Re: Proposal to add start, stop, and update events to TTS

Is this preferable to:

interface SpeechSynthesisUtterance {
      ...
      attribute Function onstart;
      attribute Function onend;


On Tue, Sep 11, 2012 at 1:19 AM, Dominic Mazzoni <dmazzoni@google.com>wrote:

> I propose adding a mechanism by which JavaScript clients can attach
> event listeners to an utterance to get notified when it starts
> speaking, when it finishes, and optionally with updates of the
> progress.
>
> Here's what could be added to the spec:
>
> callback SpeechSynthesisStartCallback = void();
> callback SpeechSynthesisEndCallback = void();
> callback SpeechSynthesisUpdateCallback = void(DOMString markerName,
> unsigned long charIndex, float elapsedTime);
>
> interface SpeechSynthesisUtterance {
>   ...
>   attribute SpeechSynthesisStartCallback onstart;
>   attribute SpeechSynthesisEndCallback onend;
>   attribute SpeechSynthesisUpdateCallback onupdate;
> }
>
> I propose that "onstart" and "onend" must be supported for an
> implementation to be fully compliant. There are too many applications
> that can't be implemented without these.
>
> I think "onupdate" should be optional because it depends on what's
> possible in the speech engine. If the speech engine provides
> word-level information, for example, then every time there's a break
> between works it'd call onupdate() with the character index (into the
> original utterance string) and the elapsed time since speech began. An
> engine might also notify when certain named "markers" (e.g. in SSML)
> are reached.
>
> Other ideas - in the Chrome TTS extension API I also implemented these
> events - what do you think?
>
> * Error
> * Cancelled (stopAndFlushQueue called before it ever started playing)
> * Interrupted (stop called while it was in the middle of speaking)
>
> - Dominic
>
>