Function CMTextFormatDescriptionGetDefaultTextBox 

pub unsafe extern "C-unwind" fn CMTextFormatDescriptionGetDefaultTextBox(
    desc: &CMFormatDescription,
    origin_is_at_top_left: bool,
    height_of_text_track: CGFloat,
    default_text_box_out: NonNull<CGRect>,
) -> i32

Available on crate feature CMFormatDescription only.

Returns the default text box.

Within a text track, text is rendered within a text box. There is a default text box set, which can be over-ridden by a sample. The function can return kCMFormatDescriptionError_ValueNotAvailable for format descriptions that do not carry a default text box.

Safety

default_text_box_out must be a valid pointer.