[PATCH v6 wayland-protocols] Add the tablet protocol

Jason Gerecke killertofu at gmail.com
Thu Mar 3 01:38:17 UTC 2016


A number of tiny fixes, and a couple of questions:

On 02/29/2016 04:09 PM, Peter Hutterer wrote:
> Signed-off-by: Peter Hutterer <peter.hutterer at who-t.net>
> Reviewed-by: Daniel Stone <daniels at collabora.com>
> ---
> Changes to v5:
> - remove leftover statement falsely claminig wp_tablet_tool.destroy requires
>   a remove event first
> 
>  Makefile.am                            |   1 +
>  unstable/tablet/README                 |   4 +
>  unstable/tablet/tablet-unstable-v1.xml | 622 +++++++++++++++++++++++++++++++++
>  3 files changed, 627 insertions(+)
>  create mode 100644 unstable/tablet/README
>  create mode 100644 unstable/tablet/tablet-unstable-v1.xml
> 
> diff --git a/Makefile.am b/Makefile.am
> index 57d0023..a7f838b 100644
> --- a/Makefile.am
> +++ b/Makefile.am
> @@ -7,6 +7,7 @@ unstable_protocols =								\
>  	unstable/xdg-shell/xdg-shell-unstable-v5.xml				\
>  	unstable/relative-pointer/relative-pointer-unstable-v1.xml		\
>  	unstable/pointer-constraints/pointer-constraints-unstable-v1.xml	\
> +	unstable/tablet/tablet-unstable-v1.xml			                \
>  	$(NULL)
>  
>  stable_protocols =								\
> diff --git a/unstable/tablet/README b/unstable/tablet/README
> new file mode 100644
> index 0000000..7ba8e77
> --- /dev/null
> +++ b/unstable/tablet/README
> @@ -0,0 +1,4 @@
> +Tablet protocol
> +
> +Maintainers:
> +Peter Hutterer <peter.hutterer at who-t.net>
> diff --git a/unstable/tablet/tablet-unstable-v1.xml b/unstable/tablet/tablet-unstable-v1.xml
> new file mode 100644
> index 0000000..988f949
> --- /dev/null
> +++ b/unstable/tablet/tablet-unstable-v1.xml
> @@ -0,0 +1,622 @@
> +<?xml version="1.0" encoding="UTF-8"?>
> +<protocol name="tablet_unstable_v1">
> +  <copyright>
> +    Copyright 2014 © Stephen "Lyude" Chandler Paul
> +    Copyright 2015-2016 © 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.
> +  </copyright>
> +  <description summary="Wayland protocol for graphics tablets">
> +    This description provides a high-level overview of the interplay between
> +    the interfaces defined this protocol. For details, see the protocol
> +    specification.
> +
> +    More than one tablet may exist, and device-specifics matter. Tablets are
> +    not represented by a single virtual device like wl_pointer. A client
> +    binds to the tablet manager object which is just a proxy object. From
> +    that, the client requests wp_tablet_manager.get_tablet_seat(wl_seat)
> +    and that returns the actual interface that has all the tablets. With
> +    this indirection, we can avoid merging wp_tablet into the actual wayland
> +    protocol, a long-term benefit.
> +
> +    The wp_tablet_seat sends a "tablet added" for each tablet connected.
> +    That event is followed by descriptive events about the hardware;

Reads a little awkwardly. Perhaps 'The wp_tablet_seat sends a "tablet
added" event for each tablet connected. That is followed...'

> +    currently that includes events for name, vid/pid and
> +    a wp_tablet.path event that describes a local path. This path can be
> +    used to uniquely identify a tablet, or get more information through

s/,//

> +    libwacom.  Emulated or nested tablets can skip any of those, e.g. a
> +    virtual tablet may not have a vid/pid. The sequence of descriptive
> +    events is terminated by a wp_tablet.done event to signal that a client
> +    may now finalize any initialization for that tablet.
> +
> +    Events from tablets require a tool in proximity. Tools are also managed
> +    by the tablet seat, a "tool added" is sent whenever a tool is new to

s/,/;/

Also, similar request as for wording of "tablet added" above.

