/*
* Copyright 2003-2006, 2009, 2017, United States Government, as represented by the Administrator of the
* National Aeronautics and Space Administration. All rights reserved.
*
* The NASAWorldWind/WebWorldWind platform is licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
/**
* @exports DragRecognizer
*/
define(['../gesture/GestureRecognizer'],
function (GestureRecognizer) {
"use strict";
/**
* Constructs a mouse drag gesture recognizer.
* @alias DragRecognizer
* @constructor
* @augments GestureRecognizer
* @classdesc A concrete gesture recognizer subclass that looks for mouse drag gestures.
* @param {EventTarget} target The document element this gesture recognizer observes for mouse and touch events.
* @param {Function} callback An optional function to call when this gesture is recognized. If non-null, the
* function is called when this gesture is recognized, and is passed a single argument: this gesture recognizer,
* e.g., <code>gestureCallback(recognizer)</code>.
* @throws {ArgumentError} If the specified target is null or undefined.
*/
var DragRecognizer = function (target, callback) {
GestureRecognizer.call(this, target, callback);
/**
*
* @type {Number}
*/
this.button = 0;
// Intentionally not documented.
this.interpretDistance = 5;
};
DragRecognizer.prototype = Object.create(GestureRecognizer.prototype);
// Documented in superclass.
DragRecognizer.prototype.mouseMove = function (event) {
if (this.state == WorldWind.POSSIBLE) {
if (this.shouldInterpret()) {
if (this.shouldRecognize()) {
this.translationX = 0; // set translation to zero when the drag begins
this.translationY = 0;
this.state = WorldWind.BEGAN;
} else {
this.state = WorldWind.FAILED;
}
}
} else if (this.state == WorldWind.BEGAN || this.state == WorldWind.CHANGED) {
this.state = WorldWind.CHANGED;
}
};
// Documented in superclass.
DragRecognizer.prototype.mouseUp = function (event) {
if (this.mouseButtonMask == 0) { // last button up
if (this.state == WorldWind.POSSIBLE) {
this.state = WorldWind.FAILED;
} else if (this.state == WorldWind.BEGAN || this.state == WorldWind.CHANGED) {
this.state = WorldWind.ENDED;
}
}
};
// Documented in superclass.
DragRecognizer.prototype.touchStart = function (touch) {
if (this.state == WorldWind.POSSIBLE) {
this.state = WorldWind.FAILED; // mouse gestures fail upon receiving a touch event
}
};
/**
*
* @returns {Boolean}
* @protected
*/
DragRecognizer.prototype.shouldInterpret = function () {
var dx = this.translationX,
dy = this.translationY,
distance = Math.sqrt(dx * dx + dy * dy);
return distance > this.interpretDistance; // interpret mouse movement when the cursor moves far enough
};
/**
*
* @returns {Boolean}
* @protected
*/
DragRecognizer.prototype.shouldRecognize = function () {
var buttonBit = (1 << this.button);
return buttonBit == this.mouseButtonMask; // true when the specified button is the only button down
};
return DragRecognizer;
});