Appendix A. Wayland Protocol Specification

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 undefined and should be ignored.

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.

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.

This event is used internally by the object ID management logic. When a client deletes an object that it had created, 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.

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

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

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.

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.

Notify the client when the related request is done.

Ask the compositor to create a new surface.

Ask the compositor to create a new region.

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.

Destroy the shared memory pool.

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

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.

This request only changes the amount of bytes that are mmapped by the server and does not touch the file corresponding to the file descriptor passed at creation time. It is the client's responsibility to ensure that the file is at least as big as the new pool 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.

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

Objects created via this interface remain unaffected.

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

These errors can be emitted in response to wl_shm requests.

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, except argb8888 and xrgb8888. The formats actually supported by the compositor will be reported by the format event.

For all wl_shm formats and unless specified in another protocol extension, pre-multiplied alpha is used for pixel values.

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.

Sent when this wl_buffer is no longer used by the compositor.

For more information on when release events may or may not be sent, and what consequences it has, please see the description of wl_surface.attach.

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.

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.

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.

Destroy the 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.

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_data_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.

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

This event indicates the actions offered by the data source. It will be sent immediately after creating the wl_data_offer object, or anytime the source side changes its offered actions through wl_data_source.set_actions.

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.

This request adds a mime type to the set of mime types advertised to targets. Can be called several times to offer multiple types.

Destroy the data source.

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.

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.

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

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.

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.

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.

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.

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. If source is destroyed, the drag-and-drop session will be cancelled.

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.offset requests 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 input region is ignored for wl_surfaces with the role of a drag-and-drop icon.

The given source may not be used in any further set_selection or start_drag requests. Attempting to reuse a previously-used source may send a used_source error.

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.

The given source may not be used in any further set_selection or start_drag requests. Attempting to reuse a previously-used source may send a used_source error.

This request destroys the data device.

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.

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.

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.

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.

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.

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. Switching surface with keyboard focus within the same client doesn't mean a new selection will be sent. The client must destroy the previous selection data_offer, if any, upon receiving this event.

Create a new data source.

Create a new data device for a given seat.

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").

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.

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

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).

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).

Map the surface as a toplevel surface.

A toplevel surface is not fullscreen, maximized or transient.

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.

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.

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.

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.

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.

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.

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

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.

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.

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.

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

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.

Deletes the surface and invalidates its object ID.

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 at commit time the supplied buffer size must be an integer multiple of the buffer_scale. If that's not the case, an invalid_size error is sent.

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. Setting anything other than 0 as x and y arguments is discouraged, and should instead be replaced with using the separate wl_surface.offset request.

When the bound wl_surface version is 5 or higher, passing any non-zero x or y is a protocol violation, and will result in an 'invalid_offset' error being raised. The x and y arguments are ignored and do not change the pending state. To achieve equivalent semantics, use wl_surface.offset.

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.

If a pending wl_buffer has been committed to more than one wl_surface, the delivery of wl_buffer.release events becomes undefined. A well behaved client should not rely on wl_buffer.release events in this case. Alternatively, a client could create multiple wl_buffer objects from the same backing storage or use a protocol extension providing per-commit release notifications.

Destroying the wl_buffer after wl_buffer.release does not change the surface contents. Destroying the wl_buffer before wl_buffer.release is allowed as long as the underlying buffer storage isn't re-used (this can happen e.g. on client process termination). However, if the client destroys the wl_buffer before receiving the wl_buffer.release event and mutates the underlying buffer storage, 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.

If a pending wl_buffer has been destroyed, the result is not specified. Many compositors are known to remove the surface content on the following wl_surface.commit, but this behaviour is not universal. Clients seeking to maximise compatibility should not destroy pending buffers and should ensure that they explicitly remove content from surfaces, even after destroying buffers.

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.

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.

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.

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.

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

A commit request atomically creates a content update from the pending state, even if the pending state has not been touched. The content update is placed in a queue until it becomes active. After commit, the new pending state is as documented for each related request.

When the content update is applied, the wl_buffer is applied before all other state. This means that all coordinates in double-buffered state are relative to the newly attached wl_buffers, except for wl_surface.attach itself. If there is no newly attached wl_buffer, the coordinates are relative to the previous content update.

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.

This request sets the transformation that the client has already applied to the content of the buffer. The accepted values for the transform parameter are the values for wl_output.transform.

The compositor applies the inverse of this transformation whenever it uses the buffer contents.

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.

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 greater than 0 the invalid_scale protocol error is raised.

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.

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.

The exact semantics of wl_surface.offset are role-specific. Refer to the documentation of specific roles for more information.

Surface location offset is double-buffered state, see wl_surface.commit.

