Weird height behavior after 1.0.0 update

[Zatfer17]

Hello! Today I tried bumping the textual version of my tui-network tool and couldn't see any widget content. After some fiddling I figured out the app compose is not being run. Could you have a look? Perhaps this happens only with packaged apps?

I've made a branch for my app as a proof: https://github.com/Zatfer17/tui-network/tree/textual-issue

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[TomJGooding]

Have you tried debugging by adding explicit heights to your widgets/containers?

If compose wasn't being run you wouldn't see anything at all. Your print statement is sent to the dev console, not displayed in the app.

[Zatfer17]

@TomJGooding forgot about the dev console thing 😅

You are right, problem is height. Is there a reason why 100h doesn't work anymore as a height? I only managed to get it working setting the height to either auto or a fixed value (% deson't work either).

Referring to https://github.com/Zatfer17/tui-network/blob/0112b62c3cc1def2e189682413d84feaedf92402/tui_network/static/style.tcss#L16 for instance

Or was my css wrong since the beginning? Perhaps I should have set the height on the vertical group in the first place, instead of the inner widget, but I wonder why it used to work before

[TomJGooding]

I think the problem is that the VerticalGroup containers you're using have a default height: auto, so they wouldn't have any real height to base the proportional height of their children on...?

I'm not quite sure why this worked before, it looks like this changed following #5360. Probably needs a maintainer to confirm if this is expected behaviour or a possible regression!

[willmcgugan]

Could I have an MRE? You (awesome) app is too much to debug.

[TomJGooding]

@willmcgugan It's obviously been a while since I looked at this, but I think something like this demonstrates the issue.

Before Textual v1.0.0, this displays a 2x2 grid but now it looks like a blank screen:

from textual.app import App, ComposeResult
from textual.containers import Grid, VerticalGroup
from textual.widgets import Placeholder


class ExampleApp(App):
    CSS = """
    Grid {
        grid-size: 2;
    }
    """

    def compose(self) -> ComposeResult:
        with Grid():
            for _ in range(4):
                with VerticalGroup():
                    yield Placeholder()


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

[willmcgugan]

@TomJGooding Your assessment is correct. VerticalGroup has height auto. But Placeholder doesn't expose a height, since its job is to just fill any space given.

I don't think there is much to be done here. The solution is always to add borders until it is clear what is going on.

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