GPAR2 was updating its UI many times per second (each time it got a notification from the par2cmdline library). This was causing it to slow down immensely compared to the par2 command from the command line, especially on computers with slow video cards or fancy renderers.
Attached is a patch which causes it to update the UI on a (fast) interval instead of potentially hundreds of times per second.
On this machine it brings it up to par (haha) with the command line version, in terms of speed. Before patch it was ~ 15 times slower.
Note: Patch is for GPAR2. And only GPAR2. it refers to files inside GPAR2. It only refers to the main window cc and main window h. It just adds a clock watcher that updates at intervals instead of every single notification (~10 hz instead of 1000 per second)