A bit of clean up. Moved mod integration lua files to their own folder with a single file designed to check if supported mods are present and load the appropriate local file to setup for it.

central_message.lua

@@ -1,12 +0,0 @@
-if minetest.global_exists("cmsg") then
-	function quests.show_message(t, playername, text)
-		if (quests.hud[playername].central_message_enabled) then
-			local player = minetest.get_player_by_name(playername)
-			cmsg.push_message_player(player, text, quests.colors[t])
-			minetest.sound_play("quests_" .. t, {to_player = playername})
-		end
-	end
-else
-	function quests.show_message(...)
-	end
-end

init.lua

@@ -46,17 +46,11 @@ function quests.sorted_pairs(t)
 	return iter
 end
 
-dofile(MP .. "/central_message.lua")
 dofile(MP .. "/core.lua")
 dofile(MP .. "/hud.lua")
 dofile(MP .. "/formspecs.lua")
+dofile(MP .. "/mod_integrations/mod_integrations.lua")
 
--- support for unified_inventory
-if (minetest.get_modpath("unified_inventory") ~= nil) then
-	dofile(minetest.get_modpath("quests") .. "/unified_inventory.lua")
-elseif (minetest.get_modpath("inventory_plus") ~= nil) then
-	dofile(minetest.get_modpath("quests") .. "/inventory_plus.lua")
-end
 
 
 -- write the quests to file

mod_integrations/central_message.lua

@@ -0,0 +1,9 @@
+
+function quests.show_message(t, playername, text)
+	if (quests.hud[playername].central_message_enabled) then
+		local player = minetest.get_player_by_name(playername)
+		cmsg.push_message_player(player, text, quests.colors[t])
+		minetest.sound_play("quests_" .. t, {to_player = playername})
+	end
+end
+

mod_integrations/mod_integrations.lua

@@ -0,0 +1,17 @@
+-- support for several inventory mods
+if minetest.get_modpath("unified_inventory") then
+	dofile(minetest.get_modpath("quests") .. "/mod_integrations/unified_inventory.lua")
+end
+
+if minetest.get_modpath("inventory_plus") then
+	dofile(minetest.get_modpath("quests") .. "/mod_integrations/inventory_plus.lua")
+end
+
+
+--mod that displays notifications in the screen's center
+if minetest.get_modpath("central_message") then
+	dofile(minetest.get_modpath("quests") .. "/mod_integrations/central_message.lua")
+
+else -- define blank function so we can still use this in the code later
+	function quests.show_message(...) end
+end