pythonnative/src/pythonnative/navigation/host.py at v0.43.1 · pythonnative/pythonnative · GitHub

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"""Bridge between the native screen host and the navigation tree.

The host wraps the app's root element in

[`HostRoot`][pythonnative.navigation.host.HostRoot], which publishes:

- [`HostContext`][pythonnative.navigation.host.HostContext]: the

[`HostNavigator`][pythonnative.navigation.HostNavigator] a root stack

uses to push and pop real native screens, and

- [`FocusContext`][pythonnative.navigation.handle.FocusContext]: whether

the host's screen is currently presented (``on_resume`` /

``on_pause``), so [`use_is_focused`][pythonnative.use_is_focused]

and [`use_focus_effect`][pythonnative.use_focus_effect] follow the

platform lifecycle even outside any declarative navigator.

Pushed screens receive their navigation history under the

``"pn_nav"`` key of the host's launch arguments; the root stack reads

it through ``HostNavigator.initial_navigation_state``.

"""

from __future__ import annotations

from typing import Any, Dict, Optional

from ..component import component

from ..element import Element, Node

from ..hooks import Context, create_context, use_effect, use_state

from .handle import FocusContext, HostNavigator

__all__ = ["HostContext", "HostRoot", "NAV_STATE_ARG"]

NAV_STATE_ARG = "pn_nav"

"""Launch-argument key under which a pushed screen receives its serialized navigation state."""

HostContext: Context[Optional[HostNavigator]] = create_context(None, name="Host")

"""The native host bridging this tree, or ``None`` when rendering without one (tests, rows)."""

@component

def HostRoot(*children: Node, host: HostNavigator) -> Element:

"""Publish the host bridge and its focus state to the tree below."""

focused, set_focused = use_state(bool(getattr(host, "is_focused", True)))

def subscribe() -> Any:

set_focused(bool(getattr(host, "is_focused", True)))

return host.add_focus_listener(lambda value: set_focused(bool(value)))

use_effect(subscribe, [host])

return HostContext.Provider(host, FocusContext.Provider(focused, *children))

def initial_state_from_args(args: Optional[Dict[str, Any]]) -> Optional[Dict[str, Any]]:

"""Extract a serialized navigation state from host launch arguments."""

if not isinstance(args, dict):

return None

state = args.get(NAV_STATE_ARG)

if isinstance(state, dict) and state.get("routes"):

return state

return None

pythonnative/src/pythonnative/navigation/host.py at v0.43.1 · pythonnative/pythonnative · GitHub

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