Wayland protocol specification

wl_display

group iface_wl_display

The core global object.

This is a special singleton object. It is used for internal Wayland protocol features.

Defines

WL_DISPLAY_ERROR_SINCE_VERSION

WL_DISPLAY_DELETE_ID_SINCE_VERSION

WL_DISPLAY_SYNC_SINCE_VERSION

WL_DISPLAY_GET_REGISTRY_SINCE_VERSION

Enums

enum wl_display_error

global error values

These errors are global and can be emitted in response to any server request.

Values:

WL_DISPLAY_ERROR_INVALID_OBJECT = 0

server couldn’t find object

WL_DISPLAY_ERROR_INVALID_METHOD = 1

method doesn’t exist on the specified interface

WL_DISPLAY_ERROR_NO_MEMORY = 2

server is out of memory

WL_DISPLAY_ERROR_IMPLEMENTATION = 3

implementation error in compositor

Functions

static int wl_display_add_listener(struct wl_display *wl_display, const struct wl_display_listener *listener, void *data)

static void wl_display_set_user_data(struct wl_display *wl_display, void *user_data)

static void *wl_display_get_user_data(struct wl_display *wl_display)

static struct wl_callback *wl_display_sync(struct wl_display *wl_display)

The sync request asks the server to emit the ‘done’ event on the returned wl_callback object.

Since requests are handled in-order and events are delivered in-order, this can be used as a barrier to ensure all previous requests and the resulting events have been handled.

The object returned by this request will be destroyed by the compositor after the callback is fired and as such the client must not attempt to use it after that point.

The callback_data passed in the callback is the event serial.

static struct wl_registry *wl_display_get_registry(struct wl_display *wl_display)

This request creates a registry object that allows the client to list and bind the global objects available from the compositor.

It should be noted that the server side resources consumed in response to a get_registry request can only be released when the client disconnects, not when the client side proxy is destroyed. Therefore, clients should invoke get_registry as infrequently as possible to avoid wasting memory.

struct wl_display_listener

#include <wayland-client-protocol.h>

Public Members

void (*error)(void *data, struct wl_display *wl_display, void *object_id, uint32_t code, const char *message)

fatal error event

The error event is sent out when a fatal (non-recoverable) error has occurred. The object_id argument is the object where the error occurred, most often in response to a request to that object. The code identifies the error and is defined by the object interface. As such, each interface defines its own set of error codes. The message is a brief description of the error, for (debugging) convenience.

Parameters

• object_id: object where the error occurred
• code: error code
• message: error description

void (*delete_id)(void *data, struct wl_display *wl_display, uint32_t id)

acknowledge object ID deletion

This event is used internally by the object ID management logic. When a client deletes an object, the server will send this event to acknowledge that it has seen the delete request. When the client receives this event, it will know that it can safely reuse the object ID.

Parameters

• id: deleted object ID

wl_registry

group iface_wl_registry

The singleton global registry object.

The server has a number of global objects that are available to all clients. These objects typically represent an actual object in the server (for example, an input device) or they are singleton objects that provide extension functionality.

When a client creates a registry object, the registry object will emit a global event for each global currently in the registry. Globals come and go as a result of device or monitor hotplugs, reconfiguration or other events, and the registry will send out global and global_remove events to keep the client up to date with the changes. To mark the end of the initial burst of events, the client can use the wl_display.sync request immediately after calling wl_display.get_registry.

A client can bind to a global object by using the bind request. This creates a client-side handle that lets the object emit events to the client and lets the client invoke requests on the object.

Defines

WL_REGISTRY_GLOBAL_SINCE_VERSION

WL_REGISTRY_GLOBAL_REMOVE_SINCE_VERSION

WL_REGISTRY_BIND_SINCE_VERSION

Functions

static int wl_registry_add_listener(struct wl_registry *wl_registry, const struct wl_registry_listener *listener, void *data)

static void wl_registry_set_user_data(struct wl_registry *wl_registry, void *user_data)

static void *wl_registry_get_user_data(struct wl_registry *wl_registry)

static void wl_registry_destroy(struct wl_registry *wl_registry)

static void *wl_registry_bind(struct wl_registry *wl_registry, uint32_t name, const struct wl_interface *interface, uint32_t version)

Binds a new, client-created object to the server using the specified name as the identifier.

struct wl_registry_listener

#include <wayland-client-protocol.h>

Public Members

void (*global)(void *data, struct wl_registry *wl_registry, uint32_t name, const char *interface, uint32_t version)

announce global object

Notify the client of global objects.

The event notifies the client that a global object with the given name is now available, and it implements the given version of the given interface.

Parameters

• name: numeric name of the global object
• interface: interface implemented by the object
• version: interface version

void (*global_remove)(void *data, struct wl_registry *wl_registry, uint32_t name)

announce removal of global object

Notify the client of removed global objects.

This event notifies the client that the global identified by name is no longer available. If the client bound to the global using the bind request, the client should now destroy that object.

The object remains valid and requests to the object will be ignored until the client destroys it, to avoid races between the global going away and a client sending a request to it.

Parameters

• name: numeric name of the global object

wl_callback

group iface_wl_callback

Clients can handle the ‘done’ event to get notified when the related request is done.

Defines

WL_CALLBACK_DONE_SINCE_VERSION

Functions

static int wl_callback_add_listener(struct wl_callback *wl_callback, const struct wl_callback_listener *listener, void *data)

static void wl_callback_set_user_data(struct wl_callback *wl_callback, void *user_data)

static void *wl_callback_get_user_data(struct wl_callback *wl_callback)

static void wl_callback_destroy(struct wl_callback *wl_callback)

struct wl_callback_listener

#include <wayland-client-protocol.h>

Public Members

void (*done)(void *data, struct wl_callback *wl_callback, uint32_t callback_data)

done event

Notify the client when the related request is done.

Parameters

• callback_data: request-specific data for the callback

wl_compositor

group iface_wl_compositor

A compositor.

This object is a singleton global. The compositor is in charge of combining the contents of multiple surfaces into one displayable output.

Defines

WL_COMPOSITOR_CREATE_SURFACE_SINCE_VERSION

WL_COMPOSITOR_CREATE_REGION_SINCE_VERSION

Functions

static void wl_compositor_set_user_data(struct wl_compositor *wl_compositor, void *user_data)

static void *wl_compositor_get_user_data(struct wl_compositor *wl_compositor)

static void wl_compositor_destroy(struct wl_compositor *wl_compositor)

static struct wl_surface *wl_compositor_create_surface(struct wl_compositor *wl_compositor)

Ask the compositor to create a new surface.

static struct wl_region *wl_compositor_create_region(struct wl_compositor *wl_compositor)

Ask the compositor to create a new region.

wl_shm_pool

group iface_wl_shm_pool

The wl_shm_pool object encapsulates a piece of memory shared between the compositor and client.

Through the wl_shm_pool object, the client can allocate shared memory wl_buffer objects. All objects created through the same pool share the same underlying mapped memory. Reusing the mapped memory avoids the setup/teardown overhead and is useful when interactively resizing a surface or for many small buffers.

Defines

WL_SHM_POOL_CREATE_BUFFER_SINCE_VERSION

WL_SHM_POOL_DESTROY_SINCE_VERSION

WL_SHM_POOL_RESIZE_SINCE_VERSION

Functions

static void wl_shm_pool_set_user_data(struct wl_shm_pool *wl_shm_pool, void *user_data)

static void *wl_shm_pool_get_user_data(struct wl_shm_pool *wl_shm_pool)

static struct wl_buffer *wl_shm_pool_create_buffer(struct wl_shm_pool *wl_shm_pool, int32_t offset, int32_t width, int32_t height, int32_t stride, uint32_t format)

Create a wl_buffer object from the pool.

The buffer is created offset bytes into the pool and has width and height as specified. The stride argument specifies the number of bytes from the beginning of one row to the beginning of the next. The format is the pixel format of the buffer and must be one of those advertised through the wl_shm.format event.

A buffer will keep a reference to the pool it was created from so it is valid to destroy the pool immediately after creating a buffer from it.

static void wl_shm_pool_destroy(struct wl_shm_pool *wl_shm_pool)

Destroy the shared memory pool.

The mmapped memory will be released when all buffers that have been created from this pool are gone.

static void wl_shm_pool_resize(struct wl_shm_pool *wl_shm_pool, int32_t size)

This request will cause the server to remap the backing memory for the pool from the file descriptor passed when the pool was created, but using the new size.

This request can only be used to make the pool bigger.

wl_shm

group iface_wl_shm

A singleton global object that provides support for shared memory.

Clients can create wl_shm_pool objects using the create_pool request.

At connection setup time, the wl_shm object emits one or more format events to inform clients about the valid pixel formats that can be used for buffers.

Defines

WL_SHM_FORMAT_SINCE_VERSION

WL_SHM_CREATE_POOL_SINCE_VERSION

Enums

enum wl_shm_error

wl_shm error values

These errors can be emitted in response to wl_shm requests.

Values:

WL_SHM_ERROR_INVALID_FORMAT = 0

buffer format is not known

WL_SHM_ERROR_INVALID_STRIDE = 1

invalid size or stride during pool or buffer creation

WL_SHM_ERROR_INVALID_FD = 2

mmapping the file descriptor failed

enum wl_shm_format

pixel formats

This describes the memory layout of an individual pixel.

All renderers should support argb8888 and xrgb8888 but any other formats are optional and may not be supported by the particular renderer in use.

The drm format codes match the macros defined in drm_fourcc.h. The formats actually supported by the compositor will be reported by the format event.

Values:

