Usage of the textual.on decorator in parent/mixin classes

[joshua-dean]

This is more of a question of usage/feasibility than an outright feature request, so apologies if I've improperly categorized the issue.

Versions:
python 3.11.7
textual 0.46.0

The textual.on decorator is useful, but does not function if used in an inherited class:

"""Base app for 'on_decorator' testing."""
import textual
from textual.app import App, ComposeResult
from textual.events import Click
from textual.widget import Widget
from textual.widgets import Placeholder

class OnClickMixin:
    """Mixin for 'on_decorator' testing."""
    app: App
    
    def on_click(self, event):
        """Handle click event."""
        self.app.notify('mixin on_click')
    
    @textual.on(Click)
    def handle_click(self, event):
        """Handle click event."""
        self.app.notify('mixin handle_click')

class OnClickWidget(Widget, OnClickMixin):
    """Widget for 'on_decorator' testing."""
        
    def on_click(self, event):
        """Handle click event."""
        self.app.notify('widget on_click')
    
    @textual.on(Click)
    def handle_click(self, event):
        """Handle click event."""
        self.app.notify('widget handle_click')
    
    def compose(self) -> ComposeResult:
        """Compose widget."""
        yield Placeholder()

class OnDecoratorApp(App):
    """Base app for 'on_decorator' testing."""
    
    def compose(self) -> ComposeResult:
        """Compose app."""
        yield OnClickWidget()

if __name__ == "__main__":
    app = OnDecoratorApp()
    app.run()

Clicking the Placeholder in this example yields:
widget handle_click
widget on_click
mixin on_click
but does not produce mixin handle_click.

The logic for this appears to be at the _MessagePumpMeta level, as class_dict will not contain methods from OnClickMixin, so no methods in the mixin ever get checked for the _textual_on attribute.

Changing OnClickMixin to inherit MessagePump does cause all four toasts to appear. Is this within the intended use of the MessagePump class, or could utilizing it in this way create problems in the future?
If it is not good practice or the intended usage, would it be useful to implement a base class for this purpose, and/or change the logic in _MessagePumpMeta to accommodate this use case?