Topics
	The logging API


	API for receiver clients


	API for sender clients


	The seat API


	The device API


	The region API


	The keymap API

Data Structures
struct	ei
	The main context to interact with libei. More...

struct	ei_device
	A single device to generate input events from. More...

struct	ei_seat
	A logical seat for a group of devices. More...

struct	ei_event
	An event received from the EIS implementation. More...

struct	ei_keymap
	An keymap for a device with the EI_DEVICE_CAP_KEYBOARD capability. More...

struct	ei_region
	A rectangular region, defined by an x/y offset and a width and a height. More...

Typedefs
typedef uint64_t(*	ei_clock_now_func) (struct ei *ei)
	Optional override function for ei_now().

Enumerations
enum	ei_device_type { EI_DEVICE_TYPE_VIRTUAL , EI_DEVICE_TYPE_PHYSICAL }
	The device type determines what the device represents. More...

enum	ei_device_capability { EI_DEVICE_CAP_POINTER , EI_DEVICE_CAP_POINTER_ABSOLUTE , EI_DEVICE_CAP_KEYBOARD , EI_DEVICE_CAP_TOUCH , EI_DEVICE_CAP_SCROLL , EI_DEVICE_CAP_BUTTON }
	The set of supported capabilities. More...

enum	ei_keymap_type { EI_KEYMAP_TYPE_XKB }
	The set of supported keymap types for a struct ei_keymap. More...

enum	ei_event_type { EI_EVENT_CONNECT , EI_EVENT_DISCONNECT , EI_EVENT_SEAT_ADDED , EI_EVENT_SEAT_REMOVED , EI_EVENT_DEVICE_ADDED , EI_EVENT_DEVICE_REMOVED , EI_EVENT_DEVICE_PAUSED , EI_EVENT_DEVICE_RESUMED , EI_EVENT_KEYBOARD_MODIFIERS , EI_EVENT_FRAME , EI_EVENT_DEVICE_START_EMULATING , EI_EVENT_DEVICE_STOP_EMULATING , EI_EVENT_POINTER_MOTION , EI_EVENT_POINTER_MOTION_ABSOLUTE , EI_EVENT_BUTTON_BUTTON , EI_EVENT_SCROLL_DELTA , EI_EVENT_SCROLL_STOP , EI_EVENT_SCROLL_CANCEL , EI_EVENT_SCROLL_DISCRETE , EI_EVENT_KEYBOARD_KEY , EI_EVENT_TOUCH_DOWN , EI_EVENT_TOUCH_UP , EI_EVENT_TOUCH_MOTION }

Functions
const char *	ei_event_type_to_string (enum ei_event_type)
	This is a debugging helper to return a string of the name of the event type, or NULL if the event type is invalid.

struct ei *	ei_new (void *user_data)
	This is an alias for ei_new_sender.

struct ei *	ei_new_sender (void *user_data)
	Create a new sender ei context.

struct ei *	ei_new_receiver (void *user_data)
	Create a new receiver ei context.

struct ei *	ei_ref (struct ei *ei)
	Increase the refcount of this struct by one.

struct ei *	ei_unref (struct ei *ei)
	Decrease the refcount of this struct by one.

void	ei_set_user_data (struct ei ei, void user_data)
	Set a custom data pointer for this context.

void *	ei_get_user_data (struct ei *ei)
	Return the custom data pointer for this context.

bool	ei_is_sender (struct ei *ei)
	Returns true if the context is was created with ei_new_sender() or false otherwise.

void	ei_clock_set_now_func (struct ei *, ei_clock_now_func func)
	Override the function that returns the current time ei_now().

void	ei_configure_name (struct ei ei, const char name)
	Set the name for this client.

int	ei_setup_backend_fd (struct ei *ei, int fd)
	Initialize the ei context on the given socket file descriptor.

int	ei_setup_backend_socket (struct ei ei, const char socketpath)
	Set this ei context to use the socket backend.

int	ei_get_fd (struct ei *ei)
	libei keeps a single file descriptor for all events.

void	ei_dispatch (struct ei *ei)
	Main event dispatching function.

struct ei_event *	ei_get_event (struct ei *ei)
	Return the next event from the event queue, removing it from the queue.

struct ei_event *	ei_peek_event (struct ei *ei)
	Returns the next event in the internal event queue (or `NULL`) without removing that event from the queue; the next call to ei_get_event() will return that same event.

uint64_t	ei_now (struct ei *ei)

struct ei_event *	ei_event_unref (struct ei_event *event)
	Release resources associated with this event.

enum ei_event_type	ei_event_get_type (struct ei_event *event)

struct ei_device *	ei_event_get_device (struct ei_event *event)
	Return the device from this event.

uint64_t	ei_event_get_time (struct ei_event *event)
	Return the time for the event of type EI_EVENT_FRAME in microseconds.

struct ei_seat *	ei_event_get_seat (struct ei_event *event)
	Return the seat from this event.

