Program for generating joystick configuration for Visual Boy Advance 1.8.0 on Linux

vba-joy.c

// Program to generate joystick configuration for Visual Boy Advance
// 1.8.0 on Linux. I know there existed another program before to do
// this, but I could not find it so I wrote this.
//
// It has worked for me, but it might not work for you. Compile with:
//   gcc -o vba-joy vba-joy.c -Wall -Wextra $(pkg-config --libs sdl) -std=c99
//
// Usage: ./vba-joy [joystickIndex]

#include <ctype.h>
#include <stdio.h>
#include <stdlib.h>

#include <SDL/SDL.h>

static const char* ButtonNames[] = {
  "Left", "Right", "Up", "Down", "A", "B", "L", "R", "Start", "Select", "Speed"
};
#define BUTTON_COUNT (sizeof(ButtonNames) / sizeof(ButtonNames[0]))

static int ButtonValues[BUTTON_COUNT];

int main(int argc, char* argv[])
{
  int joystickIndex = 0;

  if (argc == 2 && isdigit(*argv[1])) {
    joystickIndex = atoi(argv[1]);
  }

  if (SDL_Init(SDL_INIT_VIDEO | SDL_INIT_JOYSTICK) < 0) {
    fprintf(stderr, "Couldn't initialize SDL: %s\n", SDL_GetError());
    return 1;
  }
  atexit(SDL_Quit);

  const int joystickCount = SDL_NumJoysticks();
  if (joystickCount < 0) {
    fprintf(stderr, "Got error when probing for joysticks: %s\n",
            SDL_GetError());
    return 1;
  }
  else if (joystickCount == 0) {
    fprintf(stderr, "SDL did not find any joysticks\n");
    return 1;
  }

  printf("Available joysticks (%d):\n", joystickCount);
  for(int i = 0; i < joystickCount; i++) {
    printf("  Joystick %d: %s\n", i, SDL_JoystickName(i));
  }

  if (joystickIndex >= joystickCount) {
    fprintf(stderr, "Can't configure non-existing joystick %d\n",
            joystickIndex);
    return 1;
  }
  printf("\n");

  SDL_JoystickEventState(SDL_ENABLE);
  SDL_Joystick* joystick = SDL_JoystickOpen(joystickIndex);
  if (joystick == NULL) {
    fprintf(stderr, "Could not open joystick %d: %s\n",
            joystickIndex, SDL_GetError());
    return 1;
  }

  printf("Starting configuration of joystick %d:\n", joystickIndex);
  for (size_t button = 0; button != BUTTON_COUNT; ++button) {
    printf("  Press \"%s\" button.\n", ButtonNames[button]);

    for (SDL_Event event; SDL_WaitEvent(&event);) {
      int what = 0; // Same name as in Visual Boy Advance source code.
      switch(event.type) {
      case SDL_QUIT:
        goto cleanup_and_exit;
      case SDL_JOYBUTTONDOWN:
        what = event.jbutton.button + 128;
        break;
      case SDL_JOYAXISMOTION:
        if (event.jaxis.value == 0) {
          continue; // Filter away release of axis
        }
        what = (event.jaxis.axis << 1) | (event.jaxis.value > 16384);
        break;
      default:
        continue;
      }

      what = ((joystickIndex + 1) << 12) + what;
      ButtonValues[button] = what;
      break; // Next button
    }
  }

  printf("\nResulting button configuration for VisualBoyAdvance.cfg: \n\n");

  for (size_t button = 0; button != BUTTON_COUNT; ++button) {
    printf("Joy%d_%s=%04x\n", joystickIndex,
           ButtonNames[button], ButtonValues[button]);
  }

cleanup_and_exit:
  SDL_JoystickClose(joystick);

  return 0;
}