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Appendix A. Wayland Protocol Specification


    Copyright © 2008-2011 Kristian Høgsberg
    Copyright © 2010-2011 Intel Corporation
    Copyright © 2012-2013 Collabora, Ltd.

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A.1. wl_display - core global object

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

A.1.1. Requests provided by wl_display

A.1.1.1. wl_display::sync - asynchronous roundtrip

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.

wl_display::sync arguments

callback
Type: new_id

A.1.1.2. wl_display::get_registry - get global registry object

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

wl_display::get_registry arguments

registry
Type: new_id

A.1.2. Events provided by wl_display

A.1.2.1. wl_display::error - 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 an brief description of the error, for (debugging) convenience.

wl_display::error arguments

object_id
Type: object
code
Type: uint
message
Type: string

A.1.2.2. wl_display::delete_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 receive this event, it will know that it can safely reuse the object ID.

wl_display::delete_id arguments

id
Type: uint

A.1.3. Enums provided by wl_display

A.1.3.1. wl_display::error - global error values

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

wl_display::error values

invalid_object
Value: 0
server couldn't find object
invalid_method
Value: 1
method doesn't exist on the specified interface
no_memory
Value: 2
server is out of memory

A.2. wl_registry - global registry object

The 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.

A.2.1. Requests provided by wl_registry

A.2.1.1. wl_registry::bind - bind an object to the display

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

wl_registry::bind arguments

name
Type: uint
unique name for the object
id
Type: new_id

A.2.2. Events provided by wl_registry

A.2.2.1. wl_registry::global - 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.

wl_registry::global arguments

name
Type: uint
interface
Type: string
version
Type: uint

A.2.2.2. wl_registry::global_remove - 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.

wl_registry::global_remove arguments

name
Type: uint

A.3. wl_callback - callback object

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

A.3.1. Events provided by wl_callback

A.3.1.1. wl_callback::done - done event

Notify the client when the related request is done.

wl_callback::done arguments

callback_data
Type: uint
request-specific data for the wl_callback

A.4. wl_compositor - the compositor singleton

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

A.4.1. Requests provided by wl_compositor

A.4.1.1. wl_compositor::create_surface - create new surface

Ask the compositor to create a new surface.

wl_compositor::create_surface arguments

id
Type: new_id

A.4.1.2. wl_compositor::create_region - create new region

Ask the compositor to create a new region.

wl_compositor::create_region arguments

id
Type: new_id

A.5. wl_shm_pool - a shared memory 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.

A.5.1. Requests provided by wl_shm_pool

A.5.1.1. wl_shm_pool::create_buffer - create a buffer from the pool

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 arguments specifies the number of bytes from 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.

wl_shm_pool::create_buffer arguments

id
Type: new_id
offset
Type: int
width
Type: int
height
Type: int
stride
Type: int
format
Type: uint

A.5.1.2. wl_shm_pool::destroy - destroy the pool

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

A.5.1.3. wl_shm_pool::resize - change the size of the pool mapping

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_pool::resize arguments

size
Type: int

A.6. wl_shm - shared memory support

A global singleton 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.

A.6.1. Requests provided by wl_shm

A.6.1.1. wl_shm::create_pool - create a shm pool

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.

wl_shm::create_pool arguments

id
Type: new_id
fd
Type: fd
size
Type: int

A.6.2. Events provided by wl_shm

A.6.2.1. wl_shm::format - pixel format description

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

wl_shm::format arguments

format
Type: uint

A.6.3. Enums provided by wl_shm

A.6.3.1. wl_shm::error - wl_shm error values

These errors can be emitted in response to wl_shm requests.

wl_shm::error values

invalid_format
Value: 0
buffer format is not known
invalid_stride
Value: 1
invalid size or stride during pool or buffer creation
invalid_fd
Value: 2
mmapping the file descriptor failed

A.6.3.2. 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.

