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C-/C++-Quelltext

#include <allegro.h>
#include <string>

using std::string;

const unsigned short SCREEN_W = 600;
const unsigned short SCREEN_H = 480;

volatile int timerCounter = 0;

static void timerCounterUpdater() {
    timerCounter++;
} END_OF_STATIC_FUNCTION(timerCounterUpdater);

bool set_graphic_mode(int width, int height) {
    mode = mode > 1 ? 0 : mode;
    
    static int colorDepths[] = { 16, 24, 15, 32 };
    static int modes[]       = {
        GFX_AUTODETECT_FULLSCREEN,
        GFX_AUTODETECT_FULLSCREEN,
        GFX_AUTODETECT_WINDOWED
    };
    
    for (int i = 0; i < 4; i++) {
        set_color_depth(colorDepths[i]);
        if (set_gfx_mode(modes[i], width, height, 0, 0) >= 0) {
            return true;
        }
    }

    return false;
}

void fatal_error(string msg) {
    allegro_message(msg.c_str());
    exit(0);
}

void init() {
    allegro_init();
    install_keyboard();

    if (!set_graphic_mode(SCREEN_W, SCREEN_H)) {
        fatal_error("Grafikmodus konnte nicht gesetzt werden");
    }
    
    LOCK_FUNCTION(timerCounterUpdater);
    LOCK_VARIABLE(timerCounter);
    
    install_int_ex(timerCounterUpdater, BPS_TO_TIMER(60));
}

int main() {
    init();

    BITMAP * logo         = load_bitmap("asteroid.bmp", NULL);
    BITMAP * doublebuffer = create_bitmap(SCREEN_W, SCREEN_H);

    int x  = 0;
    int y  = 0;
    int dx = 1;
    int dy = 1;

    int maxSkip = 4;
    int curSkip = 0;
    
    bool needRefresh = false;

    while (!keypressed()) {
        curSkip = 0;
        
        if (timerCounter > 0) {
            do {
                if ((x + dx) < 0) {
                    dx *= -1;
                } else if ((x + dx + logo->w) >= SCREEN_W) {
                    dx *= -1;
                }

                if ((y + dy) < 0) {
                    dy *= -1;
                } else if ((y + dy + logo->h) >= SCREEN_H) {
                    dy *= -1;
                }

                x += dx;
                y += dy;
                
                timerCounter--;
                curSkip++;
                
                if (curSkip >= maxSkip) {
                    timerCounter = 0;
                    
                    break;
                }
            } while(timerCounter > 0);

            needRefresh = true;
        }
        
        if (needRefresh) {
            acquire_bitmap(doublebuffer);
            clear(doublebuffer);

            blit(
                logo, doublebuffer,
                x, y,
                (SCREEN_W - logo->w) / 2,
                (SCREEN_H - logo->h) / 2,
                logo->w,
                logo->h
            );

            release_bitmap(doublebuffer);

            blit(
                doublebuffer, screen,
                0, 0, 0, 0,
                SCREEN_W, SCREEN_H
            );
            
            needRefresh = false;
        }
    }
} END_OF_MAIN();