Awesome! I'm really looking forward to Simon implementing all the features of Fly-Pie across different platforms including Window, Linux and Mac desktops. Please support his great work on Ko-Fi if you can!
https://ko-fi.com/schneegans
But until such a day as Fly-Pie-like features and editors are built into every desktop and application and browser user interface toolkit, I do think Blender also requires its own specialized WYSIWYG pie menu editor that knows about Blender's command and input systems and user interface capabilities. But it should be inspired by Simon's work on Gnome-Pie, Fly-Pie, and Kando. Also drawing 3D pie menu items and animated feedback would be really cool and useful, so you can easily make pie menus of 3D Blender content, like a tree-structured clipboards or asset libraries, or live iconic previews of the effects of editing commands!
All of these ideas could be applied to Gimp too, of course, but I've found the Blender developers to be much more open to entertaining other people's ideas and contributions about user interface design than the Gimp developers, who have been historically NIH-limited and stubborn (especially about changing the name to something less offensive to the general public). At least Blender already supports pie menus well, and changed the default mouse bindings in response to user demand, and has made huge strides in usability lately. At this point I think it would be much easier to just add a great image editor to Blender, integrated with its video editor, than try to change the minds of the Gimp developers.
I love the capabilities of the current Blender pie menu editor add-on, since it supports linear menus and user interface dialogs as well (even embedding them in pie menus, to make hybrid layouts). But it doesn't support WYSIWYG editing, or on-the-fly editing of menus in place (like HyperCard) without using a dialog in another window and using a linear list or outline to represent radial layout, which is very confusing and hard to use.
The first approach I took to pie menus was to represent pie menus as containing items, and then lay the items out in a circle, starting at an initial angle (typically up), and in a particular direction (either clockwise or counter clockwise). But that has its problems, when it comes to editing, and supporting other than one item per direction.
So I've taken a different approach of pie menus containing slices, and slices containing items. So to create a pie menu, first you define how many slices you want, then you add zero or more items to each slice, by dragging and dropping them in. So the directions do not all change around when you add or remove an item, and you can leave empty slices, and you can also put multiple items in any slice.
Each slice can be configured with various layout and tracking and drawing policies.
One useful policy is a "pull-out" slice that dislays one item at once (like a font size), which changes as you pull out, switching between items by the distance. And the items can be discrete (like a linear menu of font faces) or continuous (like an exact floating point font size).
Another policy is show all the items in the slice layed out in the slice direction, like a linear menu. That lets you make a linear menu by simply using one slice that points down, and putting multiple items in it. Of course long text labels only work well in the up and down directions, but icons work nicely along the horizontal and diagonal directions, and you can display the selected text label in the menu center when its icon is selected, as feedback.
This shows several kinds of pull out pie menus, for selecting fonts and colors:
Just the Pie Menus from All the Widgets:
https://www.youtube.com/watch?v=mOLS9I_tdKE
This shows an experiment in exaggerating the increased precision of direction that you get by moving the cursor away from the menu center:
Precision Pie Demo:
https://www.youtube.com/watch?v=c0scs59va4c
>This is a demonstration of the precision
pie menu under the NeWS window system.
It's an experiment in exaggerating the
extra precision that you get with
distance as you move out further from
the menu center of a pie menu. Normally
the further you go from the center the
more control you have over the angle, but
if you want to input an exact number
like an angle you might want to get it
down to the a certain number. But you run
out of screen space before you get
enough leverage to change the number to
what you want. Now what happens here is
that when you poke out, it makes a
flexible lever that the further out you
go the more flexible it becomes, and you
have much finer control over the number.
So as I move around back in and out I'll
poke it into a different place and just
come out further to get a lot of
leverage and dial exactly the number I
want. So here's what happens when you go
around to the other side. *POP* And as you get
nearer it gets less and less flexible.
Generally you kind of eyeball it and
then get it exact like 93: well there's
93, or 273: there's 273.