async def on_mount(self) -> None:
        """Set up the main screen once the DOM is ready."""

        # Currently Textual's Markdown can steal focus, which gets confusing
        # as it's not obvious *what* is focused. So let's stop it from
        # allowing the content to get focus.
        #
        # https://github.com/Textualize/textual/issues/2380
        self.query_one(Markdown).can_focus_children = False

        # Load up any history that might be saved.
        if history := load_history():
            self.query_one(Viewer).load_history(history)

        # If we've not been tasked to start up looking at a very specific
        # location (in other words if no location was passed on the command
        # line), and if there is some history...
        if self._initial_location is None and history:
            # ...start up revisiting the last location the user was looking
            # at.
            self.query_one(Viewer).visit(history[-1], remember=False)
            self.query_one(Omnibox).value = str(history[-1])
        elif self._initial_location is not None:
            # Seems there is an initial location; so let's start up looking
            # at that.
            (omnibox := self.query_one(Omnibox)).value = self._initial_location
            await omnibox.action_submit()
Set up the main screen once the DOM is ready.
frogmouth/screens/main.py