update footer on focus change

sandbox/will/bindings.py

@@ -0,0 +1,53 @@
+from textual.app import App, ComposeResult
+from textual.widgets import Footer, Static
+
+
+class Focusable(Static, can_focus=True):
+    DEFAULT_CSS = """
+    Focusable {
+        background: blue 20%;        
+        height: 1fr;
+        padding: 1;
+    }
+    Focusable:hover {
+        outline: solid white;
+    }
+    Focusable:focus {
+        background: red 20%;
+    }
+
+    """
+
+
+class Focusable1(Focusable):
+
+    BINDINGS = [
+        ("a", "app.bell", "Ding"),
+    ]
+
+    def render(self) -> str:
+        return repr(self)
+
+
+class Focusable2(Focusable):
+    CSS = ""
+    BINDINGS = [
+        ("b", "app.bell", "Beep"),
+    ]
+
+    def render(self) -> str:
+        return repr(self)
+
+
+class BindingApp(App):
+    BINDINGS = [("f1", "app.bell", "Bell")]
+
+    def compose(self) -> ComposeResult:
+        yield Focusable1()
+        yield Focusable2()
+        yield Footer()
+
+
+app = BindingApp()
+if __name__ == "__main__":
+    app.run()

src/textual/app.py

@@ -154,6 +154,8 @@ class App(Generic[ReturnType], DOMNode):
 
     CSS_PATH: str | None = None
 
+    focused: Reactive[Widget | None] = Reactive(None)
+
     def __init__(
         self,
         driver_class: Type[Driver] | None = None,
@@ -181,7 +183,6 @@ class App(Generic[ReturnType], DOMNode):
         self._screen_stack: list[Screen] = []
         self._sync_available = False
 
-        self.focused: Widget | None = None
         self.mouse_over: Widget | None = None
         self.mouse_captured: Widget | None = None
         self._driver: Driver | None = None

src/textual/binding.py

@@ -12,7 +12,11 @@ else:  # pragma: no cover
     from typing_extensions import TypeAlias
 
 
-BindingType: TypeAlias = "Binding | tuple[str, str] | tuple[str, str, str]"
+BindingType: TypeAlias = "Binding | tuple[str, str, str]"
+
+
+class BindingError(Exception):
+    """A binding related error."""
 
 
 class NoBinding(Exception):
@@ -39,6 +43,10 @@ class Bindings:
                 if isinstance(binding, Binding):
                     yield binding
                 else:
+                    if len(binding) != 3:
+                        raise BindingError(
+                            f"BINDINGS must contain a tuple of three strings, not {binding!r}"
+                        )
                     yield Binding(*binding)
 
         self.keys: MutableMapping[str, Binding] = (

src/textual/cli/cli.py

@@ -69,7 +69,8 @@ def import_app(import_name: str) -> App:
         except Exception as error:
             raise AppFail(str(error))
 
-        global_vars["sys"].argv = [path, *argv]
+        if "sys" in global_vars:
+            global_vars["sys"].argv = [path, *argv]
 
         if name:
             # User has given a name, use that

src/textual/reactive.py

@@ -3,6 +3,8 @@ from __future__ import annotations
 from functools import partial
 from inspect import isawaitable
 from typing import TYPE_CHECKING, Any, Callable, Generic, Type, TypeVar, Union
+from weakref import WeakSet
+
 
 from . import events
 from ._callback import count_parameters, invoke
@@ -191,7 +193,7 @@ def watch(
     watcher_name = f"__{attribute_name}_watchers"
     current_value = getattr(obj, attribute_name, None)
     if not hasattr(obj, watcher_name):
-        setattr(obj, watcher_name, set())
+        setattr(obj, watcher_name, WeakSet())
     watchers = getattr(obj, watcher_name)
     watchers.add(callback)
     Reactive._check_watchers(obj, attribute_name, current_value)

src/textual/widget.py

@@ -117,6 +117,7 @@ class Widget(DOMNode):
         self._arrangement_cache_key: tuple[int, Size] = (-1, Size())
 
         self._styles_cache = StylesCache()
+        self._rich_style_cache: dict[str, Style] = {}
 
         self._lock = Lock()
 
