CHICAGO—A triptych of films screened Thursday to Sunday, collectively marketed under the header In Focus: Dance, forms an anchor point of the 2019 Chicago International Film Festival, North America’s longest-running competitive film festival. The films—director Levan Akin’s And Then We Danced, Isadora’s Children, directed by Damien Manivel, and Cunningham, a documentary on Merce Cunningham directed by Alla Kovgan—run concurrent to…