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Virtual Keyboard/IME API aims to implement the system IME as a Web App. It will be used in Firefox OS and use cases could be found in the Firefox OS Keyboard UX document(WIP).

The API provides the communication channel between the IME App and the other App that receives user's inputs.

It is very different from the IME API from Google that aims to re-use the system's IME in a web page.


API discussion:

  1. WebAPI mailing list post
  2. Extended API mailing list post
  3. Polished Keyboard API


  1. bug 737110 - Bug 737110 - Virtual Keyboard API


The Virtual Keyboard/IME API supports the following features:

  • Notifies the VKB app when the focus text field was changing in other apps
  • Allow user to manual hide the keyboard. Check bug 737110.
  • The VKB app should be responsive to properties and the state of the input field (more than HTML5 input type, including current content, cursor position, x-inputmode bug 796544).
  • Sends trust
  • The VKB app should be able to send trusted key events such as they are considered by the other apps as user' inputs.
  • The VKB app should be able to send a character or a string to the current input cursor position.
  • Keyboard should be able to overwrite the current value of the input field of the input field and set the cursor position.
  • The VKB app should be able to move the cursor position or select a specified range of text.
  • The VKB should be able to switch the focus onto the previous/next input field.
  • The return key label of the VKB can be customized.

Proposed Manifest of a 3rd-Party IME

Just like any other apps, keyboard apps register themselves in the same apps registry. We extend the manifest syntax here to describe layout(s) available in a given keyboard app. Gaia will be paring the manifest. There are 3 special fields to distinguish and describe a 3rd-party IME:

  • [Line 4] a "role" field with value "keyboard" declares it's an IME app. Homescreen app will ignore some role types when displaying app icons, and "keyboard" is one of them. (see bug 892397)
  • [Line 6-8] a "permissions" field that requests "keyboard" permission. All IME apps need this permission for sending input keys and updating the value of a input field.
  • [Line 9-30] a "inputs" field specifies supported layouts. Each layout is described in a key-value pair, where the key represents the layout name (will be shown up on Settings app with the app name), and the value describes the detailed information of the layout, including launch path of the layout and supported input types. (See #Layout Matching Algorithm)
    • The allowed value in "types" field is a subset of type attribute of input element: text, search, tel, number, url, email. Other types will be ignored by FxOS Gaia in the initial version because at this point UI for <select> and <input type=date> (called "value selectors") are not open for 3rd-party implementation.


 "name": "3rd-party Keyboard",
 "description": "3rd-party Keyboard",
 "type": "privilege",
 "role": "input",
 "launch_path": "/settings.html",
 "developer": {
   "name": "developer's name",
   "url": "https://keyboard.example.com"
 "permissions": {
   "input": {}
 "inputs": {
   "en": {
     "launch_path": "/index.html#en",
     "name": "English",
     "description": "English layout",
     "types": ["url", "text"],
     "locales": {
       "en-US": {
         "name": "English",
         "description": "English layout"
       "zh-TW": {
         "name": "英文",
         "description": "英文鍵盤"
   "en-Dvorak": {
     "launch_path": "/index.html#en-Dvorak",
     "name": "English (Dvorak)",
     "description": "Dvorak layout",
     "types": ["url", "text"]
   "es": {
     "launch_path": "/index.html#es",
     "name": "Spanish",
     "description": "Spanish layout",
     "types": ["url", "text"]
   "pt-BR": {
     "launch_path": "/index.html#pt-BR",
     "name": "Portuguese Brazilian",
     "description": "Portuguese Brazilian layout",
     "types": ["url", "text"]
   "pl": {
     "launch_path": "/index.html#pl",
     "name": "Polish",
     "description": "Polish layout",
     "types": ["url", "text"]
   "ca": {
     "launch_path": "/index.html#ca",
     "name": "Catalan",
     "description": "Catalan layout",
     "types": ["url", "text"]
   "cz": {
     "launch_path": "/index.html#cz",
     "name": "Czech",
     "description": "Czech layout",
     "types": ["url", "text"]
   "fr": {
     "launch_path": "/index.html#fr",
     "name": "French",
     "description": "French layout",
     "types": ["url", "text"]
   "de": {
     "launch_path": "/index.html#de",
     "name": "German",
     "description": "German layout",
     "types": ["url", "text"]
   "nb": {
     "launch_path": "/index.html#nb",
     "name": "Norwegian Bokmal",
     "description": "Norwegian Bokmal layout",
     "types": ["url", "text"]
   "sk": {
     "launch_path": "/index.html#sk",
     "name": "Slovak",
     "description": "Slovak layout",
     "types": ["url", "text"]
   "tr-Q": {
     "launch_path": "/index.html#tr-Q",
     "name": "Turkish Q",
     "description": "Turkish Q layout",
     "types": ["url", "text"]
   "tr-F": {
     "launch_path": "/index.html#tr-F",
     "name": "Turkish F",
     "description": "Turkish F layout",
     "types": ["url", "text"]
   "ro": {
     "launch_path": "/index.html#ro",
     "name": "Romanian",
     "description": "Romanian layout",
     "types": ["url", "text"]
   "ru": {
     "launch_path": "/index.html#ru",
     "name": "Russian",
     "description": "Russian layout",
     "types": ["url", "text"]
   "sr-Cyrl": {
     "launch_path": "/index.html#sr-Cyrl",
     "name": "Serbian (Cyrillic)",
     "description": "Serbian (Cyrillic) layout",
     "types": ["url", "text"]
   "sr-Latn": {
     "launch_path": "/index.html#sr-Latn",
     "name": "Serbian (Latin)",
     "description": "Serbian (Latin) layout",
     "types": ["url", "text"]
   "ar": {
     "launch_path": "/index.html#ar",
     "name": "Arabic",
     "description": "Arabic layout",
     "types": ["url", "text"]
   "he": {
     "launch_path": "/index.html#he",
     "name": "Hebrew",
     "description": "Hebrew layout",
     "types": ["url", "text"]
   "hu": {
     "launch_path": "/index.html#hu",
     "name": "Hungarian",
     "description": "Hungarian layout",
     "types": ["url", "text"]
   "el": {
     "launch_path": "/index.html#el",
     "name": "Greek",
     "description": "Greek layout",
     "types": ["url", "text"]
   "zh-Hans-Pinyin": {
     "launch_path": "/index.html#zh-Hans-Pinyin",
     "name": "Pinyin",
     "description": "Pinyin",
     "types": ["url", "text"]
   "number": {
     "launch_path": "/index.html#numberLayout",
     "name": "Number",
     "description": "Number layout",
     "types": ["number"]
 "locales": {
   "en-US": {
     "name": "3rd-party Keyboard",
     "description": "3rd-party Keyboard"
   "zh-TW": {
     "name": "第三方鍵盤",
     "description": "第三方鍵盤"
 "default_locale": "en-US"


