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XSELECTEXTENSIONEVEN(3)   XSELECTEXTENSIONEVEN(3)

XSelectExtensionEvent, XGetSelectedExtensionEvents - select extension events, get the list of currently selected extension events

#include <X11/extensions/XInput.h>

XSelectExtensionEvent( Display *display,

Window w,
XEventClass *event_list,
int event_count);

XGetSelectedExtensionEvents( Display *display,

Window w,
int *this_client_event_count_return,
XEventClass **this_client_event_list_return,
int *all_clients_event_count_return,
XEventClass **all_clients_event_list_return);

display

Specifies the connection to the X server.

w

Specifies the window whose events you are interested in.

event_list

Specifies the list of event classes that describe the
events you are interested in.

event_count

Specifies the count of event classes in the event list.

this_client_event_count_return

Returns the count of event classes selected by this
client.

this_client_event_list_return

Returns a pointer to the list of event classes selected
by this client.

all_clients_event_count_return

Returns the count of event classes selected by all
clients.

all_clients_event_list_return

Returns a pointer to the list of event classes selected
by all clients.

The XSelectExtensionEvent request causes the X server to report
the events associated with the specified list of event classes.
Initially, X will not report any of these events. Events are
reported relative to a window. If a window is not interested in
a device event, it usually propagates to the closest ancestor
that is interested, unless the do_not_propagate mask prohibits
it.

Multiple clients can select for the same events on the same
window with the following restrictions:

* Multiple clients can select events on the same window
because their event masks are disjoint. When the X server
generates an event, it reports it to all interested
clients.
* Only one client at a time can select a DeviceButtonPress
event with automatic passive grabbing enabled, which is
associated with the event class DeviceButtonPressGrab. To
receive DeviceButtonPress events without automatic passive
grabbing, use event class DeviceButtonPress but do not
specify event class DeviceButtonPressGrab.

The server reports the event to all interested clients.

Information contained in the XDevice structure returned by
XOpenDevice is used by macros to obtain the event classes that
clients use in making XSelectExtensionEvent requests. Currently
defined macros include DeviceKeyPress, DeviceKeyRelease,
DeviceButtonPress, DeviceButtonRelese, DeviceMotionNotify,
DeviceFocusIn, DeviceFocusOut, ProximityIn, ProximityOut,
DeviceStateNotify, DeviceMappingNotify, ChangeDeviceNotify,
DevicePointerMotionHint, DeviceButton1Motion,
DeviceButton2Motion, DeviceButton3Motion, DeviceButton4Motion,
DeviceButton5Motion, DeviceButtonMotion, DeviceOwnerGrabButton,
DeviceButtonPressGrab, and NoExtensionEvent.

To obtain the proper event class for a particular device, one
of the above macros is invoked using the XDevice structure for
that device. For example,

DeviceKeyPress (*device, type, eventclass);

returns the DeviceKeyPress event type and the eventclass for
selecting DeviceKeyPress events from this device.

XSelectExtensionEvent can generate a BadWindow or BadClass
error. The XGetSelectedExtensionEvents request reports the
extension events selected by this client and all clients for
the specified window. This request returns pointers to two
XEventClass arrays. One lists the input extension events
selected by this client from the specified window. The other
lists the event classes selected by all clients from the
specified window. You should use XFree to free these two
arrays.

XGetSelectedExtensionEvents can generate a BadWindow error.

BadWindow

A value for a Window argument does not name a defined
window.

BadClass

A value for an XEventClass is invalid.
06/19/2019