title: Blacklisting characters in a controlP5 textField
body: <p>In the controlP5 library, I need to prohibit certain characters from being entered into a <code>textField</code>.</p>
  <p>I found a piece of code where you indicate what to prohibit, but I don’t know how to enforce the conditions (possibly by emulating the erase button?).</p>
  <p>This is what I'd like to whitelist:<img src="https://i.stack.imgur.com/vnu8m.png" alt="enter image description here" /></p>