optional actions

CHANGELOG.md

@@ -5,6 +5,12 @@ 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/).
 
+## [0.8.0] - Unreleased
+
+### Added
+
+- Added `textual.actions.SkipAction` exception which can be raised from an action to allow parents to process bindings.
+
 ## [0.7.0] - 2022-12-17
 
 ### Added

docs/guide/actions.md

@@ -75,7 +75,7 @@ When you click any of the links, Textual runs the `"set_background"` action to c
 
 ## Bindings
 
-Textual will also run actions bound to keys. The following example adds key [bindings](./input.md#bindings) for the ++r++, ++g++, and ++b++ keys which call the `"set_background"` action.
+Textual will run actions bound to keys. The following example adds key [bindings](./input.md#bindings) for the ++r++, ++g++, and ++b++ keys which call the `"set_background"` action.
 
 === "actions04.py"
 
@@ -92,7 +92,7 @@ If you run this example, you can change the background by pressing keys in addit
 
 ## Namespaces
 
-Textual will look for action methods on the widget or app where they are used. If we were to create a [custom widget](./widgets.md#custom-widgets) it can have its own set of actions.
+Textual will look for action methods in the class where they are defined (App, Screen, or Widget). If we were to create a [custom widget](./widgets.md#custom-widgets) it can have its own set of actions.
 
 The following example defines a custom widget with its own `set_background` action.
 

src/textual/actions.py

@@ -4,6 +4,10 @@
 import re
 
 
+class SkipAction(Exception):
+    """Raise in an action to skip the action (and allow any parent bindings to run)."""
+
+
 class ActionError(Exception):
     pass
 

src/textual/app.py

@@ -38,7 +38,7 @@
 from rich.segment import Segment, Segments
 from rich.traceback import Traceback
 
-from . import Logger, LogGroup, LogVerbosity, actions, events, log, messages
+from . import actions, Logger, LogGroup, LogVerbosity, events, log, messages
 from ._animator import DEFAULT_EASING, Animatable, Animator, EasingFunction
 from ._ansi_sequences import SYNC_END, SYNC_START
 from ._callback import invoke
@@ -47,6 +47,7 @@
 from ._filter import LineFilter, Monochrome
 from ._path import _make_path_object_relative
 from ._typing import Final, TypeAlias
+from .actions import SkipAction
 from .await_remove import AwaitRemove
 from .binding import Binding, Bindings
 from .css.query import NoMatches
@@ -1386,11 +1387,10 @@ async def invoke_ready_callback() -> None:
                 raise
 
             finally:
+                self._running = True
                 await self._ready()
                 await invoke_ready_callback()
 
-            self._running = True
-
             try:
                 await self._process_messages_loop()
             except asyncio.CancelledError:
@@ -1753,8 +1753,8 @@ async def check_bindings(self, key: str, priority: bool = False) -> bool:
         ):
             binding = bindings.keys.get(key)
             if binding is not None and binding.priority == priority:
-                await self.action(binding.action, default_namespace=namespace)
-                return True
+                if await self.action(binding.action, namespace):
+                    return True
         return False
 
     async def on_event(self, event: events.Event) -> None:
@@ -1823,32 +1823,41 @@ async def action(
     async def _dispatch_action(
         self, namespace: object, action_name: str, params: Any
     ) -> bool:
+        """Dispatch an action to an action method.
+
+        Args:
+            namespace (object): Namespace (object) of action.
+            action_name (str): Name of the action.
+            params (Any): Action parameters.
+
+        Returns:
+            bool: True if handled, otherwise False.
+        """
+        _rich_traceback_guard = True
+
         log(
             "<action>",
             namespace=namespace,
             action_name=action_name,
             params=params,
         )
-        _rich_traceback_guard = True
-
-        public_method_name = f"action_{action_name}"
-        private_method_name = f"_{public_method_name}"
 
-        private_method = getattr(namespace, private_method_name, None)
-        public_method = getattr(namespace, public_method_name, None)
-
-        if private_method is None and public_method is None:
+        try:
+            private_method = getattr(namespace, f"_action_{action_name}", None)
+            if callable(private_method):
+                await invoke(private_method, *params)
+                return True
+            public_method = getattr(namespace, f"action_{action_name}", None)
+            if callable(public_method):
+                await invoke(public_method, *params)
+                return True
             log(
-                f"<action> {action_name!r} has no target. Couldn't find methods {public_method_name!r} or {private_method_name!r}"
+                f"<action> {action_name!r} has no target."
+                f" Could not find methods '_action_{action_name}' or 'action_{action_name}'"
             )
-
-        if callable(private_method):
-            await invoke(private_method, *params)
-            return True
-        elif callable(public_method):
-            await invoke(public_method, *params)
-            return True
-
+        except SkipAction:
+            # The action method raised this to explicitly not handle the action
+            log("<action> {action_name!r} skipped.")
         return False
 
     async def _broker_event(
@@ -1859,7 +1868,7 @@ async def _broker_event(
         Args:
             event_name (str): _description_
             event (events.Event): An event object.
-            default_namespace (object | None): TODO: _description_
+            default_namespace (object | None): The default namespace, where one isn't supplied.
 
