Function compile 

pub fn compile(
    spec: &VideoSpec,
    facts: &Facts,
    fonts: &[Arc<[u8]>],
) -> Result<Compiled, ComposeError>

Compiles spec with facts about its files.

fonts are the font files an export registers, in fallback order; with them, text that must fit is measured and shrunk to fit.

Errors

Returns where in the spec, and why, it cannot be compiled.