WL_SHM_FORMAT_ARGB8888 = 0

32-bit ARGB format, [31:0] A:R:G:B 8:8:8:8 little endian

WL_SHM_FORMAT_XRGB8888 = 1

32-bit RGB format, [31:0] x:R:G:B 8:8:8:8 little endian

8-bit color index format, [7:0] C

8-bit RGB format, [7:0] R:G:B 3:3:2

8-bit BGR format, [7:0] B:G:R 2:3:3

16-bit xRGB format, [15:0] x:R:G:B 4:4:4:4 little endian

16-bit xBGR format, [15:0] x:B:G:R 4:4:4:4 little endian

16-bit RGBx format, [15:0] R:G:B:x 4:4:4:4 little endian

16-bit BGRx format, [15:0] B:G:R:x 4:4:4:4 little endian

WL_SHM_FORMAT_ARGB4444 = 0x32315241

16-bit ARGB format, [15:0] A:R:G:B 4:4:4:4 little endian

WL_SHM_FORMAT_ABGR4444 = 0x32314241

16-bit ABGR format, [15:0] A:B:G:R 4:4:4:4 little endian

WL_SHM_FORMAT_RGBA4444 = 0x32314152

16-bit RBGA format, [15:0] R:G:B:A 4:4:4:4 little endian

WL_SHM_FORMAT_BGRA4444 = 0x32314142

16-bit BGRA format, [15:0] B:G:R:A 4:4:4:4 little endian

16-bit xRGB format, [15:0] x:R:G:B 1:5:5:5 little endian

16-bit xBGR 1555 format, [15:0] x:B:G:R 1:5:5:5 little endian

16-bit RGBx 5551 format, [15:0] R:G:B:x 5:5:5:1 little endian

16-bit BGRx 5551 format, [15:0] B:G:R:x 5:5:5:1 little endian

WL_SHM_FORMAT_ARGB1555 = 0x35315241

16-bit ARGB 1555 format, [15:0] A:R:G:B 1:5:5:5 little endian

WL_SHM_FORMAT_ABGR1555 = 0x35314241

16-bit ABGR 1555 format, [15:0] A:B:G:R 1:5:5:5 little endian

WL_SHM_FORMAT_RGBA5551 = 0x35314152

16-bit RGBA 5551 format, [15:0] R:G:B:A 5:5:5:1 little endian

WL_SHM_FORMAT_BGRA5551 = 0x35314142

16-bit BGRA 5551 format, [15:0] B:G:R:A 5:5:5:1 little endian

WL_SHM_FORMAT_RGB565 = 0x36314752

16-bit RGB 565 format, [15:0] R:G:B 5:6:5 little endian

WL_SHM_FORMAT_BGR565 = 0x36314742

16-bit BGR 565 format, [15:0] B:G:R 5:6:5 little endian

WL_SHM_FORMAT_RGB888 = 0x34324752

24-bit RGB format, [23:0] R:G:B little endian

WL_SHM_FORMAT_BGR888 = 0x34324742

24-bit BGR format, [23:0] B:G:R little endian

32-bit xBGR format, [31:0] x:B:G:R 8:8:8:8 little endian

32-bit RGBx format, [31:0] R:G:B:x 8:8:8:8 little endian

32-bit BGRx format, [31:0] B:G:R:x 8:8:8:8 little endian

WL_SHM_FORMAT_ABGR8888 = 0x34324241

32-bit ABGR format, [31:0] A:B:G:R 8:8:8:8 little endian

WL_SHM_FORMAT_RGBA8888 = 0x34324152

32-bit RGBA format, [31:0] R:G:B:A 8:8:8:8 little endian

WL_SHM_FORMAT_BGRA8888 = 0x34324142

32-bit BGRA format, [31:0] B:G:R:A 8:8:8:8 little endian

32-bit xRGB format, [31:0] x:R:G:B 2:10:10:10 little endian

32-bit xBGR format, [31:0] x:B:G:R 2:10:10:10 little endian

32-bit RGBx format, [31:0] R:G:B:x 10:10:10:2 little endian

32-bit BGRx format, [31:0] B:G:R:x 10:10:10:2 little endian

WL_SHM_FORMAT_ARGB2101010 = 0x30335241

32-bit ARGB format, [31:0] A:R:G:B 2:10:10:10 little endian

WL_SHM_FORMAT_ABGR2101010 = 0x30334241

32-bit ABGR format, [31:0] A:B:G:R 2:10:10:10 little endian

WL_SHM_FORMAT_RGBA1010102 = 0x30334152

32-bit RGBA format, [31:0] R:G:B:A 10:10:10:2 little endian

WL_SHM_FORMAT_BGRA1010102 = 0x30334142

32-bit BGRA format, [31:0] B:G:R:A 10:10:10:2 little endian

packed YCbCr format, [31:0] Cr0:Y1:Cb0:Y0 8:8:8:8 little endian

packed YCbCr format, [31:0] Cb0:Y1:Cr0:Y0 8:8:8:8 little endian

packed YCbCr format, [31:0] Y1:Cr0:Y0:Cb0 8:8:8:8 little endian

packed YCbCr format, [31:0] Y1:Cb0:Y0:Cr0 8:8:8:8 little endian

packed AYCbCr format, [31:0] A:Y:Cb:Cr 8:8:8:8 little endian

WL_SHM_FORMAT_NV12 = 0x3231564e

2 plane YCbCr Cr:Cb format, 2x2 subsampled Cr:Cb plane

WL_SHM_FORMAT_NV21 = 0x3132564e

2 plane YCbCr Cb:Cr format, 2x2 subsampled Cb:Cr plane

WL_SHM_FORMAT_NV16 = 0x3631564e

2 plane YCbCr Cr:Cb format, 2x1 subsampled Cr:Cb plane

WL_SHM_FORMAT_NV61 = 0x3136564e

2 plane YCbCr Cb:Cr format, 2x1 subsampled Cb:Cr plane

3 plane YCbCr format, 4x4 subsampled Cb (1) and Cr (2) planes

3 plane YCbCr format, 4x4 subsampled Cr (1) and Cb (2) planes

3 plane YCbCr format, 4x1 subsampled Cb (1) and Cr (2) planes

3 plane YCbCr format, 4x1 subsampled Cr (1) and Cb (2) planes

3 plane YCbCr format, 2x2 subsampled Cb (1) and Cr (2) planes

3 plane YCbCr format, 2x2 subsampled Cr (1) and Cb (2) planes

3 plane YCbCr format, 2x1 subsampled Cb (1) and Cr (2) planes

3 plane YCbCr format, 2x1 subsampled Cr (1) and Cb (2) planes

3 plane YCbCr format, non-subsampled Cb (1) and Cr (2) planes

3 plane YCbCr format, non-subsampled Cr (1) and Cb (2) planes

Functions

static int wl_shm_add_listener(struct wl_shm *wl_shm, const struct wl_shm_listener *listener, void *data)

static void wl_shm_set_user_data(struct wl_shm *wl_shm, void *user_data)

static void *wl_shm_get_user_data(struct wl_shm *wl_shm)

static void wl_shm_destroy(struct wl_shm *wl_shm)

static struct wl_shm_pool *wl_shm_create_pool(struct wl_shm *wl_shm, int32_t fd, int32_t size)

Create a new wl_shm_pool object.

The pool can be used to create shared memory based buffer objects. The server will mmap size bytes of the passed file descriptor, to use as backing memory for the pool.

struct wl_shm_listener

#include <wayland-client-protocol.h>

Public Members

void (*format)(void *data, struct wl_shm *wl_shm, uint32_t format)

pixel format description

Informs the client about a valid pixel format that can be used for buffers. Known formats include argb8888 and xrgb8888.

Parameters

• format: buffer pixel format

wl_buffer

group iface_wl_buffer

A buffer provides the content for a wl_surface.

Buffers are created through factory interfaces such as wl_drm, wl_shm or similar. It has a width and a height and can be attached to a wl_surface, but the mechanism by which a client provides and updates the contents is defined by the buffer factory interface.

Defines

WL_BUFFER_RELEASE_SINCE_VERSION

WL_BUFFER_DESTROY_SINCE_VERSION

Functions

static int wl_buffer_add_listener(struct wl_buffer *wl_buffer, const struct wl_buffer_listener *listener, void *data)

static void wl_buffer_set_user_data(struct wl_buffer *wl_buffer, void *user_data)

static void *wl_buffer_get_user_data(struct wl_buffer *wl_buffer)

static void wl_buffer_destroy(struct wl_buffer *wl_buffer)

Destroy a buffer.

If and how you need to release the backing storage is defined by the buffer factory interface.

For possible side-effects to a surface, see wl_surface.attach.

struct wl_buffer_listener

#include <wayland-client-protocol.h>

Public Members

void (*release)(void *data, struct wl_buffer *wl_buffer)

compositor releases buffer

Sent when this wl_buffer is no longer used by the compositor. The client is now free to reuse or destroy this buffer and its backing storage.

If a client receives a release event before the frame callback requested in the same wl_surface.commit that attaches this wl_buffer to a surface, then the client is immediately free to reuse the buffer and its backing storage, and does not need a second buffer for the next surface content update. Typically this is possible, when the compositor maintains a copy of the wl_surface contents, e.g. as a GL texture. This is an important optimization for GL(ES) compositors with wl_shm clients.

wl_data_offer

group iface_wl_data_offer

A wl_data_offer represents a piece of data offered for transfer by another client (the source client).

It is used by the copy-and-paste and drag-and-drop mechanisms. The offer describes the different mime types that the data can be converted to and provides the mechanism for transferring the data directly from the source client.

Defines

WL_DATA_OFFER_OFFER_SINCE_VERSION

WL_DATA_OFFER_SOURCE_ACTIONS_SINCE_VERSION

WL_DATA_OFFER_ACTION_SINCE_VERSION

WL_DATA_OFFER_ACCEPT_SINCE_VERSION

WL_DATA_OFFER_RECEIVE_SINCE_VERSION

WL_DATA_OFFER_DESTROY_SINCE_VERSION

WL_DATA_OFFER_FINISH_SINCE_VERSION

WL_DATA_OFFER_SET_ACTIONS_SINCE_VERSION

Functions

static int wl_data_offer_add_listener(struct wl_data_offer *wl_data_offer, const struct wl_data_offer_listener *listener, void *data)

static void wl_data_offer_set_user_data(struct wl_data_offer *wl_data_offer, void *user_data)

static void *wl_data_offer_get_user_data(struct wl_data_offer *wl_data_offer)

static void wl_data_offer_accept(struct wl_data_offer *wl_data_offer, uint32_t serial, const char *mime_type)

Indicate that the client can accept the given mime type, or NULL for not accepted.

For objects of version 2 or older, this request is used by the client to give feedback whether the client can receive the given mime type, or NULL if none is accepted; the feedback does not determine whether the drag-and-drop operation succeeds or not.

For objects of version 3 or newer, this request determines the final result of the drag-and-drop operation. If the end result is that no mime types were accepted, the drag-and-drop operation will be cancelled and the corresponding drag source will receive wl_data_source.cancelled. Clients may still use this event in conjunction with wl_data_source.action for feedback.

static void wl_data_offer_receive(struct wl_data_offer *wl_data_offer, const char *mime_type, int32_t fd)

To transfer the offered data, the client issues this request and indicates the mime type it wants to receive.

The transfer happens through the passed file descriptor (typically created with the pipe system call). The source client writes the data in the mime type representation requested and then closes the file descriptor.

The receiving client reads from the read end of the pipe until EOF and then closes its end, at which point the transfer is complete.

This request may happen multiple times for different mime types, both before and after wl_data_device.drop. Drag-and-drop destination clients may preemptively fetch data or examine it more closely to determine acceptance.

static void wl_data_offer_destroy(struct wl_data_offer *wl_data_offer)

Destroy the data offer.

static void wl_data_offer_finish(struct wl_data_offer *wl_data_offer)

Notifies the compositor that the drag destination successfully finished the drag-and-drop operation.

Upon receiving this request, the compositor will emit wl_data_source.dnd_finished on the drag source client.

It is a client error to perform other requests than wl_data_offer.destroy after this one. It is also an error to perform this request after a NULL mime type has been set in wl_data_offer.accept or no action was received through wl_data_offer.action.

If wl_data_offer.finish request is received for a non drag and drop operation, the invalid_finish protocol error is raised.

static void wl_data_offer_set_actions(struct wl_data_offer *wl_data_offer, uint32_t dnd_actions, uint32_t preferred_action)

Sets the actions that the destination side client supports for this operation.

This request may trigger the emission of wl_data_source.action and wl_data_offer.action events if the compositor needs to change the selected action.

This request can be called multiple times throughout the drag-and-drop operation, typically in response to wl_data_device.enter or wl_data_device.motion events.

This request determines the final result of the drag-and-drop operation. If the end result is that no action is accepted, the drag source will receive wl_drag_source.cancelled.

The dnd_actions argument must contain only values expressed in the wl_data_device_manager.dnd_actions enum, and the preferred_action argument must only contain one of those values set, otherwise it will result in a protocol error.

While managing an “ask” action, the destination drag-and-drop client may perform further wl_data_offer.receive requests, and is expected to perform one last wl_data_offer.set_actions request with a preferred action other than “ask” (and optionally wl_data_offer.accept) before requesting wl_data_offer.finish, in order to convey the action selected by the user. If the preferred action is not in the wl_data_offer.source_actions mask, an error will be raised.

If the “ask” action is dismissed (e.g. user cancellation), the client is expected to perform wl_data_offer.destroy right away.

This request can only be made on drag-and-drop offers, a protocol error will be raised otherwise.

struct wl_data_offer_listener

#include <wayland-client-protocol.h>

Public Members

void (*offer)(void *data, struct wl_data_offer *wl_data_offer, const char *mime_type)

advertise offered mime type

Sent immediately after creating the wl_data_offer object. One event per offered mime type.

Parameters

• mime_type: offered mime type

void (*source_actions)(void *data, struct wl_data_offer *wl_data_offer, uint32_t source_actions)

notify the source-side available actions

This event indicates the actions offered by the data source. It will be sent right after wl_data_device.enter, or anytime the source side changes its offered actions through wl_data_source.set_actions.

Since

3

Parameters

• source_actions: actions offered by the data source

void (*action)(void *data, struct wl_data_offer *wl_data_offer, uint32_t dnd_action)

notify the selected action

This event indicates the action selected by the compositor after matching the source/destination side actions. Only one action (or none) will be offered here.

This event can be emitted multiple times during the drag-and-drop operation in response to destination side action changes through wl_data_offer.set_actions.

This event will no longer be emitted after wl_data_device.drop happened on the drag-and-drop destination, the client must honor the last action received, or the last preferred one set through wl_data_offer.set_actions when handling an “ask” action.

Compositors may also change the selected action on the fly, mainly in response to keyboard modifier changes during the drag-and-drop operation.

The most recent action received is always the valid one. Prior to receiving wl_data_device.drop, the chosen action may change (e.g. due to keyboard modifiers being pressed). At the time of receiving wl_data_device.drop the drag-and-drop destination must honor the last action received.

Action changes may still happen after wl_data_device.drop, especially on “ask” actions, where the drag-and-drop destination may choose another action afterwards. Action changes happening at this stage are always the result of inter-client negotiation, the compositor shall no longer be able to induce a different action.

Upon “ask” actions, it is expected that the drag-and-drop destination may potentially choose a different action and/or mime type, based on wl_data_offer.source_actions and finally chosen by the user (e.g. popping up a menu with the available options). The final wl_data_offer.set_actions and wl_data_offer.accept requests must happen before the call to wl_data_offer.finish.

Since

3

Parameters

• dnd_action: action selected by the compositor

wl_data_source

group iface_wl_data_source

The wl_data_source object is the source side of a wl_data_offer.

It is created by the source client in a data transfer and provides a way to describe the offered data and a way to respond to requests to transfer the data.

