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third_party/polymer/v1_0/components-chromium/iron-a11y-keys/README.md

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-[![Build Status](https://travis-ci.org/PolymerElements/iron-a11y-keys.svg?branch=master)](https://travis-ci.org/PolymerElements/iron-a11y-keys)
-
-_[Demo and API Docs](https://elements.polymer-project.org/elements/iron-a11y-keys)_
-
-
-##&lt;iron-a11y-keys&gt;
-
-
-`iron-a11y-keys` provides a cross-browser interface for processing 
-keyboard commands. The interface adheres to [WAI-ARIA best 
-practices](http://www.w3.org/TR/wai-aria-practices/#kbd_general_binding). 
-It uses an expressive syntax to filter key presses.
-
-## Basic usage
-
-The sample code below is a portion of a custom element. The goal is to call
-the `onEnter` method whenever the `paper-input` element is in focus and 
-the `Enter` key is pressed.
-
-    <iron-a11y-keys id="a11y" target="[[target]]" keys="enter"
-                        on-keys-pressed="onEnter"></iron-a11y-keys>
-    <paper-input id="input"
-                 placeholder="Type something. Press enter. Check console."
-                 value="{{userInput::input}}"></paper-input>
-
-The custom element declares an `iron-a11y-keys` element that is bound to a 
-property called `target`. The `target` property
-needs to evaluate to the `paper-input` node. `iron-a11y-keys` registers 
-an event handler for the target node using Polymer's [annotated event handler
-syntax](https://www.polymer-project.org/1.0/docs/devguide/events.html#annotated-listeners). `{{userInput::input}}` sets the `userInput` property to the 
-user's input on each keystroke. 
-
-The last step is to link the two elements within the custom element's 
-registration.
-
-    ...
-    properties: {
-      userInput: {
-        type: String,
-        notify: true,
-      },
-      target: {
-        type: Object,
-        value: function() {
-          return this.$.input;
-        }
-      },
-    },
-    onEnter: function() {
-      console.log(this.userInput);
-    }
-    ...
-
-## The `keys` attribute
-
-The `keys` attribute expresses what combination of keys triggers the event.
-
-The attribute accepts a space-separated, plus-sign-concatenated 
-set of modifier keys and some common keyboard keys.
-
-The common keys are: `a-z`, `0-9` (top row and number pad), `*` (shift 8 and 
-number pad), `F1-F12`, `Page Up`, `Page Down`, `Left Arrow`, `Right Arrow`,
-`Down Arrow`, `Up Arrow`, `Home`, `End`, `Escape`, `Space`, `Tab`, `Enter`.
-
-The modifier keys are: `Shift`, `Control`, `Alt`.
-
-All keys are expected to be lowercase and shortened. E.g.
-`Left Arrow` is `left`, `Page Down` is `pagedown`, `Control` is `ctrl`, 
-`F1` is `f1`, `Escape` is `esc`, etc.
-
-### Grammar
-
-Below is the [EBNF](http://en.wikipedia.org/wiki/Extended_Backus%E2%80%93Naur_Form) 
-Grammar of the `keys` attribute.
-
-    modifier = "shift" | "ctrl" | "alt";
-    ascii = ? /[a-z0-9]/ ? ;
-    fnkey = ? f1 through f12 ? ;
-    arrow = "up" | "down" | "left" | "right" ;
-    key = "tab" | "esc" | "space" | "*" | "pageup" | "pagedown" | 
-          "home" | "end" | arrow | ascii | fnkey;
-    keycombo = { modifier, "+" }, key ;
-    keys = keycombo, { " ", keycombo } ;
-
-### Example
-
-Given the following value for `keys`: 
-
-`ctrl+shift+f7 up pagedown esc space alt+m`
-
-The event is fired if any of the following key combinations are fired: 
-`Control` and `Shift` and `F7` keys, `Up Arrow` key, `Page Down` key, 
-`Escape` key, `Space` key, `Alt` and `M` keys.
-
-### WAI-ARIA Slider Example
-
-The following is an example of the set of keys that fulfills WAI-ARIA's 
-"slider" role [best
-practices](http://www.w3.org/TR/wai-aria-practices/#slider):
-
-    <iron-a11y-keys target="[[target]]" keys="left pagedown down" 
-                    on-keys-pressed="decrement"></iron-a11y-keys>
-    <iron-a11y-keys target=""[[target]] keys="right pageup up" 
-                    on-keys-pressed="increment"></iron-a11y-keys>
-    <iron-a11y-keys target="[[target]]" keys="home" 
-                    on-keys-pressed="setMin"></iron-a11y-keys>
-    <iron-a11y-keys target=""[[target]] keys="end" 
-                    on-keys-pressed="setMax"></iron-a11y-keys>
-
-The `target` properties must evaluate to a node. See the basic usage 
-example above.
-
-Each of the values for the `on-keys-pressed` attributes must evalute
-to methods. The `increment` method should move the slider a set amount 
-toward the maximum value. `decrement` should move the slider a set amount 
-toward the minimum value. `setMin` should move the slider to the minimum 
-value. `setMax` should move the slider to the maximum value.
-
-