Fix polygon fill and opacity interaction.

[manthey]

When using a constant opacity but a non-constant fill, the fill would appear to not be honored.

[manthey]

Paste this code into the editor tutorial to see the problem in master and the fix in this branch:

var map = geo.map({
  node: '#map',
  center: {
    x: -88.0,
    y: 29
  },
  zoom: 4
});
map.createLayer('osm');
var layer = map.createLayer('feature', {
  features: ['polygon']
});
var polygons = layer.createFeature('polygon', {selectionAPI: true});
$.getJSON('../../data/land_polygons.json').done(function (data) {
  polygons
    .position(function (d) {
      return {x: d[0], y: d[1]};
    })
    .data(data)
    .style({
      uniformPolygon: true,
      fill: function (d, i) { return i!=125; },  // Cuba
      fillOpacity: 0.5,
      fillColor: function (d, idx, poly, polyidx) {
        return poly.hover ? 'blue' : 'yellow';
      },
      stroke: function (poly, polyidx) {
        return poly.hover;
      },
      strokeWidth: 1,
      strokeColor: {r: 0, g: 0, b: 0}
    })
    .geoOn(geo.event.feature.mouseover, function (evt) {
      if (!evt.data.hover) {
        evt.data.hover = true;
        this.modified();
        this.draw();
      }
    })
    .geoOn(geo.event.feature.mouseout, function (evt) {
      if (evt.data.hover) {
        evt.data.hover = false;
        this.modified();
        this.draw();
      }
    })
    .draw();
});

[aashish24]

@matthewma7 this should fix your use-case I believe. Perhaps you want to go back to changing fill and not opacity since that would optimize the code I think.