Event control (#3099)

* Add control

* added control

* post to parent

Author: willmcgugan

CHANGELOG.md

@@ -21,6 +21,9 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 - Added widgets.Digit https://github.com/Textualize/textual/pull/3073
 - Added `BORDER_TITLE` and `BORDER_SUBTITLE` classvars to Widget https://github.com/Textualize/textual/pull/3097
 
+### Changed
+- DescendantBlur and DescendantFocus can now be used with @on decorator
+
 ## [0.32.0] - 2023-08-03
 
 ### Added

src/textual/events.py

@@ -13,6 +13,7 @@
 
 from __future__ import annotations
 
+from dataclasses import dataclass
 from typing import TYPE_CHECKING, Type, TypeVar
 
 import rich.repr
@@ -547,21 +548,39 @@ class Blur(Event, bubble=False):
     """
 
 
+@dataclass
 class DescendantFocus(Event, bubble=True, verbose=True):
     """Sent when a child widget is focussed.
 
     - [X] Bubbles
     - [X] Verbose
     """
 
+    widget: Widget
+    """The widget that was focused."""
 
+    @property
+    def control(self) -> Widget:
+        """The widget that was focused (alias of `widget`)."""
+        return self.widget
+
+
+@dataclass
 class DescendantBlur(Event, bubble=True, verbose=True):
     """Sent when a child widget is blurred.
 
     - [X] Bubbles
     - [X] Verbose
     """
 
+    widget: Widget
+    """The widget that was blurred."""
+
+    @property
+    def control(self) -> Widget:
+        """The widget that was blurred (alias of `widget`)."""
+        return self.widget
+
 
 @rich.repr.auto
 class Paste(Event, bubble=True):

src/textual/widget.py

@@ -3290,12 +3290,14 @@ def _on_enter(self, event: events.Enter) -> None:
     def _on_focus(self, event: events.Focus) -> None:
         self.has_focus = True
         self.refresh()
-        self.post_message(events.DescendantFocus())
+        if self.parent is not None:
+            self.parent.post_message(events.DescendantFocus(self))
 
     def _on_blur(self, event: events.Blur) -> None:
         self.has_focus = False
         self.refresh()
-        self.post_message(events.DescendantBlur())
+        if self.parent is not None:
+            self.parent.post_message(events.DescendantBlur(self))
 
     def _on_mouse_scroll_down(self, event: events.MouseScrollDown) -> None:
         if event.ctrl or event.shift: