From 97bfc9035117c519cd5092ff2de8f7a045406d10 Mon Sep 17 00:00:00 2001
From: DD Liu <liudi@media.mit.edu>
Date: Wed, 10 May 2017 11:22:03 -0400
Subject: [PATCH] add comment to monitor block listener filtering of events

---
 src/virtual-machine.js | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/src/virtual-machine.js b/src/virtual-machine.js
index c56e289c0..b39d74d8a 100644
--- a/src/virtual-machine.js
+++ b/src/virtual-machine.js
@@ -350,6 +350,8 @@ class VirtualMachine extends EventEmitter {
      * @param {!Blockly.Event} e Any Blockly event.
      */
     monitorBlockListener (e) {
+        // Filter events by type, since monitor blocks only need to listen to these events.
+        // Monitor blocks shouldn't be destroyed when flyout blocks are deleted.
         if (['create', 'change'].indexOf(e.type) !== -1) {
             this.runtime.monitorBlocks.blocklyListen(e, this.runtime);
         }