pub fn shape_visual_items<T: ParsedFontTrait>(
visual_items: &[VisualItem],
font_chain_cache: &HashMap<FontChainKey, FontFallbackChain>,
fc_cache: &FcFontCache,
loaded_fonts: &LoadedFonts<T>,
debug_messages: &mut Option<Vec<LayoutDebugMessage>>,
) -> Result<Vec<ShapedItem>, LayoutError>