Since upgrading to Fedora 22 Spoon (the client tool of PDI) was not working properly any more: Although I could start Spoon properly and create transformations etc, once I wanted to execute a transformation or sometimes even when trying to open settings, nothing was working and the terminal window showed several (SWT:20352): GLib-CRITICAL error messages. In a nutshell, Spoon was rendered useless.

On this wonderful Sunday morning - clear blue sky in Britain - I finally figured out how to fix this dilemma:

1. Go to the Eclipse Download Page and download the latest 64bit verion of Eclipse IDE for Java EE Developers. Note: There is a separate download area for SWT, however, for Linux there is no 64 bit version available. The only way to get one is to build it yourself. So I just went the easier way and downloaded Eclipse instead.
2. Unzip the file and search for swt. A search result will show a few files, but the ones interesting for us are (your version number might be different): org.eclipse.swt_3.103.2.v20150203-1313.jar and org.eclipse.swt.gtk.linux.x86_64_3.103.2.v20150203-1351.jar.
3. Copy the first one of these files into <PDI_HOME>/libswt/linux/x86 and the second into <PDI_HOME>/libswt/linux/x86_64.
4. Both folders still have the original jar files in them. Rename them to swt-jar-old (Note: no extension, so that they are not picked up).
5. Start spoon. There will be a few error messages shown, but so far Spoon is working way better for me then before.

Good luck! Now it’s time for me to enjoy some of this splendid sunshine - before clouds come in again - which happens all too often and all too quickly.

UPDATE 2016-02-08:

In eclipse-jee-mars I found the relevant files in the plugins folder:

Here is a rough outline of the approach:

$ ls plugins/*swt*
$ cd ~/apps/pdi-ce-6.0.1/libswt/linux/x86_64
$ mv swt.jar swt-old-jar
$ cp plugins/org.eclipse.swt.gtk.linux.x86_64_3.104.1.v20150825-0743.jar .
$ cp plugins/org.eclipse.swt_3.104.1.v20150825-0743.jar .