Improve threading when predicting the wardrobe

don't use single-underscore names
if available, use the thread-safer invoke_in_main_thread (not required when setting the global variables)
set __lock to True outside of the thread, otherwise if the thread starts late, the while loop is skipped
call get_character_object in the main thread

(cherry picked from commit 7a25a13926)

game/scripts/wardrobe/wardrobe.rpy

@@ -1,4 +1,3 @@
-
 default wardrobe_music = False
 default wardrobe_chitchats = True
 default wardrobe_autosave = False
@@ -19,20 +18,28 @@ define wardrobe_subcategories_sorted = {
 
 define wardrobe_categories = ("head", "piercings & tattoos", "upper body", "upper undergarment", "lower body", "lower undergarment", "legwear", "misc")
 define wardrobe_outfit_schedule = ("day", "night", "cloudy", "rainy", "snowy")
+default __lock = False
+default __predicted = None
 
 init python:
+    def preload_wardrobe_assets(c):
+        global __lock, __predicted
 
-    _lock = False
-
-    def preload_wardrobe_assets():
-        global _lock, _predicted
-        _lock = True
+        if renpy.version_tuple < (8, 2):
             renpy.start_predict_screen("wardrobe")
-        c = get_character_object(states.active_girl)
+        else:
+            # use the new renpy.invoke_in_main_thread
+            renpy.invoke_in_main_thread(renpy.start_predict_screen, "wardrobe")
+
+        # this is not thread-safe, but there's no better way : it's the slow part
         d = [v[0] for i in c.wardrobe_list for v in i.get_layers(i._hash).values()]
+
+        if renpy.version_tuple < (8, 2):
             renpy.start_predict(*d, "interface/wardrobe/*.webp")
-        _predicted = d
-        _lock = False
+        else:
+            renpy.invoke_in_main_thread(renpy.start_predict, *d, "interface/wardrobe/*.webp")
+        __predicted = d
+        __lock = False
 
     def rebuild_wardrobe_icons(items, subcat):
         if not settings.get("multithreading"):
@@ -185,14 +192,15 @@ label _wardrobe:
     show loading zorder 1000
 
     # Ensure there's no thread in use before assigning a new one.
-    while _lock:
+    while __lock:
         $ renpy.pause(0.5, hard=True)
 
-    $ renpy.invoke_in_thread(preload_wardrobe_assets)
+    $ __lock = True
+    $ renpy.invoke_in_thread(preload_wardrobe_assets, get_character_object(states.active_girl))
 
     # Await thread return
     # Note: renpy.pause must be called from within the main thread
-    while _lock:
+    while __lock:
         $ renpy.pause(0.5, predict=True)
 
     hide loading
@@ -203,10 +211,10 @@ label _wardrobe:
 
     show screen main_room
     show screen ui_top_bar
-    $ _game_menu_screen = "save"
-    $ _skipping = True
-    $ renpy.stop_predict(_predicted)
-    $ del _predicted
+    $ _game_menu_screen = "save" # documented
+    $ _skipping = True # documented
+    $ renpy.stop_predict(__predicted)
+    $ __predicted = None
     $ renpy.suspend_rollback(False)
     $ renpy.block_rollback()
     return