goog.provide('ol.has');

goog.require('goog.dom');
goog.require('goog.dom.TagName');
goog.require('ol');
goog.require('ol.dom');
goog.require('ol.webgl');


/**
 * The ratio between physical pixels and device-independent pixels
 * (dips) on the device (`window.devicePixelRatio`).
 * @const
 * @type {number}
 * @api stable
 */
ol.has.DEVICE_PIXEL_RATIO = goog.global.devicePixelRatio || 1;


/**
 * True if the browser's Canvas implementation implements {get,set}LineDash.
 * @type {boolean}
 */
ol.has.CANVAS_LINE_DASH = false;


/**
 * True if both the library and browser support Canvas.  Always `false`
 * if `ol.ENABLE_CANVAS` is set to `false` at compile time.
 * @const
 * @type {boolean}
 * @api stable
 */
ol.has.CANVAS = ol.ENABLE_CANVAS && (
    /**
     * @return {boolean} Canvas supported.
     */
    function() {
      if (!('HTMLCanvasElement' in goog.global)) {
        return false;
      }
      try {
        var context = ol.dom.createCanvasContext2D();
        if (goog.isNull(context)) {
          return false;
        } else {
          if (context.setLineDash !== undefined) {
            ol.has.CANVAS_LINE_DASH = true;
          }
          return true;
        }
      } catch (e) {
        return false;
      }
    })();


/**
 * Indicates if DeviceOrientation is supported in the user's browser.
 * @const
 * @type {boolean}
 * @api stable
 */
ol.has.DEVICE_ORIENTATION = 'DeviceOrientationEvent' in goog.global;


/**
 * True if `ol.ENABLE_DOM` is set to `true` at compile time.
 * @const
 * @type {boolean}
 */
ol.has.DOM = ol.ENABLE_DOM;


/**
 * Is HTML5 geolocation supported in the current browser?
 * @const
 * @type {boolean}
 * @api stable
 */
ol.has.GEOLOCATION = 'geolocation' in goog.global.navigator;


/**
 * True if browser supports touch events.
 * @const
 * @type {boolean}
 * @api stable
 */
ol.has.TOUCH = ol.ASSUME_TOUCH || 'ontouchstart' in goog.global;


/**
 * True if browser supports pointer events.
 * @const
 * @type {boolean}
 */
ol.has.POINTER = 'PointerEvent' in goog.global;


/**
 * True if browser supports ms pointer events (IE 10).
 * @const
 * @type {boolean}
 */
ol.has.MSPOINTER = !!(goog.global.navigator.msPointerEnabled);


/**
 * True if both OpenLayers and browser support WebGL.  Always `false`
 * if `ol.ENABLE_WEBGL` is set to `false` at compile time.
 * @const
 * @type {boolean}
 * @api stable
 */
ol.has.WEBGL;


(function() {
  if (ol.ENABLE_WEBGL) {
    var hasWebGL = false;
    var textureSize;
    var /** @type {Array.<string>} */ extensions = [];

    if ('WebGLRenderingContext' in goog.global) {
      try {
        var canvas = /** @type {HTMLCanvasElement} */
            (goog.dom.createElement(goog.dom.TagName.CANVAS));
        var gl = ol.webgl.getContext(canvas, {
          failIfMajorPerformanceCaveat: true
        });
        if (!goog.isNull(gl)) {
          hasWebGL = true;
          textureSize = /** @type {number} */
              (gl.getParameter(gl.MAX_TEXTURE_SIZE));
          extensions = gl.getSupportedExtensions();
        }
      } catch (e) {}
    }
    ol.has.WEBGL = hasWebGL;
    ol.WEBGL_EXTENSIONS = extensions;
    ol.WEBGL_MAX_TEXTURE_SIZE = textureSize;
  }
})();
