React to any remaining key (non bound ones)

[pawamoy]

I sometimes push a modal that reacts to scroll keys (up, down, left, right, pageup, pagedown, home, end), and wanted to bind any remaining key to a "dismiss" action.

Turns out it's quite easy to do:

class MyModal(ModalScreen):
    BINDINGS = [...]

    @property
    def bound_keys(self) -> Iterator[str]:
        for binding in self.BINDINGS:
            if isinstance(binding, Binding):
                yield from binding.key.split(",")
            else:
                yield from binding[0].split(",")

    def on_key(self, event: Key) -> None:
        if event.key not in self.bound_keys:
            self.dismiss()

Could be nice-to-haves in Textual itself:

• a bindings attribute that always returns actual Binding instances, and not tuples
• a keys attribute on Binding that does the comma split

This way bound_keys could be rewritten:

for binding in self.bindings:
    yield from binding.keys

...and maybe this could become part of Textual too 🙂

[davep]

Adjacent to #2269 too, I'd say. While not directly related, this feels like something to keep in mind if/when doing a full review of the binding system.

[pawamoy]

(it's a shame that there's no backlink functionality between issues and discussions...)

[davep]

As an aside, if you don't mind a sneaky dip into one internal on App, this should do the trick without needing to worry about splitting up the keys yourself, I think?

from textual.app import App, ComposeResult
from textual.containers import VerticalScroll
from textual.events import Key
from textual.screen import ModalScreen
from textual.widgets import Static

class AnyKeyScreen(ModalScreen[None]):

    def compose(self) -> ComposeResult:
        with VerticalScroll():
            yield Static(
                "\n".join([
                    f"{n} on_key and no Binding make Jack a dull boy"
                    for n in range(1000)
                ])
            )

    def on_key(self, event: Key) -> None:
        if not any(bindings.keys.get(event.key) for _, bindings in self.app._binding_chain):
            self.dismiss()

class AnyKeyDismissApp(App[None]):

    def on_mount(self) -> None:
        self.push_screen(AnyKeyScreen())

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

Could also be that self.app._modal_binding_chain is more appropriate for your needs.

[pawamoy]

Thanks! I'll probably stay on beaten (trusted? known? blessed? what's the expression again?) paths and avoid using internals, but that's a good thing to know such attributes already exist 🙂 Maybe just a matter of exposing them then.

[davep]

Yeah, I was wondering if something akin to:

def is_bound(self, key: Key | str) -> bool:
    key = key.key if isinstance(key, Key) else key
    return any(bindings.keys.get(key) for _, bindings in self._binding_chain)

might be a good idea for App.

[pawamoy]

    def on_key(self, event: Key) -> None:
        if not self.app.is_bound(key):
            self.dismiss()

That'd be nice indeed.

[pawamoy]

Actually I went with your suggestion and _modal_binding_chain, it lets me write much less code. Let see what these internals become! Thanks again!