# Source code for enaml.widgets.flow_item

    #------------------------------------------------------------------------------
    # Copyright (c) 2013-2025, 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 Enum, Range, Coerced, Typed, ForwardTyped

    from enaml.core.declarative import d_, observe
    from enaml.layout.geometry import Size

    from .container import Container
    from .widget import Widget, ProxyWidget

    class ProxyFlowItem(ProxyWidget):
        """ The abstract definition of a proxy FlowItem object.

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

        def set_preferred_size(self, size):
            raise NotImplementedError

        def set_align(self, align):
            raise NotImplementedError

        def set_stretch(self, stretch):
            raise NotImplementedError

        def set_ortho_stretch(self, stretch):
            raise NotImplementedError

    class FlowItem(Widget):
        """ A widget which can be used as an item in a FlowArea.

        A FlowItem is a widget which can be used as a child of a FlowArea
        widget. It can have at most a single child widget which is an
        instance of Container.

        """
        #: The preferred size of this flow item. This size will be used as
        #: the size of the item in the layout, bounded to the computed min
        #: and max size. A size of (-1, -1) indicates to use the widget's
        #: size hint as the preferred size.
        preferred_size = d_(Coerced(Size, (-1, -1)))

        #: The alignment of this item in the direction orthogonal to the
        #: layout flow.
        align = d_(Enum('leading', 'trailing', 'center'))

        #: The stretch factor for this item in the flow direction, relative
        #: to other items in the same line. The default is zero which means
        #: that the item will not expand in the direction orthogonal to the
        #: layout flow.
        stretch = d_(Range(low=0, value=0))

        #: The stretch factor for this item in the orthogonal direction
        #: relative to other items in the layout. The default is zero
        #: which means that the item will not expand in the direction
        #: orthogonal to the layout flow.
        ortho_stretch = d_(Range(low=0, value=0))

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

        def flow_widget(self):
            """ Get the flow widget defined on this flow item.

            The last Container defined on the item is the flow widget.

            """
            for child in reversed(self.children):
                if isinstance(child, Container):
                    return child

        #--------------------------------------------------------------------------
        # Observers
        #--------------------------------------------------------------------------
        @observe('preferred_size', 'align', 'stretch', 'ortho_stretch')
        def _update_proxy(self, change):
            """ An observer which sends state change to the proxy.

            """
            # The superclass handler implementation is sufficient.
            super(FlowItem, self)._update_proxy(change)