Maybe we should move this somewhere else then
Good point. I've moved this in to `session_set_source_object_state`.
does first Start() with non-zero position qualify as seeking, does it produce NOTIFY_START_OF_STREAM
I believe it should. The documentation for `MFT_MESSAGE_NOTIFY_START_OF_STREAM` states:
Notifies a Media Foundation transform (MFT) that the first sample is about to be processed
So it should be notified on the first start no matter the starting position.
In the current version, I have it so it'll be called when `event_type == MESourceStarted || event_type == MEStreamStarted`. And our `IMFMediaSource` implementations currently always send `MESourceStarted` if the source state was stopped.
Note that I only added the commit with this change to fix a failing test, but more tests could probably be added. Although that would be separate MR.