client API: add a way to notify clients of property changes

This turned out ridiculously complex. I think it will have to be
simplified some day. Main reason for the complexity are:
- filtering properties by forcing clients to observe individual
  properties explicitly
  (to avoid spamming clients with changes they don't want)
- optional retrieval of property value with the notification
  (the basic idea was that this is more user friendly)
- allowing to the client to specify a format in which the value
  should be retrieved
  (because if a property changes its type, the client API couldn't
  convert it properly, and compatibility would break)

I don't know yet which of these are important, and everything could
change. In particular, the interface and semantics should be adjusted
to reduce the implementation complexity.

While I consider the API complete, there could (and probably will) be
bugs left. Also while the implementation is complete, it's inefficient.
The complexity of the property matching is O(a*b*c) with a clients,
b observed properties, and c properties changing at once. I threw away
an earlier implementation using bitmasks, because it was too unwieldy.

1 files changed, 1 insertions, 0 deletions

diff --git a/player/client.h b/player/client.h
index 4c0c23c614..6e078e9d7b 100644
--- a/player/client.h
+++ b/player/client.h
@@ -17,6 +17,7 @@ int mp_clients_num(struct MPContext *mpctx);
 void mp_client_broadcast_event(struct MPContext *mpctx, int event, void *data);
 int mp_client_send_event(struct MPContext *mpctx, const char *client_name,
                          int event, void *data);
+void mp_client_property_change(struct MPContext *mpctx, const char **list);
 
 struct mpv_handle *mp_new_client(struct mp_client_api *clients, const char *name);
 struct mp_log *mp_client_get_log(struct mpv_handle *ctx);