Implement single-step debugging for Gameboy cores

[getCursorsExe]

[CasualPokePlayer]

Use subframe cores and set the "input length" to 1.

[getCursorsExe]

SubGBHawk doesn't support disassembling yet, which makes it currently impossible to implement this without disassembling.

[CasualPokePlayer]

Use Gambatte and set "Frame Length" to "User Defined Frames"

Also SubGBHawk could trivally implement disassembling considering the base core supports it, seems more like an oversight in this case.

[CasualPokePlayer]

You can "step" by setting input length to 1 and frame advancing.

Stepping probably won't ever be "properly" implemented in Gambatte due to its various definitions for a "frame" and stepping would wreck havoc with that. GBHawk would be better suited for that. Even so, the debugger mostly doesn't work in any case (hence why Step is not bothered to be implemented in most cores). You are better off using other emulators such as bgb.

[getCursorsExe]

Well, it is not present in Gambatte options yet. It has to be somewhere else.

[CasualPokePlayer]

Input Length is an axis input, which is present when the "Frame Length" sync setting is "User Defined Frames."

[getCursorsExe]

Input length doesn't appear at all in my case, no matter what I do.

[getCursorsExe]

SameBoy actually supports this.

[getCursorsExe]

Too bad we can't port BGB core to BizHawk yet because the source code is completely private.