Hi, for the button mapping you can take a look here
. The Power slider is mapped to KEY_POWER on linux events or "SDLK_POWER" on SDL events. But you're right, it's better to avoid it because of the power daemon.
You can't use the SDL events to check for a combination of keys, every key pressed or released triggers an independant event. The event.key.keysym.sym returns the code of that key, but the AND of two key codes makes the code of another key.
You can do two things:
1 - Save all the events in variables for every key (set a boolean variable "buttonA" to true if the A was pressed, set it to false if it's released), and when you check for the input check those booleans instead of the event.
2 - What Shin-Nil said, use SDL_GetKeyState instead wich returns the state of all the keys at the same time, so you can check for any combination you want.
With the events you have the advantage of doing things only when you have to, with the SDL_GetKeyState you have to check the state periodically.
Anyway, I think that the Dingoo has enough buttons to map the Game Boy buttons AND emulator shortcuts without using combinations.