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"""Rendering engine parameter handling."""
import typing
from . import base
__all__ = ['ENGINES', 'verify_engine', 'Engine']
ENGINES = {'dot', # https://www.graphviz.org/pdf/dot.1.pdf
'neato',
'twopi',
'circo',
'fdp',
'sfdp',
'patchwork',
'osage'}
DEFAULT_ENGINE = 'dot'
REQUIRED = True
def verify_engine(engine: str, *, required: bool = REQUIRED) -> None:
if engine is None:
if required:
raise ValueError('missing engine')
elif engine.lower() not in ENGINES:
raise ValueError(f'unknown engine: {engine!r}'
f' (must be one of {sorted(ENGINES)})')
class Engine(base.ParameterBase):
"""Rendering engine parameter with ``'dot''`` default."""
_engine = DEFAULT_ENGINE
_verify_engine = staticmethod(verify_engine)
def __init__(self, *, engine: typing.Optional[str] = None, **kwargs) -> None:
super().__init__(**kwargs)
if engine is not None:
self.engine = engine
def _copy_kwargs(self, **kwargs):
"""Return the kwargs to create a copy of the instance."""
engine = self._getattr_from_dict('_engine')
if engine is not None:
kwargs['engine'] = engine
return super()._copy_kwargs(**kwargs)
@property
def engine(self) -> str:
"""The layout engine used for rendering
(``'dot'``, ``'neato'``, ...)."""
return self._engine
@engine.setter
def engine(self, engine: str) -> None:
engine = engine.lower()
self._verify_engine(engine)
self._engine = engine
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