WIP: Add option for displaying figures below cells that create them.

[danielballan]

Description

It is often useful to place the figure(s) in a tabbed viewer in one cell, rather than "plopping" them into the output area below the currently-running cell. However, there is still a use case for this mode of placing figure "in line" with the work. (Not to be confused with %matplotlib inline which kills interactive pan and zoom.) See #95.

See screenshot below.

TO DO

• Add option for placing figures below running cell.
• Embed figures so that they can be viewed if the notebook is opened later. The action item here is probably just to wait for ipympl. They are working on this. Perhaps, while we wait, we could implement %matplotlib inline-like behavior as a stop-gap. That is, when cell execution completes, close the figure and replace it with an embedded PNG.
• Tests

Motivation and Context

Closes #95. See that issue for motivation and context.

How Has This Been Tested?

Needs tests

Screenshots:

[mrakitin]

Thanks for the update!