egui::containers::popup

Function show_tooltip_at_dyn

Source 
fn show_tooltip_at_dyn<'c, R>(
    ctx: &Context,
    parent_layer: LayerId,
    widget_id: Id,
    allow_placing_below: bool,
    widget_rect: &Rect,
    add_contents: Box<dyn FnOnce(&mut Ui) -> R + 'c>,
) -> R