wl_shm::format values

argb8888
Value: 0
32-bit ARGB format
xrgb8888
Value: 1
32-bit RGB format
c8
Value: 0x20203843
rgb332
Value: 0x38424752
bgr233
Value: 0x38524742
xrgb4444
Value: 0x32315258
xbgr4444
Value: 0x32314258
rgbx4444
Value: 0x32315852
bgrx4444
Value: 0x32315842
argb4444
Value: 0x32315241
abgr4444
Value: 0x32314241
rgba4444
Value: 0x32314152
bgra4444
Value: 0x32314142
xrgb1555
Value: 0x35315258
xbgr1555
Value: 0x35314258
rgbx5551
Value: 0x35315852
bgrx5551
Value: 0x35315842
argb1555
Value: 0x35315241
abgr1555
Value: 0x35314241
rgba5551
Value: 0x35314152
bgra5551
Value: 0x35314142
rgb565
Value: 0x36314752
bgr565
Value: 0x36314742
rgb888
Value: 0x34324752
bgr888
Value: 0x34324742
xbgr8888
Value: 0x34324258
rgbx8888
Value: 0x34325852
bgrx8888
Value: 0x34325842
abgr8888
Value: 0x34324241
rgba8888
Value: 0x34324152
bgra8888
Value: 0x34324142
xrgb2101010
Value: 0x30335258
xbgr2101010
Value: 0x30334258
rgbx1010102
Value: 0x30335852
bgrx1010102
Value: 0x30335842
argb2101010
Value: 0x30335241
abgr2101010
Value: 0x30334241
rgba1010102
Value: 0x30334152
bgra1010102
Value: 0x30334142
yuyv
Value: 0x56595559
yvyu
Value: 0x55595659
uyvy
Value: 0x59565955
vyuy
Value: 0x59555956
ayuv
Value: 0x56555941
nv12
Value: 0x3231564e
nv21
Value: 0x3132564e
nv16
Value: 0x3631564e
nv61
Value: 0x3136564e
yuv410
Value: 0x39565559
yvu410
Value: 0x39555659
yuv411
Value: 0x31315559
yvu411
Value: 0x31315659
yuv420
Value: 0x32315559
yvu420
Value: 0x32315659
yuv422
Value: 0x36315559
yvu422
Value: 0x36315659
yuv444
Value: 0x34325559
yvu444
Value: 0x34325659

A.7. wl_buffer - content for a wl_surface

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.

A.7.1. Requests provided by wl_buffer

A.7.1.1. wl_buffer::destroy - destroy a 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.

A.7.2. Events provided by wl_buffer

A.7.2.1. wl_buffer::release - compositor releases buffer

Sent when this wl_buffer is no longer used by the compositor. The client is now free to re-use 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 re-use 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.

A.8. wl_data_offer - offer to transfer data

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.

A.8.1. Requests provided by wl_data_offer

A.8.1.1. wl_data_offer::accept - accept one of the offered mime types

Indicate that the client can accept the given mime type, or NULL for not accepted.
Used for feedback during drag-and-drop.

wl_data_offer::accept arguments

serial
Type: uint
mime_type
Type: string

A.8.1.2. wl_data_offer::receive - request that the data is transferred

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 the closes its end, at which point the transfer is complete.

wl_data_offer::receive arguments

mime_type
Type: string
fd
Type: fd

A.8.1.3. wl_data_offer::destroy - destroy data offer

Destroy the data offer.

A.8.2. Events provided by wl_data_offer

A.8.2.1. wl_data_offer::offer - advertise offered mime type

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

wl_data_offer::offer arguments

mime_type
Type: string

A.9. wl_data_source - offer to transfer data

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.

A.9.1. Requests provided by wl_data_source

A.9.1.1. wl_data_source::offer - add an offered 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.

wl_data_source::offer arguments

mime_type
Type: string

A.9.1.2. wl_data_source::destroy - destroy the data source

Destroy the data source.

