Yup, there's no question that mGBA is a better core. And yup, VBA-M is poorly engineered. As far as the actual experience playing games, the challenge for me was just to improve what was already there.
I've never even tried that feature, so it's no wonder it's not working. I took a look though - that code needed a lot of love. I've released a new version and tested the borders out (sized to 256x224)
I decided to give my VBA-M port some love - so I wrote a JIT thumb compiler for it. I didn't want to leave GameCube behind - so I've also written a whole new backend for handling paging (since GameCube only has 24MB of RAM). Note - I haven't put...