Detailed Description

libei is the client-side module. This API should be used by processes that need to emulate devices or capture logical events from existing devices.

For an example client see the tools/ directory in the libei repository. At its core, a libei client will

create a context with ei_new_sender() or ei_new_receiver()
set up a backend with ei_setup_backend_fd() or ei_setup_backend_socket()
register the ei_get_fd() with its own event loop
call ei_dispatch() whenever the fd triggers
call ei_get_event() and process incoming events

Those events are typically a sequence of

EI_EVENT_CONNECT - notification that the client was connected
EI_EVENT_SEAT_ADDED - notification that a ei_seat is available. The client should respond with ei_seat_bind_capabilities()
EI_EVENT_DEVICE_ADDED - notification that a ei_device is available in a seat.
EI_EVENT_DEVICE_RESUMED - notification that the ei_device is ready to emulate events. The client should respond with ei_device_start_emulating() and the required events to emulate input

libei clients come in sender and receiver modes, depending on whether the client sends or receives events from the EIS implementation. See API for sender clients and API for receiver clients for API calls specific to either mode.

Note: A libei context is restricted to either sender or receiver mode, not both. The EIS implementation however may accept both sender and receiver clients, and will work as corresponding receiver or sender for this client. It is up to the implementation to disconnect clients that it does not want to allow. See eis_client_is_sender() for details.

Typedef Documentation

◆ ei_clock_now_func

typedef uint64_t(* ei_clock_now_func) (struct ei *ei)

Optional override function for ei_now().

By default ei_now() returns the current timestamp in CLOCK_MONOTONIC. This may be overridden by a caller to provide a different timestamp.

There is rarely a need to override this function. It exists for the libei-internal test suite.

Enumeration Type Documentation

◆ ei_device_capability

enum ei_device_capability

The set of supported capabilities.

A device may have zero or more capabilities, a device with perceived zero capabilities is typically a device with capabilities unsupported by the client - such a device should be closed immediately by the client.

The EIS implementation decides which capabilities may exist on a seat and which capabilities exist on any individual seat. However, a device may only have capabilities the client has bound to, see ei_seat_bind_capabilities().

For example, a client may bind to a seat with the pointer and keyboard capability but a given device only has the pointer capability. Keyboard events sent through that device will be treated as client bug.

If a client calls ei_seat_unbind_capabilities() for a capability, the EIS implementation may remove any or all devices that have that capability.

See ei_device_has_capability().

Enumerator
EI_DEVICE_CAP_POINTER	The device can send relative motion events.
EI_DEVICE_CAP_POINTER_ABSOLUTE	The device can send absolute motion events.
EI_DEVICE_CAP_KEYBOARD	The device can send keyboard events.
EI_DEVICE_CAP_TOUCH	The device can send touch events.
EI_DEVICE_CAP_SCROLL	The device can send scroll events.
EI_DEVICE_CAP_BUTTON	The device can send button events.

◆ ei_device_type

enum ei_device_type

The device type determines what the device represents.

If the device type is EI_DEVICE_TYPE_VIRTUAL, the device is a virtual device representing input as applied on the EIS implementation's screen. A relative virtual device generates input events in logical pixels, an absolute virtual device generates input events in logical pixels on one of the device's regions. Virtual devices do not have a size.

If the device type is EI_DEVICE_TYPE_PHYSICAL, the device is a representation of a physical device as if connected to the EIS implementation's host computer. A relative physical device generates input events in mm, an absolute physical device generates input events in mm within the device's specified physical size. Physical devices do not have regions.

