F3 key triggered when inline and VerticalScroll takes up 100% of the screen

[radiac]

I see a lot of F3 key events on the console when I have a VerticalScroll which is taking up 100% of the height of an inline app, eg:

Key(key='f3', character=None, name='f3', is_printable=False) >>> VerticalScroll() method=<Widget.on_key>
Key(key='f3', character=None, name='f3', is_printable=False) >>> Screen(id='_default') method=<Widget.on_key>
Key(key='f3', character=None, name='f3', is_printable=False) >>> MyApp(title='MyApp', classes={'-dark-mode'}, pseudo_classes={'focus', 'dark', 'inline'}) method=<App.on_key>

To recreate:

from textual.app import App, ComposeResult
from textual.containers import VerticalScroll
from textual.widgets import Button


class TestApp(App):
    def compose(self) -> ComposeResult:
        # yield Header()
        with VerticalScroll():
            yield Button("hello", id="output")


if __name__ == "__main__":
    app = TestApp()
    app.run(inline=True)

run with textual run --dev test.py and you will see f3 key events in the console; it appears they are raised each time the app gains or loses focus, or redraws.

Uncomment the Header, run with inline=False, or set a css height under 100% and they stop appearing.

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[TomJGooding]

If you're running in inline mode, presumably you wouldn't want the app to take up the full screen anyway? Adding a max-height to the screen seems to fix this issue:

    CSS = """
    Screen:inline {
        max-height: 97vh;
    }
    """

---

Running this in debug mode, it looks like it is the cursor position that's being misinterpreted as a F3 key press.

I don't quite understand why, but I'm guessing related to the screen height being auto in inline mode? From a quick git bisect, it looks like this was introduced in 80175f0, if it helps someone figure this out!

Extract from keys.log

FEED '\x1b[1;1R\x1b[1;1R\x1b[1;1R'
character='\x1b'
sequence='\x1b['
sequence='\x1b[1'
sequence='\x1b[1;'
sequence='\x1b[1;1'
sequence='\x1b[1;1R'
Key(key='f3', character=None, name='f3', is_printable=False)
character='\x1b'
sequence='\x1b['
sequence='\x1b[1'
sequence='\x1b[1;'
sequence='\x1b[1;1'
sequence='\x1b[1;1R'
Key(key='f3', character=None, name='f3', is_printable=False)
character='\x1b'
sequence='\x1b['
sequence='\x1b[1'
sequence='\x1b[1;'
sequence='\x1b[1;1'
sequence='\x1b[1;1R'
Key(key='f3', character=None, name='f3', is_printable=False)