[vlc-devel] [PATCH v2 1/3] Introduce media source and media tree API

[Romain Vimont]

On Tue, Jun 26, 2018 at 11:39:04AM +0300, Rémi Denis-Courmont wrote:
> Le lundi 25 juin 2018, 13:09:24 EEST Jean-Baptiste Kempf a écrit :
> > On Fri, 22 Jun 2018, at 21:21, Rémi Denis-Courmont wrote:
> > > Nack. We already have an SD abstraction and so far I have not seen a
> > > justification for replacing it. Hence adding any new VLC object
> > > derivative seems wrong.
> > 
> > I don't understand.
> > Are you against the media_source, media_source_provider or the
> > media_tree part?
> 
> The design rationale is to get rid of the playlist. That only explains why 
> media-tree is needed, which replaces the playlist, the playlist lock and the 
> input item callbacks.

Yes, that was the main point.

> It does not explain why you need anything else.

You get a point: I failed to explain the rationale of the remaining.
Here is an attempt to fix this.

Several interfaces (qt, macosx) do the same work:
 - open SDs;
 - listen to SD, and add/remove items on SD events;
 - listen to input (preparsing), and add items on events;
 - close SD.

One initial idea of media source/tree was to factorize this common work,
and expose a "higher level" API: the exposed tree contains both item
detected by SD and added by preparsing.

In addition, to avoid to open the same SD several times by several
clients/interfaces, I added a single "media source provider" (bad name,
but I did not manage to get a better one yet), child of the libvlc
object, which allows to retrieve (refcounted) media sources (it handles
SD open/close automatically). Thus, several client may use the same
media source instance, holding a tree containing media detected by the
same "services discovery".

The clients may connect callbacks at any time (i.e. not necessarily on
SD open), without "missing" events.