igeom/app/components/circumference.js

var circunference = (function() {
  // dashed line

  var tool = {};

  var states = ["center", "radius"];

  var state = undefined;

  var coordinates = [0, 0, 0, 0];

  var points = [0, 0, 0];

  function draw() {
    if (state == undefined) {
      state = states[0];
      app.setStatus("Selecione o centro da Circunferência");
    } else if (state == states[0]) {
      var pos = app.pos();
      coordinates[0] = pos.x;
      coordinates[1] = pos.y;
      state = states[1];
      app.setStatus("Selecione o raio da Circunferência");
    } else if (state == states[1]) {
      var layer = app.currentLayer();
      var pos = app.pos();
      coordinates[2] = pos.x;
      coordinates[3] = pos.y;
      var legA = coordinates[2] - coordinates[0];
      legB = coordinates[1] - coordinates[3];
      var radius = Math.sqrt(Math.pow(legA, 2)) + Math.sqrt(Math.pow(legB, 2));
      points = [coordinates[0], coordinates[1], radius];
      var p = points.slice();
      var circle = new Konva.Circle({
        x: p[0],
        y: p[1],
        radius: p[2],
        fill: "transparent",
        stroke: "black",
        strokeWidth: 1,
        strokeScaleEnabled: false,
        draggable: true
      });

      layer.add(circle);
      app.stage.draw();

      clearState();
      app.clearSelectedTool();
      app.setStatus("");
    }
  }

  function bootstrap() {
    app.tools.push(tool);
  }

  function click(id) {
    if (state == states[0]) {
      app.clearSelectedTool();
      clearState();
      return;
    }
    app.setSelectedTool(tool);
    state = states[0];
    app.setStatus("Selecione o primeiro ponto no canvas");
  }

  function clearState() {
    state = undefined;
  }

  tool = {
    id: "circunference",
    title: "Circunferência",
    icon: "line",
    click: click,
    draw: draw,
    points: points,
    coordinates: coordinates
  };

  bootstrap();

  return {
    draw: draw,
    click: click
  };
})();