The ..._get_text functions on Label and Textarea don't seem to be available currently. I can get text by calling the C function in an unsafe block like this:

let mut textarea = Textarea::new()?;
unsafe {
    let text = CStr::from_ptr(lv_textarea_get_text(textarea.raw().unwrap().as_ptr()));
}

However, it would be nice if I could do textarea.get_text().