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27 lines
1.1 KiB
27 lines
1.1 KiB
"""
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Filters decide whether something is active or not (they decide about a boolean
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state). This is used to enable/disable features, like key bindings, parts of
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the layout and other stuff. For instance, we could have a `HasSearch` filter
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attached to some part of the layout, in order to show that part of the user
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interface only while the user is searching.
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Filters are made to avoid having to attach callbacks to all event in order to
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propagate state. However, they are lazy, they don't automatically propagate the
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state of what they are observing. Only when a filter is called (it's actually a
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callable), it will calculate its value. So, its not really reactive
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programming, but it's made to fit for this framework.
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Filters can be chained using ``&`` and ``|`` operations, and inverted using the
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``~`` operator, for instance::
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filter = has_focus('default') & ~ has_selection
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"""
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from __future__ import unicode_literals
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from .base import Filter, Never, Always, Condition
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from .app import *
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from .utils import to_filter, is_true
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# For backwards-compatibility. Keep this import.
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from .cli import *
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