> +    the compositor. That event is followed by a number of descriptive events
> +    about the hardware; currently that includes capabilities, serial id,
> +    hardware serial and tool type. Similar to the tablet interface, a

"Serial id" and "hardware serial" sound like the same thing, though I
imagine you mean them to refer to different events...

> +    wp_tablet_tool.done event is sent to terminate that initial sequence.
> +
> +    Any event from a tool happens on the wp_tablet_tool interface. When the
> +    tool gets into proximity of the tablet, a proximity_in event is sent on
> +    the wp_tablet_tool interface, listing the tablet and the surface. That
> +    event is followed by a motion event with the coordinates. After that,
> +    it's the usual motion, axis, button, etc. events.
> +    The protocol's serialisation means events are grouped by by

Line break way earlier than necessary. Also "by by" :)

> +    wp_tablet_tool.frame events.
> +
> +    Two special events (that don't exist in X) are down and up. They signal
> +    "tip touching the surface". For tablets without real proximity
> +    detection, the sequence is: proximity_in, motion, down, frame.
> +
> +    When the tool leaves proximity, a proximity_out event is sent. If any
> +    button is still down, a button release event is sent before this
> +    proximity event. These button events are sent in the same frame as the
> +    proximity event to signal to the client that the buttons were held when
> +    the tool left proximity.
> +
> +    If the tool moves out of the surface but stays in proximity (i.e.
> +    between windows), compositor-specific grab policies apply. This usually
> +    means that the proximity-out is delayed until all buttons are released.
> +
> +    Moving a tool physically from one tablet to the other has no real effect
> +    on the protocol, since we already have the tool object from the "tool
> +    added" event. All the information is already there and the proximity
> +    events on both tablets is all a client needs to reconstruct what

s/is/are/

> +    happened.
> +
> +    Some extra axes are normalized, i.e. the client knows the range as
> +    specified in the protocol (e.g. [0, 65535]), the granularity however is
> +    unknown. The current normalized axes are pressure, distance, and slider.
> +
> +    Other extra axes are in physical units as specified in the protocol.
> +    The current extra axes with physical units are tilt, rotation and
> +    wheel rotation.
> +
> +    Since tablets work independently of the pointer controlled by the mouse,
> +    the focus handling is independent too and controlled by proximity.
> +    The wp_tablet_tool.set_cursor request sets a tool-specific cursor.
> +    This cursor surface may be the same as the mouse cursor, and it may be
> +    the same across tools but it is possible to be more fine-grained. For
> +    example, a client may set different cursors for the pen and eraser.
> +
> +    Tools are generally independent of tablets and it is
> +    compositor-specific policy when a tool can removed. Common approaches

s/can/can be/

> +    will likely include some form of removing a tool when all tablets the
> +    tool was used on is removed.
> +
> +    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.
> +  </description>
> +  <interface name="zwp_tablet_manager_v1" version="1">
> +    <description summary="controller object for graphic tablet devices">
> +      An object that provides access to the graphics tablets available on this
> +      system. Any tablet is associated with a seat, to get access to the

Don't particularly like this wording... Maybe "All tablets are"?

