setBadge.js

setBadge = function (text) {
  if (process.platform === "darwin") {
    app.dock.setBadge("" + text);
  } else if (process.platform === "win32") {
    var win = remote.getCurrentWindow();

    if (text === "") {
      win.setOverlayIcon(null, "");
      return;
    }

    // Create badge
    var canvas = document.createElement("canvas");
    canvas.height = 140;
    canvas.width = 140;
    var ctx = canvas.getContext("2d");
    ctx.fillStyle = "red";
    ctx.beginPath();
    ctx.ellipse(70, 70, 70, 70, 0, 0, 2 * Math.PI);
    ctx.fill();
    ctx.textAlign = "center";
    ctx.fillStyle = "white";

    if (text.length > 2) {
      ctx.font = "75px sans-serif";
      ctx.fillText("" + text, 70, 98);
    } else if (text.length > 1) {
      ctx.font = "100px sans-serif";
      ctx.fillText("" + text, 70, 105);
    } else {
      ctx.font = "125px sans-serif";
      ctx.fillText("" + text, 70, 112);
    }

    var badgeDataURL = canvas.toDataURL();
    var img = NativeImage.createFromDataUrl(badgeDataURL);

    win.setOverlayIcon(img, text);
  }
};