The version of swt which comes with PDI 5.4 does not work correctly on CentOS 7 x86_64. However with a simple file replacement you can get Spoon up and running.  Here are the steps:

  1. Download the file swt-4.5-gtk-linux-x86_64.zip from the eclipse website.
  2. Extract the file swt.jar from the download and copy it over the version of the file located within your spoon installation (<PDI Install Home>/data-integration/libswt/linux/x86_64).
  3. From your account home directory remove the hidden directly called .swt
  4. Start Spoon