xcb_grab_pointer man page

xcb_grab_pointer — Grab the pointer

Synopsis

#include <xcb/xproto.h>

Request function

xcb_grab_pointer_cookie_t xcb_grab_pointer(xcb_connection_t *conn, uint8_t owner_events, xcb_window_t grab_window, uint16_t event_mask, uint8_t pointer_mode, uint8_t keyboard_mode, xcb_window_t confine_to, xcb_cursor_t cursor, xcb_timestamp_t time);

Reply datastructure

typedef struct xcb_grab_pointer_reply_t {
    uint8_t  response_type;
    uint8_t  status;
    uint16_t sequence;
    uint32_t length;
} xcb_grab_pointer_reply_t;

Reply function

xcb_grab_pointer_reply_t *xcb_grab_pointer_reply(xcb_connection_t *conn, xcb_grab_pointer_cookie_t cookie, xcb_generic_error_t **e);

Request Arguments

conn
The XCB connection to X11.
owner_events
If 1, the grab_window will still get the pointer events. If 0, events are not reported to the grab_window.
grab_window
Specifies the window on which the pointer should be grabbed.
event_mask

Specifies which pointer events are reported to the client.

TODO: which values?

pointer_mode

One of the following values:

XCB_GRAB_MODE_SYNC
The state of the keyboard appears to freeze: No further keyboard events are generated by the server until the grabbing client issues a releasing AllowEvents request or until the keyboard grab is released.
XCB_GRAB_MODE_ASYNC
Keyboard event processing continues normally.
keyboard_mode

One of the following values:

XCB_GRAB_MODE_SYNC
The state of the keyboard appears to freeze: No further keyboard events are generated by the server until the grabbing client issues a releasing AllowEvents request or until the keyboard grab is released.
XCB_GRAB_MODE_ASYNC
Keyboard event processing continues normally.
confine_to

Specifies the window to confine the pointer in (the user will not be able to move the pointer out of that window).

The special value XCB_NONE means don't confine the pointer.

cursor
Specifies the cursor that should be displayed or XCB_NONE to not change the cursor.
time

The time argument allows you to avoid certain circumstances that come up if applications take a long time to respond or if there are long network delays. Consider a situation where you have two applications, both of which normally grab the pointer when clicked on. If both applications specify the timestamp from the event, the second application may wake up faster and successfully grab the pointer before the first application. The first application then will get an indication that the other application grabbed the pointer before its request was processed.

The special value XCB_CURRENT_TIME will be replaced with the current server time.

Reply Fields

response_type
The type of this reply, in this case XCB_GRAB_POINTER. 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).
status

One of the following values:

XCB_GRAB_STATUS_SUCCESS
TODO: NOT YET DOCUMENTED.
XCB_GRAB_STATUS_ALREADY_GRABBED
TODO: NOT YET DOCUMENTED.
XCB_GRAB_STATUS_INVALID_TIME
TODO: NOT YET DOCUMENTED.
XCB_GRAB_STATUS_NOT_VIEWABLE
TODO: NOT YET DOCUMENTED.
XCB_GRAB_STATUS_FROZEN
TODO: NOT YET DOCUMENTED.

TODO: NOT YET DOCUMENTED.

Description

Actively grabs control of the pointer. Further pointer events are reported only to the grabbing client. Overrides any active pointer grab by this client.

Return Value

Returns an xcb_grab_pointer_cookie_t. Errors have to be handled when calling the reply function xcb_grab_pointer_reply.

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

Errors

xcb_value_error_t
TODO: reasons?
xcb_window_error_t
The specified window does not exist.

Example

/*
 * Grabs the pointer actively
 *
 */
void my_example(xcb_connection_t *conn, xcb_screen_t *screen, xcb_cursor_t cursor) {
    xcb_grab_pointer_cookie_t cookie;
    xcb_grab_pointer_reply_t *reply;

    cookie = xcb_grab_pointer(
        conn,
        false,               /* get all pointer events specified by the following mask */
        screen->root,        /* grab the root window */
        XCB_NONE,            /* which events to let through */
        XCB_GRAB_MODE_ASYNC, /* pointer events should continue as normal */
        XCB_GRAB_MODE_ASYNC, /* keyboard mode */
        XCB_NONE,            /* confine_to = in which window should the cursor stay */
        cursor,              /* we change the cursor to whatever the user wanted */
        XCB_CURRENT_TIME
    );

    if ((reply = xcb_grab_pointer_reply(conn, cookie, NULL))) {
        if (reply->status == XCB_GRAB_STATUS_SUCCESS)
            printf("successfully grabbed the pointer\n");
        free(preply);
    }
}

See Also

xcb-requests(3), xcb-examples(3), xcb_grab_keyboard(3)

Author

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

Referenced By

xcb_button_press_event_t(3), xcb_grab_keyboard(3), xcb_ungrab_pointer(3).

xcb_grab_pointer_reply(3) and xcb_grab_pointer_unchecked(3) are aliases of xcb_grab_pointer(3).

libxcb 1.12 X Version 11 XCB Requests