Actually update panel non-sub elems (position, bg, title and title_color)

DOCS.md

@@ -41,7 +41,7 @@ Install it as any other mod `¯\_(ツ)_/¯`
 * `hide()`: makes the panel disappear (but it's still assigned to the player)
 * `is_visible()`: whether the panel is currently displayed
 * `remove()`: deletes it
-* `update(panel_params, txt_elems, img_elems)`: updates only the mentioned parameters. For instance, calling  
+* `update(panel_params, txt_elems, img_elems)`: updates only the mentioned parameters. Beware: `panel_params` only supports a few. They are `position`, `bg`, `title` and `title_color`.For instance, calling  
 
 ```
 panel:update(nil, nil, {my_custom_img = {

api.lua

@@ -192,8 +192,55 @@ end
 function Panel:update(def, txt_elems, img_elems)
 
   if def ~= nil then
+    local player = minetest.get_player_by_name(self.player_name)
+
     for k, v in pairs(def) do
-      self[k] = v
+      -- aggiorno eventuale posizione, che tratto a parte perché influisce sia su sfondo che titolo,
+      -- influenzando anche tutti i sottoelementi del pannello
+      if k == "position" then
+        self.background_def.position = v
+        self.title_def.position = v
+
+        for _, elem in pairs(self.sub_img_elems) do
+          local HUD_ID = self.hud_id[elem]
+          player:hud_change(HUD_ID, k, v)
+        end
+
+        for _, elem in pairs(self.sub_txt_elems) do
+          local HUD_ID = self.hud_id[elem]
+          player:hud_change(HUD_ID, k, v)
+        end
+
+        player:hud_change(self.hud_id.bg_hud_id, k, v)
+        player:hud_change(self.hud_id.text_hud_id, k, v)
+
+      -- aggiorno eventuale sfondo
+      elseif k == "bg" then
+        self.hud_text.bg_hud_txt = v
+        self.background_def.text = v
+
+        if self.is_visible then
+          player:hud_change(self.hud_id.bg_hud_id, "text", v)
+        end
+
+      -- aggiorno eventuali proprietà titolo
+      elseif k == "title" or k == "title_color" then
+
+        if k == "title" then
+          self.hud_text.text_hud_txt = v
+          self.title_def.text = v
+          if self.is_visible then
+            player:hud_change(self.hud_id.text_hud_id, "text", v)
+          end
+        else
+          self.title_def.number = v
+          player:hud_change(self.hud_id.text_hud_id, "number", v)
+        end
+
+      else
+        error("[PANEL_LIB] Invalid or unsupported element type, check DOCS and spelling")
+        return
+      end
     end
   end