How to make the registered font effective

[cherish-ltt]

I registered the font

let font_name = "sans-serif123";
let re = plotters::style::register_font(font_name, FontStyle::Oblique, include_bytes!("../Songti.ttc"));

When I use BitMapBackend to create x.png
i use :

...
let font_style = FontDesc::new(plotters::style::FontFamily::Name(font_name), 30.0, FontStyle::Oblique);
...
.caption("折线图aaa", font_style)

After successfully outputting PNG, only English aaa will be displayed instead of Chinese 折线图