A.9.2. Events provided by wl_data_source

A.9.2.1. wl_data_source::target - 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.

wl_data_source::target arguments

mime_type
Type: string

A.9.2.2. wl_data_source::send - 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.

wl_data_source::send arguments

mime_type
Type: string
fd
Type: fd

A.9.2.3. wl_data_source::cancelled - selection was cancelled

This data source has been replaced by another data source. The client should clean up and destroy this data source.

A.10. wl_data_device - data transfer 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.

A.10.1. Requests provided by wl_data_device

A.10.1.1. wl_data_device::start_drag - start drag-and-drop operation

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 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.

wl_data_device::start_drag arguments

source
Type: object
origin
Type: object
icon
Type: object
serial
Type: uint
serial of the implicit grab on the origin

A.10.1.2. wl_data_device::set_selection - copy data to the selection

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.

wl_data_device::set_selection arguments

source
Type: object
serial
Type: uint
serial of the event that triggered this request

A.10.2. Events provided by wl_data_device

A.10.2.1. wl_data_device::data_offer - 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.

wl_data_device::data_offer arguments

id
Type: new_id

A.10.2.2. wl_data_device::enter - 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.

wl_data_device::enter arguments

serial
Type: uint
surface
Type: object
x
Type: fixed
y
Type: fixed
id
Type: object

A.10.2.3. wl_data_device::leave - 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.

A.10.2.4. wl_data_device::motion - 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.

wl_data_device::motion arguments

time
Type: uint
timestamp with millisecond granularity
x
Type: fixed
y
Type: fixed

A.10.2.5. wl_data_device::drop - end drag-and-drag session successfully

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

A.10.2.6. wl_data_device::selection - 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.

wl_data_device::selection arguments

id
Type: object

A.11. wl_data_device_manager - data transfer interface

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.

A.11.1. Requests provided by wl_data_device_manager

A.11.1.1. wl_data_device_manager::create_data_source - create a new data source

Create a new data source.

wl_data_device_manager::create_data_source arguments

id
Type: new_id

A.11.1.2. wl_data_device_manager::get_data_device - create a new data device

Create a new data device for a given seat.

wl_data_device_manager::get_data_device arguments

id
Type: new_id
seat
Type: object

A.12. wl_shell - create desktop-style surfaces

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.

A.12.1. Requests provided by wl_shell

A.12.1.1. wl_shell::get_shell_surface - create a shell surface from a surface

Create a shell surface for an existing surface.
Only one shell surface can be associated with a given surface.

wl_shell::get_shell_surface arguments

id
Type: new_id
surface
Type: object

A.13. wl_shell_surface - desktop-style metadata interface

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 client side, wl_shell_surface_destroy() must be called before destroying the wl_surface object.

A.13.1. Requests provided by wl_shell_surface

A.13.1.1. wl_shell_surface::pong - respond to a ping event

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

wl_shell_surface::pong arguments

serial
Type: uint
serial of the ping event

A.13.1.2. wl_shell_surface::move - start an interactive move

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).

wl_shell_surface::move arguments

seat
Type: object
the wl_seat whose pointer is used
serial
Type: uint
serial of the implicit grab on the pointer

A.13.1.3. wl_shell_surface::resize - start an interactive resize

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).

wl_shell_surface::resize arguments

seat
Type: object
the wl_seat whose pointer is used
serial
Type: uint
serial of the implicit grab on the pointer
edges
Type: uint
which edge or corner is being dragged

A.13.1.4. wl_shell_surface::set_toplevel - make the surface a toplevel surface

Map the surface as a toplevel surface.
A toplevel surface is not fullscreen, maximized or transient.

