Knobs effect in QML

[LordAlexander]

Hi all,

I'm trying to implement a custom widget in QML to obtain an effect such as http://anthonyterrien.com/knob/ [× Angle offset element in the page].
I tried with canvas object but if I apply a scale to the parent object of the canvas the quality of the canvas appear very ugly.
I tried with a glsl frag shader but the variable glFragCoord bind me to the screen coordinates and anyway if I apply a scale to the parent object the rendering appears ugly.

Someone can help me please???