[PATCH v4] protocol: Extend wl_touch with touchpoint shape and orientation

[Dennis Kempin]

This CL updates the wl_touch interface with a shape and
orientation event.
The shape/orientation of a touch point is not relevant for most UI
applications, but allows a better experience in some cases
such as drawing apps.

The events are used by the compositor to inform the client
about changes in the shape and orientation of a touchpoint, which is
approximated by an ellipse and it's angle to the y-axis.

The event is optional and only sent when compositor and the
touch device support this type of information. The client is
responsible for making a reasonable assumption about the
touch shape if no shape is reported.

Signed-off-by: Dennis Kempin <denniskempin at google.com>
---
 protocol/wayland.xml | 74
+++++++++++++++++++++++++++++++++++++++++++++++++---
 1 file changed, 70 insertions(+), 4 deletions(-)

diff --git a/protocol/wayland.xml b/protocol/wayland.xml
index 6c6d078..9d1407b 100644
--- a/protocol/wayland.xml
+++ b/protocol/wayland.xml
@@ -1669,7 +1669,7 @@
     </request>
    </interface>

-  <interface name="wl_seat" version="5">
+  <interface name="wl_seat" version="6">
     <description summary="group of input devices">
       A seat is a group of keyboards, pointer and touch devices. This
       object is published as a global during start up, or when such a
@@ -1778,7 +1778,7 @@

   </interface>

-  <interface name="wl_pointer" version="5">
+  <interface name="wl_pointer" version="6">
     <description summary="pointer input device">
       The wl_pointer interface represents one or more input devices,
       such as mice, which control the pointer location and pointer_focus
@@ -2092,7 +2092,7 @@
     </event>
   </interface>

-  <interface name="wl_keyboard" version="5">
+  <interface name="wl_keyboard" version="6">
     <description summary="keyboard input device">
       The wl_keyboard interface represents one or more keyboards
       associated with a seat.
@@ -2256,7 +2256,13 @@

     <event name="frame">
       <description summary="end of touch frame event">
- Indicates the end of a contact point list.
+ Indicates the end of a set of events that logically belong together.
+ A client is expected to accumulate the data in all events within the
+ frame before proceeding.
+ A wl_touch.frame terminates at least one event but otherwise no
+ guarantee is provided about the set of events within a frame.
+ A client must assume that any state not updated in a frame is unchanged
+ from the previously known state.
       </description>
     </event>

@@ -2276,6 +2282,66 @@
     <request name="release" type="destructor" since="3">
       <description summary="release the touch object"/>
     </request>
+
+    <!-- Version 6 additions -->
+
+    <event name="shape" since="6">
+      <description summary="update shape of touch point">
+ Sent when a touchpoint has changed its shape.
+
+ This event event does not occur on its own. It is sent before a
+ wl_touch.frame event and carries the new shape information for
+ the specific touch points for that frame.
+
+ Other events describing the touch point such as wl_touch.motion or
+ wl_touch.orientation may be sent within the same wl_touch.frame. A
+ client should treat these events as a single logical touch point update.
+ The order of wl_touch.shape, wl_touch.orientation and wl_touch.motion is
+ not guaranteed.
+
+ A touchpoint shape is approximated by an ellipse through the major and
+ minor axis length. The major axis length describes the longer diameter
+ of the ellipse, while the minor axis length describes the shorter
+ diameter. Major and minor are orthogonal and both are specified in
+ surface coordinates. The center of the ellipse is always at the
+ touchpoint location as reported by wl_touch.down or wl_touch.move.
+
+ This event is only sent by the compositor if the touch device supports
shape
+ reports. The client has to make reasonable assumptions about the shape if
+ it did not receive this event.
+      </description>
+      <arg name="id" type="int" summary="the unique ID of this touch
point"/>
+      <arg name="major" type="fixed" summary="length of the major axis in
surface-local coordinates"/>
+      <arg name="minor" type="fixed" summary="length of the minor axis in
surface-local coordinates"/>
+    </event>
+
+    <event name="orientation" since="6">
+      <description summary="update orientation of touch point">
+ Sent when a touchpoint has changed its orientation.
+
+ Other events describing the touch point such as wl_touch.motion or
+ wl_touch.shape may be sent within the same wl_touch.frame. A client
+ should treat these events as a single logical touch point update.
+ The order of wl_touch.shape, wl_touch.orientation and wl_touch.motion is
+ not guaranteed.
+
+ This event may be sent alone or together with other events
+ describing the touch point, such as wl_touch.motion and
+ wl_touch.orientation. The order of wl_touch.shape,
+ wl_touch.orientation and wl_touch.motion is not guaranteed.
+
+ The orientation describes the clockwise angle of touchpoints major axis to
+ the surface y-axis and is normalized to the -180 to +180 degrees range.
+ The granuality of orientation depends on the touch device, some devices
only
+ support binary rotation values between 0 and 90 degrees.
+
+ This event is only sent by the compositor if the touch device supports
+ orientation reports.
+      </description>
+      <arg name="id" type="int" summary="the unique ID of this touch
point"/>
+      <arg name="orientation" type="fixed" summary="angle between major
axis and positive surface y-axis in degrees"/>
+    </event>
+
   </interface>

   <interface name="wl_output" version="3">
--
2.8.0.rc3.226.g39d4020
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