title: Handling Mouse Events in Overlapping SVG Layers
body: <p>I am building a map visualization with d3.js. I am drawing filled polygons for both the US states and counties. The SVG layer for counties is under the layer for states. The states are filled, but fill-opacity is set to 0; the fill is required (I think) to catch click events.</p>
  
  <p>I want to catch click events at the state level, but I want to catch mouseover events at the county level. </p>
  
  <p>However, the mouseover event is captured by the states and not passed through to the counties.</p>
  
  <p>Is there any way to pass the event down a layer or otherwise trigger the mouseover event on the county?</p>