A.13.1.5. wl_shell_surface::set_transient - make the surface a transient surface

Map the surface relative to an existing surface.
The x and y arguments specify the locations 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.

wl_shell_surface::set_transient arguments

parent
Type: object
x
Type: int
y
Type: int
flags
Type: uint

A.13.1.6. wl_shell_surface::set_fullscreen - make the surface a fullscreen surface

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 app 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.

wl_shell_surface::set_fullscreen arguments

method
Type: uint
framerate
Type: uint
output
Type: object

A.13.1.7. wl_shell_surface::set_popup - make the surface a popup surface

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 clients window. A click in any of the clients 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 locations of the upper left corner of the surface relative to the upper left corner of the parent surface, in surface local coordinates.

wl_shell_surface::set_popup arguments

seat
Type: object
the wl_seat whose pointer is used
serial
Type: uint
serial of the implicit grab on the pointer
parent
Type: object
x
Type: int
y
Type: int
flags
Type: uint

A.13.1.8. wl_shell_surface::set_maximized - make the surface a maximized surface

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 element 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.

wl_shell_surface::set_maximized arguments

output
Type: object

A.13.1.9. wl_shell_surface::set_title - set surface 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.

wl_shell_surface::set_title arguments

title
Type: string

A.13.1.10. wl_shell_surface::set_class - set surface 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.

wl_shell_surface::set_class arguments

class_
Type: string

A.13.2. Events provided by wl_shell_surface

A.13.2.1. wl_shell_surface::ping - 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.

wl_shell_surface::ping arguments

serial
Type: uint

A.13.2.2. wl_shell_surface::configure - 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.

wl_shell_surface::configure arguments

edges
Type: uint
width
Type: int
height
Type: int

A.13.2.3. wl_shell_surface::popup_done - 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.

A.13.3. Enums provided by wl_shell_surface

A.13.3.1. 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.

wl_shell_surface::resize values

none
Value: 0
top
Value: 1
bottom
Value: 2
left
Value: 4
top_left
Value: 5
bottom_left
Value: 6
right
Value: 8
top_right
Value: 9
bottom_right
Value: 10

A.13.3.2. 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.

wl_shell_surface::transient values

inactive
Value: 0x1
do not set keyboard focus

A.13.3.3. 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.

wl_shell_surface::fullscreen_method values

default
Value: 0
no preference, apply default policy
scale
Value: 1
scale, preserve the surface's aspect ratio and center on output
driver
Value: 2
switch output mode to the smallest mode that can fit the surface, add black borders to compensate size mismatch
fill
Value: 3
no upscaling, center on output and add black borders to compensate size mismatch

A.14. wl_surface - an onscreen 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 local coordinates of the pixel content, in case a buffer_transform or a buffer_scale is used.
Surfaces are also used for some special purposes, e.g. as cursor images for pointers, drag icons, etc.

A.14.1. Requests provided by wl_surface

A.14.1.1. wl_surface::destroy - delete surface

Deletes the surface and invalidates its object ID.

A.14.1.2. wl_surface::attach - set the surface contents

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 re-use 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.

wl_surface::attach arguments

buffer
Type: object
x
Type: int
y
Type: int

A.14.1.3. wl_surface::damage - mark part of the surface damaged

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 pending buffer must be set by wl_surface.attach before sending damage. 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.
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.

wl_surface::damage arguments

x
Type: int
y
Type: int
width
Type: int
height
Type: int

A.14.1.4. wl_surface::frame - request a frame throttling hint

Request a notification when it is a good time 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 them hit the next output refresh.
A server should avoid signalling 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.

wl_surface::frame arguments

callback
Type: new_id

A.14.1.5. wl_surface::set_opaque_region - set opaque 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 out 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 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.

wl_surface::set_opaque_region arguments

region
Type: object

A.14.1.6. wl_surface::set_input_region - set input 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 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.

wl_surface::set_input_region arguments

region
Type: object

A.14.1.7. wl_surface::commit - commit pending surface state

Surface state (input, opaque, and damage regions, attached buffers, etc.) is double-buffered. Protocol requests modify the pending state, as opposed to current state in use by the compositor. 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, 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.