> +      actual tablets, use wp_tablet_manager.get_tablet_seat.
> +    </description>
> +
> +    <request name="get_tablet_seat">
> +      <description summary="get the tablet seat">
> +	Get the wp_tablet_seat object for the given seat. This object
> +	provides access to all graphics tablets in this seat.
> +      </description>
> +      <arg name="tablet_seat" type="new_id" interface="zwp_tablet_seat_v1"/>
> +      <arg name="seat" type="object" interface="wl_seat" summary="The wl_seat object to retrieve the tablets for" />
> +    </request>
> +
> +    <request name="destroy" type="destructor">
> +      <description summary="release the memory for the tablet manager object">
> +	Destroy the wp_tablet_manager object. Objects created from this
> +	object are unaffected and should be destroyed separately.
> +      </description>
> +    </request>
> +  </interface>
> +
> +  <interface name="zwp_tablet_seat_v1" version="1">
> +    <description summary="controller object for graphic tablet devices of a seat">
> +      An object that provides access to the graphics tablets available on this
> +      seat. After binding to this interface, the compositor sends a set of
> +      wp_tablet_seat.tablet_added and wp_tablet_seat.tool_added events.
> +    </description>
> +
> +    <request name="destroy" type="destructor">
> +      <description summary="release the memory for the tablet seat object">
> +	Destroy the wp_tablet_seat object. Objects created from this
> +	object are unaffected and should be destroyed separately.
> +      </description>
> +    </request>
> +
> +    <event name="tablet_added">
> +      <description summary="new device notification">
> +	This event is sent whenever a new tablet becomes available on this
> +	seat. This event only provides the object id of the tablet, any
> +	static information about the tablet (device name, vid/pid, etc.) is
> +	sent through the wp_tablet interface.
> +      </description>
> +      <arg name="id" type="new_id" interface="zwp_tablet_v1" summary="the newly added graphics tablet"/>
> +    </event>
> +
> +    <event name="tool_added">
> +      <description summary="a new tool has been used with a tablet">
> +	This event is sent whenever a tool that has not previously been used
> +	with a tablet comes into use. This event only provides the object id
> +	of the tool, any static information about the tool (capabilities,

