from param import Parameter, _is_number
[docs]class Align(Parameter):
"""
A Parameter type to validate alignment options. Supports 'auto', 'start',
'center', 'end' or a two-tuple of these values corresponding
to the (vertical, horizontal) alignment.
"""
def __init__(self, default='start', **params):
super().__init__(default=default, **params)
self._validate(default)
def _validate(self, val):
self._validate_value(val, self.allow_None)
def _validate_value(self, val, allow_None, valid=('auto', 'start', 'center', 'end')):
if ((val is None and allow_None) or val in valid or
(isinstance(val, tuple) and len(val) == 2 and all(v in valid for v in val))):
return
raise ValueError(
f"Align parameter {self.name!r} must be one of 'start', "
"'center', 'end' or a two-tuple specifying the (vertical, "
f"horizontal) values for the alignment, not {val!r}."
)
[docs]class Aspect(Parameter):
"""
A Parameter type to validate aspect ratios. Supports numeric values
and auto.
"""
def __init__(self, default=None, allow_None=True, **params):
super().__init__(default=default, allow_None=allow_None, **params)
self._validate(default)
def _validate(self, val):
self._validate_value(val, self.allow_None)
def _validate_value(self, val, allow_None):
if (val is None and allow_None) or val == 'auto' or _is_number(val):
return
raise ValueError(
f"Aspect parameter {self.name!r} only takes numeric values "
"or the literal 'auto'."
)
[docs]class Margin(Parameter):
"""
A Parameter type to validate margins. Following CSS conventions
the parameter supports numeric values and tuples of length 2 and 4
corresponding to (vertical, horizontal) margins and (top, right,
bottom, left) margins.
"""
def __init__(self, default=None, allow_None=True, **params):
super().__init__(default=default, allow_None=allow_None, **params)
self._validate(default)
def _validate_value(self, val, allow_None):
if val is None and allow_None:
return
if not isinstance(val, (tuple, int)):
raise ValueError(
f'Margin parameter {self.name!r} only takes integer and '
f'tuple values, not values of not {type(val)!r}.'
)
def _validate_length(self, val):
if not isinstance(val, tuple) or len(val) in (2, 4):
return
raise ValueError(
f'Margin parameter {self.name!r} only takes integer and '
f'tuple values of length 2 (vertical, horizontal) or 4 '
'(top, right, bottom, left).'
)
def _validate(self, val):
self._validate_value(val, self.allow_None)
self._validate_length(val)
[docs] @classmethod
def serialize(cls, value):
if value is None:
return 'null'
return list(value) if isinstance(value, tuple) else value
[docs] @classmethod
def deserialize(cls, value):
if value == 'null':
return None
return tuple(value) if isinstance(value, list) else value
