A demonstration of using SDL2 to poll the state of buttons and axes on a joystick

sdl-joystick-polling.c

#include <SDL2/SDL.h>

// This program shows how to work with joysticks using SDL2.
// This example shows how to do it by manually polling the joystick
// rather than using the sdl event queue.
int main() {
    // Initialize the joystick subsystem
    SDL_Init(SDL_INIT_JOYSTICK);

    // If there are no joysticks connected, quit the program
    if (SDL_NumJoysticks() <= 0) {
        printf("There are no joysticks connected. Quitting now...\n");
        SDL_Quit();
        return -1;
    }

    // Open the joystick for reading and store its handle in the joy variable
    SDL_Joystick *joy = SDL_JoystickOpen(0);

    // If the joy variable is NULL, there was an error opening it.
    if (joy != NULL) {
        // Get information about the joystick
        const char *name = SDL_JoystickName(joy);
        const int num_axes = SDL_JoystickNumAxes(joy);
        const int num_buttons = SDL_JoystickNumButtons(joy);
        const int num_hats = SDL_JoystickNumHats(joy);

        printf("Now reading from joystick '%s' with:\n"
               "%d axes\n"
               "%d buttons\n"
               "%d hats\n\n",
               name,
               num_axes,
               num_buttons,
               num_hats);

        int quit = 0;

        // Keep reading the state of the joystick in a loop
        while (quit == 0) {
            if (SDL_QuitRequested()) {
                quit = 1;
            }

            for (int i = 0; i < num_axes; i++) {
                printf("Axis %d: %d\n", i, SDL_JoystickGetAxis(joy, i)); 
            }

            for (int i = 0; i < num_buttons; i++) {
                printf("Button %d: %d\n", i, SDL_JoystickGetButton(joy, i));
            }

            for (int i = 0; i < num_hats; i++) {
                printf("Hat %d: %d\n", i, SDL_JoystickGetHat(joy, i));
            }

            printf("\n");

            SDL_Delay(50);
        }

        SDL_JoystickClose(joy);
    } else {
        printf("Couldn't open the joystick. Quitting now...\n");
    }

    SDL_Quit();
    return 0;
}