🔧 fix: trigger preview action when color or palette changes

WallReel/main.cpp

@@ -20,6 +20,11 @@ using namespace WallReel::Core;
 WALLREEL_DECLARE_SENDER("Main")
 
 int main(int argc, char* argv[]) {
+    // Destruction order after QApplication quits its event loop:
+    // 1. QQmlApplicationEngine (with all QML objects)
+    // 2. provider (manages states and connections)
+    // 3. bootstrap (manages lifecycle of all managers)
+    // 4. QApplication
 
     QApplication a(argc, argv);
     a.setApplicationName(APP_NAME);
@@ -42,27 +47,29 @@ int main(int argc, char* argv[]) {
             return 0;
         }
 
-        Provider::Carousel provider(&a, bootstrap);
-        qmlRegisterSingletonInstance(
-            COREMODULE_URI,
-            MODULE_VERSION_MAJOR,
-            MODULE_VERSION_MINOR,
-            "CarouselProvider",
-            &provider);
         {
-            QQmlApplicationEngine engine;
+            Provider::Carousel provider(&a, bootstrap);
+            qmlRegisterSingletonInstance(
+                COREMODULE_URI,
+                MODULE_VERSION_MAJOR,
+                MODULE_VERSION_MINOR,
+                "CarouselProvider",
+                &provider);
+            {
+                QQmlApplicationEngine engine;
 
-            QObject::connect(
-                &engine,
-                &QQmlApplicationEngine::objectCreationFailed,
-                &a,
-                []() { QCoreApplication::exit(-1); },
-                Qt::QueuedConnection);
-            engine.loadFromModule(UIMODULE_URI, "Main");
+                QObject::connect(
+                    &engine,
+                    &QQmlApplicationEngine::objectCreationFailed,
+                    &a,
+                    []() { QCoreApplication::exit(-1); },
+                    Qt::QueuedConnection);
+                engine.loadFromModule(UIMODULE_URI, "Main");
 
-            provider.start();
+                bootstrap.start();
 
-            return a.exec();
+                return a.exec();
+            }
         }
     }
 }