max-height: 100% with a height: auto container causes child widget to disappear

[davep]

Given this code:

from textual.app import App, ComposeResult
from textual.widgets import DataTable, Static

class HappyDataTableFunApp(App[None]):

    CSS = """
    DataTable {
        max-height: 100%;
    }
    """

    def populate(self, table: DataTable) -> DataTable:
        for n in range(20):
            table.add_column(f"Column {n}")
        for row in range(1000):
            table.add_row(
                *[str(row * n) for n in range(20)]
            )
        return table

    def compose(self) -> ComposeResult:
        with Static():
            yield self.populate(DataTable())

if __name__ == "__main__":
    HappyDataTableFunApp().run()

the DataTable doesn't show. This seems to be the combination of a child widget that is height: auto; and max-height: 100%; with a parent container that is height: auto.

More generally the issue seems to be that if a child widget is height: auto and max-height: 100% and the parent container is height: auto there's no way to work out a height.

Perhaps there's some scope here to settle on a less astonishing outcome?

[willmcgugan]

It is less to do with styling, and more to do with the fact that Static was not designed to be a container. It doesn't make sense to allow adding children, even though the context manager allows it.

I think the only resolution would be to make this an error. i.e. something like raise NotAContainer("Can't add children to a Static").

Suggest we are fairly cautious about what we add this to. Some widgets may not be containers by default, but could be styled to be containers.

Let @willmcgugan know if this is more than half a day's work.

[davep]

Somewhat related, because I see folk using Static as a container quite often, perhaps this wording:

Can be used for Rich renderables and can also be the base for other types of widgets.

in the the docs for Static could do with a wee revamp, as I suspect it has caused people to think it should be used as a container.

Also, the tutorial uses Static as the base class for a compound widget (which now I think about it might account for why I see people do that so often).

[TomJGooding]

Yup, I can confirm this is what I was doing too when I was new to Textual based on the docs!

The specific mention of Static in the widgets guide to "create custom widgets of your own" might also be compounding this confusion: https://textual.textualize.io/guide/widgets/#static-widget

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