Consider/brainstorm about a "Unique" type modifier for inputs about magicgui HOT 1 OPEN

from typing import NewType

from magicgui import magicgui, register_type

import napari
import napari.layers
from napari.utils._magicgui import find_viewer_ancestor


def get_unique_shapes(gui):
    if not gui.parent or (viewer := find_viewer_ancestor(gui)) is None:
        return []

    # get all available layer options
    all_shapes = (
        layer
        for layer in viewer.layers
        if isinstance(layer, napari.layers.Shapes)
    )

    # get values claimed by other widgets
    # this is an ugly hack to figure out the other magicgui widgets in the same widget
    # it uses both the Qt and magicgui APIs... look into a better way
    other_values = {
        w._magic_widget.value
        for w in gui.parent.parent().children()
        if hasattr(w, '_magic_widget')
        and w._magic_widget is not gui
    }

    # return all options that are not claimed by other widgets
    return [layer for layer in all_shapes if layer not in other_values]


UniqueShapes = NewType('UniqueShapes', napari.layers.Shapes)
register_type(UniqueShapes, choices=get_unique_shapes)


@magicgui
def widget(layer1: UniqueShapes, layer2: UniqueShapes):
    ...


viewer = napari.Viewer()
viewer.window.add_dock_widget(widget)
viewer.layers.events.inserted.connect(widget.reset_choices)
viewer.layers.events.removed.connect(widget.reset_choices)
# need something like this too, but it's causing recursion errors at the moment
widget.layer1.changed.connect(widget.layer2.reset_choices)
widget.layer2.changed.connect(widget.layer1.reset_choices)
napari.run()