xcb_query_tree

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

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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);
    }
}

 

SEE ALSO

xcb-requests(3), xcb-examples(3), xwininfo(1)  

AUTHOR

Generated from xproto.xml. Contact xcb@lists.freedesktop.org for corrections and improvements.

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Index

NAME

SYNOPSIS

Request function

Reply datastructure

Reply function

Reply accessors

REQUEST ARGUMENTS

REPLY FIELDS

DESCRIPTION

RETURN VALUE

ERRORS

EXAMPLE

SEE ALSO

AUTHOR