labelWidget label; interactive widgets also use it for ID generation. A ## suffix can distinguish IDs without displaying the suffix.
v_radAngle stored in radians in Float32Array[0]; the widget displays degrees and writes radians back. Pass Float32Array storage, not a JS scalar; native access uses the supplied backing memory.
True if the widget changed the supplied value; false if it remained unchanged.
Edit an angle stored in radians using a slider displayed in degrees.