Function nf_text_push_str 

#[unsafe(no_mangle)]
pub(crate) unsafe extern "C" fn nf_text_push_str(
    text: *mut String,
    bytes: *const u8,
    len: usize,
)

Appends len bytes of UTF-8 at bytes.

Safety

text came from nf_text_new and isn’t finished; bytes points to len bytes.