This request is semantically equivalent to and the replaces the x and y arguments in the wl_surface.attach request in wl_surface versions prior to 5. See wl_surface.attach for details.

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.

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.

Clients should not use the number of outputs the surface is on for frame throttling purposes. The surface might be hidden even if no leave event has been sent, and the compositor might expect new surface content updates even if no enter event has been sent. The frame event should be used instead.

This event indicates the preferred buffer scale for this surface. It is sent whenever the compositor's preference changes.

Before receiving this event the preferred buffer scale for this surface is 1.

It is intended that scaling aware clients use this event to scale their content and use wl_surface.set_buffer_scale to indicate the scale they have rendered with. This allows clients to supply a higher detail buffer.

The compositor shall emit a scale value greater than 0.

This event indicates the preferred buffer transform for this surface. It is sent whenever the compositor's preference changes.

Before receiving this event the preferred buffer transform for this surface is normal.

Applying this transformation to the surface buffer contents and using wl_surface.set_buffer_transform might allow the compositor to use the surface buffer more efficiently.

These errors can be emitted in response to wl_surface requests.

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. The missing_capability error will be sent in this case.

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. The missing_capability error will be sent in this case.

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. The missing_capability error will be sent in this case.

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

This is sent on binding to the seat global or 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.

In a multi-seat configuration the seat name can be used by clients to help identify which physical devices the seat represents.

The seat name is a UTF-8 string with no convention defined for its contents. Each name is unique among all wl_seat globals. The name is only guaranteed to be unique for the current compositor instance.

The same seat names are used for all clients. Thus, the name can be shared across processes to refer to a specific wl_seat global.

The name event is sent after binding to the seat global, and should be sent before announcing capabilities. This event only sent once per seat object, and the name does not change over the lifetime of the wl_seat global.

Compositors may re-use the same seat name if the wl_seat global is destroyed and re-created later.

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

These errors can be emitted in response to wl_seat requests.

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 wl_surface.offset requests to the pointer surface, hotspot_x and hotspot_y are decremented by the x and y parameters passed to the request. The offset must be applied 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 input region is ignored for wl_surfaces with the role of a cursor. When the use as a cursor ends, the wl_surface is unmapped.

The serial parameter must match the latest wl_pointer.enter serial number sent to the client. Otherwise the request will be ignored.

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.

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.

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.

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

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.

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.

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.

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.

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.

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 is deprecated with wl_pointer version 8 - this event is not sent to clients supporting version 8 or later.

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. A wl_pointer.frame must not contain more than one axis_discrete event per axis type.

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.

Discrete high-resolution scroll information.

This event carries high-resolution wheel scroll information, with each multiple of 120 representing one logical scroll step (a wheel detent). For example, an axis_value120 of 30 is one quarter of a logical scroll step in the positive direction, a value120 of -240 are two logical scroll steps in the negative direction within the same hardware event. Clients that rely on discrete scrolling should accumulate the value120 to multiples of 120 before processing the event.

The value120 must not be zero.

This event replaces the wl_pointer.axis_discrete event in clients supporting wl_pointer version 8 or later.

Where a wl_pointer.axis_source event occurs in the same wl_pointer.frame, the axis source applies to this event.

The order of wl_pointer.axis_value120 and wl_pointer.axis_source is not guaranteed.

Relative directional information of the entity causing the axis motion.

For a wl_pointer.axis event, the wl_pointer.axis_relative_direction event specifies the movement direction of the entity causing the wl_pointer.axis event. For example: - if a user's fingers on a touchpad move down and this causes a wl_pointer.axis vertical_scroll down event, the physical direction is 'identical' - if a user's fingers on a touchpad move down and this causes a wl_pointer.axis vertical_scroll up scroll up event ('natural scrolling'), the physical direction is 'inverted'.

A client may use this information to adjust scroll motion of components. Specifically, enabling natural scrolling causes the content to change direction compared to traditional scrolling. Some widgets like volume control sliders should usually match the physical direction regardless of whether natural scrolling is active. This event enables clients to match the scroll direction of a widget to the physical direction.

This event does not occur on its own, it is coupled with a wl_pointer.axis event that represents this axis value. The protocol guarantees that each axis_relative_direction 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_relative_direction and its coupled axis event.

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

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

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

Describes the axis types of scroll events.

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.

This specifies the direction of the physical motion that caused a wl_pointer.axis event, relative to the wl_pointer.axis direction.

This event provides a file descriptor to the client which can be memory-mapped in read-only mode 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.

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

The compositor must send the wl_keyboard.modifiers event after this event.

In the wl_keyboard logical state, this event sets the active surface to the surface argument and the keys currently logically down to the keys in the keys argument. The compositor must not send this event if the wl_keyboard already had an active surface immediately before this event.

