pythonnative/src/pythonnative/layout.py at refs/heads/main · pythonnative/pythonnative · GitHub

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"""Yoga 3.2.1 layout for headless tests and the Python preview host.

Mobile hosts run this same pinned core beside their native widgets. This

module contains style translation and ownership, not a second flex algorithm.

"""

from __future__ import annotations

import ctypes as C

import math

import weakref

from typing import Any, Callable

LAYOUT_STYLE_KEYS = frozenset(

{

"width",

"height",

"min_width",

"max_width",

"min_height",

"max_height",

"flex",

"flex_grow",

"flex_shrink",

"flex_basis",

"flex_wrap",

"align_self",

"align_content",

"position",

"top",

"right",

"bottom",

"left",

"start",

"end",

"margin",

"margin_top",

"margin_bottom",

"margin_left",

"margin_right",

"margin_start",

"margin_end",

"margin_horizontal",

"margin_vertical",

"padding",

"padding_top",

"padding_bottom",

"padding_left",

"padding_right",

"padding_start",

"padding_end",

"padding_horizontal",

"padding_vertical",

"border_width",

"border_top_width",

"border_right_width",

"border_bottom_width",

"border_left_width",

"flex_direction",

"justify_content",

"align_items",

"gap",

"row_gap",

"column_gap",

"aspect_ratio",

"direction",

"display",

}

)

"""Style keys that affect layout (and are consumed by the layout engine)."""

_lib: Any = None

_nodes: weakref.WeakValueDictionary[int, LayoutNode] = weakref.WeakValueDictionary()

_Measure = C.CFUNCTYPE(

None, C.c_void_p, C.c_float, C.c_int, C.c_float, C.c_int, C.POINTER(C.c_float), C.POINTER(C.c_float)

)

@_Measure

def _measure(ptr: int, width: float, wm: int, height: float, hm: int, outw: Any, outh: Any) -> None:

node = _nodes.get(ptr)

try:

assert node is not None and node.measure is not None

w, h = node.measure(width if wm else math.inf, height if hm else math.inf)

outw[0], outh[0] = max(0, w), max(0, h)

except BaseException as exc:

if node is not None:

node._error = exc

outw[0] = outh[0] = 0

def _api() -> Any:

global _lib

if _lib is not None:

return _lib

from . import _yoga # type: ignore[attr-defined]

lib = C.CDLL(_yoga.__file__)

signatures: dict[str, Any] = {

"YGNodeNew": (C.c_void_p, []),

"YGNodeFree": (None, [C.c_void_p]),

"YGNodeGetOwner": (C.c_void_p, [C.c_void_p]),

"YGNodeRemoveChild": (None, [C.c_void_p, C.c_void_p]),

"YGNodeRemoveAllChildren": (None, [C.c_void_p]),

"YGNodeInsertChild": (None, [C.c_void_p, C.c_void_p, C.c_size_t]),

"YGNodeCopyStyle": (None, [C.c_void_p, C.c_void_p]),

"YGNodeMarkDirty": (None, [C.c_void_p]),

"YGNodeCalculateLayout": (None, [C.c_void_p, C.c_float, C.c_float, C.c_int]),

"pn_yoga_callback": (None, [_Measure]),

"pn_yoga_measure": (None, [C.c_void_p, C.c_int]),

}

for axis in ("Left", "Top", "Width", "Height"):

signatures["YGNodeLayoutGet" + axis] = (C.c_float, [C.c_void_p])

for name, (result, args) in signatures.items():

fn = getattr(lib, name)

fn.restype, fn.argtypes = result, args

lib.pn_yoga_callback(_measure)

_lib = lib

return lib

# Enum order follows Yoga's public C ABI in the pinned vendored headers.

ENUMS = {

"direction": ("Direction", ["inherit", "ltr", "rtl"]),

"flex_direction": ("FlexDirection", ["column", "column_reverse", "row", "row_reverse"]),

"justify_content": (

"JustifyContent",

["flex_start", "center", "flex_end", "space_between", "space_around", "space_evenly"],

"align_items": (

"AlignItems",

[

"auto",

"flex_start",

"center",

"flex_end",

"stretch",

"baseline",

"space_between",

"space_around",

"space_evenly",

"align_self": (

"AlignSelf",

[

"auto",

"flex_start",

"center",

"flex_end",

"stretch",

"baseline",

"space_between",

"space_around",

"space_evenly",

"align_content": (

"AlignContent",

[

"auto",

"flex_start",

"center",

"flex_end",

"stretch",

"baseline",

"space_between",

"space_around",

"space_evenly",

"position": ("PositionType", ["static", "relative", "absolute"]),

"flex_wrap": ("FlexWrap", ["nowrap", "wrap", "wrap_reverse"]),

"display": ("Display", ["flex", "none", "contents"]),

}

EDGES = {

name: i

for i, name in enumerate(["left", "top", "right", "bottom", "start", "end", "horizontal", "vertical", "all"])

