Removing and remounting widgets

[lyovushka]

It seems like removing a widget doesn't set the is_mounted property to False and doesn't reset _mounted_event. Below is an example where the assertion fails.

from textual.app import App
from textual.widgets import Button, Static
from textual.widget import Widget
from textual.containers import Vertical

TEXT = "Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua."


class TestWidget(Widget):
    def compose(self):
        yield Static(TEXT)


class TestApp(App):
    async def on_button_pressed(self):
        w = self.query_one("TestWidget")
        v = self.query_one("Vertical")
        with self.batch_update():
            await v.remove_children([w])
            assert not w.is_mounted
            await v.mount(w, after=0)

    def compose(self):
        with Vertical():
            yield Button()
            yield TestWidget()


TestApp().run()

The practical consequence is that the subsequent await mount returns immediately and potentially before the widget is remounted.

[edward-jazzhands]

I'm pretty sure the fact that you have it inside of an with self.batch_update() context manager means that your remove command is not doing anything until the rest of the context manager completes, that's what that method does. So when you remove it and check right after, it doesn't matter that you've awaited it. The batch_update context manager is preventing anything from being run until all the commands inside of it are complete.

[willmcgugan]

The context manager will prevent updates during that time. But it won't affect the API other than that...

[willmcgugan]

Widgets were never meant to be remounted. Once you have unmounted a widget, you should discard it.

You can changes a widget's position, and you can temporarily hide it. But you will need a fresh instance if you have unmounted it.

[lyovushka]

That makes sense. My usecase is swapping the positions of two widgets (with the same parent). Is it possible without unmounting?

[willmcgugan]

https://textual.textualize.io/api/dom_node/#textual.dom.DOMNode.sort_children

[lyovushka]

https://textual.textualize.io/api/dom_node/#textual.dom.DOMNode.sort_children

Wonderful, thank you!