on-screen-keyboard-detector


On-screen keyboard detector
=============================
> Indirect detection of the presence of the on-screen keyboard (OSK) shown by mobile browsers when the user interacts with input controls on a webpage.

Background
----------
This approach employs the browsers layout and visual viewports ([Explainer][5], [MDN][1], [Demo][2]) to
observe the appearance of the virtual keyboard.

Simplified, since it's introduction
- Mobile Safari excludes the keyboard from the visual viewport, while
- Chrome for Android the keyboard is excluded from both the visual and the layout viewport.

!Browser Viewports

Chrome's behaviour makes it necessary to also observe focusin, focusout, resize and visibilitychange events.

Limitations
------
The indirect detection relying on viewport and window DOM events brings some limitations:

- hidden and visible events are dispatched with a approximate 1 second delay.
- On Chrome for Android the keyboard must be initially hidden when subscribing to the detector.
- On iOS requires Safari v. ≥ 13
- On iPad the predictive text bar, which is shown when an external keyboard is used, is not detected as visible keyboard.

!iPad Predictive Text Bar

Because of these caveats, the straight-forward way of detecting blur and focus events on inputs should be explored before falling back on this project.

Install
-------
npm install on-screen-keyboard-detector

Usage
-----

$3

``javascript
import { subscribe, isSupported } from 'on-screen-keyboard-detector';

if (isSupported()) {
const unsubscribe = subscribe(visibility => {
if (visibility === "hidden") {
// ...
}
else { // visibility === "visible"
// ...
}
});

// After calling unsubscribe() the callback will no longer be invoked.
unsubscribe();
}
`

API
---


$3

Begins to observe browser events and invokes the provided callback function
when a change in the keyboard visibility is detected.

| Parameter | Type | Description |
|-----------|------|-------------|
| callback |function(String)| user-defined handler which receives the keyboard visibility changes |

#### Return value
function(): void : Unsubscribes to receive updates




$3


Returns true if the browser runtime supports oskd.

Advanced Usage
--------------

$3

PubSub is not part of this module and needs additional tools, e.g. [emittery][3]. See demo/pubsub.html
`javascript
import {subscribe} from 'on-screen-keyboard-detector';
import Emitter from 'emittery';

const emitter = new Emitter();

subscribe(visibility => emitter.emit(visibility));

emitter.on('hidden', function() { / ... / });
emitter.on('visible', function() { / ... / });
`

Tests
-----
#### Requirements (not listed in package.json)
- mocha :coffee:
- chai :tea:
- selenium-webdriver
- a Mac for Mobile Safari tests
- running a local webserver (see TEST_SERVER in package.json), E.g. run http-server in the project root folder http-server . --port 8081

$3


For real devices make sure
- the adb server is running (adb start-server), and
- a device is connected via USB or Wifi (adb devices -l)
- ggf. adb tcpip 5555 and adb connect (see "setup_test" in package.json)
Then run npm run test:chrome.

$3

Connect a device where Remote Automatation is enabled for Safari (see the [Webkit blog][4]). Then run npm run test:ios`

iOS tests should be performed manually (see the demo folder), because Webdriver controlled Mobile Safari does not show the virtual keyboard

Dependencies
-----------
Ramda, and Most for the reactive functional infrastructure.

Changelog (See changelog.md)
---------

[1]: https://developer.mozilla.org/en-US/docs/Web/API/Visual_Viewport_API
[2]: http://bokand.github.io/viewport/index.html
[3]: https://github.com/sindresorhus/emittery
[4]: https://webkit.org/blog/9395/webdriver-is-coming-to-safari-in-ios-13/
[5]: https://github.com/bokand/bokand.github.io/blob/master/web_viewports_explainer.md