Implement basic pager using TerminalMenus

[MichaelHatherly]

This is just a quick initial draft of a terminal pager built with TerminalMenus that can be used to display objects that might take up more than a screen's worth of space vertically. See linked demo video for an example usage. If there's interest in having something like this in base then I'll put some docs, tests, etc in.

Somewhat related: #6921, #36460, #34226

[fingolfin]

Nice! How hard would it be to implement a few more conveniences, in particular hotkeys for ...

• scrolling a full/half page back/forward (usual hotkeys: space, shift-space, page up/down, ...);
• jump to start/end;
• search forward/backwards.

[MichaelHatherly]

scrolling a full/half page back/forward (usual hotkeys: space, shift-space, page up/down, ...);

PageUp and PageDown keys are already provided for free by AbstractMenu.

jump to start/end;

Same for these, Home and End keys also already just work.

search forward/backwards.

I was also wondering whether it would be worth implementing this as well. Probably slightly more tricky to implement (as in not already provided 🤣).

[fingolfin]

Nice!

For me the most important really would be space and shift-space (can't easily type pageup/down without leaving the homerow on my keyboard.

[MichaelHatherly]

space and shift-space (can't easily type pageup/down without leaving the homerow on my keyboard.

I think those should probably be a separate PR/discussion since they're generic to scrolling any kind of menu. I'm also not sure how to capture shift-space either to be honest.

[timholy]

Looks great. Just a couple of comments. Tests would be nice!

[timholy]

Since this is a new menu type, do you need to support the legacy interface? There wouldn't be any callers of it out in the wild, and no one using Julia 1.5 or earlier will be able to use the pager. So I think you can cleanly target the new API.

In case you're unfamiliar, see #35915.

[MichaelHatherly]

Thanks for the review @timholy, I'll address the suggestions once I next get some spare time.

[fingolfin]

I think those should probably be a separate PR/discussion since they're generic to scrolling any kind of menu.

Actually, for a menu, I'd expect space to toggle the currently "selected" item; so I am not sure this is separate? Anyway, of course things can be added later! I just think that it might be useful to have a look at the less help screen and implement as many of those as one can with reasonable effort; the more of these there are, the more people will likely be happy. But again, of course this can be done later, and also by others!

I'm also not sure how to capture shift-space either to be honest.

Indeed, that seems to be a problem. But actually less also doesn't support it (web browsers do, though). Nothing to worry about, anyway :-).

[MichaelHatherly]

Thanks for updating this @vtjnash, I'm just going to add some tests to it now before it gets merged.

[StefanKarpinski]

This is cool but a bit buggy, at least under iTerm2. I'm sure it will get sorted out if we start using it though 😁

[carstenbauer]

For reference, there is a related discussion on discourse revolving around the new package TerminalPager.jl (which also supports horizontal scrolling etc. However, it has dependencies like Crayons.jl

[carstenbauer]

Eventually, I think it would be cool and useful to have a pager option in our help REPL mode (?)!