[rust] waylandsink with video overlay

[Sebastian Dröge]

On Thu, 2021-01-28 at 08:57 -0800, Joel Winarske wrote:
> 
> I'm down to https://github.com/jwinarske/waylandsink-with-video-overlay-rs/blob/main/src/main.rs#L59-L72
> 
> error[E0277]: the trait bound `Value: SetValue` is not satisfied
>   --> src/main.rs:70:25
>    |
> 70 |         s.set("handle", &value);
>    |                         ^^^^^^ the trait `SetValue` is not implemented for `Value`
>    |
>    = note: required because of the requirements on the impl of `ToSendValue` for `Value`

It indeed needs a bit more massaging. The following code should do it.

    {
        let context = context.get_mut().unwrap();
        let s = context.get_mut_structure();
        let value = unsafe {
            use gst::glib::translate::*;
            use std::mem;

            let handle = display.c_ptr();
            let mut value = mem::MaybeUninit::zeroed();
            gst::gobject_sys::g_value_init(value.as_mut_ptr(), gst::gobject_sys::G_TYPE_POINTER);
            gst::gobject_sys::g_value_set_pointer(value.as_mut_ptr(), handle as *mut c_void);
            gst::glib::SendValue::from_glib_none(&value.assume_init() as *const _)
        };
        s.set_value("handle", value);
    }

Apart from everything else there's also the problem that you need to
tell the type system that your value is actually thread-safe. So the
easiest/shortest here is actually to just create the whole GValue like
we would be doing in C.

-- 
Sebastian Dröge, Centricular Ltd · https://www.centricular.com