title: Swift adding custom keyboard or numpad in app
body: <p>What types of restrictions is there when adding a custom keyboard or numpad in an app?</p>
  
  <p>I know that some apps requires you to enable keyboards in your system settings.</p>
  
  <p>I recently saw an app using this keyboard:</p>
  
  <p><a href="https://i.stack.imgur.com/D0bL2.png" rel="noreferrer"><img src="https://i.stack.imgur.com/D0bL2.png" alt="enter image description here"></a></p>
  
  <p>The app does not require you to activate the keyboard. So how can I make my own custom numpad like this one?</p>
  
  <p>Feel free to share any tutorials/libraries</p>
  
  <p>thanks,</p>