diff -Naur -wbBE wine-0.9.54-fe/dlls/winex11.drv/x11drv_main.c wine-0.9.54-fe.rootwin/dlls/winex11.drv/x11drv_main.c
--- wine-0.9.54-fe/dlls/winex11.drv/x11drv_main.c	2008-01-26 00:05:38.000000000 +0800
+++ wine-0.9.54-fe.rootwin/dlls/winex11.drv/x11drv_main.c	2008-02-12 23:20:33.000000000 +0800
@@ -447,6 +447,8 @@
     Display *display;
     XVisualInfo *desktop_vi = NULL;
     const char *env;
+    int new_root = -1;
+    XWindowAttributes attr;
 
     setup_options();
 
@@ -525,6 +527,22 @@
 
     if (TRACE_ON(synchronous)) XSynchronize( display, True );
 
+    /* Handle WINEROOTWIN environment variable */
+    if (getenv( "WINEROOTWIN" ))
+    {
+        const char* root_str = getenv( "WINEROOTWIN" );
+        if (0 == strncmp( root_str, "0x", 2 ))
+            sscanf( root_str + 2, "%x", &new_root );
+        else
+            sscanf( root_str, "%d", &new_root );
+        if ((new_root >= 0)
+            && XGetWindowAttributes( display, (Window)new_root, &attr ))
+            root_window = (Window)new_root;
+    }
+
+    if (root_window != DefaultRootWindow( display ))
+        xinerama_init( attr.width, attr.height );
+    else
     xinerama_init( WidthOfScreen(screen), HeightOfScreen(screen) );
     X11DRV_Settings_Init();
 
diff -Naur -wbBE wine-0.9.54-fe/loader/wine.man.in wine-0.9.54-fe.rootwin/loader/wine.man.in
--- wine-0.9.54-fe/loader/wine.man.in	2008-01-26 00:05:38.000000000 +0800
+++ wine-0.9.54-fe.rootwin/loader/wine.man.in	2008-02-12 23:52:34.000000000 +0800
@@ -207,6 +207,14 @@
 .I DISPLAY
 Specifies the X11 display to use.
 .TP
+.I WINEROOTWIN
+If set,
+.B
+wine
+will embed its desktop under an existing X11 window with the ID specified by
+this variable.  This allows fullscreen Windows applications to be embedded
+inside X11 applications.
+.TP
 OSS sound driver configuration variables
 .TP
 .I AUDIODEV