Expert mode pie/marking selection has strong analogues to modern iPad OS's mystery meat gestures for navigating the home screen. (App switcher, dashboard pull down, control panel pull down)
Except that the pie menu can pop up as soon as you stop moving, revealing available menu items and their directions.
That is what I mean by "self revealing": When it pops up, the menu shows you what options you have. But you can use it with a swift gesture and it doesn't pop up at all, or you can start out with a swift gesture in the direction you want, then stop and wait for the menu to pop up to confirm you've selected the right item, then click to select it.
Also the menu can display the selected item label next to the cursor like a tooltip while you're gesturing ahead, before it's popped up the entire menu, to feed back the selected item even before popping up the menu.
The best case is when the menu can apply a preview of the currently selected item (which can include using the distance as a parameter, like setting the size of something by "pulling out"), so you just release the button when you see what you want, without ever having to see the menu itself if you move continuously, but at any time you can stop moving and see the menu.
Not all implementations of pie menus support all these features, but I've been implementing and writing about them for decades, they're not patented, and anyone who wants is free to implement them.
You really ought to try them out yourself, since just architectural armchair astronaut speculating about how a hypothetical user interface you've never actually used might work, without actually implementing it, and using it a lot, and measuring its speed and error rates, and iteratively refining it, and putting in front of users and asking them for feedback, and shipping and supporting it in real world products and open source projects, isn't really useful and doesn't provide much insight.
That is what I mean by "self revealing": When it pops up, the menu shows you what options you have. But you can use it with a swift gesture and it doesn't pop up at all, or you can start out with a swift gesture in the direction you want, then stop and wait for the menu to pop up to confirm you've selected the right item, then click to select it.
Also the menu can display the selected item label next to the cursor like a tooltip while you're gesturing ahead, before it's popped up the entire menu, to feed back the selected item even before popping up the menu.
The best case is when the menu can apply a preview of the currently selected item (which can include using the distance as a parameter, like setting the size of something by "pulling out"), so you just release the button when you see what you want, without ever having to see the menu itself if you move continuously, but at any time you can stop moving and see the menu.
Not all implementations of pie menus support all these features, but I've been implementing and writing about them for decades, they're not patented, and anyone who wants is free to implement them.
You really ought to try them out yourself, since just architectural armchair astronaut speculating about how a hypothetical user interface you've never actually used might work, without actually implementing it, and using it a lot, and measuring its speed and error rates, and iteratively refining it, and putting in front of users and asking them for feedback, and shipping and supporting it in real world products and open source projects, isn't really useful and doesn't provide much insight.