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<!doctype html>
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<title>Input Method Editor API</title>
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* v0.05 - 2009-07-31
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</style><link href="http://www.w3.org/StyleSheets/TR/W3C-WD" rel="stylesheet" type="text/css" charset="utf-8"></head>
<body style="display: inherit; "><div class="head"><p><a href="http://www.w3.org/"><img width="72" height="48" src="http://www.w3.org/Icons/w3c_home" alt="W3C"></a></p><h1 class="title" id="title">Input Method Editor API</h1><h2 id="w3c-working-draft-24-may-2012">W3C Working Draft 24 May 2012</h2><dl><dt>This version:</dt><dd><a href="http://www.w3.org/TR/2012/WD-ime-api-20120524/">http://www.w3.org/TR/2012/WD-ime-api-20120524/</a></dd><dt>Latest published version:</dt><dd><a href="http://www.w3.org/TR/ime-api/">http://www.w3.org/TR/ime-api/</a></dd><dt>Latest editor's draft:</dt><dd><a href="http://dvcs.w3.org/hg/ime-api/raw-file/default/Overview.html">http://dvcs.w3.org/hg/ime-api/raw-file/default/Overview.html</a></dd><dt>Editors:</dt><dd><span>Hironori Bono (坊野 博典)</span>, Google <span class="ed_mailto"><a href="mailto:[email protected]">[email protected]</a></span> </dd>
<dd><span>Kenji Baheux</span>, Google <span class="ed_mailto"><a href="mailto:[email protected]">[email protected]</a></span> </dd>
</dl><p class="copyright"><a href="http://www.w3.org/Consortium/Legal/ipr-notice#Copyright">Copyright</a> © 2012 <a href="http://www.w3.org/"><acronym title="World Wide Web Consortium">W3C</acronym></a><sup>®</sup> (<a href="http://www.csail.mit.edu/"><acronym title="Massachusetts Institute of Technology">MIT</acronym></a>, <a href="http://www.ercim.eu/"><acronym title="European Research Consortium for Informatics and Mathematics">ERCIM</acronym></a>, <a href="http://www.keio.ac.jp/">Keio</a>), All Rights Reserved. W3C <a href="http://www.w3.org/Consortium/Legal/ipr-notice#Legal_Disclaimer">liability</a>, <a href="http://www.w3.org/Consortium/Legal/ipr-notice#W3C_Trademarks">trademark</a> and <a href="http://www.w3.org/Consortium/Legal/copyright-documents">document use</a> rules apply.</p><hr></div>
<div id="abstract" class="introductory section"><h2>Abstract</h2>
<p>This specification defines an "IME API" that provides Web applications
with scripted access to an IME (<a href="#IME">input-method editor</a>)
associated with a hosting user agent. This IME API includes:</p>
<ul>
<li>An <a href="#idl-def-InputMethodContext" class="idlType"><code>InputMethodContext</code></a> interface, which provides methods to
retrieve detailed data from an in-progress IME
<a href="#ime-composition">composition</a>,
and to update that data.</li>
<li>A <a href="#idl-def-Composition" class="idlType"><code>Composition</code></a> dictionary, which represents read-only attributes
about the current
<a href="#ime-composition">composition</a>,
such as the actual text being input, its length, and its target
<a href="#ime-clause">clause</a>.
<p class="issue">need to define what a <i>clause</i> is</p></li>
</ul>
<p>This API is designed to be used in conjunction with DOM events and
elements on the Web platform, notably: composition events and the
<a href="http://dev.w3.org/html5/2dcontext/">Canvas 2D Context API</a>
[<cite><a class="bibref" rel="biblioentry" href="#bib-CANVAS-2D">CANVAS-2D</a></cite>].</p>
</div><div id="sotd" class="introductory section"><h2>Status of This Document</h2><p><em>This section describes the status of this document at the time of its publication. Other documents may supersede this document. A list of current W3C publications and the latest revision of this technical report can be found in the <a href="http://www.w3.org/TR/">W3C technical reports index</a> at http://www.w3.org/TR/.</em></p>
<p>
This document is a proposal that is being made available for public
review in order to solicit feedback, particularly from
implementors, with a goal of potential cross-browser implementation
and standardization.
</p>
<p>This document was published by the <a href="http://www.w3.org/2008/webapps/">Web Applications Working Group</a> as a First Public Working Draft. This document is intended to become a W3C Recommendation. If you wish to make comments regarding this document, please send them to <a href="mailto:[email protected]">[email protected]</a> (<a href="mailto:[email protected]?subject=subscribe">subscribe</a>, <a href="http://lists.w3.org/Archives/Public/public-webapps/">archives</a>). All feedback is welcome.</p><p>Publication as a Working Draft does not imply endorsement by the W3C Membership. This is a draft document and may be updated, replaced or obsoleted by other documents at any time. It is inappropriate to cite this document as other than work in progress.</p><p>This document was produced by a group operating under the <a href="http://www.w3.org/Consortium/Patent-Policy-20040205/">5 February 2004 W3C Patent Policy</a>. W3C maintains a <a href="http://www.w3.org/2004/01/pp-impl/42538/status" rel="disclosure">public list of any patent disclosures</a> made in connection with the deliverables of the group; that page also includes instructions for disclosing a patent. An individual who has actual knowledge of a patent which the individual believes contains <a href="http://www.w3.org/Consortium/Patent-Policy-20040205/#def-essential">Essential Claim(s)</a> must disclose the information in accordance with <a href="http://www.w3.org/Consortium/Patent-Policy-20040205/#sec-Disclosure">section 6 of the W3C Patent Policy</a>.</p></div><div id="toc" class="section"><h2 class="introductory">Table of Contents</h2><ul class="toc"><li class="tocline"><a href="#introduction" class="tocxref"><span class="secno">1. </span>Introduction</a></li><li class="tocline"><a href="#background" class="tocxref"><span class="secno">2. </span>Background: What’s an Input Method Editor?