215 lines
6.8 KiB
Python
215 lines
6.8 KiB
Python
"""
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Layout dimensions are used to give the minimum, maximum and preferred
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dimensions for containers and controls.
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"""
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from typing import Any, Callable, List, Optional, Union
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__all__ = [
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"Dimension",
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"D",
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"sum_layout_dimensions",
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"max_layout_dimensions",
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"AnyDimension",
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"to_dimension",
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"is_dimension",
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]
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class Dimension:
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"""
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Specified dimension (width/height) of a user control or window.
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The layout engine tries to honor the preferred size. If that is not
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possible, because the terminal is larger or smaller, it tries to keep in
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between min and max.
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:param min: Minimum size.
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:param max: Maximum size.
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:param weight: For a VSplit/HSplit, the actual size will be determined
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by taking the proportion of weights from all the children.
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E.g. When there are two children, one width a weight of 1,
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and the other with a weight of 2. The second will always be
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twice as big as the first, if the min/max values allow it.
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:param preferred: Preferred size.
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"""
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def __init__(
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self,
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min: Optional[int] = None,
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max: Optional[int] = None,
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weight: Optional[int] = None,
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preferred: Optional[int] = None,
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):
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if weight is not None:
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assert weight >= 0 # Also cannot be a float.
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assert min is None or min >= 0
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assert max is None or max >= 0
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assert preferred is None or preferred >= 0
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self.min_specified = min is not None
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self.max_specified = max is not None
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self.preferred_specified = preferred is not None
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self.weight_specified = weight is not None
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if min is None:
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min = 0 # Smallest possible value.
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if max is None: # 0-values are allowed, so use "is None"
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max = 1000 ** 10 # Something huge.
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if preferred is None:
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preferred = min
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if weight is None:
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weight = 1
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self.min = min
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self.max = max
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self.preferred = preferred
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self.weight = weight
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# Don't allow situations where max < min. (This would be a bug.)
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if max < min:
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raise ValueError("Invalid Dimension: max < min.")
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# Make sure that the 'preferred' size is always in the min..max range.
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if self.preferred < self.min:
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self.preferred = self.min
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if self.preferred > self.max:
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self.preferred = self.max
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@classmethod
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def exact(cls, amount: int) -> "Dimension":
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"""
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Return a :class:`.Dimension` with an exact size. (min, max and
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preferred set to ``amount``).
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"""
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return cls(min=amount, max=amount, preferred=amount)
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@classmethod
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def zero(cls) -> "Dimension":
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"""
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Create a dimension that represents a zero size. (Used for 'invisible'
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controls.)
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"""
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return cls.exact(amount=0)
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def is_zero(self) -> bool:
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" True if this `Dimension` represents a zero size. "
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return self.preferred == 0 or self.max == 0
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def __repr__(self) -> str:
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fields = []
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if self.min_specified:
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fields.append("min=%r" % self.min)
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if self.max_specified:
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fields.append("max=%r" % self.max)
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if self.preferred_specified:
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fields.append("preferred=%r" % self.preferred)
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if self.weight_specified:
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fields.append("weight=%r" % self.weight)
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return "Dimension(%s)" % ", ".join(fields)
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def sum_layout_dimensions(dimensions: List[Dimension]) -> Dimension:
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"""
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Sum a list of :class:`.Dimension` instances.
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"""
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min = sum(d.min for d in dimensions)
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max = sum(d.max for d in dimensions)
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preferred = sum(d.preferred for d in dimensions)
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return Dimension(min=min, max=max, preferred=preferred)
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def max_layout_dimensions(dimensions: List[Dimension]) -> Dimension:
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"""
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Take the maximum of a list of :class:`.Dimension` instances.
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Used when we have a HSplit/VSplit, and we want to get the best width/height.)
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"""
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if not len(dimensions):
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return Dimension.zero()
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# If all dimensions are size zero. Return zero.
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# (This is important for HSplit/VSplit, to report the right values to their
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# parent when all children are invisible.)
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if all(d.is_zero() for d in dimensions):
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return dimensions[0]
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# Ignore empty dimensions. (They should not reduce the size of others.)
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dimensions = [d for d in dimensions if not d.is_zero()]
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if dimensions:
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# Take the highest minimum dimension.
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min_ = max(d.min for d in dimensions)
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# For the maximum, we would prefer not to go larger than then smallest
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# 'max' value, unless other dimensions have a bigger preferred value.
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# This seems to work best:
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# - We don't want that a widget with a small height in a VSplit would
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# shrink other widgets in the split.
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# If it doesn't work well enough, then it's up to the UI designer to
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# explicitly pass dimensions.
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max_ = min(d.max for d in dimensions)
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max_ = max(max_, max(d.preferred for d in dimensions))
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# Make sure that min>=max. In some scenarios, when certain min..max
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# ranges don't have any overlap, we can end up in such an impossible
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# situation. In that case, give priority to the max value.
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# E.g. taking (1..5) and (8..9) would return (8..5). Instead take (8..8).
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if min_ > max_:
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max_ = min_
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preferred = max(d.preferred for d in dimensions)
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return Dimension(min=min_, max=max_, preferred=preferred)
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else:
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return Dimension()
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# Anything that can be converted to a dimension.
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AnyDimension = Union[
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None, # None is a valid dimension that will fit anything.
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int,
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Dimension,
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# Callable[[], 'AnyDimension'] # Recursive definition not supported by mypy.
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Callable[[], Any],
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]
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def to_dimension(value: AnyDimension) -> Dimension:
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"""
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Turn the given object into a `Dimension` object.
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"""
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if value is None:
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return Dimension()
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if isinstance(value, int):
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return Dimension.exact(value)
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if isinstance(value, Dimension):
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return value
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if callable(value):
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return to_dimension(value())
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raise ValueError("Not an integer or Dimension object.")
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def is_dimension(value: object) -> bool:
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"""
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Test whether the given value could be a valid dimension.
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(For usage in an assertion. It's not guaranteed in case of a callable.)
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"""
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if value is None:
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return True
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if callable(value):
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return True # Assume it's a callable that doesn't take arguments.
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if isinstance(value, (int, Dimension)):
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return True
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return False
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# Common alias.
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D = Dimension
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# For backward-compatibility.
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LayoutDimension = Dimension
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