title: Eclipse SWT - WizardPage widgets validation
body: <p>What is the best way to validate Text, Combo and any other SWT widget included in Eclipse Wizard? Recently, I got into a project in which there are many different wizards. I tried to add FocusListeners, ModifyListeners etc. however the size of code and it's complexity was not what I expected. </p>
  
  <p>Let's say there are two Text elements in WizardPage. They both cannot be empty and should contain only small letters. How to write a validator which checks if fields are empty or contain unexpected characters and display an error message in case something went wrong.</p>
  
  <p>The way it has to be done must be sophisticated, elegant and useful.</p>