Problem

When using a slider there it is not easy to select a precise value when using the mouse. You can do this with slider.set_val but this is not always convenient.

Proposed Solution

Use widgets.TextBox to display the slider readout. Then hook it up so that a user can enter values into the textbox and on submit the slider value will change.

To do this fully properly I think two additional things would need to happen:

1. Implement numeric only TextBox
2. if user clicks off of TextBox after typing then return the textbox to the current value of the slider.

Additional context and prior art

Inspired by examples here: https://www.smashingmagazine.com/2017/07/designing-perfect-slider/