[whatwg] Some media element details

[Antti Koivisto]

On 14.5.2008, at 23:37, Ian Hickson wrote:

>> It would be nice to have a read-only attribute (called "playing" for
>> example) that would be true when the element is "actively playing".
>> Knowing if the playback is progressing is necessary for implementing
>> basic playback UIs with JS. It is clumsy and not very obvious that  
>> you
>> need to do "var playing = !video.paused && !video.ended &&
>> video.readyState >= HTMLMediaElement.CAN_PLAY" to get this  
>> information.
>
> What's the use case?

For example a simple playing state indicator:

function updatePlayState() {
	var playIndicator = document.getElementById("playIndicator");
	var playing = !video.paused && !video.ended && video.readyState >=  
HTMLMediaElement.CAN_PLAY;
	playIndicator.className = playing ? "playing" : "stopped";
}
video.addEventListener("play", updatePlayState);
video.addEventListener("pause", updatePlayState);
video.addEventListener("ended", updatePlayState);
video.addEventListener("waiting", updatePlayState);

Knowing whether media is playing or not is needed for other common UI  
elements too, for example to activate/deactivate time display timer,  
to do play/pause button etc. A direct way to get this information  
(along with an associated event) would be good for API usability I  
think:

function updatePlayState() {
	var playIndicator = document.getElementById("playIndicator");
	playIndicator.className = video.activelyPlaying ? "playing" :  
"stopped";
}
video.addEventListener("playstatechanged", updatePlayState);

Of course it is sort of syntactical sugar...

>>
>> It might also be good to explicitly state that exceptions are  
>> ignored.
>
> Which exceptions?

Yeah, after the change to check for EMPTY networkState there are no  
longer any exceptions to could occur with the current algorithm.


   antti