from typing import TYPE_CHECKING, Generic, Iterable, Optional, TypeVar
from napari.utils.events.containers._set import EventedSet
from napari.utils.events.event import EmitterGroup
from napari.utils.translations import trans
if TYPE_CHECKING:
from pydantic.fields import ModelField
_T = TypeVar("_T")
_S = TypeVar("_S")
[docs]class Selection(EventedSet[_T]):
"""A model of selected items, with ``active`` and ``current`` item.
There can only be one ``active`` and one ``current` item, but there can be
multiple selected items. An "active" item is defined as a single selected
item (if multiple items are selected, there is no active item). The
"current" item is mostly useful for (e.g.) keyboard actions: even with
multiple items selected, you may only have one current item, and keyboard
events (like up and down) can modify that current item. It's possible to
have a current item without an active item, but an active item will always
be the current item.
An item can be the current item and selected at the same time. Qt views
will ensure that there is always a current item as keyboard navigation,
for example, requires a current item.
This pattern mimics current/selected items from Qt:
https://doc.qt.io/qt-5/model-view-programming.html#current-item-and-selected-items
Parameters
----------
data : iterable, optional
Elements to initialize the set with.
Attributes
----------
active : Any, optional
The active item, if any. An active item is the one being edited.
_current : Any, optional
The current item, if any. This is used primarily by GUI views when
handling mouse/key events.
Events
------
changed (added: Set[_T], removed: Set[_T])
Emitted when the set changes, includes item(s) that have been added
and/or removed from the set.
active (value: _T)
emitted when the current item has changed.
_current (value: _T)
emitted when the current item has changed. (Private event)
"""
def __init__(self, data: Iterable[_T] = ()) -> None:
self._active: Optional[_T] = None
self._current_ = None
self.events = EmitterGroup(source=self, _current=None, active=None)
super().__init__(data=data)
self._update_active()
def _emit_change(self, added=None, removed=None):
if added is None:
added = set()
if removed is None:
removed = set()
self._update_active()
return super()._emit_change(added=added, removed=removed)
def __repr__(self) -> str:
return f"{type(self).__name__}({self._set!r})"
def __hash__(self) -> int:
"""Make selection hashable."""
return id(self)
@property
def _current(self) -> Optional[_T]:
"""Get current item."""
return self._current_
@_current.setter
def _current(self, index: Optional[_T]):
"""Set current item."""
if index == self._current_:
return
self._current_ = index
self.events._current(value=index)
@property
def active(self) -> Optional[_T]:
"""Return the currently active item or None."""
return self._active
@active.setter
def active(self, value: Optional[_T]):
"""Set the active item.
This make `value` the only selected item, and make it current.
"""
if value == self._active:
return
self._active = value
self.clear() if value is None else self.select_only(value)
self._current = value
self.events.active(value=value)
def _update_active(self):
"""On a selection event, update the active item based on selection.
(An active item is a single selected item).
"""
if len(self) == 1:
self.active = list(self)[0]
elif self._active is not None:
self._active = None
self.events.active(value=None)
[docs] def clear(self, keep_current: bool = False) -> None:
"""Clear the selection."""
if not keep_current:
self._current = None
super().clear()
[docs] def toggle(self, obj: _T):
"""Toggle selection state of obj."""
self.symmetric_difference_update({obj})
[docs] def select_only(self, obj: _T):
"""Unselect everything but `obj`. Add to selection if not present."""
self.intersection_update({obj})
self.add(obj)
@classmethod
def __get_validators__(cls):
yield cls.validate
[docs] @classmethod
def validate(cls, v, field: 'ModelField'):
"""Pydantic validator."""
from pydantic.utils import sequence_like
if isinstance(v, dict):
data = v.get("selection", [])
current = v.get("_current", None)
elif isinstance(v, Selection):
data = v._set
current = v._current
else:
data = v
current = None
if not sequence_like(data):
raise TypeError(
trans._(
'Value is not a valid sequence: {data}',
deferred=True,
data=data,
)
)
# no type parameter was provided, just return
if not field.sub_fields:
obj = cls(data=data)
obj._current_ = current
return obj
# Selection[type] parameter was provided. Validate contents
type_field = field.sub_fields[0]
errors = []
for i, v_ in enumerate(data):
_, error = type_field.validate(v_, {}, loc=f'[{i}]')
if error:
errors.append(error)
if current is not None:
_, error = type_field.validate(current, {}, loc='current')
if error:
errors.append(error)
if errors:
from pydantic import ValidationError
raise ValidationError(errors, cls) # type: ignore
obj = cls(data=data)
obj._current_ = current
return obj
def _json_encode(self):
"""Return an object that can be used by json.dumps."""
# we don't serialize active, as it's gleaned from the selection.
return {'selection': super()._json_encode(), '_current': self._current}
class Selectable(Generic[_S]):
"""Mixin that adds a selection model to an object."""
def __init__(self, *args, **kwargs) -> None:
self._selection: Selection[_S] = Selection()
super().__init__(*args, **kwargs) # type: ignore
@property
def selection(self) -> Selection[_S]:
"""Get current selection."""
return self._selection
@selection.setter
def selection(self, new_selection: Iterable[_S]) -> None:
"""Set selection, without deleting selection model object."""
self._selection.intersection_update(new_selection)
self._selection.update(new_selection)