Drop explicit sender attribute from messages (#1940)

* remove sender

* removed priority post

* timer fix

* test fixes

* drop async version of post_message

* extended docs

* fix no app

* Added control properties

* changelog

* changelog

* changelog

* fix for stopping timers

* changelog

* added aliases to radio and checkbox

* Drop sender from Message init

* drop time

* drop cast

* Added aliases

docs/examples/events/custom01.py

@@ -10,9 +10,9 @@ class ColorButton(Static):
     class Selected(Message):
         """Color selected message."""
 
-        def __init__(self, sender: MessageTarget, color: Color) -> None:
+        def __init__(self, color: Color) -> None:
             self.color = color
-            super().__init__(sender)
+            super().__init__()
 
     def __init__(self, color: Color) -> None:
         self.color = color
@@ -24,9 +24,9 @@ class ColorButton(Static):
         self.styles.background = Color.parse("#ffffff33")
         self.styles.border = ("tall", self.color)
 
-    async def on_click(self) -> None:
+    def on_click(self) -> None:
         # The post_message method sends an event to be handled in the DOM
-        await self.post_message(self.Selected(self, self.color))
+        self.post_message(self.Selected(self.color))
 
     def render(self) -> str:
         return str(self.color)

docs/guide/events.md

@@ -107,16 +107,11 @@ The message class is defined within the widget class itself. This is not strictl
 - It reduces the amount of imports. If you import `ColorButton`, you have access to the message class via `ColorButton.Selected`.
 - It creates a namespace for the handler. So rather than `on_selected`, the handler name becomes `on_color_button_selected`. This makes it less likely that your chosen name will clash with another message.
 
+### Sending messages
 
-## Sending messages
-
-In the previous example we used [post_message()][textual.message_pump.MessagePump.post_message] to send an event to its parent. We could also have used [post_message_no_wait()][textual.message_pump.MessagePump.post_message_no_wait] for non async code. Sending messages in this way allows you to write custom widgets without needing to know in what context they will be used.
-
-There are other ways of sending (posting) messages, which you may need to use less frequently.
-
-- [post_message][textual.message_pump.MessagePump.post_message] To post a message to a particular widget.
-- [post_message_no_wait][textual.message_pump.MessagePump.post_message_no_wait] The non-async version of `post_message`.
+To send a message call the [post_message()][textual.message_pump.MessagePump.post_message] method. This will place a message on the widget's message queue and run any message handlers.
 
+It is common for widgets to send messages to themselves, and allow them to bubble. This is so a base class has an opportunity to handle the message. We do this in the example above, which means a subclass could add a `on_color_button_selected` if it wanted to handle the message itself.
 
 ## Preventing messages