textual tab change detect

main.py

"""MRE for Textual"""

from __future__ import annotations

import http

import requests
from textual import on, work
from textual.app import App, ComposeResult
from textual.message import Message
from textual.screen import Screen
from textual.widgets import (
    Header,
    Footer,
    TabbedContent,
    TabPane,
    Placeholder,
    MarkdownViewer,
)


class DataLoaded(Message):
    """Data loaded message"""


class LazyTab(TabPane):
    """Lazy tab"""

    url: str
    data: str = ""

    def __init__(self, url: str, **kwargs) -> None:
        """Initialise the tab"""
        super().__init__(**kwargs)
        self.url = url
        self.loading = True

    def compose(self) -> ComposeResult:
        self.loading = not self.data
        yield MarkdownViewer(self.data)

    @work
    async def get_data(self):
        """Fetch data from URL"""
        response = requests.get(self.url, timeout=10)
        self.data = response.text
        self.post_message(DataLoaded())

    async def on_data_loaded(self, msg: DataLoaded) -> None:
        msg.stop()
        await self.recompose()

    def on_show(self):
        """Load Data"""
        self.get_data()


class MainScreen(Screen[None]):
    """Main screen"""

    DEFAULT_CSS = """
    Placeholder {
     width: 1fr;
     height: 1fr;
    }
    """

    def __init__(self) -> None:
        """Initialise the screen."""
        super().__init__()

    def compose(self) -> ComposeResult:
        """Compose the screen"""
        yield Header()
        yield Footer()
        with TabbedContent(id="tabbed_content"):
            with LazyTab(
                title="Tab 1",
                id="tab1",
                url="https://raw.githubusercontent.com/paulrobello/parllama/main/README.md",
            ):
                yield Placeholder("Tab 1")
            with LazyTab(
                title="Tab 2",
                id="tab2",
                url="https://raw.githubusercontent.com/paulrobello/parllama/main/README.md",
            ):
                yield Placeholder("Tab 2")
            with LazyTab(
                title="Tab 3",
                id="tab3",
                url="https://raw.githubusercontent.com/paulrobello/parllama/main/README.md",
            ):
                yield Placeholder("Tab 3")

    @on(TabbedContent.TabActivated)
    def on_tab_activated(self, msg: TabbedContent.TabActivated) -> None:
        """Tab activated event"""
        msg.stop()
        self.notify(f"tab activated: {msg.tab.label.plain}")


class MyApp(App[None]):
    """App to test Textual stuff"""

    def __init__(self) -> None:
        """Initialise the app."""
        super().__init__()
        self.main_screen = MainScreen()

    async def on_mount(self) -> None:
        """Mount the screen."""
        await self.push_screen(self.main_screen)


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