}

ALIASES = {

"start": "flex_start",

"leading": "flex_start",

"top": "flex_start",

"end": "flex_end",

"trailing": "flex_end",

"bottom": "flex_end",

"fill": "stretch",

}

def _set(ptr: int, name: str, value: Any, edge: int | None = None, *, enum: bool = False) -> None:

if value is None or isinstance(value, bool):

return

suffix = ""

args: list[Any] = [ptr]

types: list[Any] = [C.c_void_p]

if edge is not None:

args.append(edge)

types.append(C.c_int)

if value == "auto":

suffix = "Auto"

else:

if isinstance(value, str) and value.endswith("%"):

suffix, value = "Percent", float(value[:-1])

args.append(int(value) if enum else float(value))

types.append(C.c_int if enum else C.c_float)

fn = getattr(_api(), "YGNodeStyleSet" + name + suffix)

fn.restype, fn.argtypes = None, types

fn(*args)

def apply_style(ptr: int, style: dict[str, Any]) -> None:

"""Translate Pythonic style keys to Yoga's native style API."""

for key, value in style.items():

if value is None:

continue

if key in ENUMS:

name, values = ENUMS[key]

value = ALIASES.get(value, value) if key.startswith(("align_", "justify_")) else value

if value not in values:

raise ValueError(f"Invalid {key}: {value!r}")

_set(ptr, name, values.index(value), enum=True)

elif key in {

"width",

"height",

"min_width",

"min_height",

"max_width",

"max_height",

"flex",

"flex_grow",

"flex_shrink",

"flex_basis",

"aspect_ratio",

_set(ptr, "".join(part.title() for part in key.split("_")), value)

elif key in {"gap", "row_gap", "column_gap"}:

_set(ptr, "Gap", value, {"column_gap": 0, "row_gap": 1}.get(key, 2))

elif key in EDGES and key not in {"all", "horizontal", "vertical"}:

_set(ptr, "Position", value, EDGES[key])

elif key.startswith(("padding", "margin")):

group, _, edge = key.partition("_")

if isinstance(value, dict):

for side, amount in value.items():

_set(ptr, group.title(), amount, EDGES[side])

else:

_set(ptr, group.title(), value, EDGES[edge or "all"])

elif key.startswith("border_") and key.endswith("width"):

_set(ptr, "Border", value, EDGES[key[7:-6] or "all"])

class LayoutNode:

"""An owned Yoga node, with Python measurement for headless backends."""

def __init__(

self,

style: dict[str, Any] | None = None,

children: list[LayoutNode] | None = None,

measure: Callable[[float, float], tuple[float, float]] | None = None,

user_data: Any = None,

) -> None:

self.style = dict(style or {})

self.children = list(children or [])

self.measure = measure

self.user_data = user_data

self.x = self.y = self.width = self.height = 0.0

self.dirty = True

self._pn_scroll_axis: str | None = None

self._ptr: int | None = None

self._last_style: Any = None

self._last_children: tuple[int, ...] = ()

self._error: BaseException | None = None

def _sync(self) -> int:

lib = _api()

if self._ptr is None:

self._ptr = lib.YGNodeNew()

_nodes[self._ptr] = self

weakref.finalize(self, lib.YGNodeFree, self._ptr)

ptr = self._ptr

style = dict(self.style)

if self._pn_scroll_axis:

style.setdefault("flex_shrink", 1)

if style != self._last_style:

fresh = lib.YGNodeNew()

apply_style(fresh, style)

if self._pn_scroll_axis:

_set(fresh, "Overflow", 1, enum=True)

lib.YGNodeCopyStyle(ptr, fresh)

lib.YGNodeFree(fresh)

self._last_style = style

measured = self.measure is not None and not self.children

lib.pn_yoga_measure(ptr, measured)

if measured and self.dirty:

lib.YGNodeMarkDirty(ptr)

children = tuple(child._sync() for child in self.children)

if children != self._last_children:

lib.YGNodeRemoveAllChildren(ptr)

for i, child in enumerate(children):

owner = lib.YGNodeGetOwner(child)

if owner:

lib.YGNodeRemoveChild(owner, child)

previous = _nodes.get(owner)

if previous is not None:

previous._last_children = ()

lib.YGNodeInsertChild(ptr, child, i)

self._last_children = children

return ptr

def _read(self) -> None:

lib = _api()

self.x = lib.YGNodeLayoutGetLeft(self._ptr)

self.y = lib.YGNodeLayoutGetTop(self._ptr)

self.width = lib.YGNodeLayoutGetWidth(self._ptr)

self.height = lib.YGNodeLayoutGetHeight(self._ptr)

self.dirty = False

if self._error is not None:

error, self._error = self._error, None

raise error

for child in self.children:

child._read()

def calculate_layout(node: LayoutNode, width: float, height: float) -> None:

"""Calculate a tree's layout with the pinned Yoga core."""

ptr = node._sync()

_api().YGNodeCalculateLayout(

ptr, width if math.isfinite(width) else math.nan, height if math.isfinite(height) else math.nan, 1

)

node._read()

def extract_layout_style(props: dict[str, Any]) -> dict[str, Any]:

"""Select properties owned by layout."""

return {key: value for key, value in props.items() if key in LAYOUT_STYLE_KEYS}

pythonnative/src/pythonnative/layout.py at refs/heads/main · pythonnative/pythonnative · GitHub

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