See also: ei_device_get_width; ei_device_get_height

Enumerator
EI_DEVICE_TYPE_VIRTUAL
EI_DEVICE_TYPE_PHYSICAL

◆ ei_event_type

enum ei_event_type

Enumerator
EI_EVENT_CONNECT	The server has approved the connection to this client. Where the server does not approve the connection, EI_EVENT_DISCONNECT is sent instead. This event is only sent once after the initial connection request.
EI_EVENT_DISCONNECT	The server has disconnected this client - all resources left to reference this server are now obsolete. Once this event has been received, the struct ei and all its associated resources should be released. This event may occur at any time after the connection has been made and is the last event to be received by this ei instance. libei guarantees that a EI_EVENT_DISCONNECT is provided to the caller even where the server does not send one.
EI_EVENT_SEAT_ADDED	The server has added a seat available to this client. libei guarantees that any seat added has a corresponding EI_EVENT_SEAT_REMOVED event before EI_EVENT_DISCONNECT. libei guarantees that any device in this seat generates a EI_EVENT_DEVICE_REMOVED event before the EI_EVENT_SEAT_REMOVED event.
EI_EVENT_SEAT_REMOVED	The server has removed a seat previously available to this client. The caller should release the struct ei_seat and all its associated resources. No devices will be added to this seat anymore. libei guarantees that any device in this seat generates a EI_EVENT_DEVICE_REMOVED event before the EI_EVENT_SEAT_REMOVED event.
EI_EVENT_DEVICE_ADDED	The server has added a device for this client. The capabilities of the device may be a subset of the seat capabilities - it is up to the client to verify the minimum required capabilities are indeed set. libei guarantees that any device added has a corresponding EI_EVENT_DEVICE_REMOVED event before EI_EVENT_DISCONNECT.
EI_EVENT_DEVICE_REMOVED	The server has removed a device belonging to this client. The caller should release the struct ei_device and all its associated resources. Any events sent through a removed device are discarded. When this event is received, the device is already removed. A caller does not need to call ei_device_close() event on this device.
EI_EVENT_DEVICE_PAUSED	Any events sent from this device will be discarded until the next resume. The state of a device is not expected to change between pause/resume - for any significant state changes the server is expected to remove the device instead.
EI_EVENT_DEVICE_RESUMED	The client may send events.
EI_EVENT_KEYBOARD_MODIFIERS	The server has changed the modifier state on the device's keymap. See ei_event_keyboard_get_xkb_mods_depressed(), ei_event_keyboard_get_xkb_mods_latched(), ei_event_keyboard_get_xkb_mods_locked(), and ei_event_keyboard_get_xkb_group(). This event is sent in response to an external modifier state change. Where the client triggers a modifier state change in response to ei_device_keyboard_key(), no such event is sent. This event may arrive while a device is paused.
EI_EVENT_FRAME	"Hardware" frame event. This event must be sent by the server and notifies the client that the previous set of events belong to the same logical hardware event. Note These events are only generated on a receiver ei context. See ei_device_frame() for the sender context API.
EI_EVENT_DEVICE_START_EMULATING	The server is about to send events for a device. This event should be used by the client to clear the logical state of the emulated devices and/or provide UI to the user. Note These events are only generated on a receiver ei context. See ei_device_start_emulating() for the sender context API. Note that a server start multiple emulating sequences simultaneously, depending on the devices available. For example, in a synergy-like situation, the server may start sending pointer and keyboard once the remote device logically entered the screen.
EI_EVENT_DEVICE_STOP_EMULATING	The server stopped emulating events on this device, see EIS_EVENT_DEVICE_START_EMULATING. Note These events are only generated on a receiver ei context. See ei_device_stop_emulating() for the sender context API.
EI_EVENT_POINTER_MOTION	A relative motion event with delta coordinates in logical pixels or mm, depending on the device type. Note This event is only generated on a receiver ei context. See ei_device_pointer_motion() for the sender context API.
EI_EVENT_POINTER_MOTION_ABSOLUTE	An absolute motion event with absolute position within the device's regions or size, depending on the device type. Note This event is only generated on a receiver ei context. See ei_device_pointer_motion_absolute() for the sender context API.
EI_EVENT_BUTTON_BUTTON	A button press or release event. Note This event is only generated on a receiver ei context. See ei_device_button_button() for the sender context API.
EI_EVENT_SCROLL_DELTA	A vertical and/or horizontal scroll event with logical-pixels or mm precision, depending on the device type. Note This event is only generated on a receiver ei context. See ei_device_scroll_delta() for the sender context API.
EI_EVENT_SCROLL_STOP	An ongoing scroll sequence stopped. Note This event is only generated on a receiver ei context. See ei_device_scroll_stop() for the sender context API.
EI_EVENT_SCROLL_CANCEL	An ongoing scroll sequence was cancelled. Note This event is only generated on a receiver ei context. See ei_device_scroll_cancel() for the sender context API.
EI_EVENT_SCROLL_DISCRETE	A vertical and/or horizontal scroll event with a discrete range in logical scroll steps, like a scroll wheel. Note This event is only generated on a receiver ei context. See ei_device_scroll_discrete() for the sender context API.
EI_EVENT_KEYBOARD_KEY	A key press or release event. Note This event is only generated on a receiver ei context. See ei_device_keyboard_key() for the sender context API.
EI_EVENT_TOUCH_DOWN	Event for a single touch set down on the device's logical surface. A touch sequence is always down/up with an optional motion event in between. On multitouch capable devices, several touchs eqeuences may be active at any time. Note This event is only generated on a receiver ei context. See ei_device_touch_new() and ei_touch_down() for the sender context API.
EI_EVENT_TOUCH_UP	Event for a single touch released from the device's logical surface. Note This event is only generated on a receiver ei context. See ei_device_touch_new() and ei_touch_up() for the sender context API.
EI_EVENT_TOUCH_MOTION	Event for a single currently-down touch changing position (or other properties). Note This event is only generated on a receiver ei context. See ei_device_touch_new() and ei_touch_motion() for the sender context API.

