derive_more | Some more derive options

After much messing around I think I have something that works, although I'm happy to accept other answers that are better as I feel this is a bit messy:

I cannot build your simplified Dockerfile as-is because I do not have the source files you reference in COPY statements, so I get "COPY failed" errors. You say "Building and running a new cargo default project with the x86_64-unknown-linux-musl target works" and indeed this Dockerfile (your simplified Dockerfile with the COPY commands removed) works fine for me:

Multiple problems here:

1. so how do you change the output type to a u32 number?

The output of your application already tells you that this is a glib::Value, so the first step would be to check it's docs: You need to get the value out of it, in your case via value.get::() or value.get_some::().

1. myEnc.set_caps(Some(&caps)); however this generates compile errors

You can't just set caps on an element, that conceptually makes no sense and as the compiler tells you there is also no such function. If you want to enforce specific caps between pads of two elements you need to use a capsfilter element (set the caps on its caps property via set_property()) or by using element1.link_pads_filtered(Some("src"), &element2, Some("sink"), Some(&caps)).