Constant TITLE_BAR_HEIGHT 

pub const TITLE_BAR_HEIGHT: f64 = _; // 40f64

The unscaled title-bar height: a floating window’s title bar is a Bar (HIG §9.1/§9.6), so it takes metrics.bar_height — the same 40 px the top bar, a toolbar and the shared Button use. Live geometry reads the ui_scaled token from the theme the window was laid out with (FloatingWindow::title_bar_height); this constant is for callers that need the reference value in a const context.