s/,/;/

> +	type, etc.) is sent through the wp_tablet_tool interface.
> +      </description>
> +      <arg name="id" type="new_id" interface="zwp_tablet_tool_v1" summary="the newly added tablet tool"/>
> +    </event>
> +  </interface>
> +
> +  <interface name="zwp_tablet_tool_v1" version="1">
> +    <description summary="a physical tablet tool">
> +      An object that represents a physical tool that has been, or is
> +      currently in use with a tablet in this seat. Each wp_tablet_tool
> +      object stays valid until the client destroys it; the compositor
> +      reuses the wp_tablet_tool object to indicate that the object's
> +      respective physical tool has come into proximity of a tablet again.
> +
> +      A wp_tablet_tool object's relation to a physical tool depends on the
> +      tablet's ability to report serial numbers. If the tablet supports
> +      this capability, then the object represents a specific physical tool
> +      and can be identified even when used on multiple tablets.
> +
> +      A tablet tool has a number of static characteristics, e.g. tool type,
> +      hardware_serial and capabilities. These capabilities are sent in an
> +      event sequence after the wp_tablet_seat.tool_added event before any
> +      actual events from this tool. This initial event sequence is
> +      terminated by a wp_tablet_tool.done event.
> +
> +      Tablet tool events are grouped by wp_tablet_tool.frame events.
> +      Any events received before a wp_tablet_tool.frame event should be
> +      considered part of the same hardware state change.
> +    </description>
> +
> +    <request name="set_cursor">
> +      <description summary="set the tablet tool's surface">
> +	Sets the surface of the cursor used for this tool on the given
> +	tablet. This request only takes effect if the tool is in proximity
> +	of 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 cursor
> +	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 surface.attach requests to the pointer surface, hotspot_x and
> +	hotspot_y are decremented by the x and y parameters passed to the
> +	request. Attach must be confirmed 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 current and pending input regions of the wl_surface are cleared,
> +	and wl_surface.set_input_region is ignored until the wl_surface is no
> +	longer used as the cursor. When the use as a cursor ends, the current
> +	and pending input regions become undefined, and the wl_surface is
> +	unmapped.
> +
> +	This request gives the surface the role of a cursor. The role
> +	assigned by this request is the same as assigned by
> +	wl_pointer.set_cursor meaning the same surface can be
> +	used both as a wl_pointer cursor and a wp_tablet cursor. If the
> +	surface already has another role, it raises a protocol error
> +	The surface may be used on multiple tablets and across multiple
> +	seats.
> +      </description>
> +      <arg name="serial" type="uint" summary="serial of the enter event"/>
> +      <arg name="surface" type="object" interface="wl_surface" allow-null="true"/>
> +      <arg name="hotspot_x" type="int" summary="x coordinate in surface-relative coordinates"/>
> +      <arg name="hotspot_y" type="int" summary="y coordinate in surface-relative coordinates"/>
> +    </request>
> +
> +    <request name="destroy" type="destructor">
> +      <description summary="destroy the tool object">
> +	This destroys the client's resource for this tool object.
> +      </description>
> +    </request>
> +
> +    <enum name="type">
> +      <description summary="a physical tool type">
> +	Describes the physical type of a tool. The physical type of a tool
> +	generally defines its base usage.
> +
> +	The mouse tool represents a mouse-shaped tool that is not a relative
> +	device but bound to the tablet's surface, providing absolute
> +	coordinates.
> +
> +	The lens tool is a mouse-shaped tool with an attached lens to
> +	provide precision focus.
> +      </description>
> +      <entry name="pen" value="0x140" summary="Pen"/>
> +      <entry name="eraser" value="0x141" summary="Eraser"/>
> +      <entry name="brush" value="0x142" summary="Brush"/>
> +      <entry name="pencil" value="0x143" summary="Pencil"/>
> +      <entry name="airbrush" value="0x144" summary="Airbrush"/>
> +      <entry name="finger" value="0x145" summary="Finger"/>
> +      <entry name="mouse" value="0x146" summary="Mouse"/>
> +      <entry name="lens" value="0x147" summary="Lens"/>
> +    </enum>
> +
> +    <event name="type">
> +      <description summary="tool type">
> +	The tool type is the high-level type of the tool and usually decides
> +	the interaction expected from this tool.
> +
> +	This event is sent in the initial burst of events before the
> +	wp_tablet_tool.done event.
> +      </description>
> +      <arg name="tool_type" type="uint" enum="type" summary="the physical tool type"/>
> +    </event>
> +
> +    <event name="hardware_serial">
> +      <description summary="unique hardware serial number of the tool">
> +	If the physical tool can be identified by a unique 64-bit serial
> +	number, this event notifies the client of this serial number.
> +
> +	If multiple tablets are available in the same seat and the tool is
> +	uniquely identifiable by the serial number, that tool may move
> +	between tablets.
> +
> +	Otherwise, if the tool has no serial number and this event is
> +	missing, the tool is tied to the tablet it first comes into
> +	proximity with. Even if the physical tool is used on multiple
