ControllerScriptEngine: generate wrappers for input callbacks

This avoids calling two separate JS functions (one to convert the
ArrayBuffer to a Uint8Array then the callback) every time controller
input is received.

src/controllers/scripting/controllerscriptenginebase.cpp

@@ -57,8 +57,20 @@ bool ControllerScriptEngineBase::initialize() {
                 "midi", m_pJSEngine->newQObject(controllerProxy));
     }
 
-    m_byteArrayToScriptValueJSFunction = m_pJSEngine->evaluate(
-            "(function(arg1) { return new Uint8Array(arg1) })");
+    // Binary data is passed from the Controller as a QByteArray, which
+    // QJSEngine::toScriptValue converts to an ArrayBuffer in JavaScript.
+    // ArrayBuffer cannot be accessed with the [] operator in JS; it needs
+    // to be converted to a typed array (Uint8Array in this case) first.
+    // This function generates a wrapper function from a JS callback to do
+    // that conversion automatically.
+    m_makeArrayBufferWrapperFunction = m_pJSEngine->evaluate(QStringLiteral(
+            // arg2 is the timestamp for ControllerScriptModuleEngine.
+            // In ControllerScriptEngineLegacy it is the length of the array.
+            "(function(callback) {"
+            "    return function(arrayBuffer, arg2) {"
+            "        callback(new Uint8Array(arrayBuffer), arg2);"
+            "    };"
+            "})"));
 
     return true;
 }
@@ -235,16 +247,6 @@ void ControllerScriptEngineBase::throwJSError(const QString& message) {
 #endif
 }
 
-QJSValue ControllerScriptEngineBase::byteArrayToScriptValue(
-        const QByteArray& byteArray) {
-    // The QJSEngine converts the QByteArray to an ArrayBuffer object.
-    QJSValue arrayBuffer = m_pJSEngine->toScriptValue(byteArray);
-    // Convert the ArrayBuffer to a Uint8 typed array so scripts can access its bytes
-    // with the [] operator.
-    QJSValue result =
-            m_byteArrayToScriptValueJSFunction.call(QJSValueList{arrayBuffer});
-    if (result.isError()) {
-        showScriptExceptionDialog(result);
-    }
-    return result;
+QJSValue ControllerScriptEngineBase::wrapArrayBufferCallback(const QJSValue& callback) {
+    return m_makeArrayBufferWrapperFunction.call(QJSValueList{callback});
 }

src/controllers/scripting/controllerscriptenginebase.h

@@ -42,7 +42,7 @@ class ControllerScriptEngineBase : public QObject {
 
     void scriptErrorDialog(const QString& detailedError, const QString& key, bool bFatal = false);
 
-    QJSValue byteArrayToScriptValue(const QByteArray& byteArray);
+    QJSValue wrapArrayBufferCallback(const QJSValue& callback);
 
     bool m_bDisplayingExceptionDialog;
     QJSEngine* m_pJSEngine;
@@ -58,7 +58,7 @@ class ControllerScriptEngineBase : public QObject {
     void reload();
 
   private:
-    QJSValue m_byteArrayToScriptValueJSFunction;
+    QJSValue m_makeArrayBufferWrapperFunction;
 
   private slots:
     void errorDialogButton(const QString& key, QMessageBox::StandardButton button);

src/controllers/scripting/controllerscriptmoduleengine.cpp

@@ -24,7 +24,7 @@ bool ControllerScriptModuleEngine::initialize() {
 
     QJSValue handleInputFunction = mod.property("handleInput");
     if (handleInputFunction.isCallable()) {
-        m_handleInputFunction = handleInputFunction;
+        m_handleInputFunction = wrapArrayBufferCallback(handleInputFunction);
     } else {
         scriptErrorDialog(
                 "Controller JavaScript module exports no handleInput function.",
@@ -52,7 +52,7 @@ void ControllerScriptModuleEngine::shutdown() {
 void ControllerScriptModuleEngine::handleInput(
         QByteArray data, mixxx::Duration timestamp) {
     QJSValueList args;
-    args << byteArrayToScriptValue(data);
+    args << m_pJSEngine->toScriptValue(data);
     args << timestamp.toDoubleMillis();
     executeFunction(m_handleInputFunction, args);
 }

src/controllers/scripting/legacy/controllerscriptenginelegacy.cpp

@@ -105,7 +105,9 @@ bool ControllerScriptEngineLegacy::initialize() {
             continue;
         }
         functionName.append(QStringLiteral(".incomingData"));
-        m_incomingDataFunctions.append(wrapFunctionCode(functionName, 2));
+        m_incomingDataFunctions.append(
+                wrapArrayBufferCallback(
+                        wrapFunctionCode(functionName, 2)));
     }
 
     QJSValueList args;
@@ -139,7 +141,7 @@ bool ControllerScriptEngineLegacy::handleIncomingData(const QByteArray& data) {
     }
 
     QJSValueList args;
-    args << byteArrayToScriptValue(data);
+    args << m_pJSEngine->toScriptValue(data);
     args << QJSValue(data.size());
 
     for (const QJSValue& function : m_incomingDataFunctions) {