fix script connection object trigger method

src/control/controlobjectscript.cpp

@@ -40,15 +40,7 @@ void ControlObjectScript::slotValueChanged(double value, QObject*) {
     // itself. Otherwise the this may crash since the disconnect call
     // happens during conn.function.call() in the middle of the loop below.
     QList<ControllerEngineConnection> connections = m_connectedScriptFunctions;
-    for(auto&& conn: connections) {
-        QScriptValueList args;
-        args << QScriptValue(value);
-        args << QScriptValue(getKey().group);
-        args << QScriptValue(getKey().item);
-        QScriptValue result = conn.function.call(conn.context, args);
-        if (result.isError()) {
-            qWarning() << "ControllerEngine: Invocation of callback" << conn.id
-                       << "failed:" << result.toString();
-        }
+    for (auto&& conn: connections) {
+        conn.executeCallback(value);
     }
 }

src/controllers/controllerengine.cpp

@@ -807,6 +807,23 @@ QScriptValue ControllerEngine::connectControl(
     return QScriptValue(false);
 }
 
+/* -------- ------------------------------------------------------
+   Purpose: Execute a ControllerEngineConnection's callback
+   Input:   the value of the connected ControlObject to pass to the callback
+   -------- ------------------------------------------------------ */
+void ControllerEngineConnection::executeCallback(double value) const {
+    QScriptValueList args;
+    args << QScriptValue(value);
+    args << QScriptValue(key.group);
+    args << QScriptValue(key.item);
+    QScriptValue func = function; // copy function because QScriptValue::call is not const
+    QScriptValue result = func.call(context, args);
+    if (result.isError()) {
+        qWarning() << "ControllerEngine: Invocation of callback" << id
+                   << "failed:" << result.toString();
+    }
+}
+
 /* -------- ------------------------------------------------------
    Purpose: (Dis)connects a ControllerEngineConnection
    Input:   the ControllerEngineConnection to disconnect
@@ -835,13 +852,16 @@ void ControllerEngineConnectionScriptValue::disconnect() {
    Input:   the ControllerEngineConnection to trigger
    -------- ------------------------------------------------------ */
 void ControllerEngine::triggerControl(const ControllerEngineConnection conn) {
-    ControlObjectScript* coScript = getControlObjectScript(conn.key.group, conn.key.item);
+    if (m_pEngine == nullptr) {
+        return;
+    }
 
-    if (m_pEngine == nullptr || coScript == nullptr) {
+    ControlObjectScript* coScript = getControlObjectScript(conn.key.group, conn.key.item);
+    if (coScript == nullptr) {
         return;
     }
 
-    coScript->emitValueChanged();
+    conn.executeCallback(coScript->get());
 }
 
 void ControllerEngineConnectionScriptValue::trigger() {

src/controllers/controllerengine.h

@@ -33,6 +33,8 @@ class ControllerEngineConnection {
     QScriptValue function;
     ControllerEngine *ce;
     QScriptValue context;
+
+    void executeCallback(double value) const;
 };
 
 class ControllerEngineConnectionScriptValue : public QObject {

src/test/controllerengine_test.cpp

@@ -335,3 +335,28 @@ TEST_F(ControllerEngineTest, connectControl_DisconnectByConnectionObject) {
     // The counter should have been incremented exactly once.
     EXPECT_DOUBLE_EQ(1.0, pass->get());
 }
+
+TEST_F(ControllerEngineTest, connectControl_TriggerByConnectionObject) {
+    // Test that triggering using the 'trigger' method on the connection
+    // object returned from connectControl works.
+    auto co = std::make_unique<ControlObject>(ConfigKey("[Test]", "co"));
+    auto counter = std::make_unique<ControlObject>(ConfigKey("[Test]", "counter"));
+
+    ScopedTemporaryFile script(makeTemporaryFile(
+        "var incrementCounterCO = function () {"
+        "  var counter = engine.getValue('[Test]', 'counter');"
+        "  engine.setValue('[Test]', 'counter', counter + 1);"
+        "};"
+        "var connection1 = engine.connectControl('[Test]', 'co', incrementCounterCO);"
+        // Make a second connection with the same ControlObject
+        // to check that triggering a connection object only triggers that callback,
+        // not every callback connected to its ControlObject.
+        "var connection2 = engine.connectControl('[Test]', 'co', incrementCounterCO);"
+        "connection1.trigger();"
+    ));
+
+    cEngine->evaluate(script->fileName());
+    EXPECT_FALSE(cEngine->hasErrors(script->fileName()));
+    // The counter should have been incremented exactly once.
+    EXPECT_DOUBLE_EQ(1.0, counter->get());
+}