Merge pull request #1211 from mzgoddard/broadcast-and-wait-promise

yield a tick if broadcastandwait is waiting on threads waiting for a future tick

src/blocks/scratch3_event.js

@@ -109,10 +109,20 @@ class Scratch3EventBlocks {
             const instance = this;
             const waiting = util.stackFrame.startedThreads.some(thread => instance.runtime.isActiveThread(thread));
             if (waiting) {
+                // 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();
                 }
             }
         }
     }
+}
 
 module.exports = Scratch3EventBlocks;

src/blocks/scratch3_looks.js

@@ -416,9 +416,19 @@ class Scratch3LooksBlocks {
         const instance = this;
         const waiting = util.stackFrame.startedThreads.some(thread => instance.runtime.isActiveThread(thread));
         if (waiting) {
+            // 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();
             }
         }
+    }
 
     nextBackdrop () {
         const stage = this.runtime.getTargetForStage();

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) {

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).

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.