Accurately detect mouseover event for a div with rounded corners

Question

I am trying to detect a mouseover event on a circle. I define the circle div like this:

.circle {
  width: 80px;
  height: 80px;
  -moz-border-radius: 40px;
  -         


        

Answer 1

Just ignore the mouseover event if the mouse's position is too far away. It's really simple. Take the center point of the div, and calculate the distance to the mouse pointer (distance formula = sqrt((x2 - x1)^2 + (y2 - y1)^2)) and if it's larger than the radius of the circle (half the width of the div), it's not in the circle yet.