Ticket #10: pc.c

/* gcc -DEBUG pc.c -o pc -L/usr/X11/lib -lX11 */
/* gcc pc.c -o pc -L/usr/X11/lib -lX11 */

/*
 * Cobbled together from:
 *   http://bellet.info/XVideo/testxv.c
 *   http://users.actcom.co.il/~choo/lupg/tutorials/xlib-programming/xlib-programming.html
 */

#include <errno.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <X11/Xlib.h>
#include <X11/Xutil.h>

/* trick to verbosely do an expression */
#ifdef  EBUG
#define debug(expr, fmt, args...) \
        ((void)fprintf(stderr, "%s = " fmt "\n", # expr, expr, ## args))
#else
#define debug(expr, fmt, args...)       (void)(expr)
#endif

/* Used to fill in the name class array */
#define NC(c)   { # c, c }

/* Used to match class name strings to the constants used by XLib */
static struct {
        char    *name;
        int     class;
} nc[] = {
        NC(PseudoColor),
        NC(GrayScale),
        NC(DirectColor),
        NC(TrueColor),
        NC(StaticColor),
        NC(StaticGray)
};

/* Number of elements in an array */
#define NELEM(a)        (sizeof (a)/sizeof ((a)[0]))

/* gross way of marking the falied lookup, but whatever */
static int
nclkup(char *name)
{
        int i;

        for (i = 0; i < NELEM(nc); i++) {
                debug(i, "%d:");
                debug(nc[i].name, "%s");
                debug(nc[i].class, "%d");

                if (strcmp(nc[i].name, name) != 0)
                        continue;

                return (nc[i].class);
        }

        /* Mark that the lookup failed */
        i = name[0];
        name[0] = 0;

        return (i);
}

int
main(int argc, char *argv[])
{
        int width = 320;
        int height = 200;
        Display* dpy;
        XSetWindowAttributes xswa;
        XVisualInfo xvi;
        Window window;
        XGCValues vals;
        GC gc;
        XEvent event;
        unsigned long mask;
        int res, screen, class, depth;

        if (argc != 3) {
                (void)fprintf(stderr, "Usage %s class depth\n", argv[0]);
                (void)fprintf(stderr, "  examples:\n");
                (void)fprintf(stderr, "    %s PseudoColor 8\n", argv[0]);
                (void)fprintf(stderr, "    %s TrueColor 24\n", argv[0]);
                return (2);
        }

        class = nclkup(argv[1]);
        if (argv[1][0] == 0) {
                argv[1][0] = class;
                (void)fprintf(stderr, "%s: bad class: %s\n", argv[0], argv[1]);
                return (1);
        }

        errno = 0;
        debug(depth = strtoul(argv[2], NULL, 10), "%d, argv[2] = %s", argv[2]);
        if (errno != 0) {
                (void)fprintf(stderr, "%s: bad depth argument: %s\n",
                    argv[0], strerror(errno));
                return (1);
        }

        debug(dpy = XOpenDisplay(NULL),
              "0x%x");
        if (dpy == NULL) {
                (void)fprintf(stderr, "Cannot connect to X server\n");
                return (1);
        }

        debug(screen = DefaultScreen(dpy), "%d");
        if (screen < 0) {
                fprintf(stderr, "%s: screen not found\n", argv[0]);
                return (1);
        }

        debug(res = XMatchVisualInfo(dpy, screen, depth, class, &xvi), "%d");
        if (res == 0) {
                fprintf(stderr, "%s: visual not found\n", argv[0]);
                return (1);
        }

        debug(xswa.colormap = XCreateColormap(dpy, DefaultRootWindow(dpy),
            xvi.visual, AllocNone), "0x%x");
        xswa.event_mask = StructureNotifyMask | ExposureMask;
        xswa.background_pixel = 0;
        xswa.border_pixel = 0;

        mask = CWBackPixel | CWBorderPixel | CWColormap | CWEventMask;

        debug(window = XCreateWindow(dpy, DefaultRootWindow(dpy),
            0, 0,
            width,
            height,
            0, xvi.depth,
            InputOutput,
            xvi.visual,
            mask, &xswa), "0x%x");

        debug(XMapWindow(dpy, window), "%d");

        do {
                XNextEvent(dpy, &event);
        }
        while (event.type != MapNotify || event.xmap.event != window);

        debug(gc = XCreateGC(dpy, window, 0, &vals), "0x%x");

        debug(XSetForeground(dpy, gc, BlackPixel(dpy, screen)), "%d");
        debug(XSetBackground(dpy, gc, WhitePixel(dpy, screen)), "%d");

        debug(XSetLineAttributes(dpy, gc, 2, LineSolid, CapButt, JoinBevel),
            "%d");
        debug(XSetFillStyle(dpy, gc, FillSolid), "%d");

        debug(XSync(dpy, False), "%d");

        debug(XDrawLine(dpy, window, gc, width / 2, 0, width / 2, height),
            "%d");

        debug(XSync(dpy, False), "%d");

        debug(XSetForeground(dpy, gc, WhitePixel(dpy, screen)), "%d");
        debug(XSetBackground(dpy, gc, BlackPixel(dpy, screen)), "%d");

        debug(XSetLineAttributes(dpy, gc, 2, LineSolid, CapButt, JoinBevel),
            "%d");
        debug(XSetFillStyle(dpy, gc, FillSolid), "%d");

        debug(XSync(dpy, False), "%d");

        debug(XDrawLine(dpy, window, gc, 0, height / 2, width, height / 2),
            "%d");

        debug(XFlush(dpy), "%d");

        sleep(10);

        XCloseDisplay(dpy);

        return (0);
}