# Source code for enaml.widgets.button_group

    #------------------------------------------------------------------------------
    # Copyright (c) 2019-2024, Nucleic Development Team.
    #
    # Distributed under the terms of the Modified BSD License.
    #
    # The full license is in the file LICENSE, distributed with this software.
    #------------------------------------------------------------------------------
    from atom.api import Bool, ForwardTyped, Typed

    from enaml.core.declarative import d_, observe

    from .toolkit_object import ToolkitObject, ProxyToolkitObject

    class ProxyButtonGroup(ProxyToolkitObject):
        """ The abstract defintion of a proxy ButtonGroup object.

        """
        #: A reference to the ButtonGroup declaration.
        declaration = ForwardTyped(lambda: ButtonGroup)

        def set_exclusive(self, exclusive):
            raise NotImplementedError

        def add_button(self, button):
            raise NotImplementedError

        def remove_button(self, button):
            raise NotImplementedError

    class ButtonGroup(ToolkitObject):
        """ A way to declare a group of buttons.

        This allows to group buttons even though they belong to different
        container. Note that if a button belongs to a ButtonGroup the rules
        about buttons sharing a container being in the same group do not apply.d2

        """
        #: Set of members belonging to the group.
        #: This value should be considered read-only for users.
        group_members = Typed(set, ())

        #: Can only a single button in the group be checked at a time.
        exclusive = d_(Bool(True))

        #: A reference to the ProxyButtonGroup object.
        proxy = Typed(ProxyButtonGroup)

        @observe("exclusive")
        def _update_proxy(self, change):
            super(ButtonGroup, self)._update_proxy(change)