#ifdef notdef
    set -x
    exec cc -O2 -std=c99 -pedantic -Wall $0 -fPIC -o lib${0%.c}.so -shared
#endif
#define _XOPEN_SOURCE 600
#include <X11/Xlibint.h>
#include <X11/extensions/Xinerama.h>
#include <string.h>
#include <stdio.h>
#include <stdint.h>
#include <dlfcn.h>

const char SETTINGS[] = "XINERAMA_SCREENS";
const char SEP[]      = ";";

static XineramaScreenInfo* screens;
static int num_screens;

typedef XineramaScreenInfo* (queryfn)(Display*, int*);
typedef Status (versionfn)(Display*, int*, int*);
typedef Bool (extensionfn)(Display*, int*, int*);
typedef Bool (activefn)(Display*);

static void*         libxinerama;
static queryfn*      queryscreens;
static extensionfn*  queryextension;
static versionfn*    queryversion;
static activefn*     isactive;

static _Bool
init()
{
    char *str, *p, *q;
    int i;

    if(screens || libxinerama)
        return screens;

    str = getenv(SETTINGS);
    if(!str) {
	libxinerama       = dlopen("libXinerama.so.1", RTLD_GLOBAL | RTLD_LAZY);
	if(!libxinerama)
		abort();
        isactive          = (activefn*)    (uintptr_t)dlsym(libxinerama, "XineramaIsActive");
        queryversion      = (versionfn*)   (uintptr_t)dlsym(libxinerama, "XineramaQueryVersion");
        queryextension    = (extensionfn*) (uintptr_t)dlsym(libxinerama, "XineramaQueryExtension");
        queryscreens      = (queryfn*)     (uintptr_t)dlsym(libxinerama, "XineramaQueryScreens");
        return False;
    }

    for(i=1, p=str; strchr(p, *SEP); p++)
        i++;

    screens = malloc(i * sizeof *screens);

    i = 0;
    str = strdup(str);
    for(q=str; (p = strtok(q, SEP)); q=NULL) {
        if(sscanf(p, "%hd,%hd %hdx%hd",
                  &screens[i].x_org, &screens[i].y_org,
                  &screens[i].width, &screens[i].height)
           == 4)
            i++;
    }
    num_screens = i;
    return True;
}

Bool
XineramaQueryExtension(Display *dpy, int *event_base, int *error_base)
{
    if(!init())
        return queryextension(dpy, event_base, error_base);
    *event_base = 0;
    *error_base = 0;
    return True;
}

Status
XineramaQueryVersion(Display *dpy, int *major, int *minor)
{
    if(!init())
        return queryversion(dpy, major, minor);
    *major = 1;
    *minor = 1;
    return True;
}

Bool
XineramaIsActive(Display *dpy)
{
    if(!init())
        return isactive(dpy);
    return num_screens > 0;
}

XineramaScreenInfo* 
XineramaQueryScreens(Display *dpy, int *number)
{
    XineramaScreenInfo *ret;

    if(!init())
        return queryscreens(dpy, number);
    *number = num_screens;
    ret = Xmalloc(num_screens * sizeof *screens);
    memcpy(ret, screens, num_screens * sizeof *screens);
    return screens;
}