Function prepare_font_database 

pub fn prepare_font_database()

Build the font database configured_font_system copies into every renderer now, and throw the font system away: a native launch runs this in the background from process start, so the main thread’s first renderer finds the catalog verified and every font file read instead of doing both itself. The database is a process-wide OnceLock, so a renderer asked for meanwhile waits for this one: nothing is loaded twice, and it is the database the main thread would have built.