From 84705fc463a685062474972ff4c298e6aa92e621 Mon Sep 17 00:00:00 2001
From: "Michael \"Z\" Goddard" <mzgoddard@gmail.com>
Date: Wed, 6 Jun 2018 09:53:45 -0400
Subject: [PATCH 1/4] replace new Promise(r => r()) with Promise.resolve

Promise.resolve is a Promise convenience method that creates a promise
resolved to a given argument like creating a promise with a function
that immediately calls the resolve function with the given value.
---
 src/blocks/scratch3_sound.js | 8 ++------
 1 file changed, 2 insertions(+), 6 deletions(-)

diff --git a/src/blocks/scratch3_sound.js b/src/blocks/scratch3_sound.js
index 4c637e71a..a599b314c 100644
--- a/src/blocks/scratch3_sound.js
+++ b/src/blocks/scratch3_sound.js
@@ -231,9 +231,7 @@ class Scratch3SoundBlocks {
         util.target.audioPlayer.setEffect(effect, soundState.effects[effect]);
 
         // Yield until the next tick.
-        return new Promise(resolve => {
-            resolve();
-        });
+        return Promise.resolve();
     }
 
     _syncEffectsForTarget (target) {
@@ -284,9 +282,7 @@ class Scratch3SoundBlocks {
         util.target.audioPlayer.setVolume(util.target.volume);
 
         // Yield until the next tick.
-        return new Promise(resolve => {
-            resolve();
-        });
+        return Promise.resolve();
     }
 
     getVolume (args, util) {

From 9311a274d5c2711d530b05a26e5d23f362167d64 Mon Sep 17 00:00:00 2001
From: "Michael \"Z\" Goddard" <mzgoddard@gmail.com>
Date: Wed, 6 Jun 2018 10:13:29 -0400
Subject: [PATCH 2/4] add BlockUtility.yieldTick

---
 src/engine/block-utility.js | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/src/engine/block-utility.js b/src/engine/block-utility.js
index 2026c0f0d..b456d02fa 100644
--- a/src/engine/block-utility.js
+++ b/src/engine/block-utility.js
@@ -57,6 +57,13 @@ class BlockUtility {
         this.thread.status = Thread.STATUS_YIELD;
     }
 
+    /**
+     * Set the thread to yield until the next tick of the runtime.
+     */
+    yieldTick () {
+        this.thread.status = Thread.STATUS_YIELD_TICK;
+    }
+
     /**
      * Start a branch in the current block.
      * @param {number} branchNum Which branch to step to (i.e., 1, 2).

From 0a006dc9811e9b7008189169d2e4ce45de29b5fa Mon Sep 17 00:00:00 2001
From: "Michael \"Z\" Goddard" <mzgoddard@gmail.com>
Date: Wed, 6 Jun 2018 09:57:53 -0400
Subject: [PATCH 3/4] add Runtime.isWaitingThread

Add a Runtime Thread helper to check if a thread is in a state where it
will not change at least until next frame. This includes any state
where the thread is done, as that will not change either.
---
 src/engine/runtime.js | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/src/engine/runtime.js b/src/engine/runtime.js
index ab38955e4..3acfe4bbf 100644
--- a/src/engine/runtime.js
+++ b/src/engine/runtime.js
@@ -1017,6 +1017,19 @@ class Runtime extends EventEmitter {
             this.threads.indexOf(thread) > -1);
     }
 
+    /**
+     * Return whether a thread is waiting for more information or done.
+     * @param {?Thread} thread Thread object to check.
+     * @return {boolean} True if the thread is waiting
+     */
+    isWaitingThread (thread) {
+        return (
+            thread.status === Thread.STATUS_PROMISE_WAIT ||
+            thread.status === Thread.STATUS_YIELD_TICK ||
+            !this.isActiveThread(thread)
+        );
+    }
+
     /**
      * Toggle a script.
      * @param {!string} topBlockId ID of block that starts the script.

From d161251a9b6acc45a36f5991b91ba80abd9d22d1 Mon Sep 17 00:00:00 2001
From: "Michael \"Z\" Goddard" <mzgoddard@gmail.com>
Date: Wed, 6 Jun 2018 09:59:38 -0400
Subject: [PATCH 4/4] yield a thread loop or tick in event_broadcastandwait

- yield a thread loop or tick in looks_switchbackdroptoandwait

If all threads broadcastAndWait is watching are "waiting" for a future
frame, yield until the next tick so event_broadcastandwait also defers
to a future frame.
---
 src/blocks/scratch3_event.js | 12 +++++++++++-
 src/blocks/scratch3_looks.js | 12 +++++++++++-
 2 files changed, 22 insertions(+), 2 deletions(-)

diff --git a/src/blocks/scratch3_event.js b/src/blocks/scratch3_event.js
index ba496a172..6d4eaca8a 100644
--- a/src/blocks/scratch3_event.js
+++ b/src/blocks/scratch3_event.js
@@ -100,7 +100,17 @@ class Scratch3EventBlocks {
             const instance = this;
             const waiting = util.stackFrame.startedThreads.some(thread => instance.runtime.isActiveThread(thread));
             if (waiting) {
-                util.yield();
+                // If all threads are waiting for the next tick or later yield
+                // for a tick as well. Otherwise yield until the next loop of
+                // the threads.
+                if (
+                    util.stackFrame.startedThreads
+                        .every(thread => instance.runtime.isWaitingThread(thread))
+                ) {
+                    util.yieldTick();
+                } else {
+                    util.yield();
+                }
             }
         }
     }
diff --git a/src/blocks/scratch3_looks.js b/src/blocks/scratch3_looks.js
index 4a7994a4a..21599f251 100644
--- a/src/blocks/scratch3_looks.js
+++ b/src/blocks/scratch3_looks.js
@@ -409,7 +409,17 @@ class Scratch3LooksBlocks {
         const instance = this;
         const waiting = util.stackFrame.startedThreads.some(thread => instance.runtime.isActiveThread(thread));
         if (waiting) {
-            util.yield();
+            // If all threads are waiting for the next tick or later yield
+            // for a tick as well. Otherwise yield until the next loop of
+            // the threads.
+            if (
+                util.stackFrame.startedThreads
+                    .every(thread => instance.runtime.isWaitingThread(thread))
+            ) {
+                util.yieldTick();
+            } else {
+                util.yield();
+            }
         }
     }