On May 16, 2008, at 9:29 PM, James Justin Harrell wrote:
The current HTMLMediaElement interface is inconsistent and is
designed in such a way that making changes to it will be extremely
difficult.
The network state is given by the "networkState" attribute, and is
one of:
EMPTY, LOADING, LOADED_METADATA, LOADED_FIRST_FRAME, LOADED
The ready state is given by the "readyState" attribute, and is one of:
DATA_UNAVAILABLE, CAN_SHOW_CURRENT_FRAME, CAN_PLAY, CAN_PLAY_THROUGH
Although adding states for either of these would not be fun, it
could be done. But the playback state is different.
The consistent and upgradeable design would be to have a
"playbackState" attribute that is one of:
PAUSED, PLAYING
But because there are currently only two states, we instead have a
single boolean attribute. Boolean attributes are great when you're
sure there will always be only two states, but they're terrible if
there's a chance you'll want to add additional states.
I'm not sure adding states is all that safe. Any code that does a
switch on the state would now fall through to an untested code path.
It isn't difficult to imagine all kinds of additional playback
states. For example, what if there was great demand for forward-
seeking and backward-seeking states? (e.g. the states that are
usually associated with those >> and << buttons) How could those
states be added?
Then you would treat the video as playing, and the playback rate as
different than 1.0.
The media error state is also inconsistent, and this time for no
apparent reason, although it would at least be easy to update. A
more consistent design would be to have an "errorState" attribute
that is one of:
NO_ERROR, ABORTED, NETWORK_ERROR, DECODING_ERROR
The type of error is not a state. There is no state transition that
will move you from one to the other. An error is something that
happened. There could however be a type of error that you reached.
- Maciej
And why are the error state names prefixed with "MEDIA_ERR" when the
names for the other states are not prefixed? e.g. LOADING instead of
MEDIA_NET_LOADING.
If NO_ERROR was given a value of 0, testing for an error with this
design wouldn't be any more difficult.
if( videoElement.error ) {...}
if( videoElement.errorState ) {...}
----- Original Message ----
Wouldn't you want something like that to know, for example, whether
to
display a "play" or a "pause" button?
We have that -- the "paused" attribute. When it's true, show play, and
when it's paused, show false. You don't want to show play when the
reason
you aren't playing is that you're buffered or seeking for instance.
The
client is trying to play. It can't.