◆ ei_keymap_type

enum ei_keymap_type

The set of supported keymap types for a struct ei_keymap.

Enumerator
EI_KEYMAP_TYPE_XKB	A libxkbcommon-compatible XKB keymap.

Function Documentation

◆ ei_clock_set_now_func()

void ei_clock_set_now_func	(	struct ei *	,
		ei_clock_now_func	func )

Override the function that returns the current time ei_now().

There is rarely a need to override this function. It exists for the libei-internal test suite.

◆ ei_configure_name()

void ei_configure_name	(	struct ei *	ei,
		const char *	name )

Set the name for this client.

This is a suggestion to the server only and may not be honored.

The client name may be used for display to the user, for example in an authorization dialog that requires the user to approve a connection to the EIS implementation.

This function must be called immediately after ei_new() and before setting up a backend with ei_setup_backend_fd() or ei_setup_backend_socket().

◆ ei_dispatch()

void ei_dispatch ( struct ei * ei )

Main event dispatching function.

Reads events of the file descriptors and processes them internally. Use ei_get_event() to retrieve the events.

Dispatching does not necessarily queue events. This function should be called immediately once data is available on the file descriptor returned by libei_get_fd().

◆ ei_event_get_device()

struct ei_device * ei_event_get_device ( struct ei_event * event )

Return the device from this event.

For events of type EI_EVENT_CONNECT and EI_EVENT_DISCONNECT, this function returns NULL.

This does not increase the refcount of the device. Use eis_device_ref() to keep a reference beyond the immediate scope.

◆ ei_event_get_seat()

struct ei_seat * ei_event_get_seat ( struct ei_event * event )

Return the seat from this event.

For events of type EI_EVENT_CONNECT and EI_EVENT_DISCONNECT, this function returns NULL.

This does not increase the refcount of the seat. Use eis_seat_ref() to keep a reference beyond the immediate scope.

◆ ei_event_get_time()

uint64_t ei_event_get_time ( struct ei_event * event )

Return the time for the event of type EI_EVENT_FRAME in microseconds.

Note: Only events of type EI_EVENT_FRAME carry a timestamp. For convenience, the timestamp for other device events is retrofitted by this library.

Returns: the event time in microseconds

◆ ei_event_get_type()

enum ei_event_type ei_event_get_type ( struct ei_event * event )

Returns: the type of this event

◆ ei_event_type_to_string()

const char * ei_event_type_to_string ( enum ei_event_type )

This is a debugging helper to return a string of the name of the event type, or NULL if the event type is invalid.

For example, for EI_EVENT_TOUCH_UP this function returns the string "EI_EVENT_TOUCH_UP".

◆ ei_event_unref()

struct ei_event * ei_event_unref ( struct ei_event * event )

Release resources associated with this event.

This function always returns NULL.

The caller cannot increase the refcount of an event. Events should be considered transient data and not be held longer than required. ei_event_unref() is provided for consistency (as opposed to, say, ei_event_free()).

◆ ei_get_event()

struct ei_event * ei_get_event ( struct ei * ei )

Return the next event from the event queue, removing it from the queue.

The returned object must be released by the caller with ei_event_unref()

◆ ei_get_fd()

int ei_get_fd ( struct ei * ei )

libei keeps a single file descriptor for all events.

