arc message could mean "arc fill" instead of "show arc"
BUGS:
fix jump on click in circular mode, it actually acts now as jump on click and we need to make it not jump for non jump on click mode.
More Ideas
there could be a mode where the knob displays the number, like in VCV. This could be displayed if clicked with the 'alt' key. Also like in VCV we could also allow to type in a number value, so it's like a built in number box - this could happen by hitting the alt key and then double clicking. This is also like having a built in number box with the same background color and foreground color for the text (with a black outline). The number box should be to the right of the center circle and be focused on top. Typing when the object is active just updates this value, hitting enter updates it.
add resize handle
add outline to background arc
force tick value at least init value (a small discrete area)
document forget
BUGS:
More Ideas