[PATCH weston] libinput-device: use the discrete axis value for wheel events

[Peter Hutterer]

libinput < 0.8 sent wheel click events with value 10. Since 0.8
the value is the angle of the click in degrees but it now provides
the click count as separate value. To keep backwards-compat with
existing clients, we just send multiples of the click count.

Signed-off-by: Peter Hutterer <peter.hutterer at who-t.net>
---
Use the new discrete axis values for scroll wheels to maintain backwards
compatibility. This isn't merged in libinput yet but I think at this point
it's just a discussion re naming so worst case this patch would need a
search/replace.

But to get an early review, here it is.

 src/libinput-device.c | 30 ++++++++++++++++++++++++++----
 1 file changed, 26 insertions(+), 4 deletions(-)

diff --git a/src/libinput-device.c b/src/libinput-device.c
index e68b54d..9451675 100644
--- a/src/libinput-device.c
+++ b/src/libinput-device.c
@@ -126,6 +126,30 @@ handle_pointer_button(struct libinput_device *libinput_device,
 		      libinput_event_pointer_get_button_state(pointer_event));
 }
 
+static int
+normalize_scroll(struct libinput_event_pointer *pointer_event,
+		 enum libinput_pointer_axis axis)
+{
+	enum libinput_pointer_axis_source source;
+	double value;
+
+	source = libinput_event_pointer_get_axis_source(pointer_event);
+	/* libinput < 0.8 sent wheel click events with value 10. Since 0.8
+	   the value is the angle of the click in degrees. To keep
+	   backwards-compat with existing clients, we just send multiples of
+	   the click count.
+	 */
+	if (source == LIBINPUT_POINTER_AXIS_SOURCE_WHEEL)
+		value = 10 * libinput_event_pointer_get_axis_value_discrete(
+							   pointer_event,
+							   axis);
+	else
+		value = libinput_event_pointer_get_axis_value(pointer_event,
+							      axis);
+
+	return value;
+}
+
 static void
 handle_pointer_axis(struct libinput_device *libinput_device,
 		    struct libinput_event_pointer *pointer_event)
@@ -137,8 +161,7 @@ handle_pointer_axis(struct libinput_device *libinput_device,
 
 	axis = LIBINPUT_POINTER_AXIS_SCROLL_VERTICAL;
 	if (libinput_event_pointer_has_axis(pointer_event, axis)) {
-		value = libinput_event_pointer_get_axis_value(pointer_event,
-							      axis);
+		value = normalize_scroll(pointer_event, axis);
 		notify_axis(device->seat,
 			    libinput_event_pointer_get_time(pointer_event),
 			    WL_POINTER_AXIS_VERTICAL_SCROLL,
@@ -147,8 +170,7 @@ handle_pointer_axis(struct libinput_device *libinput_device,
 
 	axis = LIBINPUT_POINTER_AXIS_SCROLL_HORIZONTAL;
 	if (libinput_event_pointer_has_axis(pointer_event, axis)) {
-		value = libinput_event_pointer_get_axis_value(pointer_event,
-							      axis);
+		value = normalize_scroll(pointer_event, axis);
 		notify_axis(device->seat,
 			    libinput_event_pointer_get_time(pointer_event),
 			    WL_POINTER_AXIS_HORIZONTAL_SCROLL,
-- 
2.1.0