Implements screen modes

[rodrigogiraoserrao]

As it stands, the modes "work" but the API feels a bit rough.
Discussion in the related issue: #2327

The app below lets you play with modes.
Press 1 and 2 to switch between modes 1 and 2.
Press P to push random fruit modals into the screen.
Press O to pop a screen from the stack.

Demo code.

from random import choice

from textual.app import App, ComposeResult
from textual.screen import Screen, ModalScreen
from textual.widgets import Footer, Header, Label


FRUITS = "apple mango strawberry banana peach pear melon watermelon".split()


class BaseScreen(Screen[None]):
    BINDINGS = [
        ("1", "one", "Mode 1"),
        ("2", "two", "Mode 2"),
        ("p", "push", "Push rnd scrn"),
        ("o", "pop_screen", "Pop"),
        ("r", "remove", "Remove mode 1"),
    ]

    def __init__(self, label):
        super().__init__()
        self.label = label

    def compose(self) -> ComposeResult:
        yield Header()
        yield Label(self.label)
        yield Footer()

    def action_one(self) -> None:
        self.app.switch_mode("one")

    def action_two(self) -> None:
        self.app.switch_mode("two")

    def action_push(self) -> None:
        self.app.push_screen(FruitModal())

    def action_remove(self) -> None:
        self.app.remove_mode("one")


class FruitModal(ModalScreen[None]):
    BINDINGS = [
        ("1", "one", "Mode 1"),
        ("2", "two", "Mode 2"),
        ("p", "push", "Push rnd scrn"),
        ("o", "pop_screen", "Pop"),
    ]

    def compose(self) -> ComposeResult:
        yield Label(choice(FRUITS))

    def action_one(self) -> None:
        self.app.switch_mode("one")

    def action_two(self) -> None:
        self.app.switch_mode("two")

    def action_push(self) -> None:
        self.app.push_screen(FruitModal())


class ModesApp(App[None]):
    MODES = ["one", "two"]

    def on_mount(self) -> None:
        self.switch_mode("two")
        self.push_screen(BaseScreen("two"))
        self.switch_mode("one")
        self.push_screen(BaseScreen("one"))


app = ModesApp()
if __name__ == "__main__":
    app.run()

This will close #2327

[willmcgugan]

@rodrigogiraoserrao Where are we with this? Is it in progress or are you blocked?

[rodrigogiraoserrao]

@rodrigogiraoserrao Where are we with this? Is it in progress or are you blocked?

I'm waiting for you to give feedback on this iteration of the API.

[willmcgugan]

Looks good! just one request.

[willmcgugan]

Could you have a property for self._screen_stacks[self._current_mode][-1] ? Seems to pop up in a few places. It could be name _screen_stack ?

[rodrigogiraoserrao]

Did you mean to ask for a property for self._screen_stacks[self._current_mode]?

[rodrigogiraoserrao]

There is already a screen_stack property that returns a copy of the current stack but in some places I want the actual stack.

[willmcgugan]

How about a _screen_stack property then?

[davep]

I just noticed while looking in app.py at something else (a week or so after this PR was merged), all of the ModeError classes seem to have been duplicated.

[rodrigogiraoserrao]

Fixed in #2715.
What a weird thing, though...