switch between hsplit and vsplit paging (request for feedback)

[ivanov]

So I hacked this together, and as long as the qtconsole was started in either hsplit or vsplit modes, you can switch between them using a new "Pager" submenu.

I wanted to get feedback if I should continue by trying to make it possible to switch to the default inside paging mode as well. It looks like it'll be a little bit involved, but doable, if it's worth having.

Otherwise, I can scale this PR back to just be hsplit and vsplit switching

[takluyver]

I think being able to change between them without a command line flag is useful, but I'm not sure that ever more menu items is the right UI for it. Should we think about some sort of configuration dialog for things like this?

[ivanov]

A configuration dialog makes sense when we have many more options -
such as if we want to expose all of the configuration system with
knobs and dials. The thing I like about menus is that they are
discoverable. You can quickly explore all of them just with one click
on any of the menu items, and then moving your mouse around to look
through all of them.

Menus are more a more lightweight UI. With the current setup, you
click on the menu, move it to the selection, and click hsplit or
vsplit (or move on once you've checked out the options if you're just
going through checking what's in all of the menus) - that's one or two
clicks. With a configuration dialog it would be click on the menu,
click on the dialog, click on hsplit or vsplit, click to confirm your
selection - four clicks (it's still four clicks if you saw the dialog
and decided not to change hsplit/vsplit, it's a click to cancel, and
the click again to get back to the menu).

I'm not wed to this menu UI, but I think it's already better than what
we previously had.

[takluyver]

Of course - but there's an enormous wealth of features and options, and it would be completely overwhelming to have them all in the menu. Is this particular setting important enough to warrant a slot? It strikes me as the sort of rarely-changed option that could happily live in a settings dialog.

[fperez]

The nasty complexity with a config dialog is that ultimately we'll wand that to be persisted (any decent GUI program that has a settings dialog will save your choices). But some of those options are already in our python config files. Having GUI-controlled options on top of human-editable-file ones is tricky and unpleasant to deal with.

This is a bullet we'll need to bite at some point, though I'm not sure now we have the bandwidth for it...

[fperez]

Since there's some disagreement here, I'm marking it as 0.14 material.

[bfroehle]

I agree that it should be possible to switch between the different paging options in the gui. At this point I think a menu bar option would be more appropriate because folks don't necessarily expect that to live between instances (vs. a configuration window which generally seems more permanent).

As for the actual code to switch between the different options, I agree that it won't be too hard to implement.

[bfroehle]

What more is required before this can be merged? The ability to change between all paging styles on the fly?

Can that be done quickly?

[Carreau]

Well, this is still an improvement, at least because it allows the switch.

I vote for merging as is. We can still refine the UI later.

[Carreau]

merging in 24h if nobody object.