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Add foreign toplevel icon protocol. #2

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271 changes: 271 additions & 0 deletions protocols/shell-foreign-toplevel-icon-v1.xml
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<?xml version="1.0" encoding="UTF-8"?>
<protocol name="shell_foreign_toplevel_icon_v1">
<copyright>
Copyright © 2025 outfoxxed

Permission to use, copy, modify, distribute, and sell this
software and its documentation for any purpose is hereby granted
without fee, provided that the above copyright notice appear in
all copies and that both that copyright notice and this permission
notice appear in supporting documentation, and that the name of
the copyright holders not be used in advertising or publicity
pertaining to distribution of the software without specific,
written prior permission. The copyright holders make no
representations about the suitability of this software for any
purpose. It is provided "as is" without express or implied
warranty.

THE COPYRIGHT HOLDERS DISCLAIM ALL WARRANTIES WITH REGARD TO THIS
SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND
FITNESS, IN NO EVENT SHALL THE COPYRIGHT HOLDERS BE LIABLE FOR ANY
SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN
AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION,
ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF
THIS SOFTWARE.
</copyright>

<description summary="protocol for foreign toplevel icon discovery">
This protocol allows clients to discover icons set for foreign toplevel
windows from client provided pixel buffers or XDG icons.

A toplevel icon represents the individual toplevel (unlike the application
or launcher icon, which represents the application as a whole), and may be
shown in window switchers, window overviews and taskbars that list
individual windows.

The key words "must", "must not", "required", "shall", "shall not",
"should", "should not", "recommended", "may", and "optional" in this
document are to be interpreted as described in IETF RFC 2119.

Warning! The protocol described in this file is intended as a stopgap
and is expected to be superseded by a solution in wayland-protocols.
Clients should not assume this protocol will continue to exist in the
future.
</description>

<interface name="shell_foreign_toplevel_icon_manager_v1" version="1">
<description summary="interface for foreign toplevel icon discovery">
This interface allows clients to discover icons set for foreign toplevels.
</description>

<enum name="error">
<entry name="uncommitted"
summary="a get_handle request was made prior to commit"
value="1"/>
<entry name="live_icon_handles"
summary="the manager was destroyed without destroying all icon handles"
value="2"/>
</enum>

<request name="destroy" type="destructor">
<description summary="destroy the manager">
Destroy the manager. It is an error to destroy the manager without
destroying all icon handles created by it.
</description>
</request>

<request name="commit">
<description summary="commit the client's icon size preference">
Commit the client's icon size preferences.

May be sent multiple times. Each commit creates a new list,
discarding preferred_size requests from the prior commit.
</description>
</request>

<request name="preferred_size">
<description summary="add a preferred icon size">
Indicates an icon size that the client would prefer to have available.
The compositor should pass this request on to foreign clients, but
this preference may be ignored.

A sequence of preferred_size events must be finished with a 'done'
event. If the client has no size preferences, it must still send
the 'commit' request.

The client may revise its size preferences at any time by sending
a new preferred size list followed by another commit.
</description>

<arg name="size", type="int"/>
</request>

<request name="get_handle">
<description summary="create a new icon handle">
Creates a new icon handle for the given toplevel.

This request must not be made before the first commit request.
</description>

<arg name="handle" type="new_id" interface="shell_foreign_toplevel_icon_handle_v1"/>
<arg name="toplevel" type="object" interface="ext_foreign_toplevel_handle_v1"/>
</request>

<event name="icon">
<description summary="a new icon has been provided">
This event is emitted when an icon that the client does not have
a reference to is required to send the
shell_foreign_toplevel_icon_handle_v1.icon event.

Multiple toplevel icon handles may refer to the same icon
simultaneously.
</description>

<arg name="icon" type="new_id" interface="shell_foreign_toplevel_icon_v1"/>
</event>
</interface>

<interface name="shell_foreign_toplevel_icon_handle_v1" version="1">
<description summary="a handle referencing a foreign toplevel's icon">
A handle tracking the current icon of a foreign toplevel.
</description>

<request name="destroy" type="destructor">
<description summary="">
This request destroys the icon handle and instructs the compositor
to stop sending 'icon' events for icons it would receive.

Any icons for which this toplevel is the only user will receive
a 'finished' event, including new icons sent before the
compositor has processed this request.
</description>
</request>

<event name="icon">
<description summary="a new icon has been set for this toplevel">
Sent when a new icon is set for this toplevel.

A null icon indicates that the toplevel's icon has been unset and
the client should fall back on a different strategy such as
desktop entries for the toplevel's icon.