         Returns:
             bool: True if an action was processed.

src/textual/demo.css

@@ -29,7 +29,7 @@ Sidebar {
 }
 
 Sidebar:focus-within {
-    offset: 0 0 !important;    
+    offset: 0 0 !important;
 }
 
 Sidebar.-hidden {

src/textual/screen.py

@@ -295,22 +295,19 @@ def set_focus(self, widget: Widget | None, scroll_visible: bool = True) -> None:
             # No focus, so blur currently focused widget if it exists
             if self.focused is not None:
                 self.focused.post_message_no_wait(events.Blur(self))
-                self.focused.emit_no_wait(events.DescendantBlur(self))
                 self.focused = None
             self.log.debug("focus was removed")
         elif widget.can_focus:
             if self.focused != widget:
                 if self.focused is not None:
                     # Blur currently focused widget
                     self.focused.post_message_no_wait(events.Blur(self))
-                    self.focused.emit_no_wait(events.DescendantBlur(self))
                 # Change focus
                 self.focused = widget
                 # Send focus event
                 if scroll_visible:
                     self.screen.scroll_to_widget(widget)
                 widget.post_message_no_wait(events.Focus(self))
-                widget.emit_no_wait(events.DescendantFocus(self))
                 self.log.debug(widget, "was focused")
 
     async def _on_idle(self, event: events.Idle) -> None:

src/textual/widget.py

@@ -44,6 +44,7 @@
 from ._segment_tools import align_lines
 from ._styles_cache import StylesCache
 from ._types import Lines
+from .actions import SkipAction
 from .await_remove import AwaitRemove
 from .binding import Binding
 from .box_model import BoxModel, get_box_model
@@ -2344,17 +2345,22 @@ def _on_enter(self, event: events.Enter) -> None:
         self.mouse_over = True
 
     def _on_focus(self, event: events.Focus) -> None:
-        for node in self.ancestors_with_self:
-            if node._has_focus_within:
-                self.app.update_styles(node)
         self.has_focus = True
         self.refresh()
+        self.emit_no_wait(events.DescendantFocus(self))
 
     def _on_blur(self, event: events.Blur) -> None:
-        if any(node._has_focus_within for node in self.ancestors_with_self):
-            self.app.update_styles(self)
         self.has_focus = False
         self.refresh()
+        self.emit_no_wait(events.DescendantBlur(self))
+
+    def _on_descendant_blur(self, event: events.DescendantBlur) -> None:
+        if self._has_focus_within:
+            self.app.update_styles(self)
+
+    def _on_descendant_focus(self, event: events.DescendantBlur) -> None:
+        if self._has_focus_within:
+            self.app.update_styles(self)
 
     def _on_mouse_scroll_down(self, event) -> None:
         if self.allow_vertical_scroll:
@@ -2399,33 +2405,41 @@ def _on_scroll_to_region(self, message: messages.ScrollToRegion) -> None:
         self.scroll_to_region(message.region, animate=True)
 
     def action_scroll_home(self) -> None:
-        if self._allow_scroll:
-            self.scroll_home()
+        if not self._allow_scroll:
+            raise SkipAction()
+        self.scroll_home()
 
     def action_scroll_end(self) -> None:
-        if self._allow_scroll:
-            self.scroll_end()
+        if not self._allow_scroll:
+            raise SkipAction()
+        self.scroll_end()
 
     def action_scroll_left(self) -> None:
-        if self.allow_horizontal_scroll:
-            self.scroll_left()
+        if not self.allow_horizontal_scroll:
+            raise SkipAction()
+        self.scroll_left()
 
     def action_scroll_right(self) -> None:
-        if self.allow_horizontal_scroll:
-            self.scroll_right()
+        if not self.allow_horizontal_scroll:
+            raise SkipAction()
+        self.scroll_right()
 
     def action_scroll_up(self) -> None:
-        if self.allow_vertical_scroll:
-            self.scroll_up()
+        if not self.allow_vertical_scroll:
+            raise SkipAction()
+        self.scroll_up()
 
     def action_scroll_down(self) -> None:
-        if self.allow_vertical_scroll:
-            self.scroll_down()
+        if not self.allow_vertical_scroll:
+            raise SkipAction()
+        self.scroll_down()
 
     def action_page_down(self) -> None:
-        if self.allow_vertical_scroll:
-            self.scroll_page_down()
+        if not self.allow_vertical_scroll:
+            raise SkipAction()
+        self.scroll_page_down()
 
     def action_page_up(self) -> None:
-        if self.allow_vertical_scroll:
-            self.scroll_page_up()
+        if not self.allow_vertical_scroll:
+            raise SkipAction()
+        self.scroll_page_up()

src/textual/widgets/_static.py

@@ -24,7 +24,7 @@ def _check_renderable(renderable: object):
         )
 
 
-class Static(Widget):
+class Static(Widget, inherit_bindings=False):
     """A widget to display simple static content, or use as a base class for more complex widgets.
 
     Args: