Static works but TextLog raises NoActiveAppError()

[frawau]

I am having a strange issue.

I building an application to monitor some devices over MQTT and, after stumbling on Textual, I really want to use it .

I do have a strange issue.

The application is started with

async def amain(opts, datapoint, tls):
    app = DevConsole()
    dispatcher = DeviceManager(datapoint, tls, opts, app)
    _ = asyncio.create_task(dispatcher.dispatch())
    _ = asyncio.create_task(dispatcher.send_queue_task())
    _ = asyncio.create_task(dispatcher.get_devices())
    _ = asyncio.create_task(dispatcher.update_display_list())
    await app.run_async()

The application includes a method used by the dispatcher to update some panel. The method reads:

    def output_update(self, msg):
        self.query_one("#outputp").output = msg

If I define the panel with

class OutputPanel(Static):
    """Command output"""

    output = reactive("")

    def compose(self) -> ComposeResult:
        yield Static("", expand=True, id="cmd_console")

    def render(self):
        _log.debug(f"Rendering ST {self.output}")
        return f"\n{self.output}"

It all work as expected, but the output has no scrollbar, ....

If I define the panel with

class OutputPanel(Static):
    """Command output"""

    output = reactive("")

    def compose(self) -> ComposeResult:
        yield TextLog(markup=True, id="cmd_console")

    def watch_output(self):
        _log.debug(f"Rendering TL {self.output}")
        self.query_one("#cmd_console").clear()
        self.query_one("#cmd_console").write(self.output)

A NoActiveAppError() exception is raised.

I tried to subclass TextLog, to insert TextLog directly ( and have "output_update" do the clear/write.) but to no avail.

Any suggestion?

How could I get 'Static' to scroll?

Thanks

[TomJGooding]

How could I get 'Static' to scroll?

You could add a container like Vertical or VerticalScroll depending on your version of Textual (the latter has only just been released in v0.16). See below for a quick example.

Static works but TextLog raises NoActiveAppError()

I'm afraid I don't really understand what the rest of your app might be doing, but I found this issue which might be helpful?

from textual.app import App, ComposeResult
from textual.containers import VerticalScroll
from textual.widgets import Footer, Static


class OutputApp(App):
    CSS = """
    Screen {
        align: center middle;
    }

    #cmd-console {
        width: auto;
        min-height: 100%;
    }

    VerticalScroll {
        height: 30;
        overflow: auto;
        border: round $primary;
    }
    """

    BINDINGS = [
        ("space", "send_message", "Send message to output"),
    ]

    def compose(self) -> ComposeResult:
        yield VerticalScroll(Static(id="cmd-console"))
        yield Footer()

    def output_update(self, msg: str) -> None:
        cmd_console = self.query_one("#cmd-console", Static)
        cmd_console.update(msg)

    def action_send_message(self) -> None:
        self.output_update(TEXT * 10)


TEXT = """[bold red]I must not fear.[/bold red]
Fear is the mind-killer.
Fear is the little-death that brings total obliteration.
I will face my fear.
I will permit it to pass over me and through me.
And when it has gone past, I will turn the inner eye to see its path.
Where the fear has gone there will be nothing. Only I will remain.
"""

[frawau]

Thanks.

Even if it does not explain why Static works and TextLog does not, I updated to v0.16 and your recommendation to use VerticalScroll works good. So I marked as "answered".

Thanks again.