Defines

WL_DATA_SOURCE_TARGET_SINCE_VERSION

WL_DATA_SOURCE_SEND_SINCE_VERSION

WL_DATA_SOURCE_CANCELLED_SINCE_VERSION

WL_DATA_SOURCE_DND_DROP_PERFORMED_SINCE_VERSION

WL_DATA_SOURCE_DND_FINISHED_SINCE_VERSION

WL_DATA_SOURCE_ACTION_SINCE_VERSION

WL_DATA_SOURCE_OFFER_SINCE_VERSION

WL_DATA_SOURCE_DESTROY_SINCE_VERSION

WL_DATA_SOURCE_SET_ACTIONS_SINCE_VERSION

Functions

static int wl_data_source_add_listener(struct wl_data_source *wl_data_source, const struct wl_data_source_listener *listener, void *data)

static void wl_data_source_set_user_data(struct wl_data_source *wl_data_source, void *user_data)

static void *wl_data_source_get_user_data(struct wl_data_source *wl_data_source)

static void wl_data_source_offer(struct wl_data_source *wl_data_source, const char *mime_type)

This request adds a mime type to the set of mime types advertised to targets.

Can be called several times to offer multiple types.

static void wl_data_source_destroy(struct wl_data_source *wl_data_source)

Destroy the data source.

static void wl_data_source_set_actions(struct wl_data_source *wl_data_source, uint32_t dnd_actions)

Sets the actions that the source side client supports for this operation.

This request may trigger wl_data_source.action and wl_data_offer.action events if the compositor needs to change the selected action.

The dnd_actions argument must contain only values expressed in the wl_data_device_manager.dnd_actions enum, otherwise it will result in a protocol error.

This request must be made once only, and can only be made on sources used in drag-and-drop, so it must be performed before wl_data_device.start_drag. Attempting to use the source other than for drag-and-drop will raise a protocol error.

struct wl_data_source_listener

#include <wayland-client-protocol.h>

Public Members

void (*target)(void *data, struct wl_data_source *wl_data_source, const char *mime_type)

a target accepts an offered mime type

Sent when a target accepts pointer_focus or motion events. If a target does not accept any of the offered types, type is NULL.

Used for feedback during drag-and-drop.

Parameters

• mime_type: mime type accepted by the target

void (*send)(void *data, struct wl_data_source *wl_data_source, const char *mime_type, int32_t fd)

send the data

Request for data from the client. Send the data as the specified mime type over the passed file descriptor, then close it.

Parameters

• mime_type: mime type for the data
• fd: file descriptor for the data

void (*cancelled)(void *data, struct wl_data_source *wl_data_source)

selection was cancelled

This data source is no longer valid. There are several reasons why this could happen:

• The data source has been replaced by another data source. - The drag-and-drop operation was performed, but the drop destination did not accept any of the mime types offered through wl_data_source.target. - The drag-and-drop operation was performed, but the drop destination did not select any of the actions present in the mask offered through wl_data_source.action. - The drag-and-drop operation was performed but didn’t happen over a surface. - The compositor cancelled the drag-and-drop operation (e.g. compositor dependent timeouts to avoid stale drag-and-drop transfers).

The client should clean up and destroy this data source.

For objects of version 2 or older, wl_data_source.cancelled will only be emitted if the data source was replaced by another data source.

void (*dnd_drop_performed)(void *data, struct wl_data_source *wl_data_source)

the drag-and-drop operation physically finished

The user performed the drop action. This event does not indicate acceptance, wl_data_source.cancelled may still be emitted afterwards if the drop destination does not accept any mime type.

However, this event might however not be received if the compositor cancelled the drag-and-drop operation before this event could happen.

Note that the data_source may still be used in the future and should not be destroyed here.

Since

3

void (*dnd_finished)(void *data, struct wl_data_source *wl_data_source)

the drag-and-drop operation concluded

The drop destination finished interoperating with this data source, so the client is now free to destroy this data source and free all associated data.

If the action used to perform the operation was “move”, the source can now delete the transferred data.

Since

3

void (*action)(void *data, struct wl_data_source *wl_data_source, uint32_t dnd_action)

notify the selected action

This event indicates the action selected by the compositor after matching the source/destination side actions. Only one action (or none) will be offered here.

This event can be emitted multiple times during the drag-and-drop operation, mainly in response to destination side changes through wl_data_offer.set_actions, and as the data device enters/leaves surfaces.

It is only possible to receive this event after wl_data_source.dnd_drop_performed if the drag-and-drop operation ended in an “ask” action, in which case the final wl_data_source.action event will happen immediately before wl_data_source.dnd_finished.

Compositors may also change the selected action on the fly, mainly in response to keyboard modifier changes during the drag-and-drop operation.

The most recent action received is always the valid one. The chosen action may change alongside negotiation (e.g. an “ask” action can turn into a “move” operation), so the effects of the final action must always be applied in wl_data_offer.dnd_finished.

Clients can trigger cursor surface changes from this point, so they reflect the current action.

Since

3

Parameters

• dnd_action: action selected by the compositor

wl_data_device

group iface_wl_data_device

There is one wl_data_device per seat which can be obtained from the global wl_data_device_manager singleton.

A wl_data_device provides access to inter-client data transfer mechanisms such as copy-and-paste and drag-and-drop.

Defines

WL_DATA_DEVICE_DATA_OFFER_SINCE_VERSION

WL_DATA_DEVICE_ENTER_SINCE_VERSION

WL_DATA_DEVICE_LEAVE_SINCE_VERSION

WL_DATA_DEVICE_MOTION_SINCE_VERSION

WL_DATA_DEVICE_DROP_SINCE_VERSION

WL_DATA_DEVICE_SELECTION_SINCE_VERSION

WL_DATA_DEVICE_START_DRAG_SINCE_VERSION

WL_DATA_DEVICE_SET_SELECTION_SINCE_VERSION

WL_DATA_DEVICE_RELEASE_SINCE_VERSION

Functions

static int wl_data_device_add_listener(struct wl_data_device *wl_data_device, const struct wl_data_device_listener *listener, void *data)

static void wl_data_device_set_user_data(struct wl_data_device *wl_data_device, void *user_data)

static void *wl_data_device_get_user_data(struct wl_data_device *wl_data_device)

static void wl_data_device_destroy(struct wl_data_device *wl_data_device)

static void wl_data_device_start_drag(struct wl_data_device *wl_data_device, struct wl_data_source *source, struct wl_surface *origin, struct wl_surface *icon, uint32_t serial)

This request asks the compositor to start a drag-and-drop operation on behalf of the client.

The source argument is the data source that provides the data for the eventual data transfer. If source is NULL, enter, leave and motion events are sent only to the client that initiated the drag and the client is expected to handle the data passing internally.

The origin surface is the surface where the drag originates and the client must have an active implicit grab that matches the serial.

The icon surface is an optional (can be NULL) surface that provides an icon to be moved around with the cursor. Initially, the top-left corner of the icon surface is placed at the cursor hotspot, but subsequent wl_surface.attach request can move the relative position. Attach requests must be confirmed with wl_surface.commit as usual. The icon surface is given the role of a drag-and-drop icon. If the icon surface already has another role, it raises a protocol error.

The current and pending input regions of the icon wl_surface are cleared, and wl_surface.set_input_region is ignored until the wl_surface is no longer used as the icon surface. When the use as an icon ends, the current and pending input regions become undefined, and the wl_surface is unmapped.

static void wl_data_device_set_selection(struct wl_data_device *wl_data_device, struct wl_data_source *source, uint32_t serial)

This request asks the compositor to set the selection to the data from the source on behalf of the client.

To unset the selection, set the source to NULL.

static void wl_data_device_release(struct wl_data_device *wl_data_device)

This request destroys the data device.

struct wl_data_device_listener

#include <wayland-client-protocol.h>

Public Members

void (*data_offer)(void *data, struct wl_data_device *wl_data_device, struct wl_data_offer *id)

introduce a new wl_data_offer

The data_offer event introduces a new wl_data_offer object, which will subsequently be used in either the data_device.enter event (for drag-and-drop) or the data_device.selection event (for selections). Immediately following the data_device_data_offer event, the new data_offer object will send out data_offer.offer events to describe the mime types it offers.

Parameters

• id: the new data_offer object

void (*enter)(void *data, struct wl_data_device *wl_data_device, uint32_t serial, struct wl_surface *surface, wl_fixed_t x, wl_fixed_t y, struct wl_data_offer *id)

initiate drag-and-drop session

This event is sent when an active drag-and-drop pointer enters a surface owned by the client. The position of the pointer at enter time is provided by the x and y arguments, in surface-local coordinates.

Parameters

• serial: serial number of the enter event
• surface: client surface entered
• x: surface-local x coordinate
• y: surface-local y coordinate
• id: source data_offer object

void (*leave)(void *data, struct wl_data_device *wl_data_device)

end drag-and-drop session

This event is sent when the drag-and-drop pointer leaves the surface and the session ends. The client must destroy the wl_data_offer introduced at enter time at this point.

void (*motion)(void *data, struct wl_data_device *wl_data_device, uint32_t time, wl_fixed_t x, wl_fixed_t y)

drag-and-drop session motion

This event is sent when the drag-and-drop pointer moves within the currently focused surface. The new position of the pointer is provided by the x and y arguments, in surface-local coordinates.

Parameters

• time: timestamp with millisecond granularity
• x: surface-local x coordinate
• y: surface-local y coordinate

void (*drop)(void *data, struct wl_data_device *wl_data_device)

end drag-and-drop session successfully

The event is sent when a drag-and-drop operation is ended because the implicit grab is removed.

The drag-and-drop destination is expected to honor the last action received through wl_data_offer.action, if the resulting action is “copy” or “move”, the destination can still perform wl_data_offer.receive requests, and is expected to end all transfers with a wl_data_offer.finish request.

If the resulting action is “ask”, the action will not be considered final. The drag-and-drop destination is expected to perform one last wl_data_offer.set_actions request, or wl_data_offer.destroy in order to cancel the operation.

void (*selection)(void *data, struct wl_data_device *wl_data_device, struct wl_data_offer *id)

advertise new selection

The selection event is sent out to notify the client of a new wl_data_offer for the selection for this device. The data_device.data_offer and the data_offer.offer events are sent out immediately before this event to introduce the data offer object. The selection event is sent to a client immediately before receiving keyboard focus and when a new selection is set while the client has keyboard focus. The data_offer is valid until a new data_offer or NULL is received or until the client loses keyboard focus. The client must destroy the previous selection data_offer, if any, upon receiving this event.

Parameters

• id: selection data_offer object

wl_data_device_manager

group iface_wl_data_device_manager

The wl_data_device_manager is a singleton global object that provides access to inter-client data transfer mechanisms such as copy-and-paste and drag-and-drop.

These mechanisms are tied to a wl_seat and this interface lets a client get a wl_data_device corresponding to a wl_seat.

Depending on the version bound, the objects created from the bound wl_data_device_manager object will have different requirements for functioning properly. See wl_data_source.set_actions, wl_data_offer.accept and wl_data_offer.finish for details.

Defines

WL_DATA_DEVICE_MANAGER_CREATE_DATA_SOURCE_SINCE_VERSION

WL_DATA_DEVICE_MANAGER_GET_DATA_DEVICE_SINCE_VERSION

Enums

enum wl_data_device_manager_dnd_action

drag and drop actions

This is a bitmask of the available/preferred actions in a drag-and-drop operation.

In the compositor, the selected action is a result of matching the actions offered by the source and destination sides. “action” events with a “none” action will be sent to both source and destination if there is no match. All further checks will effectively happen on (source actions ∩ destination actions).

In addition, compositors may also pick different actions in reaction to key modifiers being pressed. One common design that is used in major toolkits (and the behavior recommended for compositors) is:

• If no modifiers are pressed, the first match (in bit order) will be used.
• Pressing Shift selects “move”, if enabled in the mask.
• Pressing Control selects “copy”, if enabled in the mask.

Behavior beyond that is considered implementation-dependent. Compositors may for example bind other modifiers (like Alt/Meta) or drags initiated with other buttons than BTN_LEFT to specific actions (e.g. “ask”).

Values:

WL_DATA_DEVICE_MANAGER_DND_ACTION_NONE = 0

no action

WL_DATA_DEVICE_MANAGER_DND_ACTION_COPY = 1

copy action

WL_DATA_DEVICE_MANAGER_DND_ACTION_MOVE = 2

move action

WL_DATA_DEVICE_MANAGER_DND_ACTION_ASK = 4

ask action

Functions

static void wl_data_device_manager_set_user_data(struct wl_data_device_manager *wl_data_device_manager, void *user_data)

static void *wl_data_device_manager_get_user_data(struct wl_data_device_manager *wl_data_device_manager)

static void wl_data_device_manager_destroy(struct wl_data_device_manager *wl_data_device_manager)

static struct wl_data_source *wl_data_device_manager_create_data_source(struct wl_data_device_manager *wl_data_device_manager)

Create a new data source.

static struct wl_data_device *wl_data_device_manager_get_data_device(struct wl_data_device_manager *wl_data_device_manager, struct wl_seat *seat)

Create a new data device for a given seat.

wl_shell

group iface_wl_shell

This interface is implemented by servers that provide desktop-style user interfaces.

It allows clients to associate a wl_shell_surface with a basic surface.