Layout Matching Algorithm

When an input field is focused, if its type attribute is one of the allowed values stated above, it will be used to filter a set of candidate layouts. A candidate layout means it can handle this input type or is possible to let user input all characters that this input field can accept. For example, if the type of a input is "url", then a layout with "url" or "text" listed in the types of its manifest will be matched. However, if a input field with type "text", then all layouts that support "text" will be matched, but those layouts that only support "url" will not. This is because we believe layouts that can handle "text" could be a fallback for "url" input type, but not vice versa. We also believe "text" could be a fallback for all allowed types stated above.

The matching algorithm of keyboard manager in System app is as follows:

  1. With the given type, find all layouts claims to support the said type and put it into the list.
  2. Next, find layouts claims to support "text" and put it into the list. Layouts do not get duplicated listing even if it supports both types.
  3. Present the user with the choice of the layouts available to handle the input field. The order of presenting list is depend on UX design and/or user preferences in Settings.

Proposed API

The API has made available to privileged apps. See the WebIDL for the current interface.

History of this section

Use cases for each of the methods

  • For a simple virtual keyboard action (send a character and key events w/ each user action), use sendKey(). TODO: should we allow backspace key to be sent from the method? If not, how do send these non-printable characters and it's effect with key events?
    • [yxl] I perfer to allowing non-printable character, such as backspace key, to be sent, if there is no security issue. This would give the IME more flexibility.
  • For spellcheck, autocomplete etc, use surrounding text methods.
  • For cursor moment helper features, use setSelectionRange() and related attributes.
  • For Asian IMEs that sends characters and composition along with the composition events, use setComposition() and endComposition().

It is important to stick with the given use cases because the web application might need to react with what the user actually do. To test the events currently sent to the web, see http://jsfiddle.net/timdream/YDGgk/ .


The following "snowman filler" Keyboard app will start filling snowman character ("☃") and follow by characters "SNOW" with key events to the input field whenever the user is focus on a input field and switch to the keyboard app.

If the field is a numeric field, it will fill "1337".

var timer;
function startTyping(inputContext) {
  timer = setInterval(function typing() {
    /* [JJ] So I think that this code shouldn't be here, because you'll get lots of clutter
     *      as you'll also have to take languages into account.
     *      Rather rely on entry points in manifest...

    if (inputContext.inputmode === 'numeric' || inputContext.type === 'number') {
      ['1', '3', '3', '7'].forEach(function (k) {
        // For numbers, keyCode is same as the charCode.
        inputContext.sendKey(k.charCodeAt(0), k.charCodeAt(0));
    } else {
      // It's not a good idea to commit text w/o sending events. So we should first send composition events.
      // end the composition and commit the text.
      ['S', 'N', 'O', 'W'].forEach(function (k) {
        // For capital Latin letters, keyCode is same as the charCode.
        inputContext.sendKey(k.charCodeAt(0), k.charCodeAt(0));
  }, 1000);

function stopTyping() {

var im = navigator.inputMethod;

im.addEventListener('inputcontextchange', function contextchanged(evt) {
  if (evt.inputcontext) {
     // Got a new context, start working with it.
  } else {
     // The user have removed the focus, we are not allow to type into the text field anymore.

if (im.inputcontext) {
  // The webpage here is loaded *after* the user has place the focus on the text field,
  // let's start typing now.


Android IME API:


iOS Keyboard Management:


Chrome Extensions API: