If the eframe web app is in hidden (e.g. is in a background tab in the browser), then any call to request_repaint will be ignored, and not result in a call to App::update.

That's because eframe checks if request_repaint has been called from requestAnimationFrame callback, which is not called if the application is hidden.

Solution

If the web page is hidden, then calling request_repaint should schedule a setTimer(…) callback to call App::update() (must done via a setTimer delay, or we could have App::update call request_repaint which in turn calls App::update.

We also need some guards to make sure that multiple calls to request_repaint in a row only results in one call to App::update, for instance via this pseudo-code:

// Won't be called if hidden
fn on_request_animation_frame() {
    if state.needs_repaint {
       app.update();
       paint();
       state.needs_repaint = false;
    }
}

fn on_request_repaint() {
   state.needs_repaint = true;
    if document.is_hidden {
       setTime(10ms, app_update_if_needed);
    }
}

fn app_update_if_needed() {
   if state.needs_repaint {
       app.update();
       state.needs_repaint = false;  
    }
}

Related

• App::logic #5113