in src/platform_impl/macos/view.rs [653:663]
fn update_potentially_stale_modifiers(state: &mut ViewState, event: id) {
let event_modifiers = event_mods(event);
if state.modifiers != event_modifiers {
state.modifiers = event_modifiers;
AppState::queue_event(EventWrapper::StaticEvent(Event::WindowEvent {
window_id: WindowId(get_window_id(state.ns_window)),
event: WindowEvent::ModifiersChanged(state.modifiers),
}));
}
}