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Stupid Simple Question.

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OzzoNation    142
I made a simple little SDL app that blits a square in the center of the window of random color. Every time you make any mouse or keyboard event, it changes color. However, every time I start the application, the square is always a light green. I don't know why? Here's the source:
#include <iostream>
#include <string>
#include <stdio.h>
#include <stdlib.h>
#include <SDL/SDL.h>
#include <SDL/SDL_mixer.h>
#include <SDL/SDL_image.h>
#include <SDL/SDL_ttf.h>

int main(int argc, char* argv[])
    if (SDL_Init(SDL_INIT_VIDEO) != 0)
        fprintf (stderr, "Unable to initialize the SDL Video Subsystem.", SDL_GetError());
        exit (1);
        fprintf (stdout, "SDL Video Subsystem initialized.");
    SDL_Surface *window = SDL_SetVideoMode(640, 480, 0, SDL_HWSURFACE);
    SDL_WM_SetCaption("SDL Shell", 0);
    Uint8 red, green, blue;
    Uint32 color;
    SDL_Rect rect;
    SDL_Event event;
    bool is_game_running = true;
    while (is_game_running == true)
        if (SDL_PollEvent(&event))
            red = rand() % 256;
            green = rand() % 256;
            blue = rand() % 256;
            color = SDL_MapRGB(window -> format, red, green, blue);
            rect.x = 200;
            rect.y = 150;
            rect.w = 200;
            rect.h = 200;
            SDL_FillRect(window, &rect, color);
            SDL_UpdateRect(window, 0, 0, 0, 0);
            if (event.type == SDL_QUIT)
                is_game_running = false;
    return 0;

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SiCrane    11839
It looks like you never seed the random number generator with srand(), so it always uses the default seed. If you use srand() with a number source that is different everytime you run the program, such as time() (well, within a second anyways), then you'll get different random numbers.

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ScottC    100
rand is psuedo-random, theres no actual true random calls, but you can make it seem like it by calling srand and seeding it with the system time, like so: srand(time(NULL));

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