Re: Proposal to ammend the composition event spec.

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在 2010年5月20日 下午4:58，James Su <suzhe@google.com>写道：

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> 在 2010年5月18日 上午7:49，Daniel Danilatos <daniel@danilatos.com>写道：
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> The spec should make it clear that mutations must be bounded between
>> compositionstart and compositionend events.
>>
>> Background:
>>
>> https://bugs.webkit.org/show_bug.cgi?id=31902
>> Hironori has asked me to write up this email arguing for adjusting the
>> spec.
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>> Summary:
>>
>> >From our implementation experience, it is broken not to bound
>> mutations with compositionstart and compositionend events. not having
>> this severely limits their utility - and requires large amounts of
>> hacky workaround code, even involving asynchronous logic.
>> Firefox already has the correct behaviour, and it is off firefox that
>> we largely based the spec (so the spec should be adjusted)
>> The fix for webkit is already implemented - it was just rejected
>> because it supposedly doesn't match the spec; once the spec is
>> adjusted, both Webkit and FF will be in line with eachother with
>> respect to the composition events.
>> The tricky thing to consider is, when should a textinput event be
>> fired. This is a secondary issue to the strong requirement, that
>> mutations must be bounded by composition events. The options then seem
>> to be:
>>
>> (Compatible with existing spec) Fire textInput after the composition
>> has ended - thus textInput would no longer be a pre-input-event, but
>> really, it never was, as the dom is mutating before the event anyway.
>> Currently, webkit creates the composition text, then removes it again,
>> just so it can then fire the textInput event, and if not cancelled,
>> will then insert the content.
>> (Compatible with existing spec) If textInput really, really must fire
>> before input, even though the dom has already been mutating from the
>> composition, then delete the composition, but do that BEFORE the
>> compositionend event. then fire a regular cancellable textInput. In my
>> opinion this seems wasteful, though.
>>
> I'd prefer the second solution. Though as you said, it's a little wasteful,
> this solution won't change the semantic of textInput event, and make
> compositionend event really finish the composition mode.
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>> (Incompatible with existing spec) Fire textInput before every change.
>> This is more generally consistent, especially with other proposals to
>> extend textInput (or introduce a similar event) that fires before
>> every change to the DOM at all, including for things like paste, undo,
>> and deletion. For the use case where the application wants to know
>> when some content is ready and in a consistent state (i.e. not during
>> composition), a post-change event is more applicable. Such an event
>> does not have to fire after every single change.
>> We shouldn't fear the final option above - the composition events spec
>> is still in its infancy. Now is the time to make meaningful changes.
>>
> If I understand correctly, this solution will change the semantic of
> textInput event and may cause multiple useless textInput events during
> composition mode, which would be wasteful. Correct me if I'm wrong.
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> Regards
> James Su
>
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>> Best,
>> Dan
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