A.14.1.8. wl_surface::set_buffer_transform - sets the buffer transformation

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 permiting 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.

wl_surface::set_buffer_transform arguments

transform
Type: int

A.14.1.9. wl_surface::set_buffer_scale - sets the buffer scaling factor

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. Its 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.

wl_surface::set_buffer_scale arguments

scale
Type: int

A.14.2. Events provided by wl_surface

A.14.2.1. wl_surface::enter - 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.

wl_surface::enter arguments

output
Type: object

A.14.2.2. wl_surface::leave - 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.

wl_surface::leave arguments

output
Type: object

A.14.3. Enums provided by wl_surface

A.14.3.1. wl_surface::error - wl_surface error values

These errors can be emitted in response to wl_surface requests.

wl_surface::error values

invalid_scale
Value: 0
buffer scale value is invalid
invalid_transform
Value: 1
buffer transform value is invalid

A.15. wl_seat - group of input devices

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.

A.15.1. Requests provided by wl_seat

A.15.1.1. wl_seat::get_pointer - return pointer object

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.

wl_seat::get_pointer arguments

id
Type: new_id

A.15.1.2. wl_seat::get_keyboard - return keyboard object

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.

wl_seat::get_keyboard arguments

id
Type: new_id

A.15.1.3. wl_seat::get_touch - return touch object

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.

wl_seat::get_touch arguments

id
Type: new_id

A.15.2. Events provided by wl_seat

A.15.2.1. wl_seat::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.

wl_seat::capabilities arguments

capabilities
Type: uint

A.15.2.2. wl_seat::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.

wl_seat::name arguments

name
Type: string

A.15.3. Enums provided by wl_seat

A.15.3.1. 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.

wl_seat::capability values

pointer
Value: 1
The seat has pointer devices
keyboard
Value: 2
The seat has one or more keyboards
touch
Value: 4
The seat has touch devices

A.16. wl_pointer - pointer input device

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.

A.16.1. Requests provided by wl_pointer

A.16.1.1. wl_pointer::set_cursor - set the pointer surface

Set the pointer surface, i.e., the surface that contains the pointer image (cursor). This request only takes effect 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.

wl_pointer::set_cursor arguments

serial
Type: uint
serial of the enter event
surface
Type: object
hotspot_x
Type: int
x coordinate in surface-relative coordinates
hotspot_y
Type: int
y coordinate in surface-relative coordinates

A.16.1.2. wl_pointer::release - release the pointer object

A.16.2. Events provided by wl_pointer

A.16.2.1. wl_pointer::enter - enter event

Notification that this seat's pointer is focused on a certain surface.
When an 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.

wl_pointer::enter arguments

serial
Type: uint
surface
Type: object
surface_x
Type: fixed
x coordinate in surface-relative coordinates
surface_y
Type: fixed
y coordinate in surface-relative coordinates

A.16.2.2. wl_pointer::leave - 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.

wl_pointer::leave arguments

serial
Type: uint
surface
Type: object

A.16.2.3. wl_pointer::motion - pointer motion event

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

wl_pointer::motion arguments

time
Type: uint
timestamp with millisecond granularity
surface_x
Type: fixed
x coordinate in surface-relative coordinates
surface_y
Type: fixed
y coordinate in surface-relative coordinates

A.16.2.4. wl_pointer::button - 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.

wl_pointer::button arguments

serial
Type: uint
time
Type: uint
timestamp with millisecond granularity
button
Type: uint
state
Type: uint

A.16.2.5. wl_pointer::axis - 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, clients can transform its view relative to the scroll distance.

wl_pointer::axis arguments

time
Type: uint
timestamp with millisecond granularity
axis
Type: uint
value
Type: fixed

A.16.3. Enums provided by wl_pointer

A.16.3.1. wl_pointer::button_state - physical button state

Describes the physical state of a button which provoked the button event.

wl_pointer::button_state values

released
Value: 0
The button is not pressed
pressed
Value: 1
The button is pressed

A.16.3.2. wl_pointer::axis - axis types

Describes the axis types of scroll events.

