Allow inserting a track into the middle of the playlist

src/scripting/lua_audio.cpp

@@ -107,6 +107,11 @@ static int intf_music_play(lua_State* L) {
 }
 
 static int intf_music_add(lua_State* L) {
+	int i = -1;
+	if(lua_isinteger(L, 1)) {
+		i = lua_tointeger(L, 1);
+		lua_remove(L, 1);
+	}
 	config cfg = config_of
 		("name", luaL_checkstring(L, 1))
 		("append", true);
@@ -132,7 +137,7 @@ static int intf_music_add(lua_State* L) {
 			return luaL_argerror(L, i, "unrecognized argument");
 		}
 	}
-	sound::play_music_config(cfg);
+	sound::play_music_config(cfg, i);
 	return 0;
 }
 

src/sound.cpp

@@ -577,7 +577,7 @@ void play_music_repeatedly(const std::string &id)
 	}
 }
 
-void play_music_config(const config &music_node)
+void play_music_config(const config &music_node, int i)
 {
 	music_track track( music_node );
 
@@ -609,7 +609,14 @@ void play_music_config(const config &music_node)
 		}
 
 		if(itor == current_track_list.end()) {
-			current_track_list.push_back(track);
+			if(i < 0 || static_cast<size_t>(i) >= current_track_list.size()) {
+				current_track_list.push_back(track);
+			} else {
+				current_track_list.insert(current_track_list.begin() + 1, track);
+				if(current_track_index >= static_cast<size_t>(i)) {
+					current_track_index++;
+				}
+			}
 		} else {
 			ERR_AUDIO << "tried to add duplicate track '" << track.file_path() << "'" << std::endl;
 		}

src/sound.hpp

@@ -41,7 +41,7 @@ void stop_UI_sound();
 void stop_bell();
 
 // Read config entry, alter track list accordingly.
-void play_music_config(const config &music_node);
+void play_music_config(const config &music_node, int i = -1);
 // Act on any track list changes from above.
 void commit_music_changes();