This fd should be monitored for events by the caller's mainloop, e.g. using select(). When events are available on this fd, call ei_dispatch() immediately to process.

◆ ei_get_user_data()

void * ei_get_user_data ( struct ei * ei )

Return the custom data pointer for this context.

libei will not look at or modify the pointer. Use ei_set_user_data() to change the user data.

◆ ei_is_sender()

bool ei_is_sender ( struct ei * ei )

Returns true if the context is was created with ei_new_sender() or false otherwise.

◆ ei_new()

struct ei * ei_new ( void * user_data )

This is an alias for ei_new_sender.

◆ ei_new_receiver()

struct ei * ei_new_receiver ( void * user_data )

Create a new receiver ei context.

The context is refcounted and must be released with ei_unref().

A receiver ei context receives events from the EIS implementation but cannot send events.

A context supports exactly one backend, set up with one of ei_setup_backend_fd() or ei_setup_backend_socket().

Parameters

user_data An opaque pointer to be returned with ei_get_user_data()

See also: ei_set_user_data; ei_get_user_data; ei_setup_backend_fd; ei_setup_backend_socket

◆ ei_new_sender()

struct ei * ei_new_sender ( void * user_data )

Create a new sender ei context.

The context is refcounted and must be released with ei_unref().

A sender ei context sends events to the EIS implementation but cannot receive events.

A context supports exactly one backend, set up with one of ei_setup_backend_fd() or ei_setup_backend_socket().

Parameters

user_data An opaque pointer to be returned with ei_get_user_data()

See also: ei_set_user_data; ei_get_user_data; ei_setup_backend_fd; ei_setup_backend_socket

◆ ei_now()

uint64_t ei_now ( struct ei * ei )

Returns: a timestamp in microseconds for the current time to pass into ei_device_frame().

By default, the returned timestamp is CLOCK_MONOTONIC for compatibility with evdev and libinput. This can be overridden with ei_clock_set_now_func().

◆ ei_peek_event()

struct ei_event * ei_peek_event ( struct ei * ei )

Returns the next event in the internal event queue (or NULL) without removing that event from the queue; the next call to ei_get_event() will return that same event.

This call is useful for checking whether there is an event and/or what type of event it is.

Repeated calls to ei_peek_event() return the same event.

The returned event is refcounted, use ei_event_unref() to drop the reference.

A caller must not call ei_get_event() while holding a ref to an event returned by ei_peek_event(). Doing so is undefined behavior.

◆ ei_ref()

struct ei * ei_ref ( struct ei * ei )

Increase the refcount of this struct by one.

Use ei_unref() to decrease the refcount.

Returns: the argument passed into the function

◆ ei_set_user_data()

void ei_set_user_data	(	struct ei *	ei,
		void *	user_data )

Set a custom data pointer for this context.

libei will not look at or modify the pointer. Use ei_get_user_data() to retrieve a previously set user data.

◆ ei_setup_backend_fd()

int ei_setup_backend_fd	(	struct ei *	ei,
		int	fd )

Initialize the ei context on the given socket file descriptor.

The ei context will initiate the conversation with the EIS server listening on the other end of this socket.

This is the preferred entry point for libei and should be the default used in new clients. It allows for private-by-default socket file descriptors and the policy on how the socket is created is delegated to the caller.

If the connection was successful, an event of type EI_EVENT_CONNECT or EI_EVENT_DISCONNECT will become available after a future call to ei_dispatch().

If the connection failed, use ei_unref() to release the data allocated for this context.

This function takes ownership of the file descriptor, and will close it when tearing down.

Returns: zero on success or a negative errno on failure

◆ ei_setup_backend_socket()

int ei_setup_backend_socket	(	struct ei *	ei,
		const char *	socketpath )

Set this ei context to use the socket backend.

The ei context will connect to the socket at the given path and initiate the conversation with the EIS server listening on that socket.

Note: This backend requires the socket to be accessible to connect to and forces the EIS implementation to to identification and access control for clients. In almost all cases, the EIS implementation should use pre-created fds per client and the client should instead use ei_setup_backend_fd(). This backend is primarily useful for testing and debugging.

If socketpath is NULL, the value of the environment variable LIBEI_SOCKET is used. If socketpath does not start with '/', it is relative to $XDG_RUNTIME_DIR. If XDG_RUNTIME_DIR is not set, this function fails.