XISELECTEVENTS(3) |  | XISELECTEVENTS(3)

# NAME

XISelectEvents, XIGetSelectedEvents - select for or get selected XI2 events on the window.

# SYNOPSIS

    #include <X11/extensions/XInput2.h>

    Status XISelectEvents( Display *display,

                           Window win,

                           XIEventMask *masks,

                           int num_masks);

    display

           Specifies the connection to the X server.

    masks

           Device event mask.

    num_masks

           Number of masks in masks.

    win

           Specifies the window.

    XIEventMask *XIGetSelectedEvents( Display *display,

                                      Window win,

                                      int *num_masks_return);

    display

           Specifies the connection to the X server.

    num_masks_return

           Number of masks in the return value.

    win

           Specifies the window.

# DESCRIPTION

    XI2 events must be selected using XISelectEvents.

    XISelectEvents sets the event mask for this client on win.
    Further events are only reported to this client if the event
    type matches the selected event mask. The masks overrides the
    previously selected event mask for the given device.

    If deviceid is a valid device, the event mask is selected only
    for this device. If deviceid is XIAllDevices or
    XIAllMasterDevices, the event mask is selected for all devices
    or all master devices, respectively. The effective event mask
    is the bit-wise OR of the XIAllDevices, XIAllMasterDevices and
    the respective device's event mask.

    typedef struct {

        int deviceid;

        int mask_len;

        unsigned char* mask;
    } XIEventMask;

    The mask_len specifies the length of mask in bytes. mask is a
    binary mask in the form of (1 << event type). deviceid must be
    either a device or XIAllDevices or XIAllMasterDevices. A client
    may submit several masks with the same deviceid in one request
    but only the last mask will be effective.

    XISelectEvents can generate a BadValue, a BadDevice, and a
    BadWindow error.

    XIGetSelectedEvents returns the events selected by this client on the given
    window. If no events were selected on this window, XIGetSelectedEvents
    returns NULL and num_masks_return is set to 0. If an internal error occurs,
    XIGetSelectedEvents returns NULL and num_masks_return is set to -1.
    Otherwise, XIGetSelectedEvent returns the selected event masks for all
    devices including the masks for XIAllDevices and XIAllMasterDevices

    The caller must free the returned data using XFree().

# DIAGNOSTICS

    BadValue

           A value is outside of the permitted range.

    BadWindow

           A value for a Window argument does not name a defined

           window.

    BadDevice

           An invalid device was specified. The device does not

           exist.

05/18/2026 |