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Feedback about W3C Input Method Editor API draft

From: James Su <suzhe@google.com>
Date: Tue, 23 Apr 2013 16:35:05 +0800
Message-ID: <CAFah6LmqQYuAyvxYGXErpCWDwKEfE5txsu0vpo+OqY0abupYcg@mail.gmail.com>
To: public-webapps@w3.org
Hi all,
  Please see below my initial feedback about *

* 5. The getInputContext() method

partial interface HTMLElement {


1. The name of the method and its return value type doesn’t match. Suggest
to rename the method to getInputMethodContext().

6. The Composition Dictionary

dictionary Composition {
   readonly attribute Node
   readonly attribute Range

Question: I’m wondering how should a web app render the styled text on a
canvas? Can you provide an example code?

Feedback: how about rename caret to selectedRange?
7. The InputMethodContext Interface

interface InputMethodContext {
   readonly    attribute
               attribute boolean
   readonly    attribute DOMString
   void    confirmComposition<http://www.w3.org/TR/ime-api/#widl-InputMethodContext-confirmComposition-void>();
   void    setCaretRectangle<http://www.w3.org/TR/ime-api/#widl-InputMethodContext-setCaretRectangle-void-Node-anchor-long-x-long-y-long-w-long-h>(
Node anchor, long x, long y, long w, long h);
   void    setExclusionRectangle<http://www.w3.org/TR/ime-api/#widl-InputMethodContext-setExclusionRectangle-void-Node-anchor-long-x-long-y-long-w-long-h>(
Node anchor, long x, long y, long w, long h);
   boolean open<http://www.w3.org/TR/ime-api/#widl-InputMethodContext-open-boolean>();


1. attribute boolean

Instead of using a boolean value to tell the system whether or not the IME
should be enabled, I suggest to add a mechanism to tell the IME the
supported input type of the current focused node, it may either be a
DOMString attribute or a method like setInputType(DOMString type).

The acceptable values of the input type can be a subset of the types
defined for HTML Input
So that the browser can enable/disable the IME or maybe switch to a
specific IME according to the input type. For example, if the web app wants
to implement a password input box by itself, it can specify the input type
to ‘password’, then the browser will switch the current IME to a special
one suitable for inputting password. Setting the input type to ‘none’ or an
empty value to disable the input method.

2. readonly    attribute DOMString

Having this attribute is good, but may not enough. We probably need a
mechanism to notify the web app whenever the IME’s locale gets changed. For
example, when the locale is changed from a LTR to a RTL one, the web app
may want to adjust its text alignment and cursor position automatically.

3. void    confirmComposition<http://www.w3.org/TR/ime-api/#widl-InputMethodContext-confirmComposition-void>();

I suggest to change this method to cancelComposition(), which asks the IME
to cancel the current composition session by resetting its internal state
without committing anything. The web app is responsible for converting the
latest composition text into the final text. The reason is that,
confirmComposition() may require a round-trip call between IME and the web
app, which may be an asynchronous call. So if the IME wants to commit
anything when this method gets called, the result may be sent to the web
app asynchronously any time after calling confirmComposition() method. This
will cause unexpected behavior if the web app wants to manipulate the text
content immediately after calling confirmComposition().

For example: assuming the current composition text is “Hello world|”, and
the caret is at the end. If the web app decides to finish the composition
and move the caret when the user clicks the composition text or any other
place, the web app needs to call confirmComposition() method to ask the IME
to finish the current composition session, but as the result may be sent
back asynchronously after confirmComposition() method returns, the result
may be inserted into a wrong place if the web app moves the caret
immediately after calling confirmComposition().

4. boolean open<http://www.w3.org/TR/ime-api/#widl-InputMethodContext-open-boolean>();
This method may not be necessary, as the User Agent should take care of
opening/closing the IME according to the current input type when necessary.



James Su |  Software Engineer | suzhe@google.com |  +8610 62504149
Received on Tuesday, 23 April 2013 08:35:58 UTC

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