libinput-device: use the discrete axis value for wheel events

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@who-t.net>
Signed-off-by: Jonas Ådahl <jadahl@gmail.com>
Reviewed-by: Jonas Ådahl <jadahl@gmail.com>

src/libinput-device.c

@@ -126,6 +126,44 @@ handle_pointer_button(struct libinput_device *libinput_device,
 		      libinput_event_pointer_get_button_state(pointer_event));
 }
 
+static double
+normalize_scroll(struct libinput_event_pointer *pointer_event,
+		 enum libinput_pointer_axis axis)
+{
+	static int warned;
+	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.
+	 */
+	switch (source) {
+	case LIBINPUT_POINTER_AXIS_SOURCE_WHEEL:
+		value = 10 * libinput_event_pointer_get_axis_value_discrete(
+								   pointer_event,
+								   axis);
+		break;
+	case LIBINPUT_POINTER_AXIS_SOURCE_FINGER:
+	case LIBINPUT_POINTER_AXIS_SOURCE_CONTINUOUS:
+		value = libinput_event_pointer_get_axis_value(pointer_event,
+							      axis);
+		break;
+	default:
+		value = 0;
+		if (warned < 5) {
+			weston_log("Unknown scroll source %d. Event discarded\n",
+				   source);
+			warned++;
+		}
+		break;
+	}
+
+	return value;
+}
+
 static void
 handle_pointer_axis(struct libinput_device *libinput_device,
 		    struct libinput_event_pointer *pointer_event)
@@ -137,8 +175,7 @@ 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 +184,7 @@ 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,