Tooltip improvements

* Moved calculations into a transform function.
* Reduced overhead

game/scripts/interface/tooltip.rpy

@@ -4,33 +4,13 @@ screen tooltip():
     zorder 5
     style_prefix "tooltip"
 
-    default last_tooltip = ""
+    $ tooltip = GetTooltip()
 
-    if settings.get("tooltip"):
-        $ mouseclick = any(pygame.mouse.get_pressed()[:3])
-
-        # Do not remove the empty string from the statement below,
-        # it is a rare case when the save file gets updated but the old tooltip
-        # and its scope defaults last_tooltip to None value
-        # because it was previously unknown at the runtime,
-        # and we cannot hide the screen fast enough, causing a hard crash.
-        # This ensures it never happens.
-        $ tooltip = GetTooltip() or last_tooltip or ""
-        $ last_tooltip = tooltip
-
-        showif GetTooltip() and not mouseclick:
-            $ x, y = renpy.get_mouse_pos()
-            $ xflip = x > 980
-            $ yflip = y > 500
-            $ xanchor = 1.0 if xflip else 0.0
-            $ yanchor = 1.0 if yflip else 0.0
-            $ xoffset = 11 if xflip else 0
-            $ yoffset = 14 if yflip else 0
-
-            window:
-                id tooltip
-                at tooltip_follow((x+xoffset, y+yoffset), (xanchor, yanchor))
-                text "[tooltip]"
+    if settings.get("tooltip") and tooltip:
+        window:
+            id tooltip
+            at tooltip_follow
+            text "[tooltip]"
 
 style tooltip_window is empty:
     background "#00000080"
@@ -42,17 +22,20 @@ style tooltip_text is default:
     size 10
     outlines [(1, "#00000080", 1, 0)]
 
+transform tooltip_follow:
+    events False
+    function tooltip_func
+
 init python:
-    config.per_frame_screens.append("tooltip")
 
-transform tooltip_follow(pos, anchor):
-    on start:
-        alpha 0.0
+    def tooltip_func(trans, st, at):
+        x, y = renpy.get_mouse_pos()
+        xanchor = 1.0 if (x > 980) else 0.0
+        yanchor = 1.0 if (y > 500) else 0.0
+        xoffset = 11 if xanchor else 0
+        yoffset = 14 if yanchor else 0
+        trans.pos = (x, y)
+        trans.anchor = (xanchor, yanchor)
+        trans.offset = (xoffset, yoffset)
 
-    on show:
-        anchor anchor
-        pos pos
-        linear 0.1 alpha 1.0
-
-    on hide:
-        linear 0.1 alpha 0.0
+        return 0