# Source code for enaml.widgets.flow_area

    #------------------------------------------------------------------------------
    # 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, set_default

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

    from .frame import Frame, ProxyFrame, Border
    from .flow_item import FlowItem

    class ProxyFlowArea(ProxyFrame):
        """ The abstract definition of a proxy FlowArea object.

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

        def set_direction(self, direction):
            raise NotImplementedError

        def set_align(self, align):
            raise NotImplementedError

        def set_horizontal_spacing(self, spacing):
            raise NotImplementedError

        def set_vertical_spacing(self, spacing):
            raise NotImplementedError

        def set_margins(self, margins):
            raise NotImplementedError

    class FlowArea(Frame):
        """ A widget which lays out its children in flowing manner, wrapping
        around at the end of the available space.

        """
        #: The flow direction of the layout.
        direction = d_(Enum(
            'left_to_right', 'right_to_left', 'top_to_bottom', 'bottom_to_top'
        ))

        #: The alignment of a line of items within the layout.
        align = d_(Enum('leading', 'trailing', 'center', 'justify'))

        #: The amount of horizontal space to place between items.
        horizontal_spacing = d_(Range(low=0, value=10))

        #: The amount of vertical space to place between items.
        vertical_spacing = d_(Range(low=0, value=10))

        #: The margins to use around the outside of the flow area.
        margins = d_(Coerced(Box, (10, 10, 10, 10)))

        #: A FlowArea expands freely in width and height by default.
        hug_width = set_default('ignore')
        hug_height = set_default('ignore')

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

        def flow_items(self):
            """ Get the flow item children defined on this area.

            """
            return [c for c in self.children if isinstance(c, FlowItem)]

        #--------------------------------------------------------------------------
        # Default Handlers
        #--------------------------------------------------------------------------
        def _default_border(self):
            """ Get the default border for the flow area.

            The default value matches the default for Qt's QScrollArea.

            """
            return Border(style='styled_panel', line_style='sunken')

        #--------------------------------------------------------------------------
        # Observers
        #--------------------------------------------------------------------------
        @observe('direction', 'align', 'horizontal_spacing', 'vertical_spacing',
            'margins')
        def _update_proxy(self, change):
            """ An observer which sends state change to the proxy.

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