[PATCH v4 wayland-protocols 4/4] tablet: Add pad support to the tablet protocol

[Peter Hutterer]

On Tue, Jun 28, 2016 at 11:21:50PM +0200, Carlos Garnacho wrote:
> The pad's interface is similar to the tool interface, a client is notified of
> the pad after the tablet_added event.
> 
> The pad has three functionalities: buttons, rings and strips.
> Buttons are fairly straightforward, rings and strips are separate interfaces
> with a pointer-axis-like source/value/frame events.
> The two interfaces are effectively identical but for the actual value they
> send (degrees vs normalized position).
> 
> Buttons are sequentially indexed starting with zero, unlike other protocols
> where a linux/input.h-style semantic event code is used. Since we expect all
> buttons to have client-specific functionality, an additional event tells the
> client when a given button index is not available, usually because the
> compositor assignes some function to it (e.g. mode switching, see below).
> 
> Specific to the pad device is the set_feedback request which enables a client
> to set a user-defined string to display for an OSD on the current mappings.
> This request is available for buttons, rings and strips.
> 
> Finally, the pad supports groups, effectively sets of button/ring/strip
> configurations. Those groups may have multiple modes each, so that
> users/clients may map several actions to a single element.
> 
> Signed-off-by: Carlos Garnacho <carlosg at gnome.org>
> Signed-off-by: Peter Hutterer <peter.hutterer at who-t.net>
> Reviewed-by: Jason Gerecke <jason.gerecke at wacom.com>
> ---
> 
> Changes since v3:
> 
> - Added wp_tablet_pad_group, this divides buttons/strips/rings into subsets,
>   groups may have separate modes which are announced through a mode_switch
>   event.
> - Added serial argument to the set_feedback requests, to be obtained from
>   the wp_tablet_pad_group.mode_switch events.
> - Now that groups announce the buttons belonging to those, the
>   wp_tablet_pad.buttons_reserved event has been removed in favor of implicit
>   information (i.e. buttons not belonging to any group are reserved by the
>   compositor).
> - Added wp_tablet_pad.path event, similar to wp_tablet.path
> - Button indices are now explicitly mentioned in docs where relevant
> - Fixed several typos and improved docs here and there
> 
>  unstable/tablet/tablet-unstable-v2.xml | 546 ++++++++++++++++++++++++++++++++-
>  1 file changed, 543 insertions(+), 3 deletions(-)
> 
> diff --git a/unstable/tablet/tablet-unstable-v2.xml b/unstable/tablet/tablet-unstable-v2.xml
> index 5248c64..63172e2 100644
> --- a/unstable/tablet/tablet-unstable-v2.xml
> +++ b/unstable/tablet/tablet-unstable-v2.xml
> @@ -172,6 +172,22 @@
>        </description>
>        <arg name="id" type="new_id" interface="zwp_tablet_tool_v2" summary="the newly added tablet tool"/>
>      </event>
> +
> +    <event name="pad_added">
> +      <description summary="new pad notification">
> +	This event is sent whenever a new pad is known to the system. Typically,
> +	pads are physically attached to tablets and a pad_added event is
> +	sent immediately after the wp_tablet_seat.tablet_added.
> +	However, some standalone pad devices logically attach to tablets at
> +	runtime, and the client must wait for wp_tablet_pad.enter to know
> +	the tablet a pad is attached to.
> +
> +	This event only provides the object id of the pad. All further
> +	features (buttons, strips, rings) are sent through the wp_tablet_pad
> +	interface.
> +      </description>
> +      <arg name="id" type="new_id" interface="zwp_tablet_pad_v2" summary="the newly added pad"/>
> +    </event>
>    </interface>
>  
>    <interface name="zwp_tablet_tool_v2" version="1">
> @@ -508,9 +524,9 @@
>        <description summary="Wheel delta event">
>  	Sent whenever the wheel on the tool emits an event. This event
>  	contains two values for the same axis change. The degrees value is
> -	in degrees in the same orientation as the wl_pointer.vertical_scroll
> -	axis. The clicks value is in discrete logical clicks of the mouse
> -	wheel. This value may be zero if the movement of the wheel was less
> +	in the same orientation as the wl_pointer.vertical_scroll axis. The
> +	clicks value is in discrete logical clicks of the mouse wheel. This
> +	value may be zero if the movement of the wheel was less
>  	than one logical click.

this hunk looks like rebase detritus
>  
>  	Clients should choose either value and avoid mixing degrees and
> @@ -636,4 +652,528 @@
>      </event>
>    </interface>
>  
> +  <interface name="zwp_tablet_pad_ring_v2" version="1">
> +    <description summary="pad ring">
> +      A circular interaction area.

I think it'd be best to add " such as the touch ring on the Wacom Intuos Pro
series tablets", just to save us from having to explain what a ring is ;)
Same goes for the strip.

[...]
> +    <enum name="source">
> +      <description summary="ring axis source">
> +     Describes the source types for ring events. This indicates to the
> +     client how a ring event was physically generated; a client may
> +     adjust the user interface accordingly. For example, events
> +     from a "finger" source may trigger kinetic scrolling.
> +      </description>
> +      <entry name="finger" value="1" summary="finger"/>
> +    </enum>
> +
> +    <event name="source">
> +      <description summary="ring event source">
> +     Source information for ring events.
> +
> +     This event does not occur on its own. It is sent before a
> +     wp_tablet_pad_ring.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
> +     wp_tablet_pad_ring.source.finger, a wp_tablet_pad_ring.stop event
> +     will be sent when the user lifts the finger off the device.
> +
> +     This event is optional. If the source is unknown for an interaction,
> +     no event is sent.
> +      </description>
> +      <arg name="source" type="uint" summary="the event source"/>

this should ref the enum, same with the strip and the button event.

[...]

> +
> +  <interface name="zwp_tablet_pad_group_v2" version="2">
> +    <description summary="a set of buttons, rings and strips">
> +      A pad group describes a distinct (sub)set of buttons, rings and strips
> +      present in the tablet. The criteria of this grouping is usually positional,
> +      eg. if a tablet has buttons on left and right sides, 2 groups will be

"on the left and right side"

> +      presented. Clients should perform no further assumptions on the actual

s/further//
I'm not sure you can perform assumptions but some native english speaker may
have more idea here. :)

> +      position of each group.
> +
> +      Pad groups will announce their features during pad initialization. Between
> +      the corresponding wp_tablet_pad.group event and wp_tablet_pad_group.done, the
> +      pad group will announce the buttons, rings and strips comprised in it,
> +      plus the number of supported modes.
> +
> +      Modes are a mechanism to allow multiple groups of actions for every element
> +      in the pad group. The number of groups and available modes in each is
> +      persistent across device plugs. The current mode is user-switchable and
> +      compositor-global, it will be announced through the
> +      wp_tablet_pad_group.mode_switch event both after wp_tablet_pad.enter, and
> +      whenever it is switched.
> +
> +      The current mode logically applies to all elements in the pad group,
> +      although it is at clients' discretion whether to actually perform different
> +      actions, and/or issue the respective .set_feedback requests to notify the
> +      compositor.

for extra clarification, add "see wl_tablet_pad_group.mode_switch for more
details".

Reviewed-by: Peter Hutterer <peter.hutterer at who-t.net>

Cheers,
   Peter