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You are here: manpages

xcb_query_tree

Section: XCB Requests (3)
Updated: libxcb 1.12
Index Return to Main Contents

NAME

xcb_query_tree - query the window tree

SYNOPSIS

#include <xcb/xproto.h>

Request function

: xcb_query_tree_cookie_t xcb_query_tree(xcb_connection_t *conn, xcb_window_t window);

Reply datastructure


typedef struct xcb_query_tree_reply_t {
    uint8_t      response_type;
    uint8_t      pad0;
    uint16_t     sequence;
    uint32_t     length;
    xcb_window_t root;
    xcb_window_t parent;
    uint16_t     children_len;
    uint8_t      pad1[14];
} xcb_query_tree_reply_t;

Reply function

: xcb_query_tree_reply_t *xcb_query_tree_reply(xcb_connection_t *conn, xcb_query_tree_cookie_t cookie, xcb_generic_error_t **e);

Reply accessors

: xcb_window_t *xcb_query_tree_children(const xcb_query_tree_request_t *reply);
: int xcb_query_tree_children_length(const xcb_query_tree_reply_t *reply);
: xcb_generic_iterator_t xcb_query_tree_children_end(const xcb_query_tree_reply_t *reply);

REQUEST ARGUMENTS

conn: The XCB connection to X11.
window: The window to query.

REPLY FIELDS

response_type: The type of this reply, in this case XCB_QUERY_TREE. This field is also present in the xcb_generic_reply_t and can be used to tell replies apart from each other.
sequence: The sequence number of the last request processed by the X11 server.
length: The length of the reply, in words (a word is 4 bytes).
root: The root window of window.
parent: The parent window of window.
children_len: The number of child windows.

DESCRIPTION

Gets the root window ID, parent window ID and list of children windows for the specified window. The children are listed in bottom-to-top stacking order.

RETURN VALUE

Returns an xcb_query_tree_cookie_t. Errors have to be handled when calling the reply function xcb_query_tree_reply.

If you want to handle errors in the event loop instead, use xcb_query_tree_unchecked. See xcb-requests(3) for details.

ERRORS

This request does never generate any errors.

EXAMPLE


/*
 * Displays the root, parent and children of the specified window.
 *
 */
void my_example(xcb_connection_t *conn, xcb_window_t window) {
    xcb_query_tree_cookie_t cookie;
    xcb_query_tree_reply_t *reply;

    cookie = xcb_query_tree(conn, window);
    if ((reply = xcb_query_tree_reply(conn, cookie, NULL))) {
        printf("root = 0x%08x\n", reply->root);
        printf("parent = 0x%08x\n", reply->parent);

        xcb_window_t *children = xcb_query_tree_children(reply);
        for (int i = 0; i < xcb_query_tree_children_length(reply); i++)
            printf("child window = 0x%08x\n", children[i]);

        free(reply);
    }
}