4.2 裏に描いて適当なタイミングでコピー

/*
 * testlayer1.c
 */

#include <stdio.h>
#include <math.h>
#include <eggxlib.h>

double f(double x)
{
  return sin(x) + sin(3 * x);
}

int main()
{
  /* */
  int win;
  double xmin, xmax, ymin, ymax;
  double a, b, pi, x, y, c, t, dt;
  int i, j, N, Nt;
  double dx;
  /* 描画範囲 */
  pi = 4 * atan(1.0);
  a = 0; b = 2 * pi;
  /* ウィンドウを開く */
  win = eggx_gopen(500, 500);
  eggx_winname(win, "mygraph");
  eggx_gclr(win);
  xmin = a - (b - a) / 10; xmax = b + (b - a) / 10; ymin = - 2.0; ymax = 2.0;
  eggx_window(win, xmin, ymin, xmax, ymax);
  eggx_newcolor(win, "green");
  /* */
  N = 200;
  dx = (b - a) / N;

  Nt = 500;
  c = 1; dt = 10.0 / Nt;

  /* layer=1 を表示、layer=0 に描画 */
  eggx_layer(win, 1, 0);
  for (i = 0; i <= Nt; i++) {
    eggx_gclr(win);
    t = i * dt;
    x = a; y = f(x - c * t);
    eggx_line(win, x, y, PENUP);
    for (j = 1; j <= N; j++) {
      x = j * dx; y = f(x - c * t);
      eggx_line(win, x, y, PENDOWN);
    }
    /* layer=0 の画像を layer=1 にコピーする */
    eggx_copylayer(win, 0, 1);
  }
  eggx_ggetch(win);
  /* eggx のウィンドウを閉じる */
  eggx_gclose(win);
  return 0;
}