> Chorded input is rare these days - the movement of software to touchscreen devices argues against it.

Multitouch gestures are a form of chorded input, no? And one we’ve greatly under-explored, IMHO.

Probably mostly because people tend to be using either touchscreens that are mobile, or touch pads that are rather small, and so you can only fit one hand’s worth of fingers on the digitizer, and one hand’s fingers can’t (without training) do too many different things at the same time. So mostly we come up with gestures that move some or all the fingers of the hand in concert.

But if you had a digitizer surface that had room for two hands, you could do a lot with that. Moving a finger of one hand in a circle while the other swipes toward/away from it; “unfolding” something by interlacing eight fingers in a line and sliding them to opposite ends of the digitizer; etc.

(I think Apple could easily introduce these for people who own both an iPad and a Mac. It seems their Sidecar support is already moving toward this, as it sends native touchpad input to apps—acting, in est, as a large Bluetooth multitouch digitizer—rather than just doing HLE emulation + transmission of the particular gestures possible in macOS currently.)

And sure, that all sounds a bit mystery-meat at first—no clear affordances. But it’s not any more mystery-meat than voice navigation is. Voice navigation is a “grammar” on top of regular spoken-language words; you expect the user to learn language at some point. Similarly, a “vocabulary” of multitouch gestures could all be taught to the user at some point—even practiced in an OS-shipped program resembling a typing tutor. (Back when mice first became prominent, OSes shipped with mouse-requiring games specifically to serve as mousing tutors!) Then you just have to teach the users visual/symbolic mnemonics for these gestures; and then you can use those symbols as accelerator indicators in your regular menus and label text.

(Oh, and don’t get me started on what’s possible with a depth-of-field sensing camera, ala Windows Hello. I’m constantly surprised that competition isn’t already heating up to be the first OS to natively support American Sign Language watched-gesture input.)