Note! This protocol is deprecated and not intended for production use. For desktop-style user interfaces, use xdg_shell.

Defines

WL_SHELL_GET_SHELL_SURFACE_SINCE_VERSION

Functions

static void wl_shell_set_user_data(struct wl_shell *wl_shell, void *user_data)

static void *wl_shell_get_user_data(struct wl_shell *wl_shell)

static void wl_shell_destroy(struct wl_shell *wl_shell)

static struct wl_shell_surface *wl_shell_get_shell_surface(struct wl_shell *wl_shell, struct wl_surface *surface)

Create a shell surface for an existing surface.

This gives the wl_surface the role of a shell surface. If the wl_surface already has another role, it raises a protocol error.

Only one shell surface can be associated with a given surface.

wl_shell_surface

group iface_wl_shell_surface

An interface that may be implemented by a wl_surface, for implementations that provide a desktop-style user interface.

It provides requests to treat surfaces like toplevel, fullscreen or popup windows, move, resize or maximize them, associate metadata like title and class, etc.

On the server side the object is automatically destroyed when the related wl_surface is destroyed. On the client side, wl_shell_surface_destroy() must be called before destroying the wl_surface object.

Defines

WL_SHELL_SURFACE_PING_SINCE_VERSION

WL_SHELL_SURFACE_CONFIGURE_SINCE_VERSION

WL_SHELL_SURFACE_POPUP_DONE_SINCE_VERSION

WL_SHELL_SURFACE_PONG_SINCE_VERSION

WL_SHELL_SURFACE_MOVE_SINCE_VERSION

WL_SHELL_SURFACE_RESIZE_SINCE_VERSION

WL_SHELL_SURFACE_SET_TOPLEVEL_SINCE_VERSION

WL_SHELL_SURFACE_SET_TRANSIENT_SINCE_VERSION

WL_SHELL_SURFACE_SET_FULLSCREEN_SINCE_VERSION

WL_SHELL_SURFACE_SET_POPUP_SINCE_VERSION

WL_SHELL_SURFACE_SET_MAXIMIZED_SINCE_VERSION

WL_SHELL_SURFACE_SET_TITLE_SINCE_VERSION

WL_SHELL_SURFACE_SET_CLASS_SINCE_VERSION

Enums

enum wl_shell_surface_resize

edge values for resizing

These values are used to indicate which edge of a surface is being dragged in a resize operation. The server may use this information to adapt its behavior, e.g. choose an appropriate cursor image.

Values:

WL_SHELL_SURFACE_RESIZE_NONE = 0

no edge

WL_SHELL_SURFACE_RESIZE_TOP = 1

top edge

WL_SHELL_SURFACE_RESIZE_BOTTOM = 2

bottom edge

WL_SHELL_SURFACE_RESIZE_LEFT = 4

left edge

WL_SHELL_SURFACE_RESIZE_TOP_LEFT = 5

top and left edges

WL_SHELL_SURFACE_RESIZE_BOTTOM_LEFT = 6

bottom and left edges

WL_SHELL_SURFACE_RESIZE_RIGHT = 8

right edge

WL_SHELL_SURFACE_RESIZE_TOP_RIGHT = 9

top and right edges

WL_SHELL_SURFACE_RESIZE_BOTTOM_RIGHT = 10

bottom and right edges

enum wl_shell_surface_transient

details of transient behaviour

These flags specify details of the expected behaviour of transient surfaces. Used in the set_transient request.

Values:

WL_SHELL_SURFACE_TRANSIENT_INACTIVE = 0x1

do not set keyboard focus

enum wl_shell_surface_fullscreen_method

different method to set the surface fullscreen

Hints to indicate to the compositor how to deal with a conflict between the dimensions of the surface and the dimensions of the output. The compositor is free to ignore this parameter.

Values:

WL_SHELL_SURFACE_FULLSCREEN_METHOD_DEFAULT = 0

no preference, apply default policy

WL_SHELL_SURFACE_FULLSCREEN_METHOD_SCALE = 1

scale, preserve the surface’s aspect ratio and center on output

WL_SHELL_SURFACE_FULLSCREEN_METHOD_DRIVER = 2

switch output mode to the smallest mode that can fit the surface, add black borders to compensate size mismatch

WL_SHELL_SURFACE_FULLSCREEN_METHOD_FILL = 3

no upscaling, center on output and add black borders to compensate size mismatch

Functions

static int wl_shell_surface_add_listener(struct wl_shell_surface *wl_shell_surface, const struct wl_shell_surface_listener *listener, void *data)

static void wl_shell_surface_set_user_data(struct wl_shell_surface *wl_shell_surface, void *user_data)

static void *wl_shell_surface_get_user_data(struct wl_shell_surface *wl_shell_surface)

static void wl_shell_surface_destroy(struct wl_shell_surface *wl_shell_surface)

static void wl_shell_surface_pong(struct wl_shell_surface *wl_shell_surface, uint32_t serial)

A client must respond to a ping event with a pong request or the client may be deemed unresponsive.

static void wl_shell_surface_move(struct wl_shell_surface *wl_shell_surface, struct wl_seat *seat, uint32_t serial)

Start a pointer-driven move of the surface.

This request must be used in response to a button press event. The server may ignore move requests depending on the state of the surface (e.g. fullscreen or maximized).

static void wl_shell_surface_resize(struct wl_shell_surface *wl_shell_surface, struct wl_seat *seat, uint32_t serial, uint32_t edges)

Start a pointer-driven resizing of the surface.

This request must be used in response to a button press event. The server may ignore resize requests depending on the state of the surface (e.g. fullscreen or maximized).

static void wl_shell_surface_set_toplevel(struct wl_shell_surface *wl_shell_surface)

Map the surface as a toplevel surface.

A toplevel surface is not fullscreen, maximized or transient.

static void wl_shell_surface_set_transient(struct wl_shell_surface *wl_shell_surface, struct wl_surface *parent, int32_t x, int32_t y, uint32_t flags)

Map the surface relative to an existing surface.

The x and y arguments specify the location of the upper left corner of the surface relative to the upper left corner of the parent surface, in surface-local coordinates.

The flags argument controls details of the transient behaviour.

static void wl_shell_surface_set_fullscreen(struct wl_shell_surface *wl_shell_surface, uint32_t method, uint32_t framerate, struct wl_output *output)

Map the surface as a fullscreen surface.

If an output parameter is given then the surface will be made fullscreen on that output. If the client does not specify the output then the compositor will apply its policy - usually choosing the output on which the surface has the biggest surface area.

The client may specify a method to resolve a size conflict between the output size and the surface size - this is provided through the method parameter.

The framerate parameter is used only when the method is set to “driver”, to indicate the preferred framerate. A value of 0 indicates that the client does not care about framerate. The framerate is specified in mHz, that is framerate of 60000 is 60Hz.

A method of “scale” or “driver” implies a scaling operation of the surface, either via a direct scaling operation or a change of the output mode. This will override any kind of output scaling, so that mapping a surface with a buffer size equal to the mode can fill the screen independent of buffer_scale.

A method of “fill” means we don’t scale up the buffer, however any output scale is applied. This means that you may run into an edge case where the application maps a buffer with the same size of the output mode but buffer_scale 1 (thus making a surface larger than the output). In this case it is allowed to downscale the results to fit the screen.

The compositor must reply to this request with a configure event with the dimensions for the output on which the surface will be made fullscreen.

static void wl_shell_surface_set_popup(struct wl_shell_surface *wl_shell_surface, struct wl_seat *seat, uint32_t serial, struct wl_surface *parent, int32_t x, int32_t y, uint32_t flags)

Map the surface as a popup.

A popup surface is a transient surface with an added pointer grab.

An existing implicit grab will be changed to owner-events mode, and the popup grab will continue after the implicit grab ends (i.e. releasing the mouse button does not cause the popup to be unmapped).

The popup grab continues until the window is destroyed or a mouse button is pressed in any other client’s window. A click in any of the client’s surfaces is reported as normal, however, clicks in other clients’ surfaces will be discarded and trigger the callback.

The x and y arguments specify the location of the upper left corner of the surface relative to the upper left corner of the parent surface, in surface-local coordinates.

static void wl_shell_surface_set_maximized(struct wl_shell_surface *wl_shell_surface, struct wl_output *output)

Map the surface as a maximized surface.

If an output parameter is given then the surface will be maximized on that output. If the client does not specify the output then the compositor will apply its policy - usually choosing the output on which the surface has the biggest surface area.

The compositor will reply with a configure event telling the expected new surface size. The operation is completed on the next buffer attach to this surface.

A maximized surface typically fills the entire output it is bound to, except for desktop elements such as panels. This is the main difference between a maximized shell surface and a fullscreen shell surface.

The details depend on the compositor implementation.

static void wl_shell_surface_set_title(struct wl_shell_surface *wl_shell_surface, const char *title)

Set a short title for the surface.

This string may be used to identify the surface in a task bar, window list, or other user interface elements provided by the compositor.

The string must be encoded in UTF-8.

static void wl_shell_surface_set_class(struct wl_shell_surface *wl_shell_surface, const char *class_)

Set a class for the surface.

The surface class identifies the general class of applications to which the surface belongs. A common convention is to use the file name (or the full path if it is a non-standard location) of the application’s .desktop file as the class.

struct wl_shell_surface_listener

#include <wayland-client-protocol.h>

Public Members

void (*ping)(void *data, struct wl_shell_surface *wl_shell_surface, uint32_t serial)

ping client

Ping a client to check if it is receiving events and sending requests. A client is expected to reply with a pong request.

Parameters

• serial: serial number of the ping

void (*configure)(void *data, struct wl_shell_surface *wl_shell_surface, uint32_t edges, int32_t width, int32_t height)

suggest resize

The configure event asks the client to resize its surface.

The size is a hint, in the sense that the client is free to ignore it if it doesn’t resize, pick a smaller size (to satisfy aspect ratio or resize in steps of NxM pixels).

The edges parameter provides a hint about how the surface was resized. The client may use this information to decide how to adjust its content to the new size (e.g. a scrolling area might adjust its content position to leave the viewable content unmoved).

The client is free to dismiss all but the last configure event it received.

The width and height arguments specify the size of the window in surface-local coordinates.

Parameters

• edges: how the surface was resized
• width: new width of the surface
• height: new height of the surface

void (*popup_done)(void *data, struct wl_shell_surface *wl_shell_surface)

popup interaction is done

The popup_done event is sent out when a popup grab is broken, that is, when the user clicks a surface that doesn’t belong to the client owning the popup surface.

wl_surface

group iface_wl_surface

A surface is a rectangular area that is displayed on the screen.

It has a location, size and pixel contents.

The size of a surface (and relative positions on it) is described in surface-local coordinates, which may differ from the buffer coordinates of the pixel content, in case a buffer_transform or a buffer_scale is used.

A surface without a “role” is fairly useless: a compositor does not know where, when or how to present it. The role is the purpose of a wl_surface. Examples of roles are a cursor for a pointer (as set by wl_pointer.set_cursor), a drag icon (wl_data_device.start_drag), a sub-surface (wl_subcompositor.get_subsurface), and a window as defined by a shell protocol (e.g. wl_shell.get_shell_surface).

A surface can have only one role at a time. Initially a wl_surface does not have a role. Once a wl_surface is given a role, it is set permanently for the whole lifetime of the wl_surface object. Giving the current role again is allowed, unless explicitly forbidden by the relevant interface specification.

Surface roles are given by requests in other interfaces such as wl_pointer.set_cursor. The request should explicitly mention that this request gives a role to a wl_surface. Often, this request also creates a new protocol object that represents the role and adds additional functionality to wl_surface. When a client wants to destroy a wl_surface, they must destroy this ‘role object’ before the wl_surface.

Destroying the role object does not remove the role from the wl_surface, but it may stop the wl_surface from “playing the role”. For instance, if a wl_subsurface object is destroyed, the wl_surface it was created for will be unmapped and forget its position and z-order. It is allowed to create a wl_subsurface for the same wl_surface again, but it is not allowed to use the wl_surface as a cursor (cursor is a different role than sub-surface, and role switching is not allowed).

Defines

WL_SURFACE_ENTER_SINCE_VERSION

WL_SURFACE_LEAVE_SINCE_VERSION

WL_SURFACE_DESTROY_SINCE_VERSION

WL_SURFACE_ATTACH_SINCE_VERSION

WL_SURFACE_DAMAGE_SINCE_VERSION

WL_SURFACE_FRAME_SINCE_VERSION

WL_SURFACE_SET_OPAQUE_REGION_SINCE_VERSION

WL_SURFACE_SET_INPUT_REGION_SINCE_VERSION

WL_SURFACE_COMMIT_SINCE_VERSION

WL_SURFACE_SET_BUFFER_TRANSFORM_SINCE_VERSION

WL_SURFACE_SET_BUFFER_SCALE_SINCE_VERSION

WL_SURFACE_DAMAGE_BUFFER_SINCE_VERSION

Enums

enum wl_surface_error

wl_surface error values

These errors can be emitted in response to wl_surface requests.

