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# All rights reserved.
#
# This software is provided without warranty under the terms of the BSD
# license included in LICENSE.txt and may be redistributed only under
# the conditions described in the aforementioned license. The license
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from traits.api import Any, Constant, Dict, Str, Type

from pyface.fields.i_field import IField
from .action import Action
from .action_event import ActionEvent


class FieldAction(Action):
    """ A widget action containing an IField

    When the value in the field is changed, the `on_perform` method is called
    with the new value as the argument.
    """

    #: This is a widget action.
    style = Constant("widget")

    #: The field to display.
    field_type = Type(IField)

    #: The default trait values for the field.
    field_defaults = Dict(Str, Any)

    def create_control(self, parent):
        """ Called when creating a "widget" style action.

        This constructs an IField-based control directly and binds changes to
        the value to the `value_updated` method.

        Parameters
        ----------
        parent : toolkit control
            The toolkit control, usually a toolbar.

        Returns
        -------
        control : toolkit control
            A toolkit control or None.
        """
        field = self.field_type(parent=parent, **self.field_defaults)
        field.create()
        field.observe(self.value_updated, "value")
        field.control._field = field
        return field.control

    def value_updated(self, event):
        """ Handle changes to the field value by calling perform.

        The event passed to `perform` has the `value` as an attribute.
        """
        value = event.new
        action_event = ActionEvent(value=value)
        self.perform(action_event)

    def perform(self, event):
        """ Performs the action.

        This dispacthes to the on_perform method with the new value passed
        as an argument.

        Parameters
        ----------
        event : ActionEvent
            The event which triggered the action.
        """
        if self.on_perform is not None:
            self.on_perform(event.value)