diff --git a/src/widgets/viewport_widget.h b/src/widgets/viewport_widget.h
--- a/src/widgets/viewport_widget.h
+++ b/src/widgets/viewport_widget.h
@@ -13,13 +13,13 @@
 #define WIDGETS_VIEWPORT_WIDGET_H
 
 /** Widgets of the WC_EXTRA_VIEW_PORT. */
-enum ExtraViewportWindowWidgets {
-	EVW_CAPTION,
-	EVW_VIEWPORT,
-	EVW_ZOOMIN,
-	EVW_ZOOMOUT,
-	EVW_MAIN_TO_VIEW,
-	EVW_VIEW_TO_MAIN,
+enum ExtraViewportWidgets {
+	WID_EV_CAPTION,      ///< Caption of window.
+	WID_EV_VIEWPORT,     ///< The viewport.
+	WID_EV_ZOOM_IN,      ///< Zoom in.
+	WID_EV_ZOOM_OUT,     ///< Zoom out.
+	WID_EV_MAIN_TO_VIEW, ///< Center the view of this viewport on the main view.
+	WID_EV_VIEW_TO_MAIN, ///< Center the main view on the view of this viewport.
 };
 
 #endif /* WIDGETS_VIEWPORT_WIDGET_H */