a bug in the app caused it to not buffer taps made while the gui was still rendering an animation the application told the gui to disable buffering during the animation (or neglected to indicate it wanted buffering, if it's not the default action) the developer used an animation api that specifically does not buffer taps when there was a buffering api available he should have used the gui always disables tap detection while the specific sort of animation used on the '2' is being done So what went wrong here? There's several possibilities, depending on what the gui supports. This is generally considered poor design but I still see it from time to time. In those cases you can mash a bunch of keys and then look at the screen as they are animated one at a time until all keys are animated. SOME apps I've seen just linearly buffer and the app won't be notified of the '3' until the '2' is done animating. If it notifies immediately, I would expect the app to tell the gui to stop the '2' animation and start the '3' animation, as this leads to better response time. I don't know which approach the gui takes. If in the meanwhile, the gui is displaying the fading of the '2', the user taps '3', the interface should buffer the tap, and it can either notify the app immediately ( during the animation) of the new tap, OR it can wait until the animation is done and then notify the app. Then you go back to waiting for another tap.

You look at the location on the screen, figure out the user pressed '2, remember it, and tell the gui to do the fade on the '2' to indicate the press was accepted. So the app waits for you to tap, and the user taps a coordinate on the screen and your app is notified of this. The person that wrote the app was probably 'safe to assume' that taps on the screen will be buffered during animations and other gui actions. This is a case of the person writing the app making assumptions about how the user interface behaves, and these assumptions turning out to be wrong OR the interface not behaving as documented. As a developer I can see exactly how something like this can happen, and I've had variations of it happen to me numerous times over the years.

Where did my calculator go