Why doesn't my galaxy s4 screen display anything?
Try removing the battery and pulling it back in again. Then hold power button + home + volume up for a few seconds until the screen lights up. If nothing shows up the screen make sure your battery if loaded. Try it again and if that doesn't work either. Try exactly the same except you use the volume down now and not the volume up. If that doesn't work it's probably a hardware problem. It's not software because the last update was a few months ago so then it would've been occurred earlier. 

It could be a software problem if you've rooted your phone. Try flashing your stock software on it. You can't see anything but moving through download mode isn't that hard. Power + home + volume down. Wait a few secs, press volume up. Plug into PC using USB and flash stock software using Odin. If it isn't rooted it's a hardware problem. Go to your nearest Samsung Repair Center and maybe the repair is free because of the warranty. Unless it's rooted of course.