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1 | |
2 | |
3 /* | |
4 `iron-a11y-keys` provides a normalized interface for processing keyboard command
s that pertain to [WAI-ARIA best | |
5 practices](http://www.w3.org/TR/wai-aria-practices/#kbd_general_binding). The el
ement takes care of browser differences | |
6 with respect to Keyboard events and uses an expressive syntax to filter key pres
ses. | |
7 | |
8 Use the `keys` attribute to express what combination of keys will trigger the ev
ent to fire. | |
9 | |
10 Use the `target` attribute to set up event handlers on a specific node. | |
11 The `keys-pressed` event will fire when one of the key combinations set with the
`keys` attribute is pressed. | |
12 | |
13 Example: | |
14 | |
15 This element will call `arrowHandler` on all arrow keys: | |
16 | |
17 <iron-a11y-keys target="{{}}" keys="up down left right" on-keys-pressed="{{a
rrowHandler}}"></iron-a11y-keys> | |
18 | |
19 Keys Syntax: | |
20 | |
21 The `keys` attribute can accepts a space seprated, `+` concatenated set of modif
ier keys and some common keyboard keys. | |
22 | |
23 The common keys are `a-z`, `0-9` (top row and number pad), `*` (shift 8 and numb
er pad), `F1-F12`, `Page Up`, `Page | |
24 Down`, `Left Arrow`, `Right Arrow`, `Down Arrow`, `Up Arrow`, `Home`, `End`, `Es
cape`, `Space`, `Tab`, and `Enter` keys. | |
25 | |
26 The modifier keys are `Shift`, `Control`, and `Alt`. | |
27 | |
28 All keys are expected to be lowercase and shortened: | |
29 `Left Arrow` is `left`, `Page Down` is `pagedown`, `Control` is `ctrl`, `F1` is
`f1`, `Escape` is `esc` etc. | |
30 | |
31 Keys Syntax Example: | |
32 | |
33 Given the `keys` attribute value "ctrl+shift+f7 up pagedown esc space alt+m", th
e `<iron-a11y-keys>` element will send | |
34 the `keys-pressed` event if any of the follow key combos are pressed: Control an
d Shift and F7 keys, Up Arrow key, Page | |
35 Down key, Escape key, Space key, Alt and M key. | |
36 | |
37 Slider Example: | |
38 | |
39 The following is an example of the set of keys that fulfil the WAI-ARIA "slider"
role [best | |
40 practices](http://www.w3.org/TR/wai-aria-practices/#slider): | |
41 | |
42 <iron-a11y-keys target="{{}}" keys="left pagedown down" on-keys-pressed="{{d
ecrement}}"></iron-a11y-keys> | |
43 <iron-a11y-keys target="{{}}" keys="right pageup up" on-keys-pressed="{{incr
ement}}"></iron-a11y-keys> | |
44 <iron-a11y-keys target="{{}}" keys="home" on-keys-pressed="{{setMin}}"></iro
n-a11y-keys> | |
45 <iron-a11y-keys target="{{}}" keys="end" on-keys-pressed="{{setMax}}"></iron
-a11y-keys> | |
46 | |
47 The `increment` function will move the slider a set amount toward the maximum va
lue. | |
48 The `decrement` function will move the slider a set amount toward the minimum va
lue. | |
49 The `setMin` function will move the slider to the minimum value. | |
50 The `setMax` function will move the slider to the maximum value. | |
51 | |
52 Keys Syntax Grammar: | |
53 | |
54 [EBNF](http://en.wikipedia.org/wiki/Extended_Backus%E2%80%93Naur_Form) Grammar o
f the `keys` attribute. | |
55 | |
56 modifier = "shift" | "ctrl" | "alt"; | |
57 ascii = ? /[a-z0-9]/ ? ; | |
58 fnkey = ? f1 through f12 ? ; | |
59 arrow = "up" | "down" | "left" | "right" ; | |
60 key = "tab" | "esc" | "space" | "*" | "pageup" | "pagedown" | "home" | "end"
| arrow | ascii | fnkey ; | |
61 keycombo = { modifier, "+" }, key ; | |
62 keys = keycombo, { " ", keycombo } ; | |
63 | |
64 @demo demo/index.html | |
65 */ | |
66 | |
67 | |
68 Polymer({ | |
69 is: 'iron-a11y-keys', | |
70 | |
71 behaviors: [ | |
72 Polymer.IronA11yKeysBehavior | |
73 ], | |
74 | |
75 properties: { | |
76 target: { | |
77 type: Object, | |
78 observer: '_targetChanged' | |
79 }, | |
80 | |
81 keys: { | |
82 type: String, | |
83 reflectToAttribute: true, | |
84 observer: '_keysChanged' | |
85 } | |
86 }, | |
87 | |
88 attached: function() { | |
89 if (!this.target) { | |
90 this.target = this.parentNode; | |
91 } | |
92 }, | |
93 | |
94 _targetChanged: function(target) { | |
95 this.keyEventTarget = target; | |
96 }, | |
97 | |
98 _keysChanged: function() { | |
99 this.removeOwnKeyBindings(); | |
100 this.addOwnKeyBinding(this.keys, '_fireKeysPressed'); | |
101 }, | |
102 | |
103 _fireKeysPressed: function(event) { | |
104 this.fire('keys-pressed', event.detail, {}); | |
105 } | |
106 }); | |
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