From 6bd2307c992286fa1825d66b93bb69d1b8dd7596 Mon Sep 17 00:00:00 2001
From: Paul Kaplan <pkaplan@media.mit.edu>
Date: Tue, 4 Dec 2018 16:43:31 -0500
Subject: [PATCH] Clear the pen layer when runtime dispose happens.

---
 src/engine/runtime.js                |  9 +++++++++
 src/extensions/scratch3_pen/index.js |  1 +
 test/unit/engine_runtime.js          | 11 +++++++++++
 3 files changed, 21 insertions(+)

diff --git a/src/engine/runtime.js b/src/engine/runtime.js
index 4031ea49d..0547e622d 100644
--- a/src/engine/runtime.js
+++ b/src/engine/runtime.js
@@ -626,6 +626,14 @@ class Runtime extends EventEmitter {
         return 'RUNTIME_STARTED';
     }
 
+    /**
+     * Event name when the runtime dispose has been called.
+     * @const {string}
+     */
+    static get RUNTIME_DISPOSED () {
+        return 'RUNTIME_DISPOSED';
+    }
+
     /**
      * Event name for reporting that a block was updated and needs to be rerendered.
      * @const {string}
@@ -1547,6 +1555,7 @@ class Runtime extends EventEmitter {
         this.stopAll();
         this.targets.map(this.disposeTarget, this);
         this._monitorState = OrderedMap({});
+        this.emit(Runtime.RUNTIME_DISPOSED);
         // @todo clear out extensions? turboMode? etc.
 
         // *********** Cloud *******************
diff --git a/src/extensions/scratch3_pen/index.js b/src/extensions/scratch3_pen/index.js
index 4c46ce370..da36ba4f3 100644
--- a/src/extensions/scratch3_pen/index.js
+++ b/src/extensions/scratch3_pen/index.js
@@ -67,6 +67,7 @@ class Scratch3PenBlocks {
         this._onTargetMoved = this._onTargetMoved.bind(this);
 
         runtime.on('targetWasCreated', this._onTargetCreated);
+        runtime.on('RUNTIME_DISPOSED', this.clear.bind(this));
     }
 
     /**
diff --git a/test/unit/engine_runtime.js b/test/unit/engine_runtime.js
index c9f92385e..26ffe8c87 100644
--- a/test/unit/engine_runtime.js
+++ b/test/unit/engine_runtime.js
@@ -239,3 +239,14 @@ test('setCompatibilityMode does not restart if it was not running', t => {
     t.equal(started, false);
     t.end();
 });
+
+test('Disposing the runtime emits an event', t => {
+    let disposed = false;
+    const rt = new Runtime();
+    rt.addListener('RUNTIME_DISPOSED', () => {
+        disposed = true;
+    });
+    rt.start();
+    t.equal(disposed, true);
+    t.end();
+});