Came across this issue and figured id post my fix. it only happened to me after deciding i wanted to move all of my emulators and roms to a different drive on my pc. Once i made the move and rebuilt all the libraries in launchbox, fusion was giving me the same fullscreen errors. if i moved it back to the original drive which also has the OS on it, it was fine. after some googling i found this youtube video to be helpful. https://www.youtube.com/watch?v=cmpKrxBvR4c
basically after changing the ForceFullScreen32=0 line in the config file to a 1, all issues resolved. hope this helps any future googlers!
Thank You. My computer is using windows 8.1, my Kega Fusion is error Direct screen, so i think change disable DPI Scale is work. But, actually its dont work so i read your say, i change the fullscreen on config file, and i restart my KEGA and here we go i can playing game sega in fullscreen mode. Thanks for your comment
Kega Fusion Emulator doesn't work in Full Screen for Sega Genesis Games
in Troubleshooting
Posted
Thank You. My computer is using windows 8.1, my Kega Fusion is error Direct screen, so i think change disable DPI Scale is work. But, actually its dont work so i read your say, i change the fullscreen on config file, and i restart my KEGA and here we go i can playing game sega in fullscreen mode. Thanks for your comment