> +	tablets, separate wp_tablet_tool objects will be created, one per
> +	tablet.
> +
> +	This event is sent in the initial burst of events before the
> +	wp_tablet_tool.done event.
> +      </description>
> +      <arg name="hardware_serial_hi" type="uint" summary="the unique serial number of the tool, most significant bits"/>
> +      <arg name="hardware_serial_lo" type="uint" summary="the unique serial number of the tool, least significant bits"/>
> +    </event>
> +
> +    <event name="hardware_id_wacom">
> +      <description summary="hardware id notification in Wacom's format">
> +	This event notifies the client of a hardware id available on this tool.
> +
> +	The hardware id is a device-specific 64-bit id that provides extra
> +	information about the tool in use, beyond the wl_tool.type
> +	enumeration. The format of the id is specific to tablets made by
> +	Wacom Inc. For example, the hardware id of a Wacom Grip
> +	Pen (a stylus) is 0x802.
> +
> +	This event is sent in the initial burst of events before the
> +	wp_tablet_tool.done event.
> +      </description>
> +      <arg name="hardware_id_hi" type="uint" summary="the hardware id, most significant bits"/>
> +      <arg name="hardware_id_lo" type="uint" summary="the hardware id, least significant bits"/>
> +    </event>
> +
> +    <enum name="capability">
> +      <description summary="capability flags for a tool">
> +	Describes extra capabilities on a tablet.
> +
> +	Any tool must provide x and y values, extra axes are
> +	device-specific.
> +      </description>
> +      <entry name="tilt" value="1" summary="Tilt axes"/>
> +      <entry name="pressure" value="2" summary="Pressure axis"/>
> +      <entry name="distance" value="3" summary="Distance axis"/>
> +      <entry name="rotation" value="4" summary="Z-rotation axis"/>
> +      <entry name="slider" value="5" summary="Slider axis"/>
> +      <entry name="wheel" value="6" summary="Wheel axis"/>
> +    </enum>
> +
> +    <event name="capability">
> +      <description summary="tool capability notification">
> +	This event notifies the client of any capabilities of this tool,
> +	beyond the main set of x/y axes and tip up/down detection.
> +
> +	One event is sent for each extra capability available on this tool.
> +
> +	This event is sent in the initial burst of events before the
> +	wp_tablet_tool.done event.
> +      </description>
> +      <arg name="capability" type="uint" enum="capability" summary="the capability"/>
> +    </event>
> +
> +    <event name="done">
> +      <description summary="tool description events sequence complete">
> +	This event signals the end of the initial burst of descriptive
> +	events. A client may consider the static description of the tool to
> +	be complete and finalize initialization of the tool.
> +      </description>
> +    </event>
> +
> +    <event name="removed">
> +      <description summary="tool removed">
> +	This event is sent when the tool is removed from the system and will
> +	send no further events. Should the physical tool comes back into
> +	proximity later, a new wp_tablet_tool object will be created.
> +
> +	It is compositor-dependent when a tool is removed. A compositor may
> +	remove a tool on proximity out, tablet removal or any other reason.
> +	A compositor may also keep a tool alive until shutdown.
> +
> +	If the tool is currently in proximity, a proximity_out event will be
> +	sent before the removed event. See wp_tablet_tool.proximity_out for
> +	the handling of any buttons logically down.
> +
> +	When this event is received, the client must wp_tablet_tool.destroy
> +	the object.
> +      </description>
> +    </event>
> +
> +    <event name="proximity_in">
> +      <description summary="proximity in event">
> +	Notification that this tool is focused on a certain surface.
> +
> +	This event can be received when the tool has moved from one surface to
> +	another, or when the tool has come back into proximity above the
> +	surface.
> +
> +	If any button is logically down when the tool comes into proximity,
> +	the respective button event is sent after the proximity_in event but
> +	within the same frame as the proximity_in event.
> +      </description>
> +      <arg name="serial" type="uint"/>
> +      <arg name="tablet" type="object" interface="zwp_tablet_v1" summary="The tablet the tool is in proximity of"/>
> +      <arg name="surface" type="object" interface="wl_surface" summary="The current surface the tablet tool is over"/>
> +    </event>
> +
> +    <event name="proximity_out">
> +      <description summary="proximity out event">
> +	Notification that this tool has either left proximity, or is no
> +	longer focused on a certain surface.
> +
> +	When the tablet tool leaves proximity of the tablet, button release
> +	events are sent for each button that was held down at the time of
> +	leaving proximity. These events are sent before the proximity_out
> +	event but within the same wp_tablet.frame.
> +
> +	If the tool stays within proximity of the tablet, but the focus
> +	changes from one surface to another, a button release event may not
> +	be sent until the button is actually released or the tool leaves the
> +	proximity of the tablet.
> +      </description>
> +    </event>
> +
> +    <event name="down">
> +      <description summary="tablet tool is making contact">
> +	Sent whenever the tablet tool comes in contact with the surface of the
> +	tablet. If the tablet tool moves out of a region while in contact with

