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, MDN, Demo) 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.

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.

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

Basic

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

subscribe(listenerCallback): unsubscribe

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

isSupported()

Returns true if the browser runtime supports oskd.

Advanced Usage

Multiple Subscriptions (PubSub)

PubSub is not part of this module and needs additional tools, e.g. emittery. See demo/pubsub.html

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 ☕
• chai 🍵
• 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

Android

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 <test phone ip address> (see "setup_test" in package.json) Then run npm run test:chrome.

iOS

Connect a device where Remote Automatation is enabled for Safari (see the Webkit blog). 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)