Clients should not use the list of pressed keys to emulate key-press events. The order of keys in the list is unspecified.

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.

In the wl_keyboard logical state, this event resets all values to their defaults. The compositor must not send this event if the active surface of the wl_keyboard was not equal to the surface argument immediately before this event.

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

The key is a platform-specific key code that can be interpreted by feeding it to the keyboard mapping (see the keymap event).

If this event produces a change in modifiers, then the resulting wl_keyboard.modifiers event must be sent after this event.

In the wl_keyboard logical state, this event adds the key to the keys currently logically down (if the state argument is pressed) or removes the key from the keys currently logically down (if the state argument is released). The compositor must not send this event if the wl_keyboard did not have an active surface immediately before this event. The compositor must not send this event if state is pressed (resp. released) and the key was already logically down (resp. was not logically down) immediately before this event.

Since version 10, compositors may send key events with the "repeated" key state when a wl_keyboard.repeat_info event with a rate argument of 0 has been received. This allows the compositor to take over the responsibility of key repetition.

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

The compositor may send this event without a surface of the client having keyboard focus, for example to tie modifier information to pointer focus instead. If a modifier event with pressed modifiers is sent without a prior enter event, the client can assume the modifier state is valid until it receives the next wl_keyboard.modifiers event. In order to reset the modifier state again, the compositor can send a wl_keyboard.modifiers event with no pressed modifiers.

In the wl_keyboard logical state, this event updates the modifiers and group.

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.

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

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

Since version 10, the key can be in a "repeated" pseudo-state which means the same as "pressed", but is used to signal repetition in the key event.

The key may only enter the repeated state after entering the pressed state and before entering the released state. This event may be generated multiple times while the key is down.

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.

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.

A touch point has changed coordinates.

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.

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.

No frame event is required after the cancel event.

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.

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.

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

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).

The geometry event will be followed by a done event (starting from version 2).

Clients should use wl_surface.preferred_buffer_transform instead of the transform advertised by this event to find the preferred buffer transform to use for a surface.

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 name and description.

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.

Non-current modes are deprecated. A compositor can decide to only advertise the current mode and never send other modes. Clients should not rely on non-current modes.

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).

The mode event will be followed by a done event (starting from version 2).

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.

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.

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. The compositor will emit a non-zero, positive value for scale. 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.

Clients should use wl_surface.preferred_buffer_scale instead of this event to find the preferred buffer scale to use for a surface.

The scale event will be followed by a done event.

Many compositors will assign user-friendly names to their outputs, show them to the user, allow the user to refer to an output, etc. The client may wish to know this name as well to offer the user similar behaviors.

The name is a UTF-8 string with no convention defined for its contents. Each name is unique among all wl_output globals. The name is only guaranteed to be unique for the compositor instance.

The same output name is used for all clients for a given wl_output global. Thus, the name can be shared across processes to refer to a specific wl_output global.

The name is not guaranteed to be persistent across sessions, thus cannot be used to reliably identify an output in e.g. configuration files.

Examples of names include 'HDMI-A-1', 'WL-1', 'X11-1', etc. However, do not assume that the name is a reflection of an underlying DRM connector, X11 connection, etc.

The name event is sent after binding the output object. This event is only sent once per output object, and the name does not change over the lifetime of the wl_output global.

Compositors may re-use the same output name if the wl_output global is destroyed and re-created later. Compositors should avoid re-using the same name if possible.

The name event will be followed by a done event.

Many compositors can produce human-readable descriptions of their outputs. The client may wish to know this description as well, e.g. for output selection purposes.

The description is a UTF-8 string with no convention defined for its contents. The description is not guaranteed to be unique among all wl_output globals. Examples might include 'Foocorp 11" Display' or 'Virtual X11 output via :1'.

The description event is sent after binding the output object and whenever the description changes. The description is optional, and may not be sent at all.

The description event will be followed by a done event.

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

This describes transformations that clients and compositors apply to buffer contents.

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.

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

Destroy the region. This will invalidate the object ID.

Add the specified rectangle to the region.

Subtract the specified rectangle from the region.

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.

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 the bad_surface 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.

The parent surface must not be one of the child surface's descendants, and the parent must be different from the child surface, otherwise the bad_parent protocol error is raised.

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

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. The wl_surface is unmapped immediately.

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.

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.

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.

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

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

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.

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.

This request destroys a wl_registry object.

The client should no longer use the wl_registry after making this request.

The compositor will emit a wl_display.delete_id event with the object ID of the registry and will no longer emit any events on the registry. The client should re-use the object ID once it receives the wl_display.delete_id event.