bug 1558123 call AudioWorkletProcessor.process() r=padenot,bzbarsky

https://heycam.github.io/webidl/#call-a-user-objects-operation may be a
simpler option here, but there are some small optimizations possible with
using JS::Call() directly:
JS::ExposeObjectToActiveJS() is not necessary because parameters are
PersistentRooted and so won't be gray.  MaybeWrapObjectValue() is not
necessary because parameters are already in the appropriate compartment.

See also WebAudio/web-audio-api#1967 and
WebAudio/web-audio-api#1933

Microtask support is tracked in
https://bugzilla.mozilla.org/show_bug.cgi?id=1566312

Differential Revision: https://phabricator.services.mozilla.com/D34838

dom/media/webaudio/AudioWorkletNode.cpp

@@ -63,13 +63,16 @@ class WorkletNodeEngine final : public AudioNodeEngine {
 
  private:
   void SendProcessorError();
+  bool CallProcess(JSContext* aCx, JS::Handle<JS::Value> aCallable,
+                   bool* aActiveRet);
 
   void ReleaseJSResources() {
     mInputs.mPorts.clearAndFree();
     mOutputs.mPorts.clearAndFree();
     mInputs.mJSArray.reset();
     mOutputs.mJSArray.reset();
     mGlobal = nullptr;
+    // This is equivalent to setting [[callable process]] to false.
     mProcessor.reset();
   }
 
@@ -231,6 +234,29 @@ static bool PrepareBufferArrays(JSContext* aCx, Span<const AudioBlock> aBlocks,
   return !(NS_WARN_IF(!PrepareArray(aCx, aPorts->mPorts, &aPorts->mJSArray)));
 }
 
+// This runs JS script.  MediaStreamGraph control messages, which would
+// potentially destroy the WorkletNodeEngine and its AudioNodeStream, cannot
+// be triggered by script.  They are not run from an nsIThread event loop and
+// do not run until after ProcessBlocksOnPorts() has returned.
+bool WorkletNodeEngine::CallProcess(JSContext* aCx,
+                                    JS::Handle<JS::Value> aCallable,
+                                    bool* aActiveRet) {
+  JS::RootedVector<JS::Value> argv(aCx);
+  if (NS_WARN_IF(!argv.resize(3))) {
+    return false;
+  }
+  argv[0].setObject(*mInputs.mJSArray);
+  argv[1].setObject(*mOutputs.mJSArray);
+  // TODO: argv[2].setObject() for parameters.
+  JS::Rooted<JS::Value> rval(aCx);
+  if (!JS::Call(aCx, mProcessor, aCallable, argv, &rval)) {
+    return false;
+  }
+
+  *aActiveRet = JS::ToBoolean(rval);
+  return true;
+}
+
 static void ProduceSilence(Span<AudioBlock> aOutput) {
   for (AudioBlock& output : aOutput) {
     output.SetNull(WEBAUDIO_BLOCK_SIZE);
@@ -262,9 +288,12 @@ void WorkletNodeEngine::ProcessBlocksOnPorts(AudioNodeStream* aStream,
   AutoEntryScript aes(mGlobal, "Worklet Process");
   JSContext* cx = aes.cx();
 
-  if (!PrepareBufferArrays(cx, aInput, &mInputs, ArrayElementInit::None) ||
+  JS::Rooted<JS::Value> process(cx);
+  if (!JS_GetProperty(cx, mProcessor, "process", &process) ||
+      !process.isObject() || !JS::IsCallable(&process.toObject()) ||
+      !PrepareBufferArrays(cx, aInput, &mInputs, ArrayElementInit::None) ||
       !PrepareBufferArrays(cx, aOutput, &mOutputs, ArrayElementInit::Zero)) {
-    // OOM.  Give up.
+    // process() not callable or OOM.
     SendProcessorError();
     ProduceSilence(aOutput);
     return;
@@ -291,7 +320,19 @@ void WorkletNodeEngine::ProcessBlocksOnPorts(AudioNodeStream* aStream,
     }
   }
 
-  // TODO call process() - bug 1558123
+  bool active;
+  if (!CallProcess(cx, process, &active)) {
+    // An exception occurred.
+    SendProcessorError();
+    /**
+     * https://webaudio.github.io/web-audio-api/#dom-audioworkletnode-onprocessorerror
+     * Note that once an exception is thrown, the processor will output silence
+     * throughout its lifetime.
+     */
+    ProduceSilence(aOutput);
+    return;
+  }
+  // TODO: Stay active even without inputs, if active is set.
 
   // Copy output values from JS objects.
   for (size_t o = 0; o < aOutput.Length(); ++o) {

testing/web-platform/meta/webaudio/the-audio-api/the-audioworklet-interface/simple-input-output.https.html.ini

@@ -4,12 +4,9 @@
   [# AUDIT TASK RUNNER FINISHED: 1 out of 2 tasks were failed.]
     expected: FAIL
 
-  [< [test\] 2 out of 2 assertions were failed.]
+  [< [test\] 1 out of 2 assertions were failed.]
     expected: FAIL
 
   [X AudioWorklet output[128:\]: Expected 1 for all values but found 47872 unexpected values: \n\tIndex\tActual\n\t[0\]\t0\n\t[1\]\t0\n\t[2\]\t0\n\t[3\]\t0\n\t...and 47868 more errors.]
     expected: FAIL
 
-  [X AudioWorklet output[0:127\] does not equal [1,1.0575640201568604,1.11493718624115,1.171929121017456,1.2283508777618408,1.2840152978897095,1.3387378454208374,1.3923370838165283,1.4446351528167725,1.4954586029052734,1.5446388721466064,1.5920131206512451,1.6374238729476929,1.6807208061218262,1.7217600345611572,1.7604057788848877...\] with an element-wise tolerance of {"absoluteThreshold":0,"relativeThreshold":0}.\n\tIndex\tActual\t\t\tExpected\t\tAbsError\t\tRelError\t\tTest threshold\n\t[0\]\t0.0000000000000000e+0\t1.0000000000000000e+0\t1.0000000000000000e+0\t1.0000000000000000e+0\t0.0000000000000000e+0\n\t[1\]\t0.0000000000000000e+0\t1.0575640201568604e+0\t1.0575640201568604e+0\t1.0000000000000000e+0\t0.0000000000000000e+0\n\t[2\]\t0.0000000000000000e+0\t1.1149371862411499e+0\t1.1149371862411499e+0\t1.0000000000000000e+0\t0.0000000000000000e+0\n\t[3\]\t0.0000000000000000e+0\t1.1719291210174561e+0\t1.1719291210174561e+0\t1.0000000000000000e+0\t0.0000000000000000e+0\n\t[4\]\t0.0000000000000000e+0\t1.2283508777618408e+0\t1.2283508777618408e+0\t1.0000000000000000e+0\t0.0000000000000000e+0\n\t...and 123 more errors.\n\tMax AbsError of 1.9998766183853149e+0 at index of 27.\n\t[27\]\t0.0000000000000000e+0\t1.9998766183853149e+0\t1.9998766183853149e+0\t1.0000000000000000e+0\t0.0000000000000000e+0\n\tMax RelError of 1.0000000000000000e+0 at index of 0.\n]
-    expected: FAIL
-