wl_pointer::axis values

vertical_scroll
Value: 0
horizontal_scroll
Value: 1

A.17. wl_keyboard - keyboard input device

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

A.17.1. Requests provided by wl_keyboard

A.17.1.1. wl_keyboard::release - release the keyboard object

A.17.2. Events provided by wl_keyboard

A.17.2.1. wl_keyboard::keymap - keyboard mapping

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

wl_keyboard::keymap arguments

format
Type: uint
fd
Type: fd
size
Type: uint

A.17.2.2. wl_keyboard::enter - enter event

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

wl_keyboard::enter arguments

serial
Type: uint
surface
Type: object
keys
Type: array
the currently pressed keys

A.17.2.3. wl_keyboard::leave - 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.

wl_keyboard::leave arguments

serial
Type: uint
surface
Type: object

A.17.2.4. wl_keyboard::key - key event

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

wl_keyboard::key arguments

serial
Type: uint
time
Type: uint
timestamp with millisecond granularity
key
Type: uint
state
Type: uint

A.17.2.5. wl_keyboard::modifiers - modifier and group state

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

wl_keyboard::modifiers arguments

serial
Type: uint
mods_depressed
Type: uint
mods_latched
Type: uint
mods_locked
Type: uint
group
Type: uint

A.17.2.6. wl_keyboard::repeat_info - 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.

wl_keyboard::repeat_info arguments

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

A.17.3. Enums provided by wl_keyboard

A.17.3.1. wl_keyboard::keymap_format - keyboard mapping format

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

wl_keyboard::keymap_format values

no_keymap
Value: 0
no keymap; client must understand how to interpret the raw keycode
xkb_v1
Value: 1
libxkbcommon compatible; to determine the xkb keycode, clients must add 8 to the key event keycode

A.17.3.2. wl_keyboard::key_state - physical key state

Describes the physical state of a key which provoked the key event.

wl_keyboard::key_state values

released
Value: 0
key is not pressed
pressed
Value: 1
key is pressed

A.18. wl_touch - touchscreen input device

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.

A.18.1. Requests provided by wl_touch

A.18.1.1. wl_touch::release - release the touch object

A.18.2. Events provided by wl_touch

A.18.2.1. wl_touch::down - 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 touchpoint reference this ID. The ID ceases to be valid after a touch up event and may be re-used in the future.

wl_touch::down arguments

serial
Type: uint
time
Type: uint
timestamp with millisecond granularity
surface
Type: object
id
Type: int
the unique ID of this touch point
x
Type: fixed
x coordinate in surface-relative coordinates
y
Type: fixed
y coordinate in surface-relative coordinates

A.18.2.2. wl_touch::up - end of a touch event sequence

The touch point has disappeared. No further events will be sent for this touchpoint and the touch point's ID is released and may be re-used in a future touch down event.

wl_touch::up arguments

serial
Type: uint
time
Type: uint
timestamp with millisecond granularity
id
Type: int
the unique ID of this touch point

A.18.2.3. wl_touch::motion - update of touch point coordinates

A touchpoint has changed coordinates.

wl_touch::motion arguments

time
Type: uint
timestamp with millisecond granularity
id
Type: int
the unique ID of this touch point
x
Type: fixed
x coordinate in surface-relative coordinates
y
Type: fixed
y coordinate in surface-relative coordinates

A.18.2.4. wl_touch::frame - end of touch frame event

Indicates the end of a contact point list.

A.18.2.5. wl_touch::cancel - 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 re-use the touch point ID.

A.19. wl_output - compositor output region

An output describes part of the compositor geometry. The compositor works in the 'compositor coordinate system' and an output corresponds to 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.

A.19.1. Events provided by wl_output

A.19.1.1. wl_output::geometry - 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.

wl_output::geometry arguments

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

A.19.1.2. wl_output::mode - 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.

wl_output::mode arguments

flags
Type: uint
bitfield of mode flags
width
Type: int
width of the mode in hardware units
height
Type: int
height of the mode in hardware units
refresh
Type: int
vertical refresh rate in mHz

A.19.1.3. wl_output::done - sent all information about output

This event is sent after all other properties has 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.

