[RFC PATCH v3] Add xdg-output protocol

Tue Jul 18 12:57:34 UTC 2017

On Thu,  6 Jul 2017 16:01:25 +0200
Olivier Fourdan <ofourdan at redhat.com> wrote:

> This protocol aims at describing outputs in 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.
> 
> The goal is to gradually move the desktop specific concepts out of the
> core wl_output protocol.
> 
> For now it just features the position and logical size which describe
> the output position and size in the global compositor space.
> 
> Signed-off-by: Olivier Fourdan <ofourdan at redhat.com>
> ---
>  v2: use "destroy" instead of "release" for destructor
>  v3: adopt a more conventional global factory interface with a 
>      get_xdg_output() method, add some clarification and example.
> 
>  Makefile.am                                    |   1 +
>  unstable/xdg-output/README                     |   4 +
>  unstable/xdg-output/xdg-output-unstable-v1.xml | 160 +++++++++++++++++++++++++
>  3 files changed, 165 insertions(+)
>  create mode 100644 unstable/xdg-output/README
>  create mode 100644 unstable/xdg-output/xdg-output-unstable-v1.xml
> 
> diff --git a/Makefile.am b/Makefile.am
> index e693afa..6c696aa 100644
> --- a/Makefile.am
> +++ b/Makefile.am
> @@ -12,6 +12,7 @@ unstable_protocols =								\
>  	unstable/tablet/tablet-unstable-v2.xml			                \
>  	unstable/xdg-foreign/xdg-foreign-unstable-v1.xml			\
>  	unstable/idle-inhibit/idle-inhibit-unstable-v1.xml			\
> +	unstable/xdg-output/xdg-output-unstable-v1.xml				\
>  	$(NULL)
>  
>  stable_protocols =								\
> diff --git a/unstable/xdg-output/README b/unstable/xdg-output/README
> new file mode 100644
> index 0000000..e42b711
> --- /dev/null
> +++ b/unstable/xdg-output/README
> @@ -0,0 +1,4 @@
> +xdg_output protocol
> +
> +Maintainers:
> +Olivier Fourdan <ofourdan at redhat.com>
> diff --git a/unstable/xdg-output/xdg-output-unstable-v1.xml b/unstable/xdg-output/xdg-output-unstable-v1.xml
> new file mode 100644
> index 0000000..74b5762
> --- /dev/null
> +++ b/unstable/xdg-output/xdg-output-unstable-v1.xml
> @@ -0,0 +1,160 @@
> +<?xml version="1.0" encoding="UTF-8"?>
> +<protocol name="xdg_output_unstable_v1">
> +

...

> +  <interface name="zxdg_output_manager" version="1">

Hi,

missing major version as per unstable protocol policy.

> +    <description summary="manage xdg_output objects">
> +      A global factory interface for xdg_output objects.
> +    </description>
> +
> +    <request name="destroy" type="destructor">
> +      <description summary="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.

Might want to add: Any objects already created through this instance
are not affected.

> +      </description>
> +    </request>
> +
> +    <request name="get_xdg_output">
> +      <description summary="create an xdg output from a wl_output">
> +	This creates a new xdg_output object for the given wl_output.
> +      </description>
> +      <arg name="id" type="new_id" interface="zxdg_output"/>
> +      <arg name="output" type="object" interface="wl_output"/>
> +    </request>
> +  </interface>
> +
> +  <interface name="zxdg_output" version="1">

Missing major version as per unstable protocol policy.

> +    <description summary="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.

I was about to ask about clone mode behaviour but realised this is
explicitly tied to how wl_outputs are advertised.

> +    </description>
> +
> +    <request name="destroy" type="destructor">
> +      <description summary="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.
> +      </description>
> +    </request>
> +
> +    <event name="logical_position">
> +      <description summary="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.
> +      </description>
> +      <arg name="x" type="int"
> +	   summary="x position within the global compositor space"/>
> +      <arg name="y" type="int"
> +	   summary="y position within the global compositor space"/>
> +    </event>
> +
> +    <event name="logical_size">
> +      <description summary="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 to 2560×1620.
> +
> +	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).
> +      </description>
> +      <arg name="width" type="int"
> +	   summary="width of the mode in global compositor space"/>
> +      <arg name="height" type="int"
> +	   summary="height of the mode in global compositor space"/>

Replace "mode" with a more appropriate word or remove it. Mode refers
to the hardware video mode, and I think it is a bit confusing to talk
about size of a mode in global compositor space, even though it is
accurate.

> +    </event>
> +
> +    <event name="done">
> +      <description summary="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.
> +      </description>
> +    </event>
> +
> +  </interface>
> +</protocol>
> +

Otherwise looks good, so:
Acked-by: Pekka Paalanen <pekka.paalanen at collabora.co.uk>

Thanks,
pq
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