New feature in 2.-3: Split Window

Hey VisiDaters, check it out!

In the bleeding-edge develop branch, VisiData can now show TWO sheets at the same time:

The ability to see two sheets on the screen at the same time has been on the v2.0 roadmap for a long time.
I've even caught myself lamenting a few times that, if we had split-screen, the design for some feature would be straightforward.
Deep down I also think it might open up a whole new dimension of user interface, where movement on the active window instantly updates the inactive window.

So I've given it a few tries already; it's not that technically challenging to do, but the interface for it remained elusive
After talking with @tsibley and @anjakefala and sitting with it for long enough, last week I finally put together a working prototype.
It's serviceable but not perfect, so hopefully it can serve as a launching pad for discussion about the finer points of split-screen workflow.

options.disp_splitwin_pct

The main option is disp_splitwin_pct, which specifies the height of the top window as a percent of the full screen height.
Currently, a positive number puts the top sheet in the top window, whereas a negative number keeps the same layout, but puts the top sheet in the bottom window.

Commands

• Shift+Z splits the screen in half so that the second-most-recently accessed sheet is visible

• g Shift+Z sets the active sheet to the whole screen (effectively disable splitwin)

• z Shift+Z specifies options.disp_splitwin_pct exactly

• Ctrl+^ (which already jumps to the previous sheet) naturally swaps the layout without changing the active panel

• TAB swaps the active panel, without changing the layout. (note that this means the replay-advance command is currently disabled; I'm still not sure how all this is going to work.)

Its full implementation could solve several issues (choosing jointype/aggregators, popup command help) and would make a two panel orthodox file manager all but inevitable.

Theme options

• color_top_status is applied to the "top window status bar" -- which is in the middle of the screen. Set by default to underline to divide the screen visually.
• color_inactive_status is applied to the status bar of the inactive window.
• color_active_status is applied to the status bar of the active window.

Limitations

• only 2 sheets at the same time; from one to two sheets is a quantum leap by itself and a reasonable constraint (at least to start with).
• only top/bottom split is supported; this implementation could be extended to include options.disp_splitwin which might specify e.g. top or left to indicate the panel of the top sheet.
• it can't be specified as a CLI option (no disp_ or color_ option can).
• canvas/graph sheets aren't reset and may have errors that require Ctrl+L to resize properly.

This is still quite experimental so if you use this feature, let me know how you feel about it! Post an issue on Github, share a tweet , or stop by for a chat in freenode #visidata.

[written by Saul Pwanson 2020-02-02]