protocol: Clarify pointer axis event

Pointer axis events are in the same coordinate space as motion events.

Signed-off-by: Jonas Ådahl <jadahl@gmail.com>

diff --git a/protocol/wayland.xml b/protocol/wayland.xml
index 48a0d77..ca04431 100644 (file)
--- a/protocol/wayland.xml
+++ b/protocol/wayland.xml
@@ -987,10 +987,22 @@
 
     <event name="axis">
       <description summary="axis event">
-       Scroll and other axis notifications.  The value parameter
-       is the length of a vector along an axis in a coordinate space
-       identical to those of motion events, representing the relative
-       movement along an axis.
+       Scroll and other axis notifications.
+
+       For scroll events (vertical and horizontal scroll axes), the
+       value parameter is the length of a vector along the specified
+       axis in a coordinate space identical to those of motion events,
+       representing a relative movement along the specified axis.
+
+       For devices that support movements non-parallel to axes multiple
+       axis events will be emitted.
+
+       When applicable, for example for touch pads, the server can
+       choose to emit scroll events where the motion vector is
+       equivalent to a motion event vector.
+
+       When applicable, clients can transform its view relative to the
+       scroll distance.
       </description>
 
       <arg name="time" type="uint"/>