They can only be called from a single thread at a time, unlike some of
the appsrc callbacks.
This change was partially done in 062403bdac
but a part was missing.
... in function signatures.
These breaking changes aim at improving usability by allowing users
to take advantage of Rust error management features sur as `ok_or`,
`map_err`, `expect` and the `?` operator. See the `examples` and
`tutorials` to get an idea of the impacts.
And also implement a FormatValue type that holds a value together with
its format to make usage of the positions/durations/seek positions/etc
more convenient and safe.
Fixes https://github.com/sdroege/gstreamer-rs/issues/3
Have to hide some properties again at a later time, which have actual
getter/setter functions already. We only need the notification signals
for those.
Depends on the GIR patch in https://github.com/gtk-rs/gir/pull/441
