Why does this small program cause an X11 BadMatch?

[Rich Burridge <Rich Burridge Sun COM>]

Hi all,

I've isolated the problem I'm seeing in converting an XView app to Gtk,
into the small example attached below.

Can somebody clue my in why this is giving me:

Gdk-ERROR **: BadMatch (invalid parameter attributes)
  serial 36 error_code 8 request_code 62 minor_code 0

It's the:

    gdk_window_copy_area(xid, svgc, 0, 0, xid, 0, 0, width, height);
    
that's bitching. 

Note that I need this GdkPixmap to be a depth of 1 as I want to use it 
later as a stencil in a GdkGC. It also needs to be created dynamically as
it might be a different width/height.

Thanks.

#include <stdio.h>
#include <gtk/gtk.h>
#include <gdk/gdkx.h>

GdkColor backgnd;
GdkColor foregnd;
GdkColormap *cmap;
GdkGC *svgc;
GdkGCValues gc_val;
GdkGCValuesMask gc_mask;
GdkPixmap *xid;

int
main(int argc, char **argv)
{
    int width = 48;
    int height = 28;

    gtk_set_locale();
    gtk_init(&argc, &argv);
    cmap = gdk_colormap_get_system();
    (void) gdk_color_black(cmap, &foregnd);
    (void) gdk_color_white(cmap, &backgnd);
    xid = gdk_pixmap_new(GDK_ROOT_PARENT(), width, height, 1);
    gc_mask = GDK_GC_FOREGROUND | GDK_GC_BACKGROUND;
    gc_val.foreground = foregnd;
    gc_val.background = backgnd;
    svgc = gdk_gc_new_with_values(GDK_ROOT_PARENT(), &gc_val, gc_mask);
    gdk_gc_set_function(svgc, GDK_CLEAR);
    gdk_window_copy_area(xid, svgc, 0, 0, xid, 0, 0, width, height);
    gdk_gc_set_function(svgc, GDK_COPY);
    gtk_main();

    return(0);
}