You may have seen JavaScript sliders before:
http://dev.jquery.com/view/tags/ui/1.5b2/demos/ui.slider.html
What I\'m envisioning is a circular slider. It would c
define a center point c current mouse point at m
in your mouse drag event handler, you'd have
var dx = m.x-c.x;
var dy = m.y-c.y;
var scale = radius/Math.sqrt(dx*dx+dy*dy);
slider.x = dx*scale + c.x;
slider.y = dy*scale + c.y;
radius would be some preset value of the slider,
I have written a jQuery plugin which supports full/half circle sliders.
Demo Page & Documentation
Check the jQuery roundSlider plugin from here http://roundsliderui.com/. This is what you want exactly.
This roundslider having the similar options like the jQuery ui slider. It support default, min-range and range slider type. Not only the round slider it also supports various circle shapes such as quarter, half and pie circle shapes.
For more details check the demos and documentation page.
Please check the demo from jsFiddle.
Related answers: https://stackoverflow.com/a/31367164/1845801 and https://stackoverflow.com/a/31369265/1845801
Screenshots:
How about this: http://www.thewebmasterservice.com/dev-blog/curved-rounded-or-circular-sliders-javascript-jquery-ui
Some explanations and a demo.