buffer: make wlr_buffer_ref return the buffer

include/wlr/types/wlr_buffer.h

@@ -36,7 +36,7 @@ struct wlr_buffer *wlr_buffer_create(struct wlr_renderer *renderer,
 /**
  * Reference the buffer.
  */
-void wlr_buffer_ref(struct wlr_buffer *buffer);
+struct wlr_buffer *wlr_buffer_ref(struct wlr_buffer *buffer);
 /**
  * Unreference the buffer. After this call, `buffer` may not be accessed
  * anymore.

types/wlr_buffer.c

@@ -105,8 +105,9 @@ struct wlr_buffer *wlr_buffer_create(struct wlr_renderer *renderer,
 	return buffer;
 }
 
-void wlr_buffer_ref(struct wlr_buffer *buffer) {
+struct wlr_buffer *wlr_buffer_ref(struct wlr_buffer *buffer) {
 	buffer->n_refs++;
+	return buffer;
 }
 
 void wlr_buffer_unref(struct wlr_buffer *buffer) {