Values:

WL_SURFACE_ERROR_INVALID_SCALE = 0

buffer scale value is invalid

WL_SURFACE_ERROR_INVALID_TRANSFORM = 1

buffer transform value is invalid

Functions

static int wl_surface_add_listener(struct wl_surface *wl_surface, const struct wl_surface_listener *listener, void *data)

static void wl_surface_set_user_data(struct wl_surface *wl_surface, void *user_data)

static void *wl_surface_get_user_data(struct wl_surface *wl_surface)

static void wl_surface_destroy(struct wl_surface *wl_surface)

Deletes the surface and invalidates its object ID.

static void wl_surface_attach(struct wl_surface *wl_surface, struct wl_buffer *buffer, int32_t x, int32_t y)

Set a buffer as the content of this surface.

The new size of the surface is calculated based on the buffer size transformed by the inverse buffer_transform and the inverse buffer_scale. This means that the supplied buffer must be an integer multiple of the buffer_scale.

The x and y arguments specify the location of the new pending buffer’s upper left corner, relative to the current buffer’s upper left corner, in surface-local coordinates. In other words, the x and y, combined with the new surface size define in which directions the surface’s size changes.

Surface contents are double-buffered state, see wl_surface.commit.

The initial surface contents are void; there is no content. wl_surface.attach assigns the given wl_buffer as the pending wl_buffer. wl_surface.commit makes the pending wl_buffer the new surface contents, and the size of the surface becomes the size calculated from the wl_buffer, as described above. After commit, there is no pending buffer until the next attach.

Committing a pending wl_buffer allows the compositor to read the pixels in the wl_buffer. The compositor may access the pixels at any time after the wl_surface.commit request. When the compositor will not access the pixels anymore, it will send the wl_buffer.release event. Only after receiving wl_buffer.release, the client may reuse the wl_buffer. A wl_buffer that has been attached and then replaced by another attach instead of committed will not receive a release event, and is not used by the compositor.

Destroying the wl_buffer after wl_buffer.release does not change the surface contents. However, if the client destroys the wl_buffer before receiving the wl_buffer.release event, the surface contents become undefined immediately.

If wl_surface.attach is sent with a NULL wl_buffer, the following wl_surface.commit will remove the surface content.

static void wl_surface_damage(struct wl_surface *wl_surface, int32_t x, int32_t y, int32_t width, int32_t height)

This request is used to describe the regions where the pending buffer is different from the current surface contents, and where the surface therefore needs to be repainted.

The compositor ignores the parts of the damage that fall outside of the surface.

Damage is double-buffered state, see wl_surface.commit.

The damage rectangle is specified in surface-local coordinates, where x and y specify the upper left corner of the damage rectangle.

The initial value for pending damage is empty: no damage. wl_surface.damage adds pending damage: the new pending damage is the union of old pending damage and the given rectangle.

wl_surface.commit assigns pending damage as the current damage, and clears pending damage. The server will clear the current damage as it repaints the surface.

Note! New clients should not use this request. Instead damage can be posted with wl_surface.damage_buffer which uses buffer coordinates instead of surface coordinates.

static struct wl_callback *wl_surface_frame(struct wl_surface *wl_surface)

Request a notification when it is a good time to start drawing a new frame, by creating a frame callback.

This is useful for throttling redrawing operations, and driving animations.

When a client is animating on a wl_surface, it can use the ‘frame’ request to get notified when it is a good time to draw and commit the next frame of animation. If the client commits an update earlier than that, it is likely that some updates will not make it to the display, and the client is wasting resources by drawing too often.

The frame request will take effect on the next wl_surface.commit. The notification will only be posted for one frame unless requested again. For a wl_surface, the notifications are posted in the order the frame requests were committed.

The server must send the notifications so that a client will not send excessive updates, while still allowing the highest possible update rate for clients that wait for the reply before drawing again. The server should give some time for the client to draw and commit after sending the frame callback events to let it hit the next output refresh.

A server should avoid signaling the frame callbacks if the surface is not visible in any way, e.g. the surface is off-screen, or completely obscured by other opaque surfaces.

The object returned by this request will be destroyed by the compositor after the callback is fired and as such the client must not attempt to use it after that point.

The callback_data passed in the callback is the current time, in milliseconds, with an undefined base.

static void wl_surface_set_opaque_region(struct wl_surface *wl_surface, struct wl_region *region)

This request sets the region of the surface that contains opaque content.

The opaque region is an optimization hint for the compositor that lets it optimize the redrawing of content behind opaque regions. Setting an opaque region is not required for correct behaviour, but marking transparent content as opaque will result in repaint artifacts.

The opaque region is specified in surface-local coordinates.

The compositor ignores the parts of the opaque region that fall outside of the surface.

Opaque region is double-buffered state, see wl_surface.commit.

wl_surface.set_opaque_region changes the pending opaque region. wl_surface.commit copies the pending region to the current region. Otherwise, the pending and current regions are never changed.

The initial value for an opaque region is empty. Setting the pending opaque region has copy semantics, and the wl_region object can be destroyed immediately. A NULL wl_region causes the pending opaque region to be set to empty.

static void wl_surface_set_input_region(struct wl_surface *wl_surface, struct wl_region *region)

This request sets the region of the surface that can receive pointer and touch events.

Input events happening outside of this region will try the next surface in the server surface stack. The compositor ignores the parts of the input region that fall outside of the surface.

The input region is specified in surface-local coordinates.

Input region is double-buffered state, see wl_surface.commit.

wl_surface.set_input_region changes the pending input region. wl_surface.commit copies the pending region to the current region. Otherwise the pending and current regions are never changed, except cursor and icon surfaces are special cases, see wl_pointer.set_cursor and wl_data_device.start_drag.

The initial value for an input region is infinite. That means the whole surface will accept input. Setting the pending input region has copy semantics, and the wl_region object can be destroyed immediately. A NULL wl_region causes the input region to be set to infinite.

static void wl_surface_commit(struct wl_surface *wl_surface)

Surface state (input, opaque, and damage regions, attached buffers, etc.) is double-buffered.

Protocol requests modify the pending state, as opposed to the current state in use by the compositor. A commit request atomically applies all pending state, replacing the current state. After commit, the new pending state is as documented for each related request.

On commit, a pending wl_buffer is applied first, and all other state second. This means that all coordinates in double-buffered state are relative to the new wl_buffer coming into use, except for wl_surface.attach itself. If there is no pending wl_buffer, the coordinates are relative to the current surface contents.

All requests that need a commit to become effective are documented to affect double-buffered state.

Other interfaces may add further double-buffered surface state.

static void wl_surface_set_buffer_transform(struct wl_surface *wl_surface, int32_t transform)

This request sets an optional transformation on how the compositor interprets the contents of the buffer attached to the surface.

The accepted values for the transform parameter are the values for wl_output.transform.

Buffer transform is double-buffered state, see wl_surface.commit.

A newly created surface has its buffer transformation set to normal.

wl_surface.set_buffer_transform changes the pending buffer transformation. wl_surface.commit copies the pending buffer transformation to the current one. Otherwise, the pending and current values are never changed.

The purpose of this request is to allow clients to render content according to the output transform, thus permitting the compositor to use certain optimizations even if the display is rotated. Using hardware overlays and scanning out a client buffer for fullscreen surfaces are examples of such optimizations. Those optimizations are highly dependent on the compositor implementation, so the use of this request should be considered on a case-by-case basis.

Note that if the transform value includes 90 or 270 degree rotation, the width of the buffer will become the surface height and the height of the buffer will become the surface width.

If transform is not one of the values from the wl_output.transform enum the invalid_transform protocol error is raised.

static void wl_surface_set_buffer_scale(struct wl_surface *wl_surface, int32_t scale)

This request sets an optional scaling factor on how the compositor interprets the contents of the buffer attached to the window.

Buffer scale is double-buffered state, see wl_surface.commit.

A newly created surface has its buffer scale set to 1.

wl_surface.set_buffer_scale changes the pending buffer scale. wl_surface.commit copies the pending buffer scale to the current one. Otherwise, the pending and current values are never changed.

The purpose of this request is to allow clients to supply higher resolution buffer data for use on high resolution outputs. It is intended that you pick the same buffer scale as the scale of the output that the surface is displayed on. This means the compositor can avoid scaling when rendering the surface on that output.

Note that if the scale is larger than 1, then you have to attach a buffer that is larger (by a factor of scale in each dimension) than the desired surface size.

If scale is not positive the invalid_scale protocol error is raised.

static void wl_surface_damage_buffer(struct wl_surface *wl_surface, int32_t x, int32_t y, int32_t width, int32_t height)

This request is used to describe the regions where the pending buffer is different from the current surface contents, and where the surface therefore needs to be repainted.

The compositor ignores the parts of the damage that fall outside of the surface.

Damage is double-buffered state, see wl_surface.commit.

The damage rectangle is specified in buffer coordinates, where x and y specify the upper left corner of the damage rectangle.

The initial value for pending damage is empty: no damage. wl_surface.damage_buffer adds pending damage: the new pending damage is the union of old pending damage and the given rectangle.

wl_surface.commit assigns pending damage as the current damage, and clears pending damage. The server will clear the current damage as it repaints the surface.

This request differs from wl_surface.damage in only one way - it takes damage in buffer coordinates instead of surface-local coordinates. While this generally is more intuitive than surface coordinates, it is especially desirable when using wp_viewport or when a drawing library (like EGL) is unaware of buffer scale and buffer transform.

Note: Because buffer transformation changes and damage requests may be interleaved in the protocol stream, it is impossible to determine the actual mapping between surface and buffer damage until wl_surface.commit time. Therefore, compositors wishing to take both kinds of damage into account will have to accumulate damage from the two requests separately and only transform from one to the other after receiving the wl_surface.commit.

struct wl_surface_listener

#include <wayland-client-protocol.h>

Public Members

void (*enter)(void *data, struct wl_surface *wl_surface, struct wl_output *output)

surface enters an output

This is emitted whenever a surface’s creation, movement, or resizing results in some part of it being within the scanout region of an output.

Note that a surface may be overlapping with zero or more outputs.

Parameters

• output: output entered by the surface

void (*leave)(void *data, struct wl_surface *wl_surface, struct wl_output *output)

surface leaves an output

This is emitted whenever a surface’s creation, movement, or resizing results in it no longer having any part of it within the scanout region of an output.

Parameters

• output: output left by the surface

wl_seat

group iface_wl_seat

A seat is a group of keyboards, pointer and touch devices.

This object is published as a global during start up, or when such a device is hot plugged. A seat typically has a pointer and maintains a keyboard focus and a pointer focus.

Defines

WL_SEAT_CAPABILITIES_SINCE_VERSION

WL_SEAT_NAME_SINCE_VERSION

WL_SEAT_GET_POINTER_SINCE_VERSION

WL_SEAT_GET_KEYBOARD_SINCE_VERSION

WL_SEAT_GET_TOUCH_SINCE_VERSION

WL_SEAT_RELEASE_SINCE_VERSION

Enums

enum wl_seat_capability

seat capability bitmask

This is a bitmask of capabilities this seat has; if a member is set, then it is present on the seat.

Values:

WL_SEAT_CAPABILITY_POINTER = 1

the seat has pointer devices

WL_SEAT_CAPABILITY_KEYBOARD = 2

the seat has one or more keyboards

WL_SEAT_CAPABILITY_TOUCH = 4

the seat has touch devices

Functions

static int wl_seat_add_listener(struct wl_seat *wl_seat, const struct wl_seat_listener *listener, void *data)

static void wl_seat_set_user_data(struct wl_seat *wl_seat, void *user_data)

static void *wl_seat_get_user_data(struct wl_seat *wl_seat)

static void wl_seat_destroy(struct wl_seat *wl_seat)

static struct wl_pointer *wl_seat_get_pointer(struct wl_seat *wl_seat)

The ID provided will be initialized to the wl_pointer interface for this seat.

This request only takes effect if the seat has the pointer capability, or has had the pointer capability in the past. It is a protocol violation to issue this request on a seat that has never had the pointer capability.

static struct wl_keyboard *wl_seat_get_keyboard(struct wl_seat *wl_seat)

The ID provided will be initialized to the wl_keyboard interface for this seat.

This request only takes effect if the seat has the keyboard capability, or has had the keyboard capability in the past. It is a protocol violation to issue this request on a seat that has never had the keyboard capability.

static struct wl_touch *wl_seat_get_touch(struct wl_seat *wl_seat)

The ID provided will be initialized to the wl_touch interface for this seat.

