Merge pull request 'screen exit handler' (#37) from screen-exit-handler into master

Reviewed-on: #37

inc/screen/screen.manager.lua

@@ -21,6 +21,9 @@ function Screen.register(screen_data)
   end
   if not screen_data.init then
     screen_data.init = function() end
+  end
+    if not screen_data.exit then
+    screen_data.exit = function() end
   end
   if not screen_data.update then
     screen_data.update = function() end

inc/system/system.util.lua

@@ -14,10 +14,14 @@ end
 --- @within Util
 --- @param screen_id string The ID of the screen to go to.<br/>
 function Util.go_to_screen_by_id(screen_id)
-  local screen = Screen.get_by_id(screen_id)
-  if screen then
+  local prev_screen = Screen.get_by_id(Context.game.current_screen)
+  local new_screen = Screen.get_by_id(screen_id)
+  if new_screen then
     Context.game.current_screen = screen_id
-    screen.init()
+    if prev_screen and prev_screen.exit then
+      prev_screen.exit()
+    end
+    new_screen.init()
   else
     PopupWindow.show({"Error: Screen '" .. screen_id .. "' not found!"})
   end

inc/window/window.end.lua

@@ -59,7 +59,7 @@ function EndWindow.update()
       else
         -- NO: increment day and go home
         Day.increase()
-        Context.game.current_screen = "home"
+        Util.go_to_screen_by_id("home")
         Window.set_current("game")
         -- Initialize home screen
         local home_screen = Screen.get_by_id("home")