</a><ul class="toc"><li class="tocline"><a href="#composer-section" class="tocxref"><span class="secno">2.1 </span>Composer</a><ul class="toc"><li class="tocline"><a href="#phonetic-composer-section" class="tocxref"><span class="secno">2.1.1 </span>Phonetic composer</a></li><li class="tocline"><a href="#radical-composer-section" class="tocxref"><span class="secno">2.1.2 </span>Radical composer</a></li></ul></li><li class="tocline"><a href="#converter-section" class="tocxref"><span class="secno">2.2 </span>Converter</a></li></ul></li><li class="tocline"><a href="#conformance" class="tocxref"><span class="secno">3. </span>Conformance</a></li><li class="tocline"><a href="#terminology" class="tocxref"><span class="secno">4. </span>Terminology and algorithms</a></li><li class="tocline"><a href="#the-getinputcontext---method" class="tocxref"><span class="secno">5. </span>The getInputContext() method</a><ul class="toc"><li class="tocline"></li></ul></li><li class="tocline"><a href="#composition-dictionary" class="tocxref"><span class="secno">6. </span>The Composition Dictionary</a><ul class="toc"><li class="tocline"></li></ul></li><li class="tocline"><a href="#inputmethodcontext-interface" class="tocxref"><span class="secno">7. </span>The InputMethodContext Interface</a><ul class="toc"><li class="tocline"></li><li class="tocline"></li></ul></li><li class="tocline"><a href="#best-practices" class="tocxref"><span class="secno">8. </span>Best practices</a><ul class="toc"><li class="tocline"><a href="#javascript-imes" class="tocxref"><span class="secno">8.1 </span>JavaScript IMEs</a><ul class="toc"><li class="tocline"><a href="#composing-text" class="tocxref"><span class="secno">8.1.1 </span>Composing text</a></li><li class="tocline"><a href="#consuming-events" class="tocxref"><span class="secno">8.1.2 </span>Consuming events</a></li><li class="tocline"><a href="#enabling-disabling-js-imes" class="tocxref"><span class="secno">8.1.3 </span>Enabling or Disabling JavaScript IMEs</a></li><li class="tocline"><a href="#candidate-window-section" class="tocxref"><span class="secno">8.1.4 </span>Candidate window</a></li></ul></li><li class="tocline"><a href="#ime-aware-webapps" class="tocxref"><span class="secno">8.2 </span>IME-aware Web applications</a><ul class="toc"><li class="tocline"><a href="#using-js-imes" class="tocxref"><span class="secno">8.2.1 </span>Using JavaScript IMEs</a></li><li class="tocline"><a href="#using-system-imes" class="tocxref"><span class="secno">8.2.2 </span>Using system IMEs</a></li><li class="tocline"><a href="#does-not-use-imes" class="tocxref"><span class="secno">8.2.3 </span>Does not use IMEs</a></li></ul></li></ul></li><li class="tocline"><a href="#references" class="tocxref"><span class="secno">A. </span>References</a><ul class="toc"><li class="tocline"><a href="#normative-references" class="tocxref"><span class="secno">A.1 </span>Normative references</a></li><li class="tocline"><a href="#informative-references" class="tocxref"><span class="secno">A.2 </span>Informative references</a></li></ul></li></ul></div>
<div class="informative section" id="introduction">
<!--OddPage--><h2><span class="secno">1. </span>Introduction</h2><p><em>This section is non-normative.</em></p>
<p>Even though existing Web-platform APIs allow developers to implement very
complicated Web applications, such as visual chat applications, using
technologies such as SVG or the <code><canvas></code> element and API,
developers have difficulties when implementing Web applications that
control <a href="#IME">input-method editors</a>. To provide the
ability for hosting user agents to expose Web applications to the
<a href="#ime-composition">composition text</a>
being composed in an associated IME,
<a href="http://dev.w3.org/2006/webapi/DOM-Level-3-Events/html/DOM3-Events.html">the DOM Level 3 Events specification</a>
[<cite><a class="bibref" rel="biblioentry" href="#bib-DOM-LEVEL-3-EVENTS">DOM-LEVEL-3-EVENTS</a></cite>]
introduces <i>composition events</i>. Using composition events, Web
applications can retrieve
<a href="#ime-composition">composition text</a>
from an IME.</p>
<p>However, Web applications can still run into difficulties when
they manipulate IMEs on non-editable elements such as the
<code><canvas></code> element; those difficulties include the fact
that a Web application cannot do the following:</p>
<ul>
<li>indicate to the user whether the Web application renders
composition text by itself, or needs to ask user agents to render it</li>
<li>determine the place where user agents render composition text</li>
<li>detect whether the user agent renders
<a href="#candidate-window">candidate windows</a>
by themselves</li>
<li>determine the place where user agents render
<a href="#candidate-window">candidate windows</a></li>
</ul>
<p>The Web platform has a number of existing APIs useful for
implementing a custom IME in JavaScript. For example, the Web Storage
API can store an IME dictionary, and the WebSocket and XMLHttpRequest APIs
allow sending a server request that performs a lookup in an IME dictionary,
and so on. In fact, Web-application developers are already developing and
deploying JavaScript-based IMEs that use these APIs. However, it is
currently difficult to make those JavaScript-based IMEs work on all user
agents, because they often rely on APIs specific to the hosting user agent,
such as browser extension APIs.</p>
<p>To solve these IME-related problems, this specification introduces
an IME API that allows Web applications to read and write composition
data made available by user agents. Moreover, this specification introduces
interfaces for
<a href="#ime-composition">compositions</a>,
so Web applications can read detailed composition
data and update it. A <a href="#idl-def-Composition" class="idlType"><code>Composition</code></a> object provides a reference
to an ongoing IME
<a href="#ime-composition">composition</a>,
so Web applications can retrieve the composition text and attributes.</p>
<p>The use of those APIs allows Web applications the ability to set the
position of a <a href="#composition-window">composition window</a>
and to retrieve the text and attributes of the ongoing
<a href="#ime-composition">composition</a>.</p>
<p>Consider the following examples. The first example shows the
source for a Web application that renders composition text by itself
and uses the
<a href="#candidate-window">candidate window</a>
provided by an IME.</p>
<pre class="example sh_javascript sh_sourceCode" id="ex-candidate-window"><span class="sh_symbol"><!</span>DOCTYPE html<span class="sh_symbol">></span>
<span class="sh_symbol"><</span>html<span class="sh_symbol">></span>
<span class="sh_symbol"><</span>head<span class="sh_symbol">></span>
<span class="sh_symbol"><</span>script language<span class="sh_symbol">=</span><span class="sh_string">"javascript"</span> type<span class="sh_symbol">=</span><span class="sh_string">"text/javascript"</span><span class="sh_symbol">></span>
<span class="sh_keyword">function</span> <span class="sh_function">init</span><span class="sh_symbol">()</span> <span class="sh_cbracket">{</span>
window<span class="sh_symbol">.</span>inputmethodmanager<span class="sh_symbol">.</span><span class="sh_function">setOpenState</span><span class="sh_symbol">(</span><span class="sh_keyword">true</span><span class="sh_symbol">);</span>
<span class="sh_keyword">var</span> node <span class="sh_symbol">=</span> document<span class="sh_symbol">.</span><span class="sh_function">getElementById</span><span class="sh_symbol">(</span><span class="sh_string">'canvas0'</span><span class="sh_symbol">);</span>
node<span class="sh_symbol">.</span><span class="sh_function">getInputContext</span><span class="sh_symbol">().</span><span class="sh_function">setEnable</span><span class="sh_symbol">(</span><span class="sh_keyword">true</span><span class="sh_symbol">);</span>
node<span class="sh_symbol">.</span><span class="sh_function">addEventListener</span><span class="sh_symbol">(</span><span class="sh_string">'compositionstart'</span><span class="sh_symbol">,</span> onCompositionStart<span class="sh_symbol">,</span> <span class="sh_keyword">false</span><span class="sh_symbol">);</span>
node<span class="sh_symbol">.</span><span class="sh_function">addEventListener</span><span class="sh_symbol">(</span><span class="sh_string">'compositionupdate'</span><span class="sh_symbol">,</span> onCompositionUpdate<span class="sh_symbol">,</span> <span class="sh_keyword">false</span><span class="sh_symbol">);</span>
node<span class="sh_symbol">.</span><span class="sh_function">addEventListener</span><span class="sh_symbol">(</span><span class="sh_string">'compositionend'</span><span class="sh_symbol">,</span> onCompositionEnd<span class="sh_symbol">,</span> <span class="sh_keyword">false</span><span class="sh_symbol">);</span>
<span class="sh_cbracket">}</span>
<span class="sh_keyword">function</span> <span class="sh_function">onCompositionStart</span><span class="sh_symbol">(</span>event<span class="sh_symbol">)</span> <span class="sh_cbracket">{</span>
<span class="sh_cbracket">}</span>
<span class="sh_keyword">function</span> <span class="sh_function">onCompositionUpdate</span><span class="sh_symbol">(</span>event<span class="sh_symbol">)</span> <span class="sh_cbracket">{</span>
<span class="sh_keyword">var</span> x <span class="sh_symbol">=</span> <span class="sh_number">0</span><span class="sh_symbol">;</span>
<span class="sh_keyword">var</span> y <span class="sh_symbol">=</span> <span class="sh_number">0</span><span class="sh_symbol">;</span>
<span class="sh_keyword">var</span> canvas <span class="sh_symbol">=</span> document<span class="sh_symbol">.</span><span class="sh_function">getElementById</span><span class="sh_symbol">(</span><span class="sh_string">'canvas0'</span><span class="sh_symbol">);</span>
<span class="sh_keyword">var</span> context <span class="sh_symbol">=</span> canvas<span class="sh_symbol">.</span><span class="sh_function">getContext</span><span class="sh_symbol">(</span><span class="sh_string">'2d'</span><span class="sh_symbol">);</span>
<span class="sh_keyword">var</span> inputContext <span class="sh_symbol">=</span> canvas<span class="sh_symbol">.</span><span class="sh_function">getInputContext</span><span class="sh_symbol">();</span>
<span class="sh_keyword">var</span> composition <span class="sh_symbol">=</span> inputContext<span class="sh_symbol">.</span>composition<span class="sh_symbol">;</span>
<span class="sh_comment">// Render a caret.</span>
<span class="sh_comment">// NOTE: this just renders a caret rectangle in black for</span>
<span class="sh_comment">// simplicity.</span>
<span class="sh_keyword">if</span> <span class="sh_symbol">(</span>composition<span class="sh_symbol">.</span>caret<span class="sh_symbol">.</span>start <span class="sh_symbol">>=</span> <span class="sh_number">0</span><span class="sh_symbol">)</span> <span class="sh_cbracket">{</span>
<span class="sh_keyword">var</span> start <span class="sh_symbol">=</span> context<span class="sh_symbol">.</span><span class="sh_function">measureText</span><span class="sh_symbol">(</span>
composition<span class="sh_symbol">.</span>text<span class="sh_symbol">.</span><span class="sh_function">substring</span><span class="sh_symbol">(</span><span class="sh_number">0</span><span class="sh_symbol">,</span> composition<span class="sh_symbol">.</span>caret<span class="sh_symbol">.</span>start<span class="sh_symbol">));</span>
<span class="sh_keyword">var</span> end <span class="sh_symbol">=</span> context<span class="sh_symbol">.</span><span class="sh_function">measureText</span><span class="sh_symbol">(</span>
composition<span class="sh_symbol">.</span>text<span class="sh_symbol">.</span><span class="sh_function">substring</span><span class="sh_symbol">(</span><span class="sh_number">0</span><span class="sh_symbol">,</span> composition<span class="sh_symbol">.</span>caret<span class="sh_symbol">.</span>end<span class="sh_symbol">));</span>
context<span class="sh_symbol">.</span>fillStyle <span class="sh_symbol">=</span> ’black’<span class="sh_symbol">;</span>
context<span class="sh_symbol">.</span><span class="sh_function">fillRect</span><span class="sh_symbol">(</span>start<span class="sh_symbol">.</span>width<span class="sh_symbol">,</span> y<span class="sh_symbol">,</span> end<span class="sh_symbol">.</span>width<span class="sh_symbol">,</span> y <span class="sh_symbol">+</span> <span class="sh_number">10</span><span class="sh_symbol">);</span>
<span class="sh_cbracket">}</span>
<span class="sh_comment">// Render the clauses in the composition.</span>
<span class="sh_keyword">for</span> <span class="sh_symbol">(</span><span class="sh_keyword">var</span> i <span class="sh_symbol">=</span> <span class="sh_number">0</span><span class="sh_symbol">;</span> i <span class="sh_symbol"><</span> composition<span class="sh_symbol">.</span>clauses<span class="sh_symbol">.</span>length<span class="sh_symbol">;</span> <span class="sh_symbol">++</span>i<span class="sh_symbol">)</span> <span class="sh_cbracket">{</span>
<span class="sh_keyword">var</span> text <span class="sh_symbol">=</span> composition<span class="sh_symbol">.</span>clauses<span class="sh_symbol">[</span>i<span class="sh_symbol">].</span>text<span class="sh_symbol">;</span>
<span class="sh_keyword">var</span> metrics <span class="sh_symbol">=</span> context<span class="sh_symbol">.</span><span class="sh_function">measureText</span><span class="sh_symbol">(</span>text<span class="sh_symbol">);</span>
<span class="sh_comment">// Draw the text of this clause.</span>
context<span class="sh_symbol">.</span>fillStyle <span class="sh_symbol">=</span> composition<span class="sh_symbol">.</span>clauses<span class="sh_symbol">[</span>i<span class="sh_symbol">].</span>textColor<span class="sh_symbol">;</span>
context<span class="sh_symbol">.</span><span class="sh_function">fillText</span><span class="sh_symbol">(</span>text<span class="sh_symbol">,</span> x<span class="sh_symbol">,</span> y<span class="sh_symbol">);</span>
<span class="sh_comment">// Draw an underline under the text. For simplicity, this code</span>
<span class="sh_comment">// draws a bold underline for selected clauses or a thin</span>
<span class="sh_comment">// underline for non-selected ones.</span>
<span class="sh_keyword">if</span> <span class="sh_symbol">(</span>composition<span class="sh_symbol">.</span>clauses<span class="sh_symbol">[</span>i<span class="sh_symbol">].</span>selected<span class="sh_symbol">)</span> <span class="sh_cbracket">{</span>
context<span class="sh_symbol">.</span><span class="sh_function">fillRect</span><span class="sh_symbol">(</span>x<span class="sh_symbol">,</span> y<span class="sh_symbol">,</span> x <span class="sh_symbol">+</span> metrics<span class="sh_symbol">.</span>width<span class="sh_symbol">,</span> y <span class="sh_symbol">+</span> <span class="sh_number">2</span><span class="sh_symbol">);</span>
<span class="sh_cbracket">}</span> <span class="sh_keyword">else</span> <span class="sh_cbracket">{</span>
context<span class="sh_symbol">.</span><span class="sh_function">fillRect</span><span class="sh_symbol">(</span>x<span class="sh_symbol">,</span> y<span class="sh_symbol">,</span> x <span class="sh_symbol">+</span> metrics<span class="sh_symbol">.</span>width<span class="sh_symbol">,</span> y <span class="sh_symbol">+</span> <span class="sh_number">1</span><span class="sh_symbol">);</span>
<span class="sh_cbracket">}</span>
x <span class="sh_symbol">+=</span> metrics<span class="sh_symbol">.</span>width<span class="sh_symbol">;</span>
<span class="sh_cbracket">}</span>
<span class="sh_comment">// Move the candidate window outside of the composition text.</span>
window<span class="sh_symbol">.</span>inputmethodmanager<span class="sh_symbol">.</span><span class="sh_function">moveCandidateWindow</span><span class="sh_symbol">(</span><span class="sh_number">0</span><span class="sh_symbol">,</span> y<span class="sh_symbol">,</span> x<span class="sh_symbol">,</span> y <span class="sh_symbol">+</span> <span class="sh_number">10</span><span class="sh_symbol">);</span>
<span class="sh_cbracket">}</span>
<span class="sh_keyword">function</span> <span class="sh_function">onCompositionEnd</span><span class="sh_symbol">(</span>event<span class="sh_symbol">)</span> <span class="sh_cbracket">{</span>
<span class="sh_cbracket">}</span>
<span class="sh_symbol"></</span>script<span class="sh_symbol">></span>
<span class="sh_symbol"></</span>head<span class="sh_symbol">></span>
<span class="sh_symbol"><</span>body<span class="sh_symbol">></span>
<span class="sh_symbol"><</span>canvas id<span class="sh_symbol">=</span>”canvas0” width<span class="sh_symbol">=</span>”<span class="sh_number">640</span>” height<span class="sh_symbol">=</span>”<span class="sh_number">480</span>”<span class="sh_symbol">></</span>canvas<span class="sh_symbol">></span>
<span class="sh_symbol"></</span>body<span class="sh_symbol">></span>
<span class="sh_symbol"></</span>html<span class="sh_symbol">></span></pre>
<p>The next example shows the source for a simple IME that composes
Japanese Hiragana characters from key strokes.</p>
<p class="note">This is just a sample and not suitable for real use.</p>
<pre class="example sh_javascript sh_sourceCode" id="ex-hiragana-keystrokes"><span class="sh_symbol"><!</span>DOCTYPE html<span class="sh_symbol">></span>
<span class="sh_symbol"><</span>html<span class="sh_symbol">></span>
<span class="sh_symbol"><</span>head<span class="sh_symbol">></span>
<span class="sh_symbol"><</span>title<span class="sh_symbol">></</span>title<span class="sh_symbol">></span>
<span class="sh_symbol"><</span>script language<span class="sh_symbol">=</span><span class="sh_string">"javascript"</span> type<span class="sh_symbol">=</span><span class="sh_string">"text/javascript"</span><span class="sh_symbol">></span>
<span class="sh_keyword">var</span> imeActivated <span class="sh_symbol">=</span> <span class="sh_keyword">false</span><span class="sh_symbol">;</span>
<span class="sh_keyword">var</span> imeRomajiInput <span class="sh_symbol">=</span> <span class="sh_string">''</span><span class="sh_symbol">;</span>
<span class="sh_keyword">var</span> imeRomajiTable <span class="sh_symbol">=</span> <span class="sh_cbracket">{</span>
<span class="sh_string">'A'</span><span class="sh_symbol">:</span> <span class="sh_string">'</span><span class="sh_specialchar">\u</span><span class="sh_string">3042'</span><span class="sh_symbol">,</span> <span class="sh_string">'I'</span><span class="sh_symbol">:</span> <span class="sh_string">'</span><span class="sh_specialchar">\u</span><span class="sh_string">3044'</span><span class="sh_symbol">,</span> <span class="sh_string">'U'</span><span class="sh_symbol">:</span> <span class="sh_string">'</span><span class="sh_specialchar">\u</span><span class="sh_string">3046'</span><span class="sh_symbol">,</span> <span class="sh_string">'E'</span><span class="sh_symbol">:</span> <span class="sh_string">'</span><span class="sh_specialchar">\u</span><span class="sh_string">3048'</span><span class="sh_symbol">,</span> <span class="sh_string">'O'</span><span class="sh_symbol">:</span> <span class="sh_string">'</span><span class="sh_specialchar">\u</span><span class="sh_string">304A'</span><span class="sh_symbol">,</span>
<span class="sh_comment">/* suppressed */</span>
<span class="sh_cbracket">}</span><span class="sh_symbol">;</span>
<span class="sh_keyword">function</span> <span class="sh_function">init</span><span class="sh_symbol">()</span> <span class="sh_cbracket">{</span>
<span class="sh_comment">// Disable the system IME associated with this window.</span>
window<span class="sh_symbol">.</span>inputmethodmanager<span class="sh_symbol">.</span><span class="sh_function">setOpenState</span><span class="sh_symbol">(</span><span class="sh_keyword">false</span><span class="sh_symbol">);</span>
<span class="sh_comment">// Listens the keyboard events.</span>
<span class="sh_keyword">var</span> node <span class="sh_symbol">=</span> document<span class="sh_symbol">.</span><span class="sh_function">getElementById</span><span class="sh_symbol">(</span><span class="sh_string">'input0'</span><span class="sh_symbol">);</span>
node<span class="sh_symbol">.</span><span class="sh_function">addEventListener</span><span class="sh_symbol">(</span><span class="sh_string">'keydown'</span><span class="sh_symbol">,</span> onKeyDown<span class="sh_symbol">,</span> <span class="sh_keyword">false</span><span class="sh_symbol">);</span>
node<span class="sh_symbol">.</span><span class="sh_function">addEventListener</span><span class="sh_symbol">(</span><span class="sh_string">'keyup'</span><span class="sh_symbol">,</span> onKeyUp<span class="sh_symbol">,</span> <span class="sh_keyword">false</span><span class="sh_symbol">);</span>
<span class="sh_cbracket">}</span>
<span class="sh_keyword">function</span> <span class="sh_function">onKeyDown</span><span class="sh_symbol">(</span>event<span class="sh_symbol">)</span> <span class="sh_cbracket">{</span>
<span class="sh_comment">// Toggle the input mode when pressing a shift key.</span>
<span class="sh_keyword">if</span> <span class="sh_symbol">(</span>event<span class="sh_symbol">.</span>key <span class="sh_symbol">==</span> <span class="sh_string">'Shift'</span><span class="sh_symbol">)</span> <span class="sh_cbracket">{</span>
imeActivated <span class="sh_symbol">=</span> <span class="sh_symbol">!</span>imeActivated<span class="sh_symbol">;</span>
imeRomajiInput <span class="sh_symbol">=</span> <span class="sh_string">''</span><span class="sh_symbol">;</span>
<span class="sh_cbracket">}</span>
<span class="sh_comment">// Exit if this IME is not activated.</span>
<span class="sh_keyword">if</span> <span class="sh_symbol">(!</span>imeActivated<span class="sh_symbol">)</span>
<span class="sh_keyword">return</span> <span class="sh_keyword">true</span><span class="sh_symbol">;</span>
<span class="sh_keyword">var</span> imeComposition <span class="sh_symbol">=</span> <span class="sh_keyword">new</span> Composition<span class="sh_symbol">;</span>
<span class="sh_keyword">var</span> imeConfirm <span class="sh_symbol">=</span> <span class="sh_keyword">false</span><span class="sh_symbol">;</span>
<span class="sh_keyword">if</span> <span class="sh_symbol">(</span>event<span class="sh_symbol">.</span>keyCode <span class="sh_symbol"><</span> <span class="sh_number">0x20</span><span class="sh_symbol">)</span> <span class="sh_cbracket">{</span>
event<span class="sh_symbol">.</span><span class="sh_function">preventDefault</span><span class="sh_symbol">();</span>
<span class="sh_keyword">return</span> <span class="sh_keyword">true</span><span class="sh_symbol">;</span>
<span class="sh_cbracket">}</span>
<span class="sh_comment">// Convert the input key strokes to a Japanese character.</span>
imeRomajiInput <span class="sh_symbol">+=</span> <span class="sh_predef_func">String</span><span class="sh_symbol">.</span><span class="sh_function">fromCharCode</span><span class="sh_symbol">(</span>event<span class="sh_symbol">.</span>keyCode<span class="sh_symbol">);</span>
<span class="sh_keyword">if</span> <span class="sh_symbol">(</span>imeRomajiTable<span class="sh_symbol">[</span>imeRomajiInput<span class="sh_symbol">])</span> <span class="sh_cbracket">{</span>
imeComposition<span class="sh_symbol">.</span>text <span class="sh_symbol">=</span> imeRomajiTable<span class="sh_symbol">[</span>imeRomajiInput<span class="sh_symbol">];</span>
imeConfirm <span class="sh_symbol">=</span> <span class="sh_keyword">true</span><span class="sh_symbol">;</span>
imeRomajiInput <span class="sh_symbol">=</span> <span class="sh_string">''</span><span class="sh_symbol">;</span>
<span class="sh_cbracket">}</span> <span class="sh_keyword">else</span> <span class="sh_cbracket">{</span>
imeComposition<span class="sh_symbol">.</span>text <span class="sh_symbol">=</span> imeRomajiInput<span class="sh_symbol">;</span>
<span class="sh_cbracket">}</span>
<span class="sh_comment">// Fill the Composition object.</span>
imeComposition<span class="sh_symbol">.</span>caret<span class="sh_symbol">.</span>start <span class="sh_symbol">=</span> imeComposition<span class="sh_symbol">.</span>text<span class="sh_symbol">.</span>length<span class="sh_symbol">;</span>
imeComposition<span class="sh_symbol">.</span>caret<span class="sh_symbol">.</span>length <span class="sh_symbol">=</span> <span class="sh_number">1</span><span class="sh_symbol">;</span>
imeComposition<span class="sh_symbol">.</span>clauses<span class="sh_symbol">[</span><span class="sh_number">0</span><span class="sh_symbol">]</span> <span class="sh_symbol">=</span> <span class="sh_keyword">new</span> CompositionClause<span class="sh_symbol">;</span>
