Add auto_focus attribute to screens.

CHANGELOG.md

@@ -5,6 +5,13 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](http://keepachangelog.com/)
 and this project adheres to [Semantic Versioning](http://semver.org/).
 
+
+## Unreleased
+
+### Added
+
+- Attribute `auto_focus` to screens https://github.com/Textualize/textual/issues/2457
+
 ## [0.24.1] - 2023-05-08
 
 ### Fixed

src/textual/screen.py

@@ -30,7 +30,7 @@ from ._types import CallbackType
 from .binding import Binding
 from .css.match import match
 from .css.parse import parse_selectors
-from .css.query import QueryType
+from .css.query import NoMatches, QueryType
 from .dom import DOMNode
 from .geometry import Offset, Region, Size
 from .reactive import Reactive
@@ -101,6 +101,12 @@ class Screen(Generic[ScreenResultType], Widget):
     }
     """
 
+    auto_focus: str | None = "*"
+    """A selector to determine what to focus automatically when the screen is activated.
+
+    The widget focused is the first that matches the given [CSS selector](/guide/queries/#query-selectors).
+    Set to `None` to disable auto focus.
+    """
     focused: Reactive[Widget | None] = Reactive(None)
     """The focused [widget][textual.widget.Widget] or `None` for no focus."""
     stack_updates: Reactive[int] = Reactive(0, repaint=False)
@@ -659,6 +665,13 @@ class Screen(Generic[ScreenResultType], Widget):
         """Screen has resumed."""
         self.stack_updates += 1
         size = self.app.size
+        if self.auto_focus is not None and self.focused is None:
+            try:
+                to_focus = self.query(self.auto_focus).first()
+            except NoMatches:
+                pass
+            else:
+                self.set_focus(to_focus)
         self._refresh_layout(size, full=True)
         self.refresh()