eventdemo: add axis logging

https://bugs.freedesktop.org/show_bug.cgi?id=52453

clients/eventdemo.c

@@ -70,6 +70,9 @@ static int log_key = 0;
 /** set to log button events */
 static int log_button = 0;
 
+/** set to log axis events */
+static int log_axis = 0;
+
 /** set to log motion events */
 static int log_motion = 0;
 
@@ -229,6 +232,29 @@ button_handler(struct widget *widget, struct input *input, uint32_t time,
 	       x, y);
 }
 
+/**
+ * \brief CALLBACK function, Wayland informs about axis event
+ * \param widget widget
+ * \param input input device that caused the axis event
+ * \param time time the event happened
+ * \param axis vertical or horizontal
+ * \param value amount of scrolling
+ * \param data user data associated to the widget
+ */
+static void
+axis_handler(struct widget *widget, struct input *input, uint32_t time,
+	     uint32_t axis, wl_fixed_t value, void *data)
+{
+	if (!log_axis)
+		return;
+
+	printf("axis time: %d, axis: %s, value: %f\n",
+	       time,
+	       axis == WL_POINTER_AXIS_VERTICAL_SCROLL ? "vertical" :
+							 "horizontal",
+	       wl_fixed_to_double(value));
+}
+
 /**
  * \brief CALLBACK function, Waylands informs about pointer motion
  * \param widget widget
@@ -317,6 +343,9 @@ eventdemo_create(struct display *d)
 	/* Set the callback motion handler for the window */
 	widget_set_motion_handler(e->widget, motion_handler);
 
+	/* Set the callback axis handler for the window */
+	widget_set_axis_handler(e->widget, axis_handler);
+
 	/* Initial drawing of the window */
 	window_schedule_resize(e->window, width, height);
 
@@ -347,6 +376,7 @@ static const struct weston_option eventdemo_options[] = {
 	{ WESTON_OPTION_BOOLEAN, "log-focus", '0', &log_focus },
 	{ WESTON_OPTION_BOOLEAN, "log-key", '0', &log_key },
 	{ WESTON_OPTION_BOOLEAN, "log-button", '0', &log_button },
+	{ WESTON_OPTION_BOOLEAN, "log-axis", '0', &log_axis },
 	{ WESTON_OPTION_BOOLEAN, "log-motion", '0', &log_motion },
 };