Fix variables in Screens, remove dark reactive from Screen

sandbox/darren/screens_focus.py

@@ -16,15 +16,36 @@ class CustomScreen(Screen):
         yield Focusable(f"Screen {id(self)} - three")
         yield Focusable(f"Screen {id(self)} - four")
         yield Input(placeholder="Text input")
-        # yield Footer()
+        yield Footer()
+
+
+class MyInstalledScreen(Screen):
+    def __init__(self, string: str):
+        super().__init__()
+        self.string = string
+
+    def compose(self) -> ComposeResult:
+        yield Static(f"Hello, world! {self.string}")
 
 
 class ScreensFocusApp(App):
     BINDINGS = [
         Binding("plus", "push_new_screen", "Push"),
         Binding("minus", "pop_top_screen", "Pop"),
+        Binding("d", "toggle_dark", "Toggle Dark"),
+        Binding("q", "push_screen('q')", "Screen Q"),
+        Binding("w", "push_screen('w')", "Screen W"),
+        Binding("e", "push_screen('e')", "Screen E"),
+        Binding("r", "push_screen('r')", "Screen R"),
     ]
 
+    SCREENS = {
+        "q": MyInstalledScreen("q"),
+        "w": MyInstalledScreen("w"),
+        "e": MyInstalledScreen("e"),
+        "r": MyInstalledScreen("r"),
+    }
+
     def compose(self) -> ComposeResult:
         yield Focusable("App - one")
         yield Input(placeholder="Text input")
@@ -32,7 +53,7 @@ class ScreensFocusApp(App):
         yield Focusable("App - two")
         yield Focusable("App - three")
         yield Focusable("App - four")
-        # yield Footer()
+        yield Footer()
 
     def action_push_new_screen(self):
         self.push_screen(CustomScreen())
@@ -43,6 +64,9 @@ class ScreensFocusApp(App):
         except ScreenStackError:
             pass
 
+    def _action_toggle_dark(self):
+        self.dark = not self.dark
+
 
 app = ScreensFocusApp(css_path="screens_focus.css")
 if __name__ == "__main__":

src/textual/app.py

@@ -353,8 +353,6 @@ class App(Generic[ReturnType], DOMNode):
 
     def watch_dark(self, dark: bool) -> None:
         """Watches the dark bool."""
-
-        self.screen.dark = dark
         self.set_class(dark, "-dark-mode")
         self.set_class(not dark, "-light-mode")
         self.refresh_css()

src/textual/css/stylesheet.py

@@ -192,7 +192,7 @@ class Stylesheet:
             variables (dict[str, str]): A mapping of name to variable.
         """
         self._variables = variables
-        self._variables_tokens = None
+        self.__variable_tokens = None
 
     def _parse_rules(
         self,

src/textual/screen.py

@@ -38,7 +38,6 @@ class Screen(Widget):
     }
     """
 
-    dark: Reactive[bool] = Reactive(False)
     focused: Reactive[Widget | None] = Reactive(None)
 
     def __init__(