title: Eclipse WindowBuilder: Unknown GUI Toolkit/Cannot Resolve Imports when class file under src folder
body: <p>On Eclipse (OS X) when I create a SWT/JFace Java Project, then create an Application Window Java class file I cannot seem to resolve org.eclipse.swt imports. On the other hand, if I create a SWT/JFace Java Project and select "Use project folder as root for sources and class files" the import resolves and everything works fine. The imports also seem to resolve in the former case when I drag my .java file outside of the src folder and put it directly into the project folder, but in this case I don't have the option of selecting the 'Design' tab.</p>
  
  <p>What should I do so that my org.eclipse.swt imports work inside the src folder?</p>