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"""ButtonWidget class.
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Represents a button in the frontend using a widget. Allows user to listen for
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click events on the button and trigger backend code when the clicks are fired.
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"""
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#-----------------------------------------------------------------------------
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# Copyright (c) 2013, the IPython Development Team.
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#
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# Distributed under the terms of the Modified BSD License.
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#
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# The full license is in the file COPYING.txt, distributed with this software.
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#-----------------------------------------------------------------------------
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#-----------------------------------------------------------------------------
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# Imports
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#-----------------------------------------------------------------------------
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import inspect
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import types
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from .widget import DOMWidget
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from IPython.utils.traitlets import Unicode, Bool, Int
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#-----------------------------------------------------------------------------
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# Classes
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#-----------------------------------------------------------------------------
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class ButtonWidget(DOMWidget):
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target_name = Unicode('ButtonWidgetModel')
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view_name = Unicode('ButtonView')
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# Keys
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keys = ['description', 'disabled'] + DOMWidget.keys
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description = Unicode('', help="Description of the button (label).")
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disabled = Bool(False, help="Enable or disable user changes.")
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def __init__(self, **kwargs):
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super(ButtonWidget, self).__init__(**kwargs)
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self._click_handlers = []
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self.on_msg(self._handle_button_msg)
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def on_click(self, callback, remove=False):
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"""Register a callback to execute when the button is clicked. The
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callback can either accept no parameters or one sender parameter:
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- callback()
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- callback(sender)
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If the callback has a sender parameter, the ButtonWidget instance that
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called the callback will be passed into the method as the sender.
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Parameters
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----------
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remove : bool (optional)
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Set to true to remove the callback from the list of callbacks."""
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if remove:
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self._click_handlers.remove(callback)
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elif not callback in self._click_handlers:
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self._click_handlers.append(callback)
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def _handle_button_msg(self, content):
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"""Handle a msg from the front-end
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Parameters
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----------
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content: dict
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Content of the msg."""
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if 'event' in content and content['event'] == 'click':
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self._handle_click()
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def _handle_click(self):
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"""Handles when the button has been clicked. Fires on_click
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callbacks when appropriate."""
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for handler in self._click_handlers:
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if callable(handler):
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argspec = inspect.getargspec(handler)
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nargs = len(argspec[0])
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# Bound methods have an additional 'self' argument
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if isinstance(handler, types.MethodType):
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nargs -= 1
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# Call the callback
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if nargs == 0:
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handler()
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elif nargs == 1:
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handler(self)
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else:
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raise TypeError('ButtonWidget click callback must ' \
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'accept 0 or 1 arguments.')
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