#------------------------------------------------------------------------------
#
#  Copyright (c) 2005, Enthought, Inc.
#  All rights reserved.
#
#  This software is provided without warranty under the terms of the BSD
#  license included in enthought/LICENSE.txt and may be redistributed only
#  under the conditions described in the aforementioned license.  The license
#  is also available online at http://www.enthought.com/licenses/BSD.txt
#
#  Thanks for using Enthought open source!
#
#  Author: David C. Morrill
#  Date:   02/04/2005
#
#------------------------------------------------------------------------------

""" Defines the help interface for displaying the help associated with a
    Traits UI View object.
"""

#-------------------------------------------------------------------------
#  Imports:
#-------------------------------------------------------------------------

from __future__ import absolute_import

from .toolkit import toolkit

#-------------------------------------------------------------------------
#  Default handler for showing the help associated with a view:
#-------------------------------------------------------------------------


def default_show_help(info, control):
    """ Default handler for showing the help associated with a view.
    """
    toolkit().show_help(info.ui, control)

# The default handler for showing help
show_help = default_show_help

#-------------------------------------------------------------------------
#  Allows an application to change the default show help handler:
#-------------------------------------------------------------------------


def on_help_call(new_show_help=None):
    """ Sets a new global help provider function.

    The help provider function must have a signature of
    *function*(*info*, *control*), where *info* is a UIInfo object for the
    current view, and *control* is the UI control that invokes the function
    (typically, a **Help** button). It is provided in case the help provider
    needs to position the help window relative to the **Help** button.

    To retrieve the current help provider function, call this function with
    no arguments.

    Parameters
    ----------
    new_show_help : function
        The function to set as the new global help provider

    Returns
    -------
    previous : callable
        The previous global help provider function
    """
    global show_help

    result = show_help
    if new_show_help is not None:
        show_help = new_show_help
    return result