@@ -188,6 +189,21 @@ class Widget(DOMNode):
             self.allow_horizontal_scroll or self.allow_vertical_scroll
         )
 
+    def get_component_rich_style(self, name: str) -> Style:
+        """Get a *Rich* style for a component.
+
+        Args:
+            name (str): Name of component.
+
+        Returns:
+            Style: A Rich style object.
+        """
+        style = self._rich_style_cache.get(name)
+        if style is None:
+            style = self.get_component_styles(name).rich_style
+            self._rich_style_cache[name] = style
+        return style
+
     def _arrange(self, size: Size) -> DockArrangeResult:
         """Arrange children.
 
@@ -1383,6 +1399,7 @@ class Widget(DOMNode):
             self._set_dirty(*regions)
             self._content_width_cache = (None, 0)
             self._content_height_cache = (None, 0)
+            self._rich_style_cache.clear()
             self._repaint_required = True
             if isinstance(self.parent, Widget) and self.styles.auto_dimensions:
                 self.parent.refresh(layout=True)
@@ -1460,6 +1477,9 @@ class Widget(DOMNode):
     async def broker_event(self, event_name: str, event: events.Event) -> bool:
         return await self.app._broker_event(event_name, event, default_namespace=self)
 
+    def _on_syles_updated(self) -> None:
+        self._rich_style_cache.clear()
+
     async def _on_mouse_down(self, event: events.MouseUp) -> None:
         await self.broker_event("mouse.down", event)
 

src/textual/widgets/_footer.py

@@ -1,12 +1,12 @@
 from __future__ import annotations
 
 from rich.console import RenderableType
-from rich.style import Style
+
 from rich.text import Text
 import rich.repr
 
 from .. import events
-from ..reactive import Reactive
+from ..reactive import Reactive, watch
 from ..widget import Widget
 
 
@@ -55,6 +55,14 @@ class Footer(Widget):
         """If highlight key changes we need to regenerate the text."""
         self._key_text = None
 
+    def on_mount(self) -> None:
+        watch(self.app, "focused", self._focus_changed)
+
+    def _focus_changed(self, focused: Widget | None) -> None:
+        self.log("FOCUS CHANGED", focused)
+        self._key_text = None
+        self.refresh()
+
     async def on_mouse_move(self, event: events.MouseMove) -> None:
         """Store any key we are moving over."""
         self.highlight_key = event.style.meta.get("key")
@@ -76,11 +84,9 @@ class Footer(Widget):
             justify="left",
             end="",
         )
-        highlight_style = self.get_component_styles("footer--highlight").rich_style
-        highlight_key_style = self.get_component_styles(
-            "footer--highlight-key"
-        ).rich_style
-        key_style = self.get_component_styles("footer--key").rich_style
+        highlight_style = self.get_component_rich_style("footer--highlight")
+        highlight_key_style = self.get_component_rich_style("footer--highlight-key")
+        key_style = self.get_component_rich_style("footer--key")
         for binding in self.app.bindings.shown_keys:
             key_display = (
                 binding.key.upper()

src/textual/widgets/_tree_control.py

@@ -342,15 +342,15 @@ class TreeControl(Generic[NodeDataType], Static, can_focus=True):
 
     @property
     def _guide_style(self) -> Style:
-        return self.get_component_styles("tree--guides").rich_style
+        return self.get_component_rich_style("tree--guides")
 
     @property
     def _highlight_guide_style(self) -> Style:
-        return self.get_component_styles("tree--guides-highlight").rich_style
+        return self.get_component_rich_style("tree--guides-highlight")
 
     @property
     def _cursor_guide_style(self) -> Style:
-        return self.get_component_styles("tree--guides-cursor").rich_style
+        return self.get_component_rich_style("tree--guides-cursor")
 
     def on_mouse_move(self, event: events.MouseMove) -> None:
         self.hover_node = event.style.meta.get("tree_node")