Selecting Countries on a Canvas Globe

Uses a second canvas with different fill colors for each country to detect which country is highlighted.

forked from syntagmatic's block: Selecting Countries on a Canvas Globe

<!DOCTYPE html>
<meta charset="utf-8">
<style>

body {
  background: #fcfcfa;
}

</style>
<body>
<script src="https://d3js.org/d3.v3.min.js"></script>
<script src="https://d3js.org/topojson.v1.min.js"></script>
<script>

var width = 960,
    height = 600,
    speed = 1e-2,
    start = Date.now();

var sphere = {type: "Sphere"};

var projection = d3.geo.orthographic()
    .scale(height / 2.1)
    .translate([width / 2, height / 2])
    .clipAngle(90)
    .precision(.5);

var graticule = d3.geo.graticule();

var canvas = d3.select("body").append("canvas")
    .attr("width", width)
    .attr("height", height);

var context = canvas.node().getContext("2d");

var path = d3.geo.path()
    .projection(projection)
    .context(context);

var hiddenCanvas = d3.select("body").append("canvas")
    .attr("width", width)
    .attr("height", height);

var hiddenContext = hiddenCanvas.node().getContext("2d");

var hiddenProjection = d3.geo.equirectangular()
    .translate([width / 2, height / 2])
    .scale(width / 7);

var hiddenPath = d3.geo.path()
    .projection(hiddenProjection)
    .context(hiddenContext);

d3.json("world-110m.json", function(error, topo) {
  var selected = false;

var land = topojson.feature(topo, topo.objects.land),
      borders = topojson.feature(topo, topo.objects.countries),
      grid = graticule();

var fillToCountry = {};
  var i = borders.features.length;
  while (i--) {
    hiddenContext.beginPath();
    hiddenPath(borders.features[i]);
    hiddenContext.fillStyle = "rgb(" + i + ",0,0)";
    hiddenContext.fill();
  }

d3.timer(function() {
    select.call(context);
    
    projection.rotate([speed * (Date.now() - start), -15]);

context.clearRect(0, 0, width, height);

context.beginPath();
    path(sphere);
    context.lineWidth = 3;
    context.strokeStyle = "#000";
    context.stroke();

context.beginPath();
    path(sphere);
    context.fillStyle = "#fff";
    context.fill();

context.beginPath();
    path(land);
    context.fillStyle = "#222";
    context.fill();

context.beginPath();
    path(borders);
    context.lineWidth = .5;
    context.strokeStyle = "#fff";
    context.stroke();

context.beginPath();
    path(grid);
    context.lineWidth = .5;
    context.strokeStyle = "rgba(119,119,119,.5)";
    context.stroke();

if (selected !== false) {
      context.beginPath();
      path(borders.features[selected]);
      context.fillStyle = "#0ad";
      context.fill();
    }
  });

canvas
//     .on("mousemove", select)
    .on("touchstart", select);

d3.select(self.frameElement).style("height", (2*height) + "px");

</script>

Modified http://d3js.org/d3.v3.min.js to a secure url

Modified http://d3js.org/topojson.v1.min.js to a secure url

https://d3js.org/d3.v3.min.js

https://d3js.org/topojson.v1.min.js