Java tutorial
/**
* Xsplinefun displays colorful moving splines in a window.
*
* Taken from xsplinefun, Distribution of 02may92, by Jef Poskanzer,
* jef@netcom.com, jef@well.sf.ca.us
*
* @copyright (C) 1992 by Jef Poskanzer
*
* Permission to use, copy, modify, and distribute this software and its
* documentation for any purpose and without fee is hereby granted, provided
* that the above copyright notice appear in all copies and that both that
* copyright notice and this permission notice appear in supporting
* documentation. This software is provided "as is" without express or implied
* warranty.
*
* First step in converting to Java was to junk all the X Windows stuff; in the
* process we lost all the customization (need to re-add with getopt?).
*/
public class XSplineFun {
public static final int POINTS = 20;
public static final int DEFAULT_MAX_COLORS = 20;
/* Spline-fun smarts. */
static int x[] = new int[POINTS];
static int y[] = new int[POINTS];
static int dx[] = new int[POINTS];
static int dy[] = new int[POINTS];
static int nred, ngreen, nblue, dred, dgreen, dblue;
static int color;
static Color xcolors[] = new Color[DEFAULT_MAX_COLORS];
public static void main(String[] av) {
Frame f = new Frame("Spline Fun");
XSplineFun xf = new XSplineFun();
xf.init_splines();
f.add(xf);
while (true)
try {
xf.move_splines();
Thread.sleep(150); // msec
} catch (Exception e) {
System.out.println(e);
}
}
static void init_splines() {
int i;
/* Initialize points. */
for (i = 0; i < POINTS; ++i) {
x[i] = random() % width;
y[i] = random() % height;
dx[i] = random() % (MAX_DELTA * 2) - MAX_DELTA;
if (dx[i] <= 0)
--dx[i];
dy[i] = random() % (MAX_DELTA * 2) - MAX_DELTA;
if (dy[i] <= 0)
--dy[i];
}
/* Initalize colors. */
for (color = 0; color < ncolors; ++color) {
xcolors[color].red = xcolors[color].green = xcolors[color].blue = 0;
xcolors[color].pixel = pixels[color];
xcolors[color].flags = DoRed | DoGreen | DoBlue;
}
color = 0;
nred = ngreen = nblue = 0;
dred = random() % (MAX_COLOR_DELTA * 2) - MAX_COLOR_DELTA;
if (dred <= 0)
--dred;
dgreen = random() % (MAX_COLOR_DELTA * 2) - MAX_COLOR_DELTA;
if (dgreen <= 0)
--dgreen;
dblue = random() % (MAX_COLOR_DELTA * 2) - MAX_COLOR_DELTA;
if (dblue <= 0)
--dblue;
}
static void rotate_colormap() {
int t, i;
if (forwards) {
t = xcolors[0].pixel;
for (i = 0; i < ncolors - 1; ++i)
xcolors[i].pixel = xcolors[i + 1].pixel;
xcolors[ncolors - 1].pixel = t;
XStoreColors(display, cmap, xcolors, ncolors);
} else if (backwards) {
t = xcolors[ncolors - 1].pixel;
for (i = ncolors - 1; i > 0; --i)
xcolors[i].pixel = xcolors[i - 1].pixel;
xcolors[0].pixel = t;
XStoreColors(display, cmap, xcolors, ncolors);
}
}
static void
new_color()
{
int t;
for ( ; ; )
{
t = (int) nred + dred;
if ( t >= 0 && t < 65536 ) break;
dred = random() % ( MAX_COLOR_DELTA * 2 ) - MAX_COLOR_DELTA;
if ( dred <= 0 ) --dred;
}
xcolors[color].red = nred = t;
for ( ; ; )
{
t = (int) ngreen + dgreen;
if ( t >= 0 && t < 65536 ) break;
dgreen = random() % ( MAX_COLOR_DELTA * 2 ) - MAX_COLOR_DELTA;
if ( dgreen <= 0 ) --dgreen;
}
xcolors[color].green = ngreen = t;
for ( ; ; )
{
t = (int) nblue + dblue;
if ( t >= 0 && t < 65536 ) break;
dblue = random() % ( MAX_COLOR_DELTA * 2 ) - MAX_COLOR_DELTA;
if ( dblue <= 0 ) --dblue;
}
xcolors[color].blue = nblue = t;
XStoreColor(display, cmap, &(xcolors[color]) );
XSetForeground( display, gc, xcolors[color].pixel );
if ( ++color >= ncolors ) color -= ncolors;
}
static void
move_splines()
{
int i, t, px, py, zx, zy, nx, ny;
/* Rotate colormap if necessary. */
rotate_colormap();
/* Choose new color. */
new_color();
/* Backwards rotation requires two new colors each loop. */
if ( backwards )
new_color();
/* Move the points. */
for ( i = 0; i < POINTS; i++ )
{
for ( ; ; )
{
t = x[i] + dx[i];
if ( t >= 0 && t < width ) break;
dx[i] = random() % ( MAX_DELTA * 2 ) - MAX_DELTA;
if ( dx[i] <= 0 ) --dx[i];
}
x[i] = t;
for ( ; ; )
{
t = y[i] + dy[i];
if ( t >= 0 && t < height ) break;
dy[i] = random() % ( MAX_DELTA * 2 ) - MAX_DELTA;
if ( dy[i] <= 0 ) --dy[i];
}
y[i] = t;
}
/* Draw the figure. */
px = zx = ( x[0] + x[POINTS-1] ) / 2;
py = zy = ( y[0] + y[POINTS-1] ) / 2;
for ( i = 0; i < POINTS-1; ++i )
{
nx = ( x[i+1] + x[i] ) / 2;
ny = ( y[i+1] + y[i] ) / 2;
XDrawSpline(g, px, py, x[i], y[i], nx, ny );
px = nx;
py = ny;
}
XDrawSpline(g, px, py, x[POINTS-1], y[POINTS-1], zx, zy );
}
/* X spline routine. */
int abs(x) {
return x < 0 ? -x : x;
}
static void
XDrawSpline(Graphics g, int x0, y0, x1, y1, x2, y2) {
register int xa, ya, xb, yb, xc, yc, xp, yp;
xa = ( x0 + x1 ) / 2;
ya = ( y0 + y1 ) / 2;
xc = ( x1 + x2 ) / 2;
yc = ( y1 + y2 ) / 2;
xb = ( xa + xc ) / 2;
yb = ( ya + yc ) / 2;
xp = ( x0 + xb ) / 2;
yp = ( y0 + yb ) / 2;
if ( abs( xa - xp ) + abs( ya - yp ) > SPLINE_THRESH )
XDrawSpline( display, d, gc, x0, y0, xa, ya, xb, yb );
else
XDrawLine( display, d, gc, x0, y0, xb, yb );
xp = ( x2 + xb ) / 2;
yp = ( y2 + yb ) / 2;
if ( abs( xc - xp ) + abs( yc - yp ) > SPLINE_THRESH )
XDrawSpline( display, d, gc, xb, yb, xc, yc, x2, y2 );
else
XDrawLine( display, d, gc, xb, yb, x2, y2 );
}
}