imeComposition<span class="sh_symbol">.</span>clauses<span class="sh_symbol">[</span><span class="sh_number">0</span><span class="sh_symbol">].</span>text <span class="sh_symbol">=</span> imeComposition<span class="sh_symbol">.</span>text<span class="sh_symbol">;</span>
imeComposition<span class="sh_symbol">.</span>clauses<span class="sh_symbol">[</span><span class="sh_number">0</span><span class="sh_symbol">].</span>start <span class="sh_symbol">=</span> <span class="sh_number">0</span><span class="sh_symbol">;</span>
imeComposition<span class="sh_symbol">.</span>clauses<span class="sh_symbol">[</span><span class="sh_number">0</span><span class="sh_symbol">].</span>selected <span class="sh_symbol">=</span> <span class="sh_keyword">true</span><span class="sh_symbol">;</span>
imeComposition<span class="sh_symbol">.</span>clauses<span class="sh_symbol">[</span><span class="sh_number">0</span><span class="sh_symbol">].</span>textColor <span class="sh_symbol">=</span> <span class="sh_string">'currentColor'</span><span class="sh_symbol">;</span>
imeComposition<span class="sh_symbol">.</span>clauses<span class="sh_symbol">[</span><span class="sh_number">0</span><span class="sh_symbol">].</span>backgroundColor <span class="sh_symbol">=</span> <span class="sh_string">'transparent'</span><span class="sh_symbol">;</span>
imeComposition<span class="sh_symbol">.</span>clauses<span class="sh_symbol">[</span><span class="sh_number">0</span><span class="sh_symbol">].</span>lineStyle <span class="sh_symbol">=</span> <span class="sh_string">'solid'</span><span class="sh_symbol">;</span>
imeComposition<span class="sh_symbol">.</span>clauses<span class="sh_symbol">[</span><span class="sh_number">0</span><span class="sh_symbol">].</span>lineColor <span class="sh_symbol">=</span> <span class="sh_string">'black'</span><span class="sh_symbol">;</span>
<span class="sh_comment">// Send the Composition object to the user agent.</span>
<span class="sh_keyword">var</span> context <span class="sh_symbol">=</span> event<span class="sh_symbol">.</span>target<span class="sh_symbol">.</span><span class="sh_function">getInputContext</span><span class="sh_symbol">();</span>
context<span class="sh_symbol">.</span><span class="sh_function">setComposition</span><span class="sh_symbol">(</span>imeComposition<span class="sh_symbol">);</span>
<span class="sh_keyword">if</span> <span class="sh_symbol">(</span>imeConfirm<span class="sh_symbol">)</span>
context<span class="sh_symbol">.</span><span class="sh_function">confirmComposition</span><span class="sh_symbol">();</span>
<span class="sh_comment">// Disable the default action to prevent this key from being</span>
<span class="sh_comment">// inserted.</span>
event<span class="sh_symbol">.</span><span class="sh_function">preventDefault</span><span class="sh_symbol">();</span>
<span class="sh_keyword">return</span> <span class="sh_keyword">false</span><span class="sh_symbol">;</span>
<span class="sh_cbracket">}</span>
<span class="sh_keyword">function</span> <span class="sh_function">onKeyUp</span><span class="sh_symbol">(</span>event<span class="sh_symbol">)</span> <span class="sh_cbracket">{</span>
<span class="sh_cbracket">}</span>
<span class="sh_symbol"></</span>script<span class="sh_symbol">></span>
<span class="sh_symbol"></</span>head<span class="sh_symbol">></span>
<span class="sh_symbol"><</span>body onload<span class="sh_symbol">=</span><span class="sh_string">"init();"</span><span class="sh_symbol">></span>
<span class="sh_symbol"><</span>textarea id<span class="sh_symbol">=</span><span class="sh_string">"input0"</span> cols<span class="sh_symbol">=</span><span class="sh_string">"80"</span> rows<span class="sh_symbol">=</span><span class="sh_string">"10"</span><span class="sh_symbol">></</span>textarea<span class="sh_symbol">></span>
<span class="sh_symbol"></</span>body<span class="sh_symbol">></span>
<span class="sh_symbol"></</span>html<span class="sh_symbol">></span></pre>
</div>
<div class="informative section" id="background">
<!--OddPage--><h2><span class="secno">2. </span>Background: What’s an Input Method Editor?</h2><p><em>This section is non-normative.</em></p>
<p>An <dfn id="IME">IME</dfn> (input-method editor) is an application
that allows a standard keyboard (such as a US-101 keyboard) to be used to
type characters and symbols that are not directly represented on the
keyboard itself. In China, Japan, and Korea, IMEs are used ubiquitously to
enable standard keyboards to be employed to type the very large number
of characters required for writing in Chinese, Japanese, and Korean.</p>
<p>An IME consists of two modules; a <a href="#composer">composer</a>
and a <a href="#converter">converter</a>.</p>
<p>A <dfn id="composer">composer</dfn> is a context-free parser that
composes non-ASCII characters (including phonetic characters) from
keystrokes.</p>
<p>A <dfn id="converter">converter</dfn> is a context-sensitive parser that looks up a
dictionary to convert phonetic characters to a set of ideographic
characters.</p>
<p>An <dfn id="ime-clause">IME clause</dfn> is a grammatical word produced in an IME.</p>
<p>An <dfn id="ime-selected-clause">IME selected clause</dfn> is an <a href="ime-clause">IME clause</a> being composed by an IME.</p>
<p>An <dfn id="ime-composition">IME composition</dfn>
is an instance of text produced in an IME. For IMEs that can produce multiple words, an IME composition consists of multiple IME clauses. For IMEs that produce only one word, an IME composition is equal to an IME clause.</p>
<p>When an IME receives keystrokes, it sends the keystrokes to a
composer and receives phonetic characters matching to the keystrokes. When
an IME receives phonetic characters from a composer, it sends the phonetic
characters to a converter and receives the list of ideographic characters
matching to the phonetic characters. The following figure shows the
basic structure of an IME.</p>
<figure id="fig-ime-structure">
<p><img height="199" src="images/image10.png" width="615"></p>
<figcaption>Basic structure of an IME</figcaption>
</figure>
<div id="composer-section" class="section">
<h3><span class="secno">2.1 </span>Composer</h3>
<p>A composer consists of two types of composers: a
<a href="#phonetic-composer">phonetic composer</a>
