Adding linear gradient
add a color gradient with bgcolormid/bgcolorend and fgcolormid/fgcolorend parameter that correspond to the transitional color and gradient end color.
example of set :
Doesn't really work with varying data-angleOffset and data-angleArc for me.
I didn't test data-angleArc or data-angleOffset but here is a preview of what the foreground gradient looks like in case someone stumbles upon this..
I had to set the width and height of the knob equally (square).
P.S. I don't know much about canvas but I noticed that the arc was divided into 2 parts, start-mid and mid-end. Is this because the linear gradient actually strokes the full canvas and not the path alone?
If my memories are good (it was 2 years ago from now) data-angleArc or data-angleOffset don't work.
Yeah I need too use 2 canvas because normaly, linear gradient only take one direction (top, left, right or bottom) so it doesn't a circle gradient:

works like a charm!! thanks @ekanSSS