This request only takes effect if the seat has the touch capability, or has had the touch capability in the past. It is a protocol violation to issue this request on a seat that has never had the touch capability.

static void wl_seat_release(struct wl_seat *wl_seat)

Using this request a client can tell the server that it is not going to use the seat object anymore.

struct wl_seat_listener

#include <wayland-client-protocol.h>

Public Members

void (*capabilities)(void *data, struct wl_seat *wl_seat, uint32_t capabilities)

seat capabilities changed

This is emitted whenever a seat gains or loses the pointer, keyboard or touch capabilities. The argument is a capability enum containing the complete set of capabilities this seat has.

When the pointer capability is added, a client may create a wl_pointer object using the wl_seat.get_pointer request. This object will receive pointer events until the capability is removed in the future.

When the pointer capability is removed, a client should destroy the wl_pointer objects associated with the seat where the capability was removed, using the wl_pointer.release request. No further pointer events will be received on these objects.

In some compositors, if a seat regains the pointer capability and a client has a previously obtained wl_pointer object of version 4 or less, that object may start sending pointer events again. This behavior is considered a misinterpretation of the intended behavior and must not be relied upon by the client. wl_pointer objects of version 5 or later must not send events if created before the most recent event notifying the client of an added pointer capability.

The above behavior also applies to wl_keyboard and wl_touch with the keyboard and touch capabilities, respectively.

Parameters

• capabilities: capabilities of the seat

void (*name)(void *data, struct wl_seat *wl_seat, const char *name)

unique identifier for this seat

In a multiseat configuration this can be used by the client to help identify which physical devices the seat represents. Based on the seat configuration used by the compositor.

Since

2

Parameters

• name: seat identifier

wl_pointer

group iface_wl_pointer

The wl_pointer interface represents one or more input devices, such as mice, which control the pointer location and pointer_focus of a seat.

The wl_pointer interface generates motion, enter and leave events for the surfaces that the pointer is located over, and button and axis events for button presses, button releases and scrolling.

Defines

WL_POINTER_AXIS_SOURCE_WHEEL_TILT_SINCE_VERSION

WL_POINTER_ENTER_SINCE_VERSION

WL_POINTER_LEAVE_SINCE_VERSION

WL_POINTER_MOTION_SINCE_VERSION

WL_POINTER_BUTTON_SINCE_VERSION

WL_POINTER_AXIS_SINCE_VERSION

WL_POINTER_FRAME_SINCE_VERSION

WL_POINTER_AXIS_SOURCE_SINCE_VERSION

WL_POINTER_AXIS_STOP_SINCE_VERSION

WL_POINTER_AXIS_DISCRETE_SINCE_VERSION

WL_POINTER_SET_CURSOR_SINCE_VERSION

WL_POINTER_RELEASE_SINCE_VERSION

Enums

enum wl_pointer_button_state

physical button state

Describes the physical state of a button that produced the button event.

Values:

WL_POINTER_BUTTON_STATE_RELEASED = 0

the button is not pressed

WL_POINTER_BUTTON_STATE_PRESSED = 1

the button is pressed

enum wl_pointer_axis

axis types

Describes the axis types of scroll events.

Values:

WL_POINTER_AXIS_VERTICAL_SCROLL = 0

vertical axis

WL_POINTER_AXIS_HORIZONTAL_SCROLL = 1

horizontal axis

enum wl_pointer_axis_source

axis source types

Describes the source types for axis events. This indicates to the client how an axis event was physically generated; a client may adjust the user interface accordingly. For example, scroll events from a “finger” source may be in a smooth coordinate space with kinetic scrolling whereas a “wheel” source may be in discrete steps of a number of lines.

The “continuous” axis source is a device generating events in a continuous coordinate space, but using something other than a finger. One example for this source is button-based scrolling where the vertical motion of a device is converted to scroll events while a button is held down.

The “wheel tilt” axis source indicates that the actual device is a wheel but the scroll event is not caused by a rotation but a (usually sideways) tilt of the wheel.

Values:

WL_POINTER_AXIS_SOURCE_WHEEL = 0

a physical wheel rotation

WL_POINTER_AXIS_SOURCE_FINGER = 1

finger on a touch surface

WL_POINTER_AXIS_SOURCE_CONTINUOUS = 2

continuous coordinate space

WL_POINTER_AXIS_SOURCE_WHEEL_TILT = 3

a physical wheel tilt

Since

6

Functions

static int wl_pointer_add_listener(struct wl_pointer *wl_pointer, const struct wl_pointer_listener *listener, void *data)

static void wl_pointer_set_user_data(struct wl_pointer *wl_pointer, void *user_data)

static void *wl_pointer_get_user_data(struct wl_pointer *wl_pointer)

static void wl_pointer_destroy(struct wl_pointer *wl_pointer)

static void wl_pointer_set_cursor(struct wl_pointer *wl_pointer, uint32_t serial, struct wl_surface *surface, int32_t hotspot_x, int32_t hotspot_y)

Set the pointer surface, i.e., the surface that contains the pointer image (cursor).

This request gives the surface the role of a cursor. If the surface already has another role, it raises a protocol error.

The cursor actually changes only if the pointer focus for this device is one of the requesting client’s surfaces or the surface parameter is the current pointer surface. If there was a previous surface set with this request it is replaced. If surface is NULL, the pointer image is hidden.

The parameters hotspot_x and hotspot_y define the position of the pointer surface relative to the pointer location. Its top-left corner is always at (x, y) - (hotspot_x, hotspot_y), where (x, y) are the coordinates of the pointer location, in surface-local coordinates.

On surface.attach requests to the pointer surface, hotspot_x and hotspot_y are decremented by the x and y parameters passed to the request. Attach must be confirmed by wl_surface.commit as usual.

The hotspot can also be updated by passing the currently set pointer surface to this request with new values for hotspot_x and hotspot_y.

The current and pending input regions of the wl_surface are cleared, and wl_surface.set_input_region is ignored until the wl_surface is no longer used as the cursor. When the use as a cursor ends, the current and pending input regions become undefined, and the wl_surface is unmapped.

static void wl_pointer_release(struct wl_pointer *wl_pointer)

Using this request a client can tell the server that it is not going to use the pointer object anymore.

This request destroys the pointer proxy object, so clients must not call wl_pointer_destroy() after using this request.

struct wl_pointer_listener

#include <wayland-client-protocol.h>

Public Members

void (*enter)(void *data, struct wl_pointer *wl_pointer, uint32_t serial, struct wl_surface *surface, wl_fixed_t surface_x, wl_fixed_t surface_y)

enter event

Notification that this seat’s pointer is focused on a certain surface.

When a seat’s focus enters a surface, the pointer image is undefined and a client should respond to this event by setting an appropriate pointer image with the set_cursor request.

Parameters

• serial: serial number of the enter event
• surface: surface entered by the pointer
• surface_x: surface-local x coordinate
• surface_y: surface-local y coordinate

void (*leave)(void *data, struct wl_pointer *wl_pointer, uint32_t serial, struct wl_surface *surface)

leave event

Notification that this seat’s pointer is no longer focused on a certain surface.

The leave notification is sent before the enter notification for the new focus.

Parameters

• serial: serial number of the leave event
• surface: surface left by the pointer

void (*motion)(void *data, struct wl_pointer *wl_pointer, uint32_t time, wl_fixed_t surface_x, wl_fixed_t surface_y)

pointer motion event

Notification of pointer location change. The arguments surface_x and surface_y are the location relative to the focused surface.

Parameters

• time: timestamp with millisecond granularity
• surface_x: surface-local x coordinate
• surface_y: surface-local y coordinate

void (*button)(void *data, struct wl_pointer *wl_pointer, uint32_t serial, uint32_t time, uint32_t button, uint32_t state)

pointer button event

Mouse button click and release notifications.

The location of the click is given by the last motion or enter event. The time argument is a timestamp with millisecond granularity, with an undefined base.

The button is a button code as defined in the Linux kernel’s linux/input-event-codes.h header file, e.g. BTN_LEFT.

Any 16-bit button code value is reserved for future additions to the kernel’s event code list. All other button codes above 0xFFFF are currently undefined but may be used in future versions of this protocol.

Parameters

• serial: serial number of the button event
• time: timestamp with millisecond granularity
• button: button that produced the event
• state: physical state of the button

void (*axis)(void *data, struct wl_pointer *wl_pointer, uint32_t time, uint32_t axis, wl_fixed_t value)

axis event

Scroll and other axis notifications.

For scroll events (vertical and horizontal scroll axes), the value parameter is the length of a vector along the specified axis in a coordinate space identical to those of motion events, representing a relative movement along the specified axis.

For devices that support movements non-parallel to axes multiple axis events will be emitted.

When applicable, for example for touch pads, the server can choose to emit scroll events where the motion vector is equivalent to a motion event vector.

When applicable, a client can transform its content relative to the scroll distance.

Parameters

• time: timestamp with millisecond granularity
• axis: axis type
• value: length of vector in surface-local coordinate space

void (*frame)(void *data, struct wl_pointer *wl_pointer)

end of a pointer event sequence

Indicates the end of a set of events that logically belong together. A client is expected to accumulate the data in all events within the frame before proceeding.

All wl_pointer events before a wl_pointer.frame event belong logically together. For example, in a diagonal scroll motion the compositor will send an optional wl_pointer.axis_source event, two wl_pointer.axis events (horizontal and vertical) and finally a wl_pointer.frame event. The client may use this information to calculate a diagonal vector for scrolling.

When multiple wl_pointer.axis events occur within the same frame, the motion vector is the combined motion of all events. When a wl_pointer.axis and a wl_pointer.axis_stop event occur within the same frame, this indicates that axis movement in one axis has stopped but continues in the other axis. When multiple wl_pointer.axis_stop events occur within the same frame, this indicates that these axes stopped in the same instance.

A wl_pointer.frame event is sent for every logical event group, even if the group only contains a single wl_pointer event. Specifically, a client may get a sequence: motion, frame, button, frame, axis, frame, axis_stop, frame.

The wl_pointer.enter and wl_pointer.leave events are logical events generated by the compositor and not the hardware. These events are also grouped by a wl_pointer.frame. When a pointer moves from one surface to another, a compositor should group the wl_pointer.leave event within the same wl_pointer.frame. However, a client must not rely on wl_pointer.leave and wl_pointer.enter being in the same wl_pointer.frame. Compositor-specific policies may require the wl_pointer.leave and wl_pointer.enter event being split across multiple wl_pointer.frame groups.

Since

5

void (*axis_source)(void *data, struct wl_pointer *wl_pointer, uint32_t axis_source)

axis source event

Source information for scroll and other axes.

This event does not occur on its own. It is sent before a wl_pointer.frame event and carries the source information for all events within that frame.

The source specifies how this event was generated. If the source is wl_pointer.axis_source.finger, a wl_pointer.axis_stop event will be sent when the user lifts the finger off the device.

If the source is wl_pointer.axis_source.wheel, wl_pointer.axis_source.wheel_tilt or wl_pointer.axis_source.continuous, a wl_pointer.axis_stop event may or may not be sent. Whether a compositor sends an axis_stop event for these sources is hardware-specific and implementation-dependent; clients must not rely on receiving an axis_stop event for these scroll sources and should treat scroll sequences from these scroll sources as unterminated by default.

This event is optional. If the source is unknown for a particular axis event sequence, no event is sent. Only one wl_pointer.axis_source event is permitted per frame.

The order of wl_pointer.axis_discrete and wl_pointer.axis_source is not guaranteed.

Since

5

Parameters

• axis_source: source of the axis event

void (*axis_stop)(void *data, struct wl_pointer *wl_pointer, uint32_t time, uint32_t axis)

axis stop event

Stop notification for scroll and other axes.

For some wl_pointer.axis_source types, a wl_pointer.axis_stop event is sent to notify a client that the axis sequence has terminated. This enables the client to implement kinetic scrolling. See the wl_pointer.axis_source documentation for information on when this event may be generated.

Any wl_pointer.axis events with the same axis_source after this event should be considered as the start of a new axis motion.

The timestamp is to be interpreted identical to the timestamp in the wl_pointer.axis event. The timestamp value may be the same as a preceding wl_pointer.axis event.

Since

5

Parameters

• time: timestamp with millisecond granularity
• axis: the axis stopped with this event

void (*axis_discrete)(void *data, struct wl_pointer *wl_pointer, uint32_t axis, int32_t discrete)

axis click event

Discrete step information for scroll and other axes.

This event carries the axis value of the wl_pointer.axis event in discrete steps (e.g. mouse wheel clicks).

This event does not occur on its own, it is coupled with a wl_pointer.axis event that represents this axis value on a continuous scale. The protocol guarantees that each axis_discrete event is always followed by exactly one axis event with the same axis number within the same wl_pointer.frame. Note that the protocol allows for other events to occur between the axis_discrete and its coupled axis event, including other axis_discrete or axis events.

This event is optional; continuous scrolling devices like two-finger scrolling on touchpads do not have discrete steps and do not generate this event.

The discrete value carries the directional information. e.g. a value of -2 is two steps towards the negative direction of this axis.

The axis number is identical to the axis number in the associated axis event.

