diff --git a/src/Viewport.ts b/src/Viewport.ts
index b266dd3e..32a71dde 100644
--- a/src/Viewport.ts
+++ b/src/Viewport.ts
@@ -40,6 +40,9 @@ export class Viewport {
     this.refreshLoop();
   }
 
+  /**
+   * Queues a refresh to be done on next animation frame.
+   */
   private refreshLoop(): void {
     if (this.isRefreshQueued) {
       this.refresh();