--- configure.ac.orig	2008-06-25 23:22:27.000000000 +0200
+++ configure.ac	2008-06-25 23:17:51.000000000 +0200
@@ -18,6 +18,8 @@
 AC_SEARCH_LIBS(socket, socket)
 AC_SEARCH_LIBS(inet_aton, resolv)
 
+AC_CHECK_LIB(Xinerama, XineramaQueryScreens, AC_DEFINE(HAVE_XINERAMA) LIBS="$LIBS -lXinerama", [], [])
+
 AC_CHECK_HEADER(sys/select.h, AC_DEFINE(HAVE_SYS_SELECT_H))
 AC_CHECK_HEADER(sys/modem.h, AC_DEFINE(HAVE_SYS_MODEM_H))
 AC_CHECK_HEADER(sys/filio.h, AC_DEFINE(HAVE_SYS_FILIO_H))
--- xwin.c.orig	2008-06-25 23:50:02.000000000 +0200
+++ xwin.c	2008-06-25 23:49:25.000000000 +0200
@@ -21,6 +21,9 @@
 
 #include <X11/Xlib.h>
 #include <X11/Xutil.h>
+#ifdef HAVE_XINERAMA
+ #include <X11/extensions/Xinerama.h>
+#endif
 #include <X11/Xproto.h>
 #include <unistd.h>
 #include <sys/time.h>
@@ -570,6 +573,71 @@
 #define LOUT24(o, x) { *(o++) = x; *(o++) = x >> 8; *(o++) = x >> 16; }
 #define LOUT32(o, x) { *(o++) = x; *(o++) = x >> 8; *(o++) = x >> 16; *(o++) = x >> 24; }
 
+#ifdef HAVE_XINERAMA
+// IF XINERAMA LIBRARY
+
+int g_last_wnd_pos_x;
+int g_last_wnd_pos_y;
+
+void
+ScreenSize(XRectangle *screen)
+{
+	int screens;
+	int event_base;
+	int error_base;
+
+	if (XineramaQueryExtension(g_display, &event_base, &error_base))
+	{
+		XineramaScreenInfo *screeninfo;
+		int i;
+
+		/* Get the Xinerama screen infomation. */
+		screeninfo = XineramaQueryScreens(g_display, &screens);
+
+		/* Search for the appropriate screen. */
+		i = 0;
+		while (!(screeninfo[i].x_org <= g_last_wnd_pos_x
+			&& screeninfo[i].y_org <= g_last_wnd_pos_y
+			&& screeninfo[i].x_org + screeninfo[i].width >= g_last_wnd_pos_x
+			&& screeninfo[i].y_org + screeninfo[i].height >= g_last_wnd_pos_y ))
+		{
+			i++;
+		}
+		if (i >= screens) i = 0;
+
+		/* Position according to the present screen. */
+		screen->x = screeninfo[i].x_org;
+		screen->y = screeninfo[i].y_org;
+		screen->width = screeninfo[i].width;
+		screen->height = screeninfo[i].height;
+
+		/* Free allocated memory. */
+		XFree(screeninfo);
+	}
+	else
+	{
+		/* Xinerama is not in use, default to the XLib screensize call. */
+		screen->x = 0;
+		screen->y = 0;
+		screen->width = WidthOfScreen(g_screen);
+		screen->height = HeightOfScreen(g_screen);
+	}
+}
+
+#else
+// IF NO XINERAMA LIBRARY
+
+void
+ScreenSize(XRectangle *screen)
+{
+	screen->x = 0;
+	screen->y = 0;
+	screen->width = WidthOfScreen(g_screen);
+	screen->height = HeightOfScreen(g_screen);
+}
+
+#endif
+
 static uint32
 translate_colour(uint32 colour)
 {
@@ -1615,17 +1683,26 @@
 	 */
 	if (g_fullscreen)
 	{
-		g_width = WidthOfScreen(g_screen);
-		g_height = HeightOfScreen(g_screen);
+		XRectangle screen;
+		ScreenSize(&screen);
+
+		g_width = screen.width;
+		g_height = screen.height;
 		g_using_full_workarea = True;
 	}
 	else if (g_width < 0)
 	{
+		XRectangle screen;
+		ScreenSize(&screen);
+
+		g_width = screen.width;
+		g_height = screen.height;
+
 		/* Percent of screen */
 		if (-g_width >= 100)
 			g_using_full_workarea = True;
-		g_height = HeightOfScreen(g_screen) * (-g_width) / 100;
-		g_width = WidthOfScreen(g_screen) * (-g_width) / 100;
+		g_width = screen.width * (-g_width) / 100;
+		g_height = screen.height * (-g_width) / 100;
 	}
 	else if (g_width == 0)
 	{
@@ -1734,14 +1811,19 @@
 	long input_mask, ic_input_mask;
 	XEvent xevent;
 
-	wndwidth = g_fullscreen ? WidthOfScreen(g_screen) : g_width;
-	wndheight = g_fullscreen ? HeightOfScreen(g_screen) : g_height;
+	XRectangle screen;
+
+	ScreenSize(&screen);
+	wndwidth = g_fullscreen ? screen.width : g_width;
+	wndheight = g_fullscreen ? screen.height : g_height;
+	g_xpos = g_fullscreen ? screen.x : g_xpos;
+	g_ypos = g_fullscreen ? screen.y : g_ypos;
 
 	/* Handle -x-y portion of geometry string */
 	if (g_xpos < 0 || (g_xpos == 0 && (g_pos & 2)))
-		g_xpos = WidthOfScreen(g_screen) + g_xpos - g_width;
+		g_xpos = screen.width + g_xpos - g_width;
 	if (g_ypos < 0 || (g_ypos == 0 && (g_pos & 4)))
-		g_ypos = HeightOfScreen(g_screen) + g_ypos - g_height;
+		g_ypos = screen.height + g_ypos - g_height;
 
 	get_window_attribs(&attribs);
 
@@ -1882,6 +1964,11 @@
 void
 xwin_toggle_fullscreen(void)
 {
+#ifdef HAVE_XINERAMA
+	Window root, parent, *children;
+	unsigned int nchildren;
+	XWindowAttributes win_attrib;
+#endif
 	Pixmap contents = 0;
 
 	if (g_seamless_active)
@@ -1895,6 +1982,17 @@
 		XCopyArea(g_display, g_wnd, contents, g_gc, 0, 0, g_width, g_height, 0, 0);
 	}
 
+#ifdef HAVE_XINERAMA
+	/* Determine the parent window. */
+	XQueryTree(g_display, g_wnd, &root, &parent, &children, &nchildren);
+	if (children != NULL) XFree(children);
+
+	/* Find the present coordinates of the window. */
+	XGetWindowAttributes(g_display, parent, &win_attrib);
+	g_last_wnd_pos_x = win_attrib.x + 1;
+	g_last_wnd_pos_y = win_attrib.y + 1;
+#endif
+
 	ui_destroy_window();
 	g_fullscreen = !g_fullscreen;
 	ui_create_window();