remoting/webapp/app_remoting/js/drag_and_drop.js

   1 // Copyright 2014 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 /**
   6  * @fileoverview
   7  * Provide support for drag-and-drop operations in shaped windows. The
   8  * standard API doesn't work because no "dragover" events are generated
   9  * if the mouse moves outside the window region.
  10  */
  11 'use strict';
  12
  13 /** @suppress {duplicate} */
  14 var remoting = remoting || {};
  15
  16 /**
  17  * @constructor
  18  * @param {Element} element The element to register for drag and drop.
  19  * @param {function(number, number):void} dragUpdate Callback to receive the
  20  *     X and Y deltas as the element is dragged.
  21  * @param {function():void=} opt_dragStart Initiation callback.
  22  * @param {function():void=} opt_dragEnd Completion callback.
  23  */
  24 remoting.DragAndDrop = function(element, dragUpdate,
  25                                 opt_dragStart, opt_dragEnd) {
  26   /** @private */
  27   this.element_ = element;
  28
  29   /** @private */
  30   this.dragUpdate_ = dragUpdate;
  31
  32   /** @private */
  33   this.dragStart_ = opt_dragStart;
  34
  35   /** @private */
  36   this.dragEnd_ = opt_dragEnd;
  37
  38   /** @private {number} */
  39   this.previousDeltaX_ = 0;
  40
  41   /** @private {number} */
  42   this.previousDeltaY_ = 0;
  43
  44   /** @type {boolean} */
  45   this.seenNonZeroDelta_ = false;
  46
  47   /** @private {function(Event):void} */
  48   this.callOnMouseUp_ = this.onMouseUp_.bind(this);
  49
  50   /** @private {function(Event):void} */
  51   this.callOnMouseMove_ = this.onMouseMove_.bind(this);
  52
  53   element.addEventListener('mousedown', this.onMouseDown_.bind(this), false);
  54 };
  55
  56 /**
  57  * @param {Event} event
  58  */
  59 remoting.DragAndDrop.prototype.onMouseDown_ = function(event) {
  60   if (event.button != 0) {
  61     return;
  62   }
  63   this.previousDeltaX_ = 0;
  64   this.previousDeltaY_ = 0;
  65   this.seenNonZeroDelta_ = false;
  66   this.element_.addEventListener('mousemove', this.callOnMouseMove_, false);
  67   this.element_.addEventListener('mouseup', this.callOnMouseUp_, false);
  68   this.element_.requestPointerLock();
  69   if (this.dragStart_) {
  70     this.dragStart_();
  71   }
  72 };
  73
  74 /**
  75  * TODO(jamiewalch): Remove the workarounds in this method once the pointer-lock
  76  * API is fixed (crbug.com/419562).
  77  *
  78  * @param {Event} event
  79  */
  80 remoting.DragAndDrop.prototype.onMouseMove_ = function(event) {
  81   // Ignore the first non-zero delta. A click event will generate a bogus
  82   // mousemove event, even if the mouse doesn't move.
  83   if (!this.seenNonZeroDelta_ &&
  84       (event.movementX != 0 || event.movementY != 0)) {
  85     this.seenNonZeroDelta_ = true;
  86   }
  87
  88   /**
  89    * The mouse lock API is buggy when used with shaped windows, and occasionally
  90    * generates single, large deltas that must be filtered out.
  91    *
  92    * @param {number} previous
  93    * @param {number} current
  94    * @return {number}
  95    */
  96   var adjustDelta = function(previous, current) {
  97     var THRESHOLD = 100;  // Based on observed values.
  98     if (Math.abs(previous < THRESHOLD) && Math.abs(current) >= THRESHOLD) {
  99       return 0;
 100     }
 101     return current;
 102   };
 103   this.previousDeltaX_ = adjustDelta(this.previousDeltaX_, event.movementX);
 104   this.previousDeltaY_ = adjustDelta(this.previousDeltaY_, event.movementY);
 105   if (this.previousDeltaX_ != 0 || this.previousDeltaY_ != 0) {
 106     this.dragUpdate_(this.previousDeltaX_, this.previousDeltaY_);
 107   }
 108 };
 109
 110 /**
 111  * @param {Event} event
 112  */
 113 remoting.DragAndDrop.prototype.onMouseUp_ = function(event) {
 114   this.element_.removeEventListener('mousemove', this.callOnMouseMove_, false);
 115   this.element_.removeEventListener('mouseup', this.callOnMouseUp_, false);
 116   document.exitPointerLock();
 117   if (this.dragEnd_) {
 118     this.dragEnd_();
 119   }
 120 };