How do you create "aura" effect from the mouse pointer?

Question

If you open google chrome and open multiple tabs, you see the effect by hovering over a background tab. The pointer will have an "aura" effect which follows it around.

To clarify, I'm NOT asking how to make the entire tab glow a lighter color, I'm asking how to give the pointer the effect within some specified radius of it.

Answer 1

The key part is to get the mouse coordinates, then to place a radial gradient with those coordinates.

var originalBG = $(".nav a").css("background-color");

$('.nav li:not(".active") a').mousemove(function(e) {
    x = e.pageX - this.offsetLeft;
    y = e.pageY - this.offsetTop;
    xy = x + " " + y;
    bgWebKit = "-webkit-gradient(radial, " + xy + ", 0, " + xy + ", 100, from(rgba(255,255,255,0.8)), to(rgba(255,255,255,0.0))), " + originalBG;
    bgMoz = "-moz-radial-gradient(" + x + "px " + y + "px 45deg, circle, " + lightColor + " 0%, " + originalBG + " " + gradientSize + "px)";

    $(this)
        .css({background: bgWebKit})
        .css({background: bgMoz});
    }).mouseleave(function() {
    $(this).css({
        background: originalBG
    });
});

Something like that will do the job.

Check this demo from the illustrious Chris Coyier: http://css-tricks.com/examples/MovingHighlight/

Answer 2

some ideas --

1. use javascript to place an absolutely positioned semitransparent png under the cursor position
2. create a .cur file with your own cursor and some semi-transparent glow under it and hope the browser can render it
3. replace the entire cursor with javascript