[PATCH v3] 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 | 64 ++++++++++++++++++++++++++++++++++++++++++++++++----
 1 file changed, 59 insertions(+), 5 deletions(-)

diff --git a/protocol/wayland.xml b/protocol/wayland.xml
index 12a6efd..b8a9835 100644
--- a/protocol/wayland.xml
+++ b/protocol/wayland.xml
@@ -1656,7 +1656,7 @@
     </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
@@ -1765,7 +1765,7 @@

   </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
@@ -2078,7 +2078,7 @@
     </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.
@@ -2192,7 +2192,7 @@
     </event>
   </interface>

-  <interface name="wl_touch" version="5">
+  <interface name="wl_touch" version="6">
     <description summary="touchscreen input device">
       The wl_touch interface represents a touchscreen
       associated with a seat.
@@ -2242,7 +2242,12 @@

     <event name="frame">
       <description summary="end of touch frame event">
- Indicates the end of a contact point list.
+ Indicates the end of a contact point list. The wayland protocol requires
+ touch point updates to be sent sequentially, however all events within a
+ frame should be considered one hardware event. 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>

@@ -2262,6 +2267,55 @@
     <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. If the touch position
+ or orientation changed at the same time, the wl_touch.motion,
+ wl_touch.orientation and wl_touch.shape are sent within the same
+ wl_touch.frame. Otherwise, only a wl_touch.shape is sent within this
+ wl_touch.frame. The protocol does not guarantee specific ordering of
+ wl_touch.orientation, wl_touch.shape and wl_touch.motion events.
+
+ A touchpoint shape is approximated by an ellipse through the major and minor
+ axis length. The major axis length describes the longest diameter of the
+ ellipse, while the minor axis length describes the shortest diameter.
+ 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. If the touch position
+ or shape changed at the same time, the wl_touch.motion, wl_touch.orientation
+ and wl_touch.shape are sent within the same wl_touch.frame.
+ Otherwise, only a wl_touch.orientation is sent within this wl_touch.frame.
+ The protocol does not guarantee specific ordering of wl_touch.orientation,
+ wl_touch.shape and wl_touch.motion events.
+
+ 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 surface y-axis in degrees"/>
+    </event>
+
   </interface>

   <interface name="wl_output" version="2">
--
2.8.0.rc3.226.g39d4020