Game of life on X11

gameoflife.cc

#include <chrono>
#include <cstdlib>
#include <iostream>
#include <random>
#include <thread>
#include <X11/Xlib.h>
#include <X11/Xutil.h>

using namespace std;

int main() {
  ::Display *display = ::XOpenDisplay(nullptr);
  if (!display) {
    cout << "Error." << endl;
    exit(1);
  }

  const int ww = 1024;
  const int wh = 1024;
  const int k = 4;
  const int w = ww / k;
  const int h = wh / k;

  unsigned c[4] {
    0x00ffffff,
    0x00ffddee,
    0x004455ff,
    0x002233ff,
  };

  ::Window window = XCreateSimpleWindow(
      display, ::XDefaultRootWindow(display), 0, 0, ww, wh, 1,
      ::XBlackPixel(display, 0), ::XWhitePixel(display, 0));

  ::XSelectInput(display, window, ButtonPressMask | ExposureMask);

  ::GC gc = ::XCreateGC(display, window, 0, 0);
  ::XSetGraphicsExposures(display, gc, false);

  ::XMapWindow(display, window);
  ::XFlush(display);

  random_device rd;
  mt19937 rng(rd());
  bernoulli_distribution dist(0.5);

  ::Visual *visual = ::XDefaultVisual(display, ::XDefaultScreen(display));

  unsigned *data = reinterpret_cast<unsigned *>(malloc(4 * ww * wh));
  ::XImage *image = ::XCreateImage(
      display, visual, 24, ZPixmap, 0,
      reinterpret_cast<char *>(data), ww, wh, 8, 0);

  vector<vector<int>> cells(w, vector<int>(h));

  auto reset = [&]() {
    for (int x = 0; x < w; ++x) {
      for (int y = 0; y < h; ++y) cells[x][y] = dist(rng);
    }
  };
  reset();

  ::XEvent event;
  bool loop = true;
  unsigned time = 0;
  while (loop) {
    if (::XPending(display) > 0) {
      ::XNextEvent(display, &event);
      switch (event.type) {
        case ButtonPress:
          loop = false;
          break;
        case Expose:
          ::XPutImage(display, window, gc, image, 0, 0, 0, 0, ww, wh);
          break;
      }
    } else {
      for (int x = 0; x < w; ++x) {
        for (int y = 0; y < h; ++y) {
          int n = 0;
          for (int i = -1; i <= 1; ++i) {
            for (int j = -1; j <= 1; ++j) {
              n += cells[(x + i + w) % w][(y + j + h) % h] & 1;
            }
          }
          if (n == 3 || (n == 4 && (cells[x][y] & 1))) cells[x][y] |= 2;
        }
      }

      for (int x = 0; x < w; ++x) {
        for (int y = 0; y < h; ++y) {
          for (int i = 0; i < k; ++i) {
            for (int j = 0; j < k; ++j) {
              data[x * k + i + (y * k + j) * ww] = c[cells[x][y] & 3];
            }
          }
          cells[x][y] >>= 1;
        }
      }

      ::XPutImage(display, window, gc, image, 0, 0, 0, 0, ww, wh);
      ::XFlush(display);

      this_thread::sleep_for(chrono::microseconds(100000));
      if (++time == 500) {
        reset();
        time = 0;
      }
    }
  }

  ::XCloseDisplay(display);
  return 0;
}