Persist choice of view

[brprice]

I'm splitting this out from hackworthltd/vonnegut#545 as it will need a larger discussion that I would like to keep self contained.

In the current state of hackworthltd/vonnegut#545 (though this potentially will change to include whatever conclusions we draw in this issue) we have lost all persistance of projection selection (tree/text and split/grouped). Is this what we want? If not, then what would be better?

Perhaps it is also worth widening the discussion to include persistance of any "what the user sees" state:

• projection: tree/text and split/grouped (currently this is entirely forgotten on a reload)
• what definition and node is selected (this is weird, I think it remembers something like "where was the last action taken")
• are we in evaluation mode and what state (forgotten, always goes to "normal" mode)
• where is the canvas scrolled/zoomed to (forgotten, always default zoom and show the remembered selected definition starting at the top-left).

However, personally the important issue is the projection one, as that is currently a regression.

I think we have three options

• entirely ephemeral (current state of hackworthltd/vonnegut#545)
• save it in the backend's DB (current state of main, when we have per-node projection selections) (would need to add another field to our state (as not using each node's metadata), it would affect any user connecting to the session, perhaps from a different browser)
• save it locally to a browser (we don't currently do anything like this) (localstorage/cookie/whatever the newfangled thing is) (would not follow the session around)

Thoughts on which of these we should do?

[dhess]

I think that persisting the (tree vs text) and (grouped vs split) is a lot less important when there's a global toggle, so I'll be less bothered about this than I used to be once hackworthltd/vonnegut#545 is implemented.

Selection is still worth persisting, however.

I haven't thought much yet about (eval vs edit) and scroll/zoom.

[brprice]

Note that there was some discussion of this in issue hackworthltd/vonnegut#313