On 8/11/10 5:13 AM, Philip Jägenstedt wrote:
Yes, in the case of the parser inserting source elements that fail one
of the tests (no src, wrong type, wrong media) the algorithm will end up
at step 6.21 waiting. It doesn't matter if all sources are available
when the algorithm is first invoked or if they "trickle in", be that
from the parser or from scripts.
Right, ok. Thanks for bearing with me on this!
It's quite serious because NETWORK_EMPTY is used as a condition in many
places of the spec, so this absolutely must be consistent between browsers.
OK, gotcha.
Otherwise the pointer could potentially reach the same source element
twice, with the aforementioned problems with failing after network access.
But this would only happen in a rare case, right? Specifically, that of
source elements being inserted out of order... And if the update to new
source elements being inserted were fully async, it would only happen if
you trickle the source elements in out of order.
But yes, your idea of flagging a source when it fails would also address
this just fine.
OK, perhaps I should take this more seriously. Making the whole
algorithm synchronous probably isn't a brilliant idea unless we can also
do away with all of the state it keeps (i.e. hysteresis).
State is not necessarily a problem if it's invalidated as needed....
One way would be to introduce a magic flag on all source elements to
indicate that they have already failed. This would be cleared whenever
src, type or media is modified.
This seems eminently doable.
Yes, it sounds like it very much does, and would result in disasters
like this:
<!doctype html>
<video src="video.webm"></video>
<!-- network packet boundary or lag? -->
<script>alert(document.querySelector('video').networkState)</script>
The result will be 0 (NETWORK_EMPTY) or 2 (NETWORK_LOADING) depending on
whether or not the parser happened to return to the event loop before
the script. The only way this would not be the case is if the event loop
is spun before executing scripts, but I haven't found anything to that
effect in the spec.
I don't think there is anything, no...
-Boris