1) Based on the "up" event, I'm assuming you you want "surface" instead
of (the far more nebulous) "region" here.

2) Is there a symmetric entry policy to the exit policy (e.g. "if the
tablet tool enters a region while in contact with the surface of the
tablet, ...)

> +	the surface of the tablet, the client owning said region will receive a
> +	wp_tablet.up event, followed by a wp_tablet.proximity_out event and a
> +	wp_tablet.frame event.
> +
> +	Note that this event describes logical contact, not physical
> +	contact. On some devices, a compositor may not consider a tool in
> +	logical contact until a minimum physical pressure threshold is
> +	exceeded.
> +      </description>
> +      <arg name="serial" type="uint"/>
> +    </event>
> +
> +    <event name="up">
> +      <description summary="tablet tool is no longer making contact">
> +	Sent whenever the tablet tool stops making contact with the surface of
> +	the tablet, or when the tablet tool moves off of a surface while it was
> +	making contact with the tablet's surface.
> +

The protocol summary indicates that compositor-specific grab policies
apply when a button is pressed. Its not clear if that statement also
applied to a pen that was down and dragged off of a surface, especially
since this seems to prescribe a policy of its own.

If this is the prescribed policy, will it cause issues for clients like
GIMP where it may be desired for brush strokes to continue outside of
the drawing surface? It would seem that sending an "up" event at the
surface edges while the pen is still being dragged may result in
undesired artifacts.

> +	Note that this event describes logical contact, not physical
> +	contact. On some devices, a compositor may not consider a tool out
> +	of logical contact until physical pressure falls below a specific
> +	threshold.
> +      </description>
> +    </event>
> +
> +    <event name="motion">
> +      <description summary="motion event">
> +	Sent whenever a tablet tool moves.
> +      </description>
> +      <arg name="x" type="fixed" summary="surface-relative x coordinate"/>
> +      <arg name="y" type="fixed" summary="surface-relative y coordinate"/>
> +    </event>
> +
> +    <event name="pressure">
> +      <description summary="pressure change event">
> +	Sent whenever the pressure axis on a tool changes. The value of this
> +	event is normalized to a value between 0 and 65535.
> +
> +	Note that pressure may be nonzero even when a tool not in logical
> +	contact. See the down and up events for more details.
> +      </description>
> +      <arg name="pressure" type="uint" summary="The current pressure value"/>
> +    </event>
> +
> +    <event name="distance">
> +      <description summary="distance change event">
> +	Sent whenever the distance axis on a tool changes. The value of this
> +	event is normalized to a value between 0 and 65535.
> +
> +	Note that distance may be nonzero even when a tool is not in logical
> +	contact. See the down and up events for more details.
> +      </description>
> +      <arg name="distance" type="uint" summary="The current distance value"/>
> +    </event>
> +
> +    <event name="tilt">
> +      <description summary="tilt change event">
> +	Sent whenever one or both of the tilt axes on a tool change. Each tilt
> +	value is in 0.01 of a degree, relative to the z-axis of the tablet.
> +	The angle is postive when the top of a tool tilts along the positive

s/postive/positive/

> +	x or y axis.
> +      </description>
> +      <arg name="tilt_x" type="int" summary="The current value of the X tilt axis"/>
> +      <arg name="tilt_y" type="int" summary="The current value of the Y tilt axis"/>
> +    </event>
> +
> +    <event name="rotation">
> +      <description summary="z-rotation change event">
> +	Sent whenever the z-rotation axis on the tool changes. The
> +	rotation value is in 0.01 of a degree clockwise from the tool's
> +	logical neutral position.
> +      </description>
> +      <arg name="degrees" type="int" summary="The current rotation of the Z axis"/>
> +    </event>
> +
> +    <event name="slider">
> +      <description summary="Slider position change event">
> +	Sent whenever the slider position on the tool changes. The
> +	value is normalized between -65535 and 65535, with 0 as the logical
> +	neutral position of the slider.
> +
> +	The slider is available on e.g. the Wacom Airbrush tool.
> +      </description>
> +      <arg name="position" type="int" summary="The current position of slider"/>
> +    </event>
> +
> +    <event name="wheel">
> +      <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 0.01 of a degree 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.
> +
> +	Clients should choose either value and avoid mixing degrees and
> +	clicks. The compositor may accumulate values smaller than a logical
> +	click and emulate click events when a certain threshold is met.
> +	Thus, wl_tablet_tool.wheel events with non-zero clicks values may
> +	have different degrees values.
> +      </description>
> +      <arg name="degrees" type="int" summary="The wheel delta in 0.01 of a degree"/>
> +      <arg name="clicks" type="int" summary="The wheel delta in discrete clicks"/>
> +    </event>
> +
> +    <enum name="button_state">
> +      <description summary="physical button state">
> +	Describes the physical state of a button which provoked the button event
> +      </description>
> +      <entry name="released" value="0" summary="button is not pressed"/>
> +      <entry name="pressed" value="1" summary="button is pressed"/>
> +    </enum>
> +
> +    <event name="button">
> +      <description summary="button event">
> +	Sent whenever a button on the tool is pressed or released.

