[PATCH v2 wayland] protocol: add wl_pointer.axis_frame events

[Peter Hutterer]

To group separate vertical/horizontal scroll events together. Likewise it
enables axis_stop events to be grouped so that the final vector for kinetic
scrolling may be calculated correctly.

Signed-off-by: Peter Hutterer <peter.hutterer at who-t.net>
---
Changes to v1:
- drop the option of having multiple axis sources within the same frame
  (and reword the documentation accordingly)

Two comments here:
- the protocol feels a bit unbalanced now when discrete events are in use,
  these must still be sent before the matching axis events. i.e. we have 4
  events that commit with the axis_frame, but one event (discrete) that
  commit with the axis event:
      axis_source
      axis
      axis_discrete
      axis
      axis_frame
  though sending the source just before the frame may make this a bit easier
  on the eye
- we could now skip the source and merge it into the axis_frame event,
  though that would require the return of the "unknown" source.
 
 protocol/wayland.xml | 30 +++++++++++++++++++++++++++---
 1 file changed, 27 insertions(+), 3 deletions(-)

diff --git a/protocol/wayland.xml b/protocol/wayland.xml
index 48d0332..db9b164 100644
--- a/protocol/wayland.xml
+++ b/protocol/wayland.xml
@@ -1579,6 +1579,30 @@
     </request>
 
     <!-- Version 5 additions -->
+    <event name="axis_frame" since="5">
+      <description summary="end of axis set event">
+	Indicates the end of a set of wl_pointer.axis events that logically
+	belong together.
+
+	All wl_pointer.axis, wl_pointer.axis_stop, and
+	wl_pointer.axis_source before a wl_pointer.axis_frame event belong
+	logically together. For example, in a diagonal scroll motion the
+	compositor will send an optional wl_pointer.axis_source event, two
+	wl_pointer.axis events (horizontal and vertical) and finally a
+	wl_pointer.axis_frame event. The client may use this information to
+	calculate a diagonal vector for scrolling.
+
+	When multiple wl_pointer.axis events occur within the same frame,
+	the motion vector is the combined motion of all events.
+	When a wl_pointer.axis and a wl_pointer.axis_stop event occur within
+	the same frame, this indicates that axis movement in one axis has
+	stopped but continues in the other axis.
+	When multiple wl_pointer.axis_stop events occur within in the same
+	frame, this indicates that these axes stopped in the same instance.
+
+	Only one wl_pointer.axis_source event is permitted per axis frame.
+      </description>
+    </event>
 
     <enum name="axis_source">
       <description summary="axis source types">
@@ -1605,9 +1629,9 @@
 	Source information for scroll and other axes.
 
 	This event does not occur on its own. It is sent before a
-	wl_pointer.axis or wl_pointer.axis_stop event and carries the source
-	information for that event. A client is expected to accumulate the
-	data in both events before proceeding.
+	wl_pointer.axis_frame event and carries the source information for
+	all events within that frame. A client is expected to accumulate the
+	data in all events events within the frame before proceeding.
 
 	The source specifies how this event was generated. If the source is
 	wl_pointer.axis_source.finger, a wl_pointer.axis_stop event will be
-- 
2.4.3