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Bug 779721. Part 5: Add a comment explaining more about how MediaStream lifetimes are managed. r=jesup

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This commit is contained in:
Robert O'Callahan 2012-08-09 23:30:02 +12:00
parent 481c2bc36d
commit 8184332b0d
1 changed files with 19 additions and 0 deletions
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19
content/media/MediaStreamGraph.h
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@ -202,6 +202,25 @@ class SourceMediaStream;
*
* We make them refcounted only so that stream-related messages with MediaStream*
* pointers can be sent to the main thread safely.
*
* The lifetimes of MediaStreams are controlled from the main thread.
* For MediaStreams exposed to the DOM, the lifetime is controlled by the DOM
* wrapper; the DOM wrappers own their associated MediaStreams. When a DOM
* wrapper is destroyed, it sends a Destroy message for the associated
* MediaStream and clears its reference (the last main-thread reference to
* the object). When the Destroy message is processed on the graph
* manager thread we immediately release the affected objects (disentangling them
* from other objects as necessary).
*
* This could cause problems for media processing if a MediaStream is
* destroyed while a downstream MediaStream is still using it. Therefore
* the DOM wrappers must keep upstream MediaStreams alive as long as they
* could be being used in the media graph.
*
* At any time, however, a set of MediaStream wrappers could be
* collected via cycle collection. Destroy messages will be sent
* for those objects in arbitrary order and the MediaStreamGraph has to be able
* to handle this.
*/
class MediaStream {
public: