Expose the Collapse widget

[jasongrout]

The accordion widget is basically a vbox of Collapse widgets, with the added logic that only one collapse widget can be open at a time. We should also expose the single Collapse widget, so it's easy for people to have a single collapse widget, or multiple open, etc.

Basically, we need to expose the Collapse widget defined in https://github.com/jupyter-widgets/ipywidgets/blob/master/packages/controls/src/phosphor/accordion.ts, perhaps with a new widget, like a new box widget in https://github.com/jupyter-widgets/ipywidgets/blob/master/packages/controls/src/widget_box.ts.

[jasongrout]

As a workaround (and maybe good enough?), an accordion widget with one child is essentially this collapse widget.

[vishma]

Hi,
I need to make all the accordions to be collapsed when the notebook starts. Is it possible from the notebook itself?

[whiteboxbatteries]

@jasongrout +1

As a workaround (and maybe good enough?), an accordion widget with one child is essentially this collapse widget.

@vishma
Yes, you can do it like this.

import ipywidgets as widgets

slider = widgets.SelectionSlider(
    options=['How', 'do', 'you', 'like', 'it?'],
    value='How',
    disabled=False,
    continuous_update=False,
    orientation='horizontal',
    readout=True
)

left = widgets.Accordion([slider])
left.set_title(0, 'Left')

right = widgets.Accordion([slider])
right.set_title(0, 'Right')

top = widgets.Accordion([slider])
top.set_title(0, 'Top')

center = widgets.Accordion([slider])
center.set_title(0, 'Center')

bottom = widgets.Accordion([slider])
bottom.set_title(0, 'Bottom')

app = widgets.HBox([
    left,
    widgets.VBox([
        top,
        center,
        bottom,
    ]),
    right,
])

app

# Collapse all
left.selected_index = None
right.selected_index = None
top.selected_index = None
center.selected_index = None
bottom.selected_index = None

# Expand all
left.selected_index = 0
right.selected_index = 0
top.selected_index = 0
center.selected_index = 0
bottom.selected_index = 0

Accordion_collapse.zip

[ankostis]

Forgive my ignorance, but is this issue for having (optionally) many widgets visible at the same time in an Accordion?

[jasongrout]

Essentially, yes.

[ankostis]

Thank you. You may include this user-facing functionality in the title, if you wish (and keep the current title for the PR).

[marscher]

@jasongrout
Having the possibility of multiple opened/selected indices would be awesome! It would allow the user to focus on sub-elements of the GUI. I wonder if this change would be ported to major version 7.

would it be possible to change the allowed traits for selected_index for Accordion to a list/tuple? And just delegate this change to frontend. Should be backwards compatible and allow for multiple selection, am I wrong?