/
focustracker.js
157 lines (138 loc) · 3.9 KB
/
focustracker.js
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
/**
* @license Copyright (c) 2003-2021, CKSource - Frederico Knabben. All rights reserved.
* For licensing, see LICENSE.md or https://ckeditor.com/legal/ckeditor-oss-license
*/
/* global setTimeout, clearTimeout */
/**
* @module utils/focustracker
*/
import DomEmitterMixin from './dom/emittermixin';
import ObservableMixin from './observablemixin';
import CKEditorError from './ckeditorerror';
import mix from './mix';
/**
* Allows observing a group of `HTMLElement`s whether at least one of them is focused.
*
* Used by the {@link module:core/editor/editor~Editor} in order to track whether the focus is still within the application,
* or were used outside of its UI.
*
* **Note** `focus` and `blur` listeners use event capturing, so it is only needed to register wrapper `HTMLElement`
* which contain other `focusable` elements. But note that this wrapper element has to be focusable too
* (have e.g. `tabindex="-1"`).
*
* Check out the {@glink framework/guides/deep-dive/ui/focus-tracking "Deep dive into focus tracking" guide} to learn more.
*
* @mixes module:utils/dom/emittermixin~EmitterMixin
* @mixes module:utils/observablemixin~ObservableMixin
*/
export default class FocusTracker {
constructor() {
/**
* True when one of the registered elements is focused.
*
* @readonly
* @observable
* @member {Boolean} #isFocused
*/
this.set( 'isFocused', false );
/**
* The currently focused element.
*
* While {@link #isFocused `isFocused`} remains `true`, the focus can
* move between different UI elements. This property tracks those
* elements and tells which one is currently focused.
*
* @readonly
* @observable
* @member {HTMLElement|null} #focusedElement
*/
this.set( 'focusedElement', null );
/**
* List of registered elements.
*
* @private
* @member {Set.<HTMLElement>}
*/
this._elements = new Set();
/**
* Event loop timeout.
*
* @private
* @member {Number}
*/
this._nextEventLoopTimeout = null;
}
/**
* Starts tracking the specified element.
*
* @param {HTMLElement} element
*/
add( element ) {
if ( this._elements.has( element ) ) {
/**
* This element is already tracked by {@link module:utils/focustracker~FocusTracker}.
*
* @error focustracker-add-element-already-exist
*/
throw new CKEditorError( 'focustracker-add-element-already-exist', this );
}
this.listenTo( element, 'focus', () => this._focus( element ), { useCapture: true } );
this.listenTo( element, 'blur', () => this._blur(), { useCapture: true } );
this._elements.add( element );
}
/**
* Stops tracking the specified element and stops listening on this element.
*
* @param {HTMLElement} element
*/
remove( element ) {
if ( element === this.focusedElement ) {
this._blur( element );
}
if ( this._elements.has( element ) ) {
this.stopListening( element );
this._elements.delete( element );
}
}
/**
* Destroys the focus tracker by:
* - Disabling all event listeners attached to tracked elements.
* - Removing all tracked elements that were previously added.
*/
destroy() {
this.stopListening();
}
/**
* Stores currently focused element and set {#isFocused} as `true`.
*
* @private
* @param {HTMLElement} element Element which has been focused.
*/
_focus( element ) {
clearTimeout( this._nextEventLoopTimeout );
this.focusedElement = element;
this.isFocused = true;
}
/**
* Clears currently focused element and set {@link #isFocused} as `false`.
* This method uses `setTimeout` to change order of fires `blur` and `focus` events.
*
* @private
* @fires blur
*/
_blur() {
clearTimeout( this._nextEventLoopTimeout );
this._nextEventLoopTimeout = setTimeout( () => {
this.focusedElement = null;
this.isFocused = false;
}, 0 );
}
/**
* @event focus
*/
/**
* @event blur
*/
}
mix( FocusTracker, DomEmitterMixin );
mix( FocusTracker, ObservableMixin );