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#------------------------------------------------------------------------------
# Copyright (c) 2013-2025, Nucleic Development Team.
#
# Distributed under the terms of the Modified BSD License.
#
# The full license is in the file LICENSE, distributed with this software.
#------------------------------------------------------------------------------
from atom.api import Atom, Range
import kiwisolver as kiwi
from .strength_member import StrengthMember
class Spacer(Atom):
""" A base class for creating constraint spacers.
"""
#: The amount of space to apply for this spacer, in pixels.
size = Range(low=0)
#: The optional strength to apply to the spacer constraints.
strength = StrengthMember()
def __init__(self, size, strength=None):
""" Initialize a Spacer.
Parameters
----------
size : int
The basic size of the spacer, in pixels >= 0.
strength : strength-like, optional
A strength to apply to the generated spacer constraints.
"""
self.size = size
self.strength = strength
def __or__(self, strength):
""" Override the strength of the generated constraints.
Parameters
----------
strength : strength-like
The strength to apply to the generated constraints.
Returns
-------
result : self
The current spacer instance.
"""
self.strength = strength
return self
def when(self, switch):
""" A simple switch method to toggle a spacer.
Parameters
----------
switch : bool
Whether or not the spacer should be active.
Returns
-------
result : self or None
The current instance if the switch is True, None otherwise.
"""
return self if switch else None
def create_constraints(self, first, second):
""" Generate the spacer constraints for the given anchors.
Parameters
----------
first : LinearSymbolic
A linear symbolic representing the first constraint anchor.
second : LinearSymbolic
A linear symbolic representing the second constraint anchor.
Returns
-------
result : list
The list of constraints for the spacer.
"""
cns = self.constraints(first, second)
strength = self.strength
if strength is not None:
cns = [cn | strength for cn in cns]
return cns
def constraints(self, first, second):
""" Generate the spacer constraints for the given anchors.
This abstract method which must be implemented by subclasses.
Parameters
----------
first : LinearSymbolic
A linear symbolic representing the first constraint anchor.
second : LinearSymbolic
A linear symbolic representing the second constraint anchor.
Returns
-------
result : list
The list of constraints for the spacer.
"""
raise NotImplementedError
class EqSpacer(Spacer):
""" A spacer which represents a fixed amount of space.
"""
def constraints(self, first, second):
""" A constraint of the form: (second - first) == size
"""
return [(second - first) == self.size]
class LeSpacer(Spacer):
""" A spacer which represents a flexible space with a maximum value.
"""
def constraints(self, first, second):
""" A constraint of the form: (second - first) <= size
A second constraint is applied to prevent negative space:
(second - first) >= 0
"""
return [(second - first) <= self.size, (second - first) >= 0]
class GeSpacer(Spacer):
""" A spacer which represents a flexible space with a minimum value.
"""
def constraints(self, first, second):
""" A constraint of the form: (second - first) >= size
"""
return [(second - first) >= self.size]
class FlexSpacer(Spacer):
""" A spacer with a hard minimum and a preference for that minimum.
"""
#: The strength for the minimum space constraint.
min_strength = StrengthMember(kiwi.strength.required)
#: The strength for the equality space constraint.
eq_strength = StrengthMember(kiwi.strength.medium * 1.25)
def __init__(self, size, min_strength=None, eq_strength=None):
""" Initialize a FlexSpacer.
Parameters
----------
size : int
The basic size of the spacer, in pixels >= 0.
min_strength : strength-like, optional
The strength to apply to the minimum spacer size. The
default is kiwi.strength.required.
eq_strength : strength-like, optional
The strength to apply to preferred spacer size. The
default is 1.25 * kiwi.strength.medium.
"""
self.size = size
if min_strength is not None:
self.min_strength = min_strength
if eq_strength is not None:
self.eq_strength = eq_strength
def constraints(self, first, second):
""" Generate the constraints for the spacer.
"""
min_cn = ((second - first) >= self.size) | self.min_strength
eq_cn = ((second - first) == self.size) | self.eq_strength
return [min_cn, eq_cn]
class LayoutSpacer(Spacer):
""" A factory-like Spacer with convenient symbolic methods.
"""
def __call__(self, *args, **kwargs):
""" Create a new LayoutSpacer from the given arguments.
"""
return type(self)(*args, **kwargs)
def __or__(self, strength):
""" Create a new LayoutSpacer with the given strength.
"""
return type(self)(self.size, strength)
def __eq__(self, size):
""" Create an EqSpacer with the given size.
"""
return EqSpacer(size, self.strength)
def __le__(self, size):
""" Create an LeSpacer with the given size.
"""
return LeSpacer(size, self.strength)
def __ge__(self, size):
""" Create a GeSpacer withe the given size.
"""
return GeSpacer(size, self.strength)
def flex(self, **kwargs):
""" Create a FlexSpacer with the given configuration.
"""
return FlexSpacer(self.size, **kwargs)
def constraints(self, first, second):
""" Create the constraints for >= spacer constraint.
"""
return GeSpacer(self.size, self.strength).constraints(first, second)
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