Function text_line_metrics_ab_glyph 

pub fn text_line_metrics_ab_glyph(
    font: &FontArc,
    text: &str,
    font_px: f32,
    max_w: u32,
    max_h: u32,
) -> (usize, f32)

Line count and pitch of the layout [render_text_ab_glyph_rgba] produces.

Mirrors that function’s line breaking exactly (explicit \n, automatic wrap at max_w, line_height = scaled.height() + scaled.line_gap()) without rasterizing, so a caller that draws text as one image can still address individual rows.