The background color of xcb window is black

Question

#include <unistd.h>      /* pause() */

#include <xcb/xcb.h>

int
main ()
{
    /* Open the connection to the X server */
    xcb_connection_t *connection = xcb_connect (NULL, NULL);


    /* Get the first screen */
    const xcb_setup_t      *setup  = xcb_get_setup (connection);
    xcb_screen_iterator_t   iter   = xcb_setup_roots_iterator (setup);
    xcb_screen_t           *screen = iter.data;


    /* Create the window */
    xcb_window_t window = xcb_generate_id (connection);
    xcb_create_window (connection,                    /* Connection          */
                       XCB_COPY_FROM_PARENT,          /* depth (same as root)*/
                       window,                        /* window Id           */
                       screen->root,                  /* parent window       */
                       0, 0,                          /* x, y                */
                       150, 150,                      /* width, height       */
                       10,                            /* border_width        */
                       XCB_WINDOW_CLASS_INPUT_OUTPUT, /* class               */
                       screen->root_visual,           /* visual              */
                       0, NULL );                     /* masks, not used yet */


    /* Map the window on the screen */
    xcb_map_window (connection, window);


    /* Make sure commands are sent before we pause so that the window gets shown */
    xcb_flush (connection);


    pause ();    /* hold client until Ctrl-C */

    xcb_disconnect (connection);

    return 0;
}

I have a demo of xcb(copied from internet). In some linux platforms, it shows a window with transparent background, but other linux platfomts, it show a window filling with black background. what can I do to set default background color to transparent?

I read the reference of xcb, it said If XCB_BACK_PIXMAP_NONE is specified, the window has no defined background. The server may fill the contents with the previous screen contents or with contents of its own choosing. I don't know how to set x server then it will fill the contents of the previous screen contents.