waveform-playlist-nartj/lib/render/FadeCanvasHook.js

Multiple track web audio editor and player with waveform preview

"use strict";

var _interopRequireDefault = require("@babel/runtime/helpers/interopRequireDefault");

Object.defineProperty(exports, "__esModule", {
  value: true
});
exports["default"] = void 0;

var _classCallCheck2 = _interopRequireDefault(require("@babel/runtime/helpers/classCallCheck"));

var _createClass2 = _interopRequireDefault(require("@babel/runtime/helpers/createClass"));

var _fadeMaker = require("fade-maker");

var _fadeCurves = require("fade-curves");

/*
* virtual-dom hook for drawing the fade curve to the canvas element.
*/
var FadeCanvasHook = /*#__PURE__*/function () {
  function FadeCanvasHook(type, shape, duration, samplesPerPixel) {
    (0, _classCallCheck2["default"])(this, FadeCanvasHook);
    this.type = type;
    this.shape = shape;
    this.duration = duration;
    this.samplesPerPixel = samplesPerPixel;
  }

  (0, _createClass2["default"])(FadeCanvasHook, [{
    key: "hook",
    value: function hook(canvas, prop, prev) {
      // node is up to date.
      if (prev !== undefined && prev.shape === this.shape && prev.type === this.type && prev.duration === this.duration && prev.samplesPerPixel === this.samplesPerPixel) {
        return;
      }

      var ctx = canvas.getContext('2d');
      var width = canvas.width;
      var height = canvas.height;
      var curve = FadeCanvasHook.createCurve(this.shape, this.type, width);
      var len = curve.length;
      var y = height - curve[0] * height;
      ctx.strokeStyle = 'black';
      ctx.beginPath();
      ctx.moveTo(0, y);

      for (var i = 1; i < len; i += 1) {
        y = height - curve[i] * height;
        ctx.lineTo(i, y);
      }

      ctx.stroke();
    }
  }], [{
    key: "createCurve",
    value: function createCurve(shape, type, width) {
      var reflection;
      var curve;

      switch (type) {
        case _fadeMaker.FADEIN:
          {
            reflection = 1;
            break;
          }

        case _fadeMaker.FADEOUT:
          {
            reflection = -1;
            break;
          }

        default:
          {
            throw new Error('Unsupported fade type.');
          }
      }

      switch (shape) {
        case _fadeMaker.SCURVE:
          {
            curve = (0, _fadeCurves.sCurve)(width, reflection);
            break;
          }

        case _fadeMaker.LINEAR:
          {
            curve = (0, _fadeCurves.linear)(width, reflection);
            break;
          }

        case _fadeMaker.EXPONENTIAL:
          {
            curve = (0, _fadeCurves.exponential)(width, reflection);
            break;
          }

        case _fadeMaker.LOGARITHMIC:
          {
            curve = (0, _fadeCurves.logarithmic)(width, 10, reflection);
            break;
          }

        default:
          {
            throw new Error('Unsupported fade shape');
          }
      }

      return curve;
    }
  }]);
  return FadeCanvasHook;
}();

var _default = FadeCanvasHook;
exports["default"] = _default;