This example creates a new Display and Window using the common Xlib functions XOpenDisplay and XCreateSimpleWindow. It then calls a helper function attach_cursor that uses both XCB and Xlib facilities to set the cursor of the provided Window to whatever shape the client provides (in this case a question mark with an arrow as defined by XC_question_arrow).

#include <X11/Xlib-xcb.h>
#include <X11/cursorfont.h>
#include <unistd.h>

void attach_cursor(Display *dpy, Window w, int shape)
    static const int fgred = 0, fggreen = 0, fgblue = 0,
        bgred = 0xFFFF, bggreen = 0xFFFF, bgblue = 0xFFFF;

    xcb_connection_t *c = XGetXCBConnection(dpy);
    xcb_cursor_t cursor = xcb_generate_id(c);
    xcb_window_t window = (xcb_window_t) w;
    xcb_font_t font = xcb_generate_id(c),
           *mask_font = &font; /* An alias to clarify what is being passed
                                  to XCBCreateGlyphCursor. */

    xcb_open_font(c, font, sizeof("cursor"), "cursor");
    xcb_create_glyph_cursor (c, cursor, font, *mask_font, shape, shape + 1,
                         fgred, fggreen, fgblue, bgred, bggreen, bgblue);
    XDefineCursor(dpy, window, cursor);
    xcb_free_cursor(c, cursor);
    xcb_close_font(c, font);

int main(void)
    static const int DEPTH = 0, X = 0, Y = 0, BORDER_WIDTH = 1;
    static const size_t WIDTH = 150, HEIGHT = 150;

    Display *dpy;
    int screen_num;
    unsigned int bordercolor, bgcolor;
    Window window;

    dpy = XOpenDisplay(NULL);
    screen_num = DefaultScreen(dpy);
    bordercolor = BlackPixel(dpy, screen_num);
    bgcolor = WhitePixel(dpy, screen_num);
    window = XCreateSimpleWindow(dpy, RootWindow(dpy, screen_num), X, Y, WIDTH,
                                 HEIGHT, BORDER_WIDTH, bordercolor, bgcolor);

    attach_cursor(dpy, window, XC_question_arrow);
    XMapWindow(dpy, window);
    XSync(dpy, 0);

    pause(); /* Hit C-c to break out of this loop. */

    return 0;

Suppose that the attach_cursor function was to be ported entirely to use XCB's functionality. How could the pointer's cursor be set to the specified symbol without using XDefineCursor?

See Also