The order of wl_pointer.axis_discrete and wl_pointer.axis_source is not guaranteed.

Since

5

Parameters

• axis: axis type
• discrete: number of steps

wl_keyboard

group iface_wl_keyboard

The wl_keyboard interface represents one or more keyboards associated with a seat.

Defines

WL_KEYBOARD_KEYMAP_SINCE_VERSION

WL_KEYBOARD_ENTER_SINCE_VERSION

WL_KEYBOARD_LEAVE_SINCE_VERSION

WL_KEYBOARD_KEY_SINCE_VERSION

WL_KEYBOARD_MODIFIERS_SINCE_VERSION

WL_KEYBOARD_REPEAT_INFO_SINCE_VERSION

WL_KEYBOARD_RELEASE_SINCE_VERSION

Enums

enum wl_keyboard_keymap_format

keyboard mapping format

This specifies the format of the keymap provided to the client with the wl_keyboard.keymap event.

Values:

WL_KEYBOARD_KEYMAP_FORMAT_NO_KEYMAP = 0

no keymap; client must understand how to interpret the raw keycode

WL_KEYBOARD_KEYMAP_FORMAT_XKB_V1 = 1

libxkbcommon compatible; to determine the xkb keycode, clients must add 8 to the key event keycode

enum wl_keyboard_key_state

physical key state

Describes the physical state of a key that produced the key event.

Values:

WL_KEYBOARD_KEY_STATE_RELEASED = 0

key is not pressed

WL_KEYBOARD_KEY_STATE_PRESSED = 1

key is pressed

Functions

static int wl_keyboard_add_listener(struct wl_keyboard *wl_keyboard, const struct wl_keyboard_listener *listener, void *data)

static void wl_keyboard_set_user_data(struct wl_keyboard *wl_keyboard, void *user_data)

static void *wl_keyboard_get_user_data(struct wl_keyboard *wl_keyboard)

static void wl_keyboard_destroy(struct wl_keyboard *wl_keyboard)

static void wl_keyboard_release(struct wl_keyboard *wl_keyboard)

struct wl_keyboard_listener

#include <wayland-client-protocol.h>

Public Members

void (*keymap)(void *data, struct wl_keyboard *wl_keyboard, uint32_t format, int32_t fd, uint32_t size)

keyboard mapping

This event provides a file descriptor to the client which can be memory-mapped to provide a keyboard mapping description.

From version 7 onwards, the fd must be mapped with MAP_PRIVATE by the recipient, as MAP_SHARED may fail.

Parameters

• format: keymap format
• fd: keymap file descriptor
• size: keymap size, in bytes

void (*enter)(void *data, struct wl_keyboard *wl_keyboard, uint32_t serial, struct wl_surface *surface, struct wl_array *keys)

enter event

Notification that this seat’s keyboard focus is on a certain surface.

Parameters

• serial: serial number of the enter event
• surface: surface gaining keyboard focus
• keys: the currently pressed keys

void (*leave)(void *data, struct wl_keyboard *wl_keyboard, uint32_t serial, struct wl_surface *surface)

leave event

Notification that this seat’s keyboard focus is no longer on a certain surface.

The leave notification is sent before the enter notification for the new focus.

Parameters

• serial: serial number of the leave event
• surface: surface that lost keyboard focus

void (*key)(void *data, struct wl_keyboard *wl_keyboard, uint32_t serial, uint32_t time, uint32_t key, uint32_t state)

key event

A key was pressed or released. The time argument is a timestamp with millisecond granularity, with an undefined base.

Parameters

• serial: serial number of the key event
• time: timestamp with millisecond granularity
• key: key that produced the event
• state: physical state of the key

void (*modifiers)(void *data, struct wl_keyboard *wl_keyboard, uint32_t serial, uint32_t mods_depressed, uint32_t mods_latched, uint32_t mods_locked, uint32_t group)

modifier and group state

Notifies clients that the modifier and/or group state has changed, and it should update its local state.

Parameters

• serial: serial number of the modifiers event
• mods_depressed: depressed modifiers
• mods_latched: latched modifiers
• mods_locked: locked modifiers
• group: keyboard layout

void (*repeat_info)(void *data, struct wl_keyboard *wl_keyboard, int32_t rate, int32_t delay)

repeat rate and delay

Informs the client about the keyboard’s repeat rate and delay.

This event is sent as soon as the wl_keyboard object has been created, and is guaranteed to be received by the client before any key press event.

Negative values for either rate or delay are illegal. A rate of zero will disable any repeating (regardless of the value of delay).

This event can be sent later on as well with a new value if necessary, so clients should continue listening for the event past the creation of wl_keyboard.

Since

4

Parameters

• rate: the rate of repeating keys in characters per second
• delay: delay in milliseconds since key down until repeating starts

wl_touch

group iface_wl_touch

The wl_touch interface represents a touchscreen associated with a seat.

Touch interactions can consist of one or more contacts. For each contact, a series of events is generated, starting with a down event, followed by zero or more motion events, and ending with an up event. Events relating to the same contact point can be identified by the ID of the sequence.

Defines

WL_TOUCH_DOWN_SINCE_VERSION

WL_TOUCH_UP_SINCE_VERSION

WL_TOUCH_MOTION_SINCE_VERSION

WL_TOUCH_FRAME_SINCE_VERSION

WL_TOUCH_CANCEL_SINCE_VERSION

WL_TOUCH_SHAPE_SINCE_VERSION

WL_TOUCH_ORIENTATION_SINCE_VERSION

WL_TOUCH_RELEASE_SINCE_VERSION

Functions

static int wl_touch_add_listener(struct wl_touch *wl_touch, const struct wl_touch_listener *listener, void *data)

static void wl_touch_set_user_data(struct wl_touch *wl_touch, void *user_data)

static void *wl_touch_get_user_data(struct wl_touch *wl_touch)

static void wl_touch_destroy(struct wl_touch *wl_touch)

static void wl_touch_release(struct wl_touch *wl_touch)

struct wl_touch_listener

#include <wayland-client-protocol.h>

Public Members

void (*down)(void *data, struct wl_touch *wl_touch, uint32_t serial, uint32_t time, struct wl_surface *surface, int32_t id, wl_fixed_t x, wl_fixed_t y)

touch down event and beginning of a touch sequence

A new touch point has appeared on the surface. This touch point is assigned a unique ID. Future events from this touch point reference this ID. The ID ceases to be valid after a touch up event and may be reused in the future.

Parameters

• serial: serial number of the touch down event
• time: timestamp with millisecond granularity
• surface: surface touched
• id: the unique ID of this touch point
• x: surface-local x coordinate
• y: surface-local y coordinate

void (*up)(void *data, struct wl_touch *wl_touch, uint32_t serial, uint32_t time, int32_t id)

end of a touch event sequence

The touch point has disappeared. No further events will be sent for this touch point and the touch point’s ID is released and may be reused in a future touch down event.

Parameters

• serial: serial number of the touch up event
• time: timestamp with millisecond granularity
• id: the unique ID of this touch point

void (*motion)(void *data, struct wl_touch *wl_touch, uint32_t time, int32_t id, wl_fixed_t x, wl_fixed_t y)

update of touch point coordinates

A touch point has changed coordinates.

Parameters

• time: timestamp with millisecond granularity
• id: the unique ID of this touch point
• x: surface-local x coordinate
• y: surface-local y coordinate

void (*frame)(void *data, struct wl_touch *wl_touch)

end of touch frame event

Indicates the end of a set of events that logically belong together. A client is expected to accumulate the data in all events within the frame before proceeding.

A wl_touch.frame terminates at least one event but otherwise no guarantee is provided about the set of events within a frame. A client must assume that any state not updated in a frame is unchanged from the previously known state.

void (*cancel)(void *data, struct wl_touch *wl_touch)

touch session cancelled

Sent if the compositor decides the touch stream is a global gesture. No further events are sent to the clients from that particular gesture. Touch cancellation applies to all touch points currently active on this client’s surface. The client is responsible for finalizing the touch points, future touch points on this surface may reuse the touch point ID.

void (*shape)(void *data, struct wl_touch *wl_touch, int32_t id, wl_fixed_t major, wl_fixed_t minor)

update shape of touch point

Sent when a touchpoint has changed its shape.

This event does not occur on its own. It is sent before a wl_touch.frame event and carries the new shape information for any previously reported, or new touch points of that frame.

Other events describing the touch point such as wl_touch.down, wl_touch.motion or wl_touch.orientation may be sent within the same wl_touch.frame. A client should treat these events as a single logical touch point update. The order of wl_touch.shape, wl_touch.orientation and wl_touch.motion is not guaranteed. A wl_touch.down event is guaranteed to occur before the first wl_touch.shape event for this touch ID but both events may occur within the same wl_touch.frame.

A touchpoint shape is approximated by an ellipse through the major and minor axis length. The major axis length describes the longer diameter of the ellipse, while the minor axis length describes the shorter diameter. Major and minor are orthogonal and both are specified in surface-local coordinates. The center of the ellipse is always at the touchpoint location as reported by wl_touch.down or wl_touch.move.

This event is only sent by the compositor if the touch device supports shape reports. The client has to make reasonable assumptions about the shape if it did not receive this event.

Since

6

Parameters

• id: the unique ID of this touch point
• major: length of the major axis in surface-local coordinates
• minor: length of the minor axis in surface-local coordinates

void (*orientation)(void *data, struct wl_touch *wl_touch, int32_t id, wl_fixed_t orientation)

update orientation of touch point

Sent when a touchpoint has changed its orientation.

This event does not occur on its own. It is sent before a wl_touch.frame event and carries the new shape information for any previously reported, or new touch points of that frame.

Other events describing the touch point such as wl_touch.down, wl_touch.motion or wl_touch.shape may be sent within the same wl_touch.frame. A client should treat these events as a single logical touch point update. The order of wl_touch.shape, wl_touch.orientation and wl_touch.motion is not guaranteed. A wl_touch.down event is guaranteed to occur before the first wl_touch.orientation event for this touch ID but both events may occur within the same wl_touch.frame.

The orientation describes the clockwise angle of a touchpoint’s major axis to the positive surface y-axis and is normalized to the -180 to +180 degree range. The granularity of orientation depends on the touch device, some devices only support binary rotation values between 0 and 90 degrees.

This event is only sent by the compositor if the touch device supports orientation reports.

Since

6

Parameters

• id: the unique ID of this touch point
• orientation: angle between major axis and positive surface y-axis in degrees

wl_output

group iface_wl_output

An output describes part of the compositor geometry.

The compositor works in the ‘compositor coordinate system’ and an output corresponds to a rectangular area in that space that is actually visible. This typically corresponds to a monitor that displays part of the compositor space. This object is published as global during start up, or when a monitor is hotplugged.

Defines

WL_OUTPUT_GEOMETRY_SINCE_VERSION

WL_OUTPUT_MODE_SINCE_VERSION

WL_OUTPUT_DONE_SINCE_VERSION

WL_OUTPUT_SCALE_SINCE_VERSION

WL_OUTPUT_RELEASE_SINCE_VERSION

Enums

enum wl_output_subpixel

subpixel geometry information

This enumeration describes how the physical pixels on an output are laid out.

Values:

WL_OUTPUT_SUBPIXEL_UNKNOWN = 0

unknown geometry

WL_OUTPUT_SUBPIXEL_NONE = 1

no geometry

WL_OUTPUT_SUBPIXEL_HORIZONTAL_RGB = 2

horizontal RGB

WL_OUTPUT_SUBPIXEL_HORIZONTAL_BGR = 3

horizontal BGR

WL_OUTPUT_SUBPIXEL_VERTICAL_RGB = 4

vertical RGB

WL_OUTPUT_SUBPIXEL_VERTICAL_BGR = 5

vertical BGR

enum wl_output_transform

transform from framebuffer to output

This describes the transform that a compositor will apply to a surface to compensate for the rotation or mirroring of an output device.

The flipped values correspond to an initial flip around a vertical axis followed by rotation.

The purpose is mainly to allow clients to render accordingly and tell the compositor, so that for fullscreen surfaces, the compositor will still be able to scan out directly from client surfaces.

Values:

WL_OUTPUT_TRANSFORM_NORMAL = 0

no transform

WL_OUTPUT_TRANSFORM_90 = 1

90 degrees counter-clockwise

WL_OUTPUT_TRANSFORM_180 = 2

180 degrees counter-clockwise

WL_OUTPUT_TRANSFORM_270 = 3

270 degrees counter-clockwise

WL_OUTPUT_TRANSFORM_FLIPPED = 4

180 degree flip around a vertical axis

WL_OUTPUT_TRANSFORM_FLIPPED_90 = 5

flip and rotate 90 degrees counter-clockwise

WL_OUTPUT_TRANSFORM_FLIPPED_180 = 6

flip and rotate 180 degrees counter-clockwise

WL_OUTPUT_TRANSFORM_FLIPPED_270 = 7

flip and rotate 270 degrees counter-clockwise

enum wl_output_mode

mode information

These flags describe properties of an output mode. They are used in the flags bitfield of the mode event.

