pythonnative/src/pythonnative/hosts/native.py at main · pythonnative/pythonnative · GitHub

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"""On-device application surface hosting, shared by iOS and Android.

Native hosts send asynchronous lifecycle, viewport, and back events keyed by

surface host ID. Python attaches the application root and publishes cached

restoration state through the Host module. Navigation owns logical Screen

children in that same application tree.

"""

from __future__ import annotations

import json

import threading

from typing import Any, Dict, Optional, Sequence, Tuple

from .. import appearance, diagnostics, platform_metrics

from ..bridge import codec

from ..native_modules.registry import native_module

from .base import ScreenHost, flush_hosts

__all__ = ["NativeScreenHost", "dispatch_host_event", "host_for_screen", "live_hosts"]

_HOSTS: Dict[int, "NativeScreenHost"] = {}

_SCHEDULED: Dict[int, ScreenHost] = {}

_flush_pending = False

def host_for_screen(screen_id: int) -> Optional["NativeScreenHost"]:

"""Return the host registered for ``screen_id`` (``None`` if unknown)."""

return _HOSTS.get(int(screen_id))

def live_hosts() -> Sequence["NativeScreenHost"]:

"""Every host currently registered, in creation order."""

return list(_HOSTS.values())

def _host_module() -> Any:

return native_module("Host")

# ======================================================================

# Deferred renders

# ======================================================================

def _flush_scheduled() -> None:

global _flush_pending

_flush_pending = False

hosts = list(_SCHEDULED.values())

_SCHEDULED.clear()

if hosts:

diagnostics.log(f"render_scheduler: flushing {len(hosts)} host(s)")

flush_hosts(hosts)

def _request_flush() -> None:

"""Queue one application-thread flush of every scheduled host."""

global _flush_pending

if _flush_pending:

return

_flush_pending = True

from ..runtime import call_threadsafe

call_threadsafe(_flush_scheduled)

# ======================================================================

# Payload helpers

# ======================================================================

def _optional_float(payload: Dict[str, Any], key: str) -> Optional[float]:

"""Return ``payload[key]`` as a float, or ``None`` when absent or not a number."""

value = payload.get(key)

if isinstance(value, bool) or not isinstance(value, (int, float)):

return None

return float(value)

def _publish_metrics(payload: Any) -> Tuple[float, float]:

"""Publish viewport, insets, keyboard, density, and color scheme from a host payload.

The payload carries ``width`` and ``height`` (the window, in layout

units) and may carry ``scale``, ``font_scale``, ``screen_width``, and

``screen_height``. A missing density keeps the last published value

(``1.0`` initially); a missing screen size falls back to the window.

Returns the ``(width, height)`` it found (``0, 0`` when absent).

"""

if not isinstance(payload, dict):

return (0.0, 0.0)

width = float(payload.get("width") or 0.0)

height = float(payload.get("height") or 0.0)

scale = _optional_float(payload, "scale")

font_scale = _optional_float(payload, "font_scale")

insets = payload.get("insets")

if isinstance(insets, dict):

platform_metrics.set_safe_area_insets(

float(insets.get("top") or 0.0),

float(insets.get("left") or 0.0),

float(insets.get("bottom") or 0.0),

float(insets.get("right") or 0.0),

)

if "keyboard_height" in payload:

platform_metrics.set_keyboard_height(float(payload.get("keyboard_height") or 0.0))

scheme = payload.get("color_scheme")

if scheme in ("light", "dark"):

appearance.set_system_color_scheme(str(scheme))

if width > 0 and height > 0:

platform_metrics.set_window_dimensions(width, height, scale=scale, font_scale=font_scale)

screen_width = _optional_float(payload, "screen_width") or width

screen_height = _optional_float(payload, "screen_height") or height

platform_metrics.set_screen_dimensions(screen_width, screen_height, scale=scale, font_scale=font_scale)

return (width, height)

# ======================================================================

# Host

# ======================================================================

class NativeScreenHost(ScreenHost):

"""Screen host addressed by an integer ``screen_id`` on the bridge."""

def __init__(self, screen_id: int, component_path: str, component: Any) -> None:

super().__init__(int(screen_id), component_path, component)

self.screen_id = int(screen_id)

self._pending_viewport: Optional[Tuple[float, float]] = None

_HOSTS[self.screen_id] = self

# -- lifecycle ------------------------------------------------------

def on_destroy(self) -> None:

"""Forget the screen id, then tear down the tree."""

_HOSTS.pop(self.screen_id, None)

_SCHEDULED.pop(id(self), None)

super().on_destroy()

def apply_metrics(self, payload: Any) -> None:

"""Publish the metrics carried by a host event and resize the viewport."""

width, height = _publish_metrics(payload)

if width > 0 and height > 0:

self._pending_viewport = (width, height)

self.set_viewport_size(width, height)

# -- platform primitives -------------------------------------------

def _show_error(self, payload: Dict[str, Any]) -> None:

from ..bridge import get_transport

get_transport().call("Host", "show_error", codec.dumps({"call_id": 0, "args": payload}))

def _dismiss_error(self) -> None:

from ..bridge import get_transport

get_transport().call("Host", "dismiss_error", codec.dumps({"call_id": 0, "args": {}}))

def _initial_viewport_size(self) -> Optional[Tuple[float, float]]:

if self._pending_viewport is not None:

return self._pending_viewport

dims = platform_metrics.get_window_dimensions()

if dims.width > 0 and dims.height > 0:

return (dims.width, dims.height)

return None

def _schedule_render_async(self) -> bool:

if self._render_scheduled:

return True

self._render_scheduled = True

_SCHEDULED[id(self)] = self

try:

_request_flush()

except Exception as exc:

self._render_scheduled = False

_SCHEDULED.pop(id(self), None)

diagnostics.log(f"request_render: bridge defer failed ({exc!r}); rendering synchronously")

return False

return True

def _attach_root(self, native_view: Any) -> None:

tag = getattr(native_view, "tag", None)

if tag is None:

return

# Native answers with the viewport the root now occupies, which

# is the earliest exact size available on iOS.

result = _host_module().call("attach_root", screen=self.screen_id, tag=int(tag))

if isinstance(result, dict):

self.apply_metrics(result)

def _detach_root(self, native_view: Any) -> None:

tag = getattr(native_view, "tag", None)

if tag is None:

return

try:

_host_module().call("detach_root", screen=self.screen_id, tag=int(tag))

except Exception:

diagnostics.swallowed("hosts.native.detach_root")

def cache_navigation_state(self, state: Dict[str, Any]) -> None:

"""Cache navigation before the platform's synchronous state-saving callback."""

super().cache_navigation_state(state)

_host_module().call("cache_state", screen=self.screen_id, state=json.dumps(self.args))

def _native_set_options(self, options: Dict[str, Any]) -> None:

_host_module().call("set_options", screen=self.screen_id, options=codec.to_jsonable(options or {}))

# ======================================================================

# Inbound host events

# ======================================================================

_create_lock = threading.Lock()

def dispatch_host_event(screen_id: int, event: str, payload: Any) -> Optional[str]:

"""Route ``callback("host", screen_id, event, payload)`` to a host.

Events (payloads are what ``PNViewController`` and

``PNScreenFragment`` send):

- ``create`` ``{"path", "args", "restored_state", ...metrics}``:

import the component, create the host, and mount. ``path`` is the

dotted component path (``None`` means the app entry module) and

``args`` a JSON string. Returns ``{"root": tag}``.

- ``start`` / ``resume`` / ``pause`` / ``stop`` / ``destroy``:

lifecycle. ``resume`` and ``layout`` carry metrics.

- ``layout`` ``{width, height, insets, keyboard_height, color_scheme,

scale, font_scale, screen_width, screen_height}``.

- ``appearance`` ``{"color_scheme"}``.

- ``back_pressed``: returns ``"true"`` when a handler consumed it.

- ``save_state`` / ``restore_state``: instance-state hooks.

- ``flush``: run deferred renders now.

Returns a JSON string for request-style events, else ``None``.

"""

screen_id = int(screen_id)

if event == "create":

return _create(screen_id, payload if isinstance(payload, dict) else {})

if event == "flush":

_flush_scheduled()

return None

if event == "appearance":

_publish_metrics(payload)

return None

host = _HOSTS.get(screen_id)

if host is None:

diagnostics.log(f"dispatch_host_event: no host for screen={screen_id} event={event!r}")

return None

if event == "reload":

host.reload()

return None

if event == "layout":

host.apply_metrics(payload)

return None

if event == "resume":

host.apply_metrics(payload)

host.on_resume()

return None

if event == "pause":

host.on_pause()

return None

if event == "back_pressed":

if not host.on_back_pressed():

_host_module().call("finish", screen=host.screen_id)

return None

if event in ("save_state", "restore_state"):

# Restoration state is cached as Python publishes it; the host

# has nothing synchronous to do when the platform saves.

return None

if event == "destroy":

host.on_destroy()

return None

diagnostics.log(f"dispatch_host_event: unknown event {event!r}")

return None

def _create(screen_id: int, payload: Dict[str, Any]) -> Optional[str]:

from . import import_component

component_path = str(payload.get("path") or payload.get("component") or _entry_module())

with _create_lock:

existing = _HOSTS.get(screen_id)

if existing is not None:

existing.apply_metrics(payload)

existing.on_create()

return _root_json(existing)

component = import_component(component_path)

host = NativeScreenHost(screen_id, component_path, component)

args = payload.get("args")

if args:

host.set_args(args)

if not (payload.get("width") and payload.get("height")):

# ``create`` is sent before the first layout pass; ask native for

# its best guess so the first commit lays out at the right size.

try:

viewport = _host_module().call("viewport", screen=screen_id)

except Exception:

viewport = None

if isinstance(viewport, dict):

payload = {**viewport, **payload}

_publish_metrics(payload)

width = float(payload.get("width") or 0.0)

height = float(payload.get("height") or 0.0)

if width > 0 and height > 0:

host._pending_viewport = (width, height)

restored = payload.get("restored_state")

if restored:

decoded = codec.loads(restored) if isinstance(restored, str) else restored

if isinstance(decoded, dict):

host.args = decoded

host.on_create()

return _root_json(host)

def _entry_module() -> str:

import os

return os.environ.get("PN_ENTRY_MODULE") or "app.main"

def _root_json(host: ScreenHost) -> str:

tag = getattr(host.root_native_view, "tag", None)

return codec.dumps({"root": None if tag is None else int(tag)})

def _reset_for_tests() -> None:

global _flush_pending

_HOSTS.clear()

_SCHEDULED.clear()

_flush_pending = False

pythonnative/src/pythonnative/hosts/native.py at main · pythonnative/pythonnative · GitHub

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