Upon object creation, an icon event must be sent, with either an icon
object or null if the toplevel has not set an icon.
</description>

<arg name="icon" type="object" interface="shell_foreign_toplevel_icon_v1"/>
</event>
</interface

<interface name="shell_foreign_toplevel_icon_v1" version="1">
<description summary="an icon used by foreign toplevels">
An icon used by one or more foreign toplevels.
</description>

<enum name="error">
<entry name="missing_buffer"
summary="a copy_buffer request was issued for a buffer that does not exist"
value="1"/>
<entry name="destroyed_while_unfinished"
summary="attempted to destroy an icon which has not received a finished event"
value="2"/>
</enum>

<request name="destroy">
<description summary="destroys the icon">
This request destroys the icon object. Destroying the icon
prior to receiving a 'finished' event is a protocol error.
</description>
</request>

<event name="finished">
<description summary="the compositor is finished with this icon">
This event indicates that this icon will not be used in further
'shell_foreign_toplevel_icon_handle_v1.icon' events and is safe
to destroy.

This event may be sent in response to a release request or
when no toplevel icon handles refer to this icon anymore.
</description>
</event>

<request name="release">
<description summary="attempt to release the icon">
This request indicates that the client would like to destroy
the icon object.

The compositor must respond by either sending a
'shell_foreign_toplevel_icon_handle_v1.icon' event referencing
this icon, or sending the 'finished' event to this object.
</description>
</request>

<request name="copy_icon">
<description summary="copy a shm backed icon">
Copy an icon listed by 'buffer' into a client provided buffer.

The provided size and format must have been listed by 'buffer'
in the last icon option group.
</description>

<arg name="size" type="uint"/>
<arg name="format" type="uint" enum="wl_shm.format"/>
<arg name="buffer" type="object" interface="wl_buffer"/>
</request>

<event name="done">
<description summary="all icon representation have been sent">
This event is sent after all 'add_buffer' events and optionally
an 'icon_name' event have been sent.
</description>
</event>

<event name="icon_name">
<description summary="set an icon name">
This event assigns an icon name to this icon. It must not be
sent more than once, and must not be sent after 'done'.

The icon refered to by the provided name should be resolved
according to the XDG icon theme specification[1] using the
environment's current icon theme.

[1]: https://specifications.freedesktop.org/icon-theme-spec/icon-theme-spec-latest.html
</description>

<arg name="name" type="string"/>
</event>

<event name="add_buffer">
<description summary="provides an icon buffer">
This event exposes an available pixel buffer representing the icon.
Multiple add_buffer events may be sent at different sizes, scales,
and buffer formats. The event must not be sent after 'done'.

The buffer must be backed by wl_shm and must be square.
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Is this enforced somewhere else in icon specs or protocol? Idk but seems a bit strange a requirement

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Its enforced by xdg-toplevel-icon. The compositor could render it into a dmabuf but I see no reason to make it do that.

</description>

<arg name="size" type="uint" summary="the width and height of the icon in pixels"/>
<arg name="scale" type="uint" summary="the scaling factor of the icon"/>
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No fractional?

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xdg-toplevel-icon only exposes integer scales, but we could make this a float in case that ever changes.

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A float would be inconsistent with the fractional scale protocol which expects a uint representing "the numerator of a fraction with a denominator of 120".

I'd suggest the better option here might be to add an additional event arg (scale_fractional) that represents that, and let the client figure out which one it needs. I'm not sure where you'd need it though? Would the scale ever differ from the one advertised by the fractional scale protocol?

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If toplevel icon only has integer scales then it's probably fine to leave as uint (idk if there are any plans to change it).

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Also general comment about the fractional scale protocol: ppl are already hitting issues with its quantization to 1/120 (common scale/resolution combos are not exactly representable), so it's possible that it'll change to a float in the future

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In that case lets just leave it as an int and mirror whatever xdg-toplevel-icon does if changed.

<arg name="format" type="uint" enum="wl_shm.format"/>
</event>

<request name="copy_buffer">
<description summary="copy an icon to a client provided buffer">
This request asks the compositor to copy one of the icon's available
pixel buffers to the provided client buffer.

The selected buffer will be determined based on the format and width
of the provided client buffer, as well as the provided scale. If the
provided buffer and scale do not match a buffer associated with the icon,
the 'missing_buffer' error will be raised.

The 'buffer_copied' event will be sent once the compositor has finished
copying the image to the client buffer. The wl_buffer.release event is unused.
</description>

<arg name="buffer" type="object" interface="wl_buffer" summary="the target buffer"/>
<arg name="scale" type="uint" summary="the scaling factor of the icon"/>
</request>

<event name="buffer_copied">
<description summary="the compositor has finished copying into a buffer">
This event is sent once the compositor has finished copying pixel
data into a provided client buffer.

If multiple 'copy_buffer' requests were made, the received events
must refer to buffers in the same order the requests were made.
</description>
</event>
</interface>
</protocol>