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112 lines
3.6 KiB
Python
112 lines
3.6 KiB
Python
# Copyright (c) Jupyter Development Team.
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# Distributed under the terms of the Modified BSD License.
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"""Link and DirectionalLink classes.
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Propagate changes between widgets on the javascript side.
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"""
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from .widget import Widget, register, widget_serialization
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from .widget_core import CoreWidget
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from traitlets import Unicode, Tuple, Instance, TraitError
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class WidgetTraitTuple(Tuple):
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"""Traitlet for validating a single (Widget, 'trait_name') pair"""
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info_text = "A (Widget, 'trait_name') pair"
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def __init__(self, **kwargs):
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super().__init__(Instance(Widget), Unicode(), **kwargs)
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if "default_value" not in kwargs and not kwargs.get("allow_none", False):
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# This is to keep consistent behavior for spec generation between traitlets 4 and 5
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# Having a default empty container is explicitly not allowed in traitlets 5 when
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# there are traits specified (as the default value will be invalid), but we do it
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# anyway as there is no empty "default" that makes sense.
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self.default_args = ()
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def validate_elements(self, obj, value):
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value = super().validate_elements(obj, value)
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widget, trait_name = value
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trait = widget.traits().get(trait_name)
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trait_repr = "{}.{}".format(widget.__class__.__name__, trait_name)
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# Can't raise TraitError because the parent will swallow the message
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# and throw it away in a new, less informative TraitError
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if trait is None:
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raise TypeError("No such trait: %s" % trait_repr)
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elif not trait.metadata.get('sync'):
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raise TypeError("%s cannot be synced" % trait_repr)
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return value
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@register
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class Link(CoreWidget):
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"""Link Widget
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source: a (Widget, 'trait_name') tuple for the source trait
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target: a (Widget, 'trait_name') tuple that should be updated
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"""
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_model_name = Unicode('LinkModel').tag(sync=True)
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target = WidgetTraitTuple(help="The target (widget, 'trait_name') pair").tag(sync=True, **widget_serialization)
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source = WidgetTraitTuple(help="The source (widget, 'trait_name') pair").tag(sync=True, **widget_serialization)
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def __init__(self, source, target, **kwargs):
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kwargs['source'] = source
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kwargs['target'] = target
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super().__init__(**kwargs)
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# for compatibility with traitlet links
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def unlink(self):
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self.close()
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def jslink(attr1, attr2):
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"""Link two widget attributes on the frontend so they remain in sync.
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The link is created in the front-end and does not rely on a roundtrip
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to the backend.
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Parameters
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----------
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source : a (Widget, 'trait_name') tuple for the first trait
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target : a (Widget, 'trait_name') tuple for the second trait
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Examples
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--------
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>>> c = link((widget1, 'value'), (widget2, 'value'))
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"""
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return Link(attr1, attr2)
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@register
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class DirectionalLink(Link):
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"""A directional link
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source: a (Widget, 'trait_name') tuple for the source trait
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target: a (Widget, 'trait_name') tuple that should be updated
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when the source trait changes.
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"""
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_model_name = Unicode('DirectionalLinkModel').tag(sync=True)
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def jsdlink(source, target):
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"""Link a source widget attribute with a target widget attribute.
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The link is created in the front-end and does not rely on a roundtrip
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to the backend.
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Parameters
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----------
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source : a (Widget, 'trait_name') tuple for the source trait
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target : a (Widget, 'trait_name') tuple for the target trait
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Examples
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--------
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>>> c = dlink((src_widget, 'value'), (tgt_widget, 'value'))
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"""
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return DirectionalLink(source, target)
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