+				Taggroup_Count(tags_lines[tag]) +
+				Taggroup_Count(tags_mapthings[tag])
+		);
+}
+
 /// Remove an element from a global taggroup.
 void Taggroup_Remove (taggroup_t *garray[], const mtag_t tag, size_t id)
 {
@@ -197,10 +214,11 @@ void Taggroup_Remove (taggroup_t *garray[], const mtag_t tag, size_t id)
 	if ((rempos = Taggroup_Find(group, id)) == (size_t)-1)
 		return;
 
-	if (in_bit_array(tags_available, tag))
+	if (group->count == 1 && total_elements_with_tag(tag) == 1)
+	{
 		num_tags--;
-
-	unset_bit_array(tags_available, tag);
+		unset_bit_array(tags_available, tag);
+	}
 
 	// Strip away taggroup if no elements left.
 	if (!(oldcount = group->count--))
diff --git a/src/taglist.h b/src/taglist.h
index e5db08806..a0529ab6b 100644
--- a/src/taglist.h
+++ b/src/taglist.h
@@ -54,6 +54,7 @@ extern taggroup_t* tags_mapthings[];
 void Taggroup_Add (taggroup_t *garray[], const mtag_t tag, size_t id);
 void Taggroup_Remove (taggroup_t *garray[], const mtag_t tag, size_t id);
 size_t Taggroup_Find (const taggroup_t *group, const size_t id);
+size_t Taggroup_Count (const taggroup_t *group);
 
 INT32 Taggroup_Iterate
 (		taggroup_t *garray[],