from __future__ import print_function

"""
Explanation: Index - Back - Next
Widget Events
Special events
End of explanation
"""


from IPython.html import widgets
print(widgets.Button.on_click.__doc__)

"""
Explanation: The Button is not used to represent a data type.  Instead the button widget is used to handle mouse clicks.  The on_click method of the Button can be used to register function to be called when the button is clicked.  The doc string of the on_click can be seen below.
End of explanation
"""


from IPython.display import display
button = widgets.Button(description="Click Me!")
display(button)

def on_button_clicked(b):
    print("Button clicked.")

button.on_click(on_button_clicked)

"""
Explanation: Example
Since button clicks are stateless, they are transmitted from the front-end to the back-end using custom messages.  By using the on_click method, a button that prints a message when it has been clicked is shown below.
End of explanation
"""


text = widgets.Text()
display(text)

def handle_submit(sender):
    print(text.value)

text.on_submit(handle_submit)

"""
Explanation: on_sumbit
The Text also has a special on_submit event.  The on_submit event fires when the user hits return.
End of explanation
"""


print(widgets.Widget.on_trait_change.__doc__)

"""
Explanation: Traitlet events
Widget properties are IPython traitlets and traitlets are eventful.  To handle  changes, the on_trait_change method of the widget can be used to register a callback.  The doc string for on_trait_change can be seen below.
End of explanation
"""


int_range = widgets.IntSlider()
display(int_range)

def on_value_change(name, value):
    print(value)

int_range.on_trait_change(on_value_change, 'value')

"""
Explanation: Signatures
Mentioned in the doc string, the callback registered can have 4 possible signatures:

callback()
callback(trait_name)
callback(trait_name, new_value)
callback(trait_name, old_value, new_value)

Using this method, an example of how to output an IntSlider's value as it is changed can be seen below.
End of explanation
"""


from IPython.utils import traitlets

caption = widgets.Latex(value = 'The values of slider1, slider2 and slider3 are synchronized')
sliders1, slider2, slider3 = widgets.IntSlider(description='Slider 1'),\
                             widgets.IntSlider(description='Slider 2'),\
                             widgets.IntSlider(description='Slider 3')
l = traitlets.link((sliders1, 'value'), (slider2, 'value'), (slider3, 'value'))
display(caption, sliders1, slider2, slider3)

caption = widgets.Latex(value = 'Changes in source values are reflected in target1 and target2')
source, target1, target2 = widgets.IntSlider(description='Source'),\
                           widgets.IntSlider(description='Target 1'),\
                           widgets.IntSlider(description='Target 2')
traitlets.dlink((source, 'value'), (target1, 'value'), (target2, 'value'))
display(caption, source, target1, target2)

"""
Explanation: Linking Widgets
Often, you may want to simply link widget attributes together. Synchronization of attributes can be done in a simpler way than by using bare traitlets events. 
The first method is to use the link and directional_link functions from the traitlets module. 
Linking traitlets attributes from the server side
End of explanation
"""


# l.unlink()

"""
Explanation: Function traitlets.link returns a Link object. The link can be broken by calling the unlink method.
End of explanation
"""


caption = widgets.Latex(value = 'The values of range1, range2 and range3 are synchronized')
range1, range2, range3 = widgets.IntSlider(description='Range 1'),\
                         widgets.IntSlider(description='Range 2'),\
                         widgets.IntSlider(description='Range 3')
l = widgets.jslink((range1, 'value'), (range2, 'value'), (range3, 'value'))
display(caption, range1, range2, range3)

caption = widgets.Latex(value = 'Changes in source_range values are reflected in target_range1 and target_range2')
source_range, target_range1, target_range2 = widgets.IntSlider(description='Source range'),\
                                             widgets.IntSlider(description='Target range 1'),\
                                             widgets.IntSlider(description='Target range 2')
widgets.jsdlink((source_range, 'value'), (target_range1, 'value'), (target_range2, 'value'))
display(caption, source_range, target_range1, target_range2)

"""
Explanation: Linking widgets attributes from the client side
When synchronizing traitlets attributes, you may experience a lag because of the latency dues to the rountrip to the server side. You can also directly link widgets attributes, either in a unidirectional or a bidirectional fashion using the link widgets.
End of explanation
"""


# l.unlink()

"""
Explanation: Function widgets.jslink returns a Link widget. The link can be broken by calling the unlink method.
End of explanation
"""


