wlr-seat: implement cursor axis events

Axis events for the cursor are generated with the scroll wheel.

examples/compositor.c

@@ -417,10 +417,11 @@ static void handle_cursor_motion_absolute(struct wl_listener *listener,
 }
 
 static void handle_cursor_axis(struct wl_listener *listener, void *data) {
-	//struct sample_state *sample =
-	//wl_container_of(listener, sample, cursor_axis);
-	//struct wlr_event_pointer_axis *event = data;
-	wlr_log(L_DEBUG, "TODO: handle cursor axis");
+	struct sample_state *sample =
+		wl_container_of(listener, sample, cursor_axis);
+	struct wlr_event_pointer_axis *event = data;
+	wlr_seat_pointer_send_axis(sample->wl_seat, event->time_sec,
+		event->orientation, event->delta);
 }
 
 static void handle_cursor_button(struct wl_listener *listener, void *data) {

include/wlr/types/wlr_seat.h

@@ -109,4 +109,7 @@ void wlr_seat_pointer_send_motion(struct wlr_seat *wlr_seat, uint32_t time,
 void wlr_seat_pointer_send_button(struct wlr_seat *wlr_seat, uint32_t time,
 		uint32_t button, uint32_t state);
 
+void wlr_seat_pointer_send_axis(struct wlr_seat *wlr_seat, uint32_t time,
+		enum wlr_axis_orientation orientation, double value);
+
 #endif

types/wlr_seat.c

@@ -352,3 +352,22 @@ void wlr_seat_pointer_send_button(struct wlr_seat *wlr_seat, uint32_t time,
 		serial, time, button, state);
 	wl_pointer_send_frame(wlr_seat->pointer_state.focused_handle->pointer);
 }
+
+void wlr_seat_pointer_send_axis(struct wlr_seat *wlr_seat, uint32_t time,
+		enum wlr_axis_orientation orientation, double value) {
+	if (!wlr_seat_pointer_has_focus_resource(wlr_seat)) {
+		return;
+	}
+
+	struct wl_resource *pointer =
+		wlr_seat->pointer_state.focused_handle->pointer;
+
+	if (value) {
+		wl_pointer_send_axis(pointer, time, orientation,
+			wl_fixed_from_double(value));
+	} else {
+		wl_pointer_send_axis_stop(pointer, time, orientation);
+	}
+
+	wl_pointer_send_frame(pointer);
+}