keyboard_test.c

/*
    File name:
        keyboard_test.c

    Compile with:
        gcc -lSDLmain -lSDL -lcairo keyboard_test.c -o keyboard_test

    Run:
        ./keyboard_test
*/

#include <SDL/SDL.h>
#include <cairo/cairo.h>

int W = 500, H = 500;
char *FONT = "Liberation Mono";
int KEYS_PRESSED_CNT = 0;

void draw(cairo_t *c) {
    cairo_set_source_rgb(c, 0.1, 0.1, 0.1);
    cairo_paint(c);

    char str[3];
    sprintf(str, "%i", KEYS_PRESSED_CNT);

    cairo_set_source_rgb(c, 0, 1, 1);
    cairo_move_to(c, 145, 365);
    cairo_show_text(c, str);
}

int main() {
    SDL_Init(SDL_INIT_VIDEO);
    SDL_Surface *screen = SDL_SetVideoMode(W, H, 32, 0);

    cairo_surface_t *cairo_s;
    cairo_s = cairo_image_surface_create_for_data(screen->pixels,
              CAIRO_FORMAT_ARGB32, W, H, screen->pitch);
    cairo_t *c = cairo_create(cairo_s);
    cairo_select_font_face(c, FONT, 0, 0);
    cairo_set_font_size(c, 350);

    SDL_Event event;

    while (1) {
        draw(c); SDL_Flip(screen);

        SDL_WaitEvent(&event);
        switch (event.type) {
            case SDL_QUIT:  return 0;
            case SDL_KEYDOWN:
                if (event.key.keysym.sym == SDLK_ESCAPE)
                    return 0;
                KEYS_PRESSED_CNT += 1;
                break;
            case SDL_KEYUP:
                KEYS_PRESSED_CNT -= 1;
                if (KEYS_PRESSED_CNT < 0)
                    KEYS_PRESSED_CNT = 0;
        }
    }
}