Values:

WL_OUTPUT_MODE_CURRENT = 0x1

indicates this is the current mode

WL_OUTPUT_MODE_PREFERRED = 0x2

indicates this is the preferred mode

Functions

static int wl_output_add_listener(struct wl_output *wl_output, const struct wl_output_listener *listener, void *data)

static void wl_output_set_user_data(struct wl_output *wl_output, void *user_data)

static void *wl_output_get_user_data(struct wl_output *wl_output)

static void wl_output_destroy(struct wl_output *wl_output)

static void wl_output_release(struct wl_output *wl_output)

Using this request a client can tell the server that it is not going to use the output object anymore.

struct wl_output_listener

#include <wayland-client-protocol.h>

Public Members

void (*geometry)(void *data, struct wl_output *wl_output, int32_t x, int32_t y, int32_t physical_width, int32_t physical_height, int32_t subpixel, const char *make, const char *model, int32_t transform)

properties of the output

The geometry event describes geometric properties of the output. The event is sent when binding to the output object and whenever any of the properties change.

The physical size can be set to zero if it doesn’t make sense for this output (e.g. for projectors or virtual outputs).

Note: wl_output only advertises partial information about the output position and identification. Some compositors, for instance those not implementing a desktop-style output layout or those exposing virtual outputs, might fake this information. Instead of using x and y, clients should use xdg_output.logical_position. Instead of using make and model, clients should use xdg_output.name and xdg_output.description.

Parameters

• x: x position within the global compositor space
• y: y position within the global compositor space
• physical_width: width in millimeters of the output
• physical_height: height in millimeters of the output
• subpixel: subpixel orientation of the output
• make: textual description of the manufacturer
• model: textual description of the model
• transform: transform that maps framebuffer to output

void (*mode)(void *data, struct wl_output *wl_output, uint32_t flags, int32_t width, int32_t height, int32_t refresh)

advertise available modes for the output

The mode event describes an available mode for the output.

The event is sent when binding to the output object and there will always be one mode, the current mode. The event is sent again if an output changes mode, for the mode that is now current. In other words, the current mode is always the last mode that was received with the current flag set.

The size of a mode is given in physical hardware units of the output device. This is not necessarily the same as the output size in the global compositor space. For instance, the output may be scaled, as described in wl_output.scale, or transformed, as described in wl_output.transform. Clients willing to retrieve the output size in the global compositor space should use xdg_output.logical_size instead.

The vertical refresh rate can be set to zero if it doesn’t make sense for this output (e.g. for virtual outputs).

Clients should not use the refresh rate to schedule frames. Instead, they should use the wl_surface.frame event or the presentation-time protocol.

Note: this information is not always meaningful for all outputs. Some compositors, such as those exposing virtual outputs, might fake the refresh rate or the size.

Parameters

• flags: bitfield of mode flags
• width: width of the mode in hardware units
• height: height of the mode in hardware units
• refresh: vertical refresh rate in mHz

void (*done)(void *data, struct wl_output *wl_output)

sent all information about output

This event is sent after all other properties have been sent after binding to the output object and after any other property changes done after that. This allows changes to the output properties to be seen as atomic, even if they happen via multiple events.

Since

2

void (*scale)(void *data, struct wl_output *wl_output, int32_t factor)

output scaling properties

This event contains scaling geometry information that is not in the geometry event. It may be sent after binding the output object or if the output scale changes later. If it is not sent, the client should assume a scale of 1.

A scale larger than 1 means that the compositor will automatically scale surface buffers by this amount when rendering. This is used for very high resolution displays where applications rendering at the native resolution would be too small to be legible.

It is intended that scaling aware clients track the current output of a surface, and if it is on a scaled output it should use wl_surface.set_buffer_scale with the scale of the output. That way the compositor can avoid scaling the surface, and the client can supply a higher detail image.

Since

2

Parameters

• factor: scaling factor of output

wl_region

group iface_wl_region

A region object describes an area.

Region objects are used to describe the opaque and input regions of a surface.

Defines

WL_REGION_DESTROY_SINCE_VERSION

WL_REGION_ADD_SINCE_VERSION

WL_REGION_SUBTRACT_SINCE_VERSION

Functions

static void wl_region_set_user_data(struct wl_region *wl_region, void *user_data)

static void *wl_region_get_user_data(struct wl_region *wl_region)

static void wl_region_destroy(struct wl_region *wl_region)

Destroy the region.

This will invalidate the object ID.

static void wl_region_add(struct wl_region *wl_region, int32_t x, int32_t y, int32_t width, int32_t height)

Add the specified rectangle to the region.

static void wl_region_subtract(struct wl_region *wl_region, int32_t x, int32_t y, int32_t width, int32_t height)

Subtract the specified rectangle from the region.

wl_subcompositor

group iface_wl_subcompositor

The global interface exposing sub-surface compositing capabilities.

A wl_surface, that has sub-surfaces associated, is called the parent surface. Sub-surfaces can be arbitrarily nested and create a tree of sub-surfaces.

The root surface in a tree of sub-surfaces is the main surface. The main surface cannot be a sub-surface, because sub-surfaces must always have a parent.

A main surface with its sub-surfaces forms a (compound) window. For window management purposes, this set of wl_surface objects is to be considered as a single window, and it should also behave as such.

The aim of sub-surfaces is to offload some of the compositing work within a window from clients to the compositor. A prime example is a video player with decorations and video in separate wl_surface objects. This should allow the compositor to pass YUV video buffer processing to dedicated overlay hardware when possible.

Defines

WL_SUBCOMPOSITOR_DESTROY_SINCE_VERSION

WL_SUBCOMPOSITOR_GET_SUBSURFACE_SINCE_VERSION

Functions

static void wl_subcompositor_set_user_data(struct wl_subcompositor *wl_subcompositor, void *user_data)

static void *wl_subcompositor_get_user_data(struct wl_subcompositor *wl_subcompositor)

static void wl_subcompositor_destroy(struct wl_subcompositor *wl_subcompositor)

Informs the server that the client will not be using this protocol object anymore.

This does not affect any other objects, wl_subsurface objects included.

static struct wl_subsurface *wl_subcompositor_get_subsurface(struct wl_subcompositor *wl_subcompositor, struct wl_surface *surface, struct wl_surface *parent)

Create a sub-surface interface for the given surface, and associate it with the given parent surface.

This turns a plain wl_surface into a sub-surface.

The to-be sub-surface must not already have another role, and it must not have an existing wl_subsurface object. Otherwise a protocol error is raised.

Adding sub-surfaces to a parent is a double-buffered operation on the parent (see wl_surface.commit). The effect of adding a sub-surface becomes visible on the next time the state of the parent surface is applied.

This request modifies the behaviour of wl_surface.commit request on the sub-surface, see the documentation on wl_subsurface interface.

wl_subsurface

group iface_wl_subsurface

An additional interface to a wl_surface object, which has been made a sub-surface.

A sub-surface has one parent surface. A sub-surface’s size and position are not limited to that of the parent. Particularly, a sub-surface is not automatically clipped to its parent’s area.

A sub-surface becomes mapped, when a non-NULL wl_buffer is applied and the parent surface is mapped. The order of which one happens first is irrelevant. A sub-surface is hidden if the parent becomes hidden, or if a NULL wl_buffer is applied. These rules apply recursively through the tree of surfaces.

The behaviour of a wl_surface.commit request on a sub-surface depends on the sub-surface’s mode. The possible modes are synchronized and desynchronized, see methods wl_subsurface.set_sync and wl_subsurface.set_desync. Synchronized mode caches the wl_surface state to be applied when the parent’s state gets applied, and desynchronized mode applies the pending wl_surface state directly. A sub-surface is initially in the synchronized mode.

Sub-surfaces have also other kind of state, which is managed by wl_subsurface requests, as opposed to wl_surface requests. This state includes the sub-surface position relative to the parent surface (wl_subsurface.set_position), and the stacking order of the parent and its sub-surfaces (wl_subsurface.place_above and .place_below). This state is applied when the parent surface’s wl_surface state is applied, regardless of the sub-surface’s mode. As the exception, set_sync and set_desync are effective immediately.

The main surface can be thought to be always in desynchronized mode, since it does not have a parent in the sub-surfaces sense.

Even if a sub-surface is in desynchronized mode, it will behave as in synchronized mode, if its parent surface behaves as in synchronized mode. This rule is applied recursively throughout the tree of surfaces. This means, that one can set a sub-surface into synchronized mode, and then assume that all its child and grand-child sub-surfaces are synchronized, too, without explicitly setting them.

If the wl_surface associated with the wl_subsurface is destroyed, the wl_subsurface object becomes inert. Note, that destroying either object takes effect immediately. If you need to synchronize the removal of a sub-surface to the parent surface update, unmap the sub-surface first by attaching a NULL wl_buffer, update parent, and then destroy the sub-surface.

If the parent wl_surface object is destroyed, the sub-surface is unmapped.

Defines

WL_SUBSURFACE_DESTROY_SINCE_VERSION

WL_SUBSURFACE_SET_POSITION_SINCE_VERSION

WL_SUBSURFACE_PLACE_ABOVE_SINCE_VERSION

WL_SUBSURFACE_PLACE_BELOW_SINCE_VERSION

WL_SUBSURFACE_SET_SYNC_SINCE_VERSION

WL_SUBSURFACE_SET_DESYNC_SINCE_VERSION

Functions

static void wl_subsurface_set_user_data(struct wl_subsurface *wl_subsurface, void *user_data)

static void *wl_subsurface_get_user_data(struct wl_subsurface *wl_subsurface)

static void wl_subsurface_destroy(struct wl_subsurface *wl_subsurface)

The sub-surface interface is removed from the wl_surface object that was turned into a sub-surface with a wl_subcompositor.get_subsurface request.

The wl_surface’s association to the parent is deleted, and the wl_surface loses its role as a sub-surface. The wl_surface is unmapped immediately.

static void wl_subsurface_set_position(struct wl_subsurface *wl_subsurface, int32_t x, int32_t y)

This schedules a sub-surface position change.

The sub-surface will be moved so that its origin (top left corner pixel) will be at the location x, y of the parent surface coordinate system. The coordinates are not restricted to the parent surface area. Negative values are allowed.

The scheduled coordinates will take effect whenever the state of the parent surface is applied. When this happens depends on whether the parent surface is in synchronized mode or not. See wl_subsurface.set_sync and wl_subsurface.set_desync for details.

If more than one set_position request is invoked by the client before the commit of the parent surface, the position of a new request always replaces the scheduled position from any previous request.

The initial position is 0, 0.

static void wl_subsurface_place_above(struct wl_subsurface *wl_subsurface, struct wl_surface *sibling)

This sub-surface is taken from the stack, and put back just above the reference surface, changing the z-order of the sub-surfaces.

The reference surface must be one of the sibling surfaces, or the parent surface. Using any other surface, including this sub-surface, will cause a protocol error.

The z-order is double-buffered. Requests are handled in order and applied immediately to a pending state. The final pending state is copied to the active state the next time the state of the parent surface is applied. When this happens depends on whether the parent surface is in synchronized mode or not. See wl_subsurface.set_sync and wl_subsurface.set_desync for details.

A new sub-surface is initially added as the top-most in the stack of its siblings and parent.

static void wl_subsurface_place_below(struct wl_subsurface *wl_subsurface, struct wl_surface *sibling)

The sub-surface is placed just below the reference surface.

See wl_subsurface.place_above.

static void wl_subsurface_set_sync(struct wl_subsurface *wl_subsurface)

Change the commit behaviour of the sub-surface to synchronized mode, also described as the parent dependent mode.

In synchronized mode, wl_surface.commit on a sub-surface will accumulate the committed state in a cache, but the state will not be applied and hence will not change the compositor output. The cached state is applied to the sub-surface immediately after the parent surface’s state is applied. This ensures atomic updates of the parent and all its synchronized sub-surfaces. Applying the cached state will invalidate the cache, so further parent surface commits do not (re-)apply old state.

See wl_subsurface for the recursive effect of this mode.

static void wl_subsurface_set_desync(struct wl_subsurface *wl_subsurface)

Change the commit behaviour of the sub-surface to desynchronized mode, also described as independent or freely running mode.

In desynchronized mode, wl_surface.commit on a sub-surface will apply the pending state directly, without caching, as happens normally with a wl_surface. Calling wl_surface.commit on the parent surface has no effect on the sub-surface’s wl_surface state. This mode allows a sub-surface to be updated on its own.

If cached state exists when wl_surface.commit is called in desynchronized mode, the pending state is added to the cached state, and applied as a whole. This invalidates the cache.

Note: even if a sub-surface is set to desynchronized, a parent sub-surface may override it to behave as synchronized. For details, see wl_subsurface.

If a surface’s parent surface behaves as desynchronized, then the cached state is applied on set_desync.