and a
<a href="#radical-composer">radical composer</a>.</p>
<p>A <dfn id="phonetic-composer">phonetic composer</dfn> composes a phonetic
character from its ASCII representation.</p>
<p>A <dfn id="radical-composer">radical composer</dfn> composes a
phonetic character from <a href="#phonetic-radical">phonetic radicals</a>.</p>
<p>A <dfn id="phonetic-radical">phonetic radical</dfn> is a character component of a Latin character, a Chinese character, or a Korean character. A Latin character consists of an ASCII character and accent marks, e.g. a character 'á' consists of an ASCII character 'a' and an accent mark '´'. A Chinese character consists of Chinese character components that refer to its semantic origins, e.g. a Chinese character '略' consists of two components '田' and '各'. A Korean character consists of Korean character components that represent consonants or vowels, e.g. a Korean character '가' consists of a consonant 'ㄱ' and a vowel 'ㅏ'.</p>
<p>A <dfn id="composition-window">composition window</dfn> is a window that shows ASCII characters being composed by <a href="#phonetic-composer">phonetic composers</a> or <a href="#phonetic-radical">phonetic radicals</a> being composed by <a href="#radical-composer">radical composers</a>.</p>
<p>An IME usually shows the text
being composed by a composer with its own style to distinguish it from the
existing text. Even though most of composers output phonetic characters,
some composers (such as Bopomofo composers) output a placeholder character
instead of phonetic characters while composing text.</p>
<p class="issue">need to define <i>composition window</i></p>
<p class="issue">probably should define <i>radical</i></p>
<p class="issue">probably should define <i>clause</i> here too</p>
<div id="phonetic-composer-section" class="section">
<h4><span class="secno">2.1.1 </span>Phonetic composer</h4>
<p>Phonetic composers are not only used for typing Simplified
Chinese and Japanese, but also used for typing non-ASCII characters (such
as mathematical symbols, Yi, Amharic, etc.) with a US-101 keyboard. Each of
these languages has a mapping table from its character to a sequence of
ASCII characters representing its pronunciation: e.g.,
'か' to 'ka' in Japanese, and;
'卡' to 'ka' in Simplified Chinese. This
mapping table is called as Romaji for Japanese and Pinyin for Simplified
Chinese, respectively. A phonetic composer uses these mapping tables to
compose a phonetic character from a sequence of ASCII characters produced
by a US keyboard.</p>
<p>A phonetic composer for Simplified Chinese outputs the input
ASCII characters as its composition text.</p>
<figure id="fig-ascii-composition-text">
<p><img height="180" src="images/image11.png" width="352"></p>
<figcaption>Composition text (Simplified Chinese)</figcaption>
</figure>
<p>On the other hand, a phonetic composer for Japanese outputs
phonetic characters when the input ASCII characters have matching phonetic
characters.</p>
<figure id="fig-kana-composition-text">
<p><img height="180" src="images/image13.png" width="352"></p>
<figcaption>Composition text (Japanese)</figcaption>
</figure>
<p>A phonetic composer for mathematical symbols outputs a
composed mathematical symbol and shows the source keystrokes to its own
window, which is an example of a composition window.</p>
<figure id="fig-composition-window">
<p><img height="214" src="images/image14.png" width="435"></p>
<figcaption>Composition text (Latex input)</figcaption>
</figure>
</div>
<div id="radical-composer-section" class="section">
<h4><span class="secno">2.1.2 </span>Radical composer</h4>
<p>Radical composers are mainly used for typing Traditional
Chinese and Korean with phonetic keyboards. Each phonetic keyboard of these
languages can produce phonetic radicals: e.g., typing 'r'
produces 'ㄱ' on a Korean keyboard; typing
'o' produces '人' on a Traditional-Chinese
(or Bopomofo) keyboard, etc. A radical composer composes a phonetic
character from phonetic radicals given by these keyboards: e.g., typing
'ㄱ' (r) and 'ㅏ' (k) produces '가' on a Korean keyboard;
typing '人' (o), '弓' (n), and
'火' (f) produces '你' on a
Traditional-Chinese keyboard, etc.</p>
<p>A radical composer for Korean outputs the phonetic radicals as
its composition text.</p>
<figure id="fig-radical-composer-korean">
<p><img height="180" src="images/image15.png" width="352"></p>
<figcaption>Radical composer (Korean)</figcaption>
</figure>
<p>A radical composer for Traditional Chinese outputs a
placeholder character (U+3000) and shows the phonetic radicals being
composed to its own window. This window is an example of a composition
window.</p>
<figure id="fig-radical-composer-chinese">
<p><img height="180" src="images/image02.png" width="352"></p>
<figcaption>Radical composer (Traditional Chinese)</figcaption>
</figure>
<p>Some platforms (such as Mac and Linux) use radical composers
for typing accented characters used in European countries. For example,
typing ' ¨ ' (option+u) and 'a' (a) produces
'ä' on US keyboards of Mac.</p>
<figure id="fig-radical-composer-mac">
<p><img height="177" src="images/image01.png" width="479"></p>
<figcaption>Radical composer (Mac)</figcaption>
</figure>
</div>
</div>
<div id="converter-section" class="section">
<h3><span class="secno">2.2 </span>Converter</h3>
<p>A converter is a context-sensitive parser used for replacing
the outputs of a composer to ideographic characters on Chinese, Japanese,
and Korean.</p>
<p class="note">Korean does not use ideographic characters so often.</p>
<p>Because Chinese, Japanese, and Korean have many homonyms, each sequence of phonetic
characters usually matches many ideographic characters: e.g., a Japanese
phonetic character 'か' matches Japanese ideographic characters
'化', '科', '課',
etc.; Pinyin characters 'ka' matches Simplified-Chinese
ideographic characters '卡', '喀',
'咯', etc.; Bopomofo characters
'人弓' matches Traditional-Chinese ideographic
characters '乞', '亿',
'亇', etc.</p>
<p>A converter looks up a dictionary and shows a
list of candidates of possible ideographic characters so a user can choose
one. This list is known as a <dfn id="candidate-list">candidate list</dfn>.
