raylib: hit rect for scroller items (#36432)

* hit rect

* clean up

* comment

* oh this is actually epic

* rm line

* type

system/ui/widgets/__init__.py

@@ -14,7 +14,7 @@ class DialogResult(IntEnum):
 class Widget(abc.ABC):
   def __init__(self):
     self._rect: rl.Rectangle = rl.Rectangle(0, 0, 0, 0)
-    self._parent_rect: rl.Rectangle = rl.Rectangle(0, 0, 0, 0)
+    self._parent_rect: rl.Rectangle | None = None
     self.__is_pressed = [False] * MAX_TOUCH_SLOTS
     # if current mouse/touch down started within the widget's rectangle
     self.__tracking_is_pressed = [False] * MAX_TOUCH_SLOTS
@@ -75,6 +75,13 @@ class Widget(abc.ABC):
     if changed:
       self._update_layout_rects()
 
+  @property
+  def _hit_rect(self) -> rl.Rectangle:
+    # restrict touches to within parent rect if set, useful inside Scroller
+    if self._parent_rect is None:
+      return self._rect
+    return rl.get_collision_rec(self._rect, self._parent_rect)
+
   def render(self, rect: rl.Rectangle = None) -> bool | int | None:
     if rect is not None:
       self.set_rect(rect)
@@ -95,7 +102,7 @@ class Widget(abc.ABC):
         # Ignores touches/presses that start outside our rect
         # Allows touch to leave the rect and come back in focus if mouse did not release
         if mouse_event.left_pressed and self._touch_valid():
-          if rl.check_collision_point_rec(mouse_event.pos, self._rect):
+          if rl.check_collision_point_rec(mouse_event.pos, self._hit_rect):
             self._handle_mouse_press(mouse_event.pos)
             self.__is_pressed[mouse_event.slot] = True
             self.__tracking_is_pressed[mouse_event.slot] = True
@@ -106,18 +113,18 @@ class Widget(abc.ABC):
           self.__tracking_is_pressed[mouse_event.slot] = False
 
         elif mouse_event.left_released:
-          if self.__is_pressed[mouse_event.slot] and rl.check_collision_point_rec(mouse_event.pos, self._rect):
+          if self.__is_pressed[mouse_event.slot] and rl.check_collision_point_rec(mouse_event.pos, self._hit_rect):
             self._handle_mouse_release(mouse_event.pos)
           self.__is_pressed[mouse_event.slot] = False
           self.__tracking_is_pressed[mouse_event.slot] = False
 
         # Mouse/touch is still within our rect
-        elif rl.check_collision_point_rec(mouse_event.pos, self._rect):
+        elif rl.check_collision_point_rec(mouse_event.pos, self._hit_rect):
           if self.__tracking_is_pressed[mouse_event.slot]:
             self.__is_pressed[mouse_event.slot] = True
 
         # Mouse/touch left our rect but may come back into focus later
-        elif not rl.check_collision_point_rec(mouse_event.pos, self._rect):
+        elif not rl.check_collision_point_rec(mouse_event.pos, self._hit_rect):
           self.__is_pressed[mouse_event.slot] = False
 
     return ret