A.19.1.4. wl_output::scale - 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.

wl_output::scale arguments

factor
Type: int
scaling factor of output

A.19.2. Enums provided by wl_output

A.19.2.1. wl_output::subpixel - subpixel geometry information

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

wl_output::subpixel values

unknown
Value: 0
none
Value: 1
horizontal_rgb
Value: 2
horizontal_bgr
Value: 3
vertical_rgb
Value: 4
vertical_bgr
Value: 5

A.19.2.2. 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 render accordingly and tell the compositor, so that for fullscreen surfaces, the compositor will still be able to scan out directly from client surfaces.

wl_output::transform values

normal
Value: 0
90
Value: 1
180
Value: 2
270
Value: 3
flipped
Value: 4
flipped_90
Value: 5
flipped_180
Value: 6
flipped_270
Value: 7

A.19.2.3. wl_output::mode - mode information

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

wl_output::mode values

current
Value: 0x1
indicates this is the current mode
preferred
Value: 0x2
indicates this is the preferred mode

A.20. wl_region - region interface

A region object describes an area.
Region objects are used to describe the opaque and input regions of a surface.

A.20.1. Requests provided by wl_region

A.20.1.1. wl_region::destroy - destroy region

Destroy the region. This will invalidate the object ID.

A.20.1.2. wl_region::add - add rectangle to region

Add the specified rectangle to the region.

wl_region::add arguments

x
Type: int
y
Type: int
width
Type: int
height
Type: int

A.20.1.3. wl_region::subtract - subtract rectangle from region

Subtract the specified rectangle from the region.

wl_region::subtract arguments

x
Type: int
y
Type: int
width
Type: int
height
Type: int

A.21. wl_subcompositor - sub-surface compositing

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.

A.21.1. Requests provided by wl_subcompositor

A.21.1.1. wl_subcompositor::destroy - unbind from the subcompositor interface

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.

A.21.1.2. wl_subcompositor::get_subsurface - give a surface the role sub-surface

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 a dedicated purpose, like any shell surface type, cursor image, drag icon, or sub-surface. Otherwise a protocol error is raised.

wl_subcompositor::get_subsurface arguments

id
Type: new_id
the new subsurface object id
surface
Type: object
the surface to be turned into a sub-surface
parent
Type: object
the parent surface

A.21.2. Enums provided by wl_subcompositor

A.21.2.1. wl_subcompositor::error

wl_subcompositor::error values

bad_surface
Value: 0
the to-be sub-surface is invalid

A.22. wl_subsurface - sub-surface interface to a wl_surface

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 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.

A.22.1. Requests provided by wl_subsurface

A.22.1.1. wl_subsurface::destroy - remove sub-surface interface

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

A.22.1.2. wl_subsurface::set_position - reposition the sub-surface

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 next wl_surface.commit on the parent surface will reset the sub-surface's position to the scheduled coordinates.
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.

wl_subsurface::set_position arguments

x
Type: int
coordinate in the parent surface
y
Type: int
coordinate in the parent surface

A.22.1.3. wl_subsurface::place_above - restack the sub-surface

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, then committed to the active state on the next commit of the parent surface. See wl_surface.commit and wl_subcompositor.get_subsurface.
A new sub-surface is initially added as the top-most in the stack of its siblings and parent.

wl_subsurface::place_above arguments

sibling
Type: object
the reference surface

A.22.1.4. wl_subsurface::place_below - restack the sub-surface

The sub-surface is placed just below of the reference surface. See wl_subsurface.place_above.

wl_subsurface::place_below arguments

sibling
Type: object
the reference surface

A.22.1.5. wl_subsurface::set_sync - set sub-surface to synchronized mode

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

A.22.1.6. wl_subsurface::set_desync - set sub-surface to desynchronized mode

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 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.

A.22.2. Enums provided by wl_subsurface

A.22.2.1. wl_subsurface::error

wl_subsurface::error values

bad_surface
Value: 0
wl_surface is not a sibling or the parent