[PATCH v2] protocol: Extend wl_touch with touchpoint shape event

[Dennis Kempin]

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

The shape event is used by the compositor to inform the client
about changes in the shape of a touchpoint, which is
approximated by an ellipse.

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 | 46 +++++++++++++++++++++++++++++++++++++++++-----
 1 file changed, 41 insertions(+), 5 deletions(-)

diff --git a/protocol/wayland.xml b/protocol/wayland.xml
index 8739cd3..90a2453 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 contract 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.frames 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 +2267,37 @@
     <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 changed
+  at the same time, the wl_touch.motion 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.shape and wl_touch.motion events.
+
+  A touchpoint shape is approximated by an ellipse through an orientation and
+  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
orientation describes
+  the angle between the major axis and the surface x-axis and is normalized to
+  [0, 180) degrees.
+  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 message.
+      </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 coordinates"/>
+      <arg name="minor" type="fixed" summary="length of the minor
axis in surface coordinates"/>
+      <arg name="orientation" type="fixed"
+           summary="angle between major axis and surface x-axis in degrees"/>
+    </event>
+
   </interface>

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