Generate item slot images on the fly

mods/ITEMS/mcl_hoppers/depends.txt

@@ -1,4 +1,5 @@
 mcl_core
+mcl_formspec
 mcl_sounds
 mcl_util
 doc?

mods/ITEMS/mcl_hoppers/init.lua

@@ -4,12 +4,14 @@ local S = minetest.get_translator("mcl_hoppers")
 
 local mcl_hoppers_formspec =
 	"size[9,7]"..
-	"background[-0.19,-0.25;9.41,10.48;mcl_hoppers_inventory.png]"..
 	"label[2,0;"..minetest.formspec_escape(minetest.colorize("#313131", S("Hopper"))).."]"..
 	"list[current_name;main;2,0.5;5,1;]"..
+	mcl_formspec.get_itemslot_bg(2,0.5,5,1)..
 	"label[0,2;"..minetest.formspec_escape(minetest.colorize("#313131", S("Inventory"))).."]"..
 	"list[current_player;main;0,2.5;9,3;9]"..
+	mcl_formspec.get_itemslot_bg(0,2.5,9,3)..
 	"list[current_player;main;0,5.74;9,1;]"..
+	mcl_formspec.get_itemslot_bg(0,5.74,9,1)..
 	"listring[current_name;main]"..
 	"listring[current_player;main]"