XDG output

Protocol to describe output regions

This protocol aims at describing outputs in a way which is more in line with the concept of an output on desktop oriented systems.

Some information are more specific to the concept of an output for a desktop oriented system and may not make sense in other applications, such as IVI systems for example.

Typically, the global compositor space on a desktop system is made of a contiguous or overlapping set of rectangular regions.

Some of the information provided in this protocol might be identical to their counterparts already available from wl_output, in which case the information provided by this protocol should be preferred to their equivalent in wl_output. The goal is to move the desktop specific concepts (such as output location within the global compositor space, the connector name and types, etc.) out of the core wl_output protocol.

Warning! The protocol described in this file is experimental and backward incompatible changes may be made. Backward compatible changes may be added together with the corresponding interface version bump. Backward incompatible changes are done by bumping the version number in the protocol and interface names and resetting the interface version. Once the protocol is to be declared stable, the 'z' prefix and the version number in the protocol and interface names are removed and the interface version number is reset.

Manage xdg_output objects

A global factory interface for xdg_output objects.

destroy()
Destroy the xdg_output_manager object

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

Any objects already created through this instance are not affected.

get_xdg_output(id: new_id<zxdg_output_v1>, output: object<wl_output>)
Argument
Type
Description
idnew_id<zxdg_output_v1>
outputobject<wl_output>
Create an xdg output from a wl_output

This creates a new xdg_output object for the given wl_output.


Compositor logical output region

An xdg_output describes part of the compositor geometry.

This typically corresponds to a monitor that displays part of the compositor space.

For objects version 3 onwards, after all xdg_output properties have been sent (when the object is created and when properties are updated), a wl_output.done event is sent. This allows changes to the output properties to be seen as atomic, even if they happen via multiple events.

destroy
Type: destructor
destroy()
Destroy the xdg_output object

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

logical_position(x: int, y: int)
Argument
Type
Description
xint
x position within the global compositor space
yint
y position within the global compositor space
Position of the output within the global compositor space

The position event describes the location of the wl_output within the global compositor space.

The logical_position event is sent after creating an xdg_output (see xdg_output_manager.get_xdg_output) and whenever the location of the output changes within the global compositor space.

logical_size(width: int, height: int)
Argument
Type
Description
widthint
width in global compositor space
heightint
height in global compositor space
Size of the output in the global compositor space

The logical_size event describes the size of the output in the global compositor space.

For example, a surface without any buffer scale, transformation nor rotation set, with the size matching the logical_size will have the same size as the corresponding output when displayed.

Most regular Wayland clients should not pay attention to the logical size and would rather rely on xdg_shell interfaces.

Some clients such as Xwayland, however, need this to configure their surfaces in the global compositor space as the compositor may apply a different scale from what is advertised by the output scaling property (to achieve fractional scaling, for example).

For example, for a wl_output mode 3840×2160 and a scale factor 2:

- A compositor not scaling the surface buffers will advertise a logical size of 3840×2160,

- A compositor automatically scaling the surface buffers will advertise a logical size of 1920×1080,

- A compositor using a fractional scale of 1.5 will advertise a logical size of 2560×1440.

For example, for a wl_output mode 1920×1080 and a 90 degree rotation, the compositor will advertise a logical size of 1080x1920.

The logical_size event is sent after creating an xdg_output (see xdg_output_manager.get_xdg_output) and whenever the logical size of the output changes, either as a result of a change in the applied scale or because of a change in the corresponding output mode(see wl_output.mode) or transform (see wl_output.transform).

done()
All information about the output have been sent

This event is sent after all other properties of an xdg_output have been sent.

This allows changes to the xdg_output properties to be seen as atomic, even if they happen via multiple events.

For objects version 3 onwards, this event is deprecated. Compositors are not required to send it anymore and must send wl_output.done instead.

name(name: string)
Argument
Type
Description
namestring
output name
Name of this output

Many compositors will assign names to their outputs, show them to the user, allow them to be configured by name, etc. The client may wish to know this name as well to offer the user similar behaviors.

The naming convention is compositor defined, but limited to alphanumeric characters and dashes (-). Each name is unique among all wl_output globals, but if a wl_output global is destroyed the same name may be reused later. The names will also remain consistent across sessions with the same hardware and software configuration.

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 creating an xdg_output (see xdg_output_manager.get_xdg_output). This event is only sent once per xdg_output, and the name does not change over the lifetime of the wl_output global.

description(description: string)
Argument
Type
Description
descriptionstring
output description
Human-readable description of this output

Many compositors can produce human-readable descriptions of their outputs. The client may wish to know this description as well, to communicate the user for various purposes.

The description is a UTF-8 string with no convention defined for its contents. Examples might include 'Foocorp 11" Display' or 'Virtual X11 output via :1'.

The description event is sent after creating an xdg_output (see xdg_output_manager.get_xdg_output) and whenever the description changes. The description is optional, and may not be sent at all.

For objects of version 2 and lower, this event is only sent once per xdg_output, and the description does not change over the lifetime of the wl_output global.


Copyright © 2017 Red Hat Inc.

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice (including the next paragraph) shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.