Possibly mention the rules on button release/press on proximity change
here as well.

> +      </description>
> +
> +      <arg name="serial" type="uint"/>
> +      <arg name="button" type="uint" summary="The button whose state has changed"/>
> +      <arg name="state" type="uint" enum="button_state" summary="Whether the button was pressed or released"/>
> +    </event>
> +
> +    <event name="frame">
> +      <description summary="frame event">
> +	Marks the end of a series of axis and/or button updates from the
> +	tablet. The wayland protocol requires axis updates to be sent
> +	sequentially, however all events within a frame should be considered
> +	one hardware event.
> +      </description>
> +      <arg name="time" type="uint" summary="The time of the event with millisecond granularity"/>
> +    </event>
> +
> +    <enum name="error">
> +      <entry name="role" value="0" summary="given wl_surface has another role"/>
> +    </enum>
> +  </interface>
> +
> +  <interface name="zwp_tablet_v1" version="1">
> +    <description summary="graphics tablet device">
> +      The wp_tablet interface represents one graphics tablet device. The
> +      tablet interface itself does not generate events, all events are

s/,/;/

Jason
---
Now instead of four in the eights place /
you’ve got three, ‘Cause you added one /
(That is to say, eight) to the two, /
But you can’t take seven from three, /
So you look at the sixty-fours....

> +      generated by wp_tablet_tool objects when in proximity above a tablet.
> +
> +      A tablet has a number of static characteristics, e.g. device name and
> +      pid/vid. These capabilities are sent in an event sequence after the
> +      wp_tablet_seat.tablet_added event. This initial event sequence is
> +      terminated by a wp_tablet.done event.
> +    </description>
> +
> +    <request name="destroy" type="destructor">
> +      <description summary="destroy the tablet object">
> +	This destroys the client's resource for this tablet object.
> +      </description>
> +    </request>
> +
> +    <event name="name">
> +      <description summary="tablet device name">
> +	This event is sent in the initial burst of events before the
> +	wp_tablet.done event.
> +      </description>
> +      <arg name="name" type="string" summary="the device name"/>
> +    </event>
> +
> +    <event name="id">
> +      <description summary="tablet device USB vendor/product id">
> +	This event is sent in the initial burst of events before the
> +	wp_tablet.done event.
> +      </description>
> +      <arg name="vid" type="uint" summary="USB vendor id"/>
> +      <arg name="pid" type="uint" summary="USB product id"/>
> +    </event>
> +
> +    <event name="path">
> +      <description summary="path to the device">
> +	A system-specific device path that indicates which device is behind
> +	this wp_tablet. This information may be used to gather additional
> +	information about the device, e.g. through libwacom.
> +
> +	A device may have more than one device path, if so, multiple
> +	wp_tablet.path events are sent. A device may be emulated and not
> +	have a device path, in that case this event will not be sent.
> +
> +	The format of the path is unspecified, it may be a device node, a
> +	sysfs path, or some other identifier. It is up to the client to
> +	identify the string provided.
> +
> +	This event is sent in the initial burst of events before the
> +	wp_tablet.done event.
> +      </description>
> +      <arg name="path" type="string" summary="path to local device"/>
> +    </event>
> +
> +    <event name="done">
> +      <description summary="tablet description events sequence complete">
> +	This event is sent immediately to signal the end of the initial
> +	burst of descriptive events. A client may consider the static
> +	description of the tablet to be complete and finalize initialization
> +	of the tablet.
> +      </description>
> +    </event>
> +
> +    <event name="removed">
> +      <description summary="tablet removed event">
> +	Sent when the tablet has been removed from the system. When a tablet
> +	is removed, some tools may be removed.
> +
> +	When this event is received, the client must wp_tablet.destroy
> +	the object.
> +      </description>
> +    </event>
> +  </interface>
> +</protocol>
> 


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