Function show

pub fn show(
    ui: &mut Ui,
    state: &mut LibraryState,
    project: &mut Project,
    settings: &mut Settings,
    thumbs: Option<&mut ThumbCache>,
    live: Option<&PreviewFrame>,
    palette: &Palette,
    ytdlp: bool,
    undo: &mut dyn FnMut(&Project),
) -> LibraryResponse

thumbs: the app’s ThumbCache, so rows and the preview can show a picture. None (no cache / headless) draws the painted fallback instead. ytdlp = yt-dlp was found at start-up; the “Import URL…” button only exists when it is installed.