A candidate list is known as a <dfn id="candidate-window">candidate window</dfn>
when it has its own window.</p>
<p>Some Japanese IMEs show annotations in its <a href="#candidate-window">candidate window</a>
for a character that is not so easy to distinguish from other characters
(such as full-width alphabets, full-width Katakanas, and half-width
Katakanas, etc.), as shown in the following figure.</p>
<figure id="fig-candidate-window-japanese">
<p><img height="342" src="images/image05.png" width="393"></p>
<figcaption>Candidate window (Japanese)</figcaption>
</figure>
<p>The next figure shows a <a href="#candidate-window">candidate window</a> of a Simplified-Chinese IME.</p>
<figure id="fig-candidate-window-simplified-chinese">
<p><img height="308" src="images/image04.png" width="390"></p>
<figcaption>Candidate window (Simplified Chinese)</figcaption>
</figure>
<p>And the next figure shows a <a href="#candidate-window">candidate window</a> of a Traditional-Chinese IME.</p>
<figure id="fig-candidate-window-traditional-chinese">
<p><img height="180" src="images/image06.png" width="352"></p>
<figcaption>Candidate window (Traditional Chinese)</figcaption>
</figure>
<p>A converter often integrates an <dfn id="MRU">MRU</dfn> (Most-Recently Used) list.
Even though there are many ideographic characters for each phonetic
character (or phonetic radical), a user does not usually use all these
ideographic characters. A converter uses an <a href="MRU">MRU list</a> to filter out
ideographic characters not used so often from a
<a href="#candidate-list">candidate list</a>.
A converter
sometimes integrates a grammar parser. A converter that integrates a
grammar parser splits the given phonetic characters into grammatical
clauses and converts only one clause at once. When a sequence of phonetic
characters consists of n clauses and the i-th clause has m<subi</sub> candidates,
the total number of the candidates for the input characters become (m<sub>1</sub> ×
m<sub>2</sub> × … × m<sub>n</sub>). To reduce the number of candidates owned by a
converter, a converter usually processes one clause at once. This clause is
called as a <dfn id="selected-clause">selected clause</dfn>.</p>
<p>An IME usually renders a <a href="#selected-clause">selected clause</a> with
a special style to distinguish it from other clauses, as shown in
the following figure.</p>
<figure id="fig-selected-clause">
<p><img height="346" src="images/image08.png" width="394"></p>
<figcaption>Selected clause (Japanese)</figcaption>
</figure>
<p>When a converter converts two or more clauses, it chooses
candidates for the selected clause so it becomes grammatically consistent
with the surrounding clauses: e.g., Japanese converters usually output
'危機一髪' (not
'危機一発') for Japanese phonetic
characters 'ききいっぱつ'
because '危機一発' is grammatically
incorrect.</p>
</div>
</div>
<div id="conformance" class="section"><!--OddPage--><h2><span class="secno">3. </span>Conformance</h2><p>As well as sections marked as non-normative, all authoring guidelines, diagrams, examples, and notes in this specification are non-normative. Everything else in this specification is normative.</p>
<p>The key words <em class="rfc2119" title="must">must</em>, <em class="rfc2119" title="must not">must not</em>, <em class="rfc2119" title="required">required</em>, <em class="rfc2119" title="should">should</em>, <em class="rfc2119" title="should not">should not</em>, <em class="rfc2119" title="recommended">recommended</em>, <em class="rfc2119" title="may">may</em>, and <em class="rfc2119" title="optional">optional</em> in this specification are to be interpreted as described in [<cite><a class="bibref" rel="biblioentry" href="#bib-RFC2119">RFC2119</a></cite>].</p>
<p><i>More to be written.</i></p>
</div>
<div id="terminology" class="section">
<!--OddPage--><h2><span class="secno">4. </span>Terminology and algorithms</h2>
<p><i>To be written.</i></p>
</div>
<div id="the-getinputcontext---method" class="section">
<!--OddPage--><h2><span class="secno">5. </span>The getInputContext() method</h2>
<p>For each element, a user agent can choose an IME for the element.
To control the IME attached to an element, it is a good idea to add a
method to the HTMLElement interface.</p>
<p class="issue">If the
<code>getInputContext()</code>
method cannot be added to the HTMLElement
interface, it should be moved to the <a href="#idl-def-InputMethodContext" class="idlType"><code>InputMethodContext</code></a> interface.</p>
<pre class="idl"><span class="idlInterface" id="idl-def-HTMLElement">partial interface <span class="idlInterfaceID">HTMLElement</span>
<span class="idlMethod"> <span class="idlMethType"><a>InputMethodContext</a></span> <span class="idlMethName"><a href="#widl-HTMLElement-getInputContext-Object">getInputContext</a></span> ();</span>
};</span>
</pre><div id="methods" class="section"><h3><span class="secno">5.1 </span>Methods</h3><dl class="methods"><dt id="widl-HTMLElement-getInputContext-Object"><code>getInputContext</code></dt><dd>Returns an InputMethodContext interface associated with this element. By
default, a user agent returns an InputMethodContext interface representing
the system IME. To change the behavior of the IME associated with an
element, authors must first obtain an InputMethodContext interface by
calling the getInputContext() method of the HTMLElement interface.
<div><em>No parameters.</em></div><div><em>No exceptions.</em></div><div><em>Return type: </em><code><a>InputMethodContext</a></code></div></dd></dl></div>
</div>
<div id="composition-dictionary" class="section">
<!--OddPage--><h2><span class="secno">6. </span>The Composition Dictionary</h2>
<p>This dictionary represents an ongoing IME composition. It provides
an attribute representing the text being composed by an IME. It also
provides a method to retrieve attributes of the specified character in the
composition text.</p>
<pre class="idl"><span class="idlInterface" id="idl-def-Composition">dictionary <span class="idlInterfaceID">Composition</span> {
<span class="idlAttribute"> readonly attribute <span class="idlAttrType"><a>Node</a></span> <span class="idlAttrName"><a href="#widl-Composition-text">text</a></span>;</span>