Function estimate_text_size_styled 

pub fn estimate_text_size_styled(
    text: &str,
    font_name: &str,
    font_size: f64,
    bold: bool,
    italic: bool,
) -> (f64, f64)

estimate_textspan_size from lib/common/textspan.c with explicit bold/italic flags (HTML_BF/HTML_IF): (fontsize * width_1pt, fontsize * LINESPACING).