QFactoryLoader: generalize qLoadPlugin()

- Use perfect forwarding for the additional argument.
- Provide a variadic template version
- Deprecate qLoadPlugin1() — there's no reason for a different name
  — and fix all callers in qtbase.
- Provide non-variadic overloads for up to three additional args
  (QPlatformIntegration rolled its own function because it needs
  three args).

Change-Id: I72fb2dd9a021de704cbf5e4b6ea31c80447fb3b1
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@theqtcompany.com>
Reviewed-by: Lars Knoll <lars.knoll@theqtcompany.com>

src/corelib/plugin/qfactoryloader_p.h

@@ -85,6 +85,23 @@ public:
     QObject *instance(int index) const;
 };
 
+#ifdef Q_COMPILER_VARIADIC_TEMPLATES
+
+template <class PluginInterface, class FactoryInterface, typename ...Args>
+PluginInterface *qLoadPlugin(const QFactoryLoader *loader, const QString &key, Args &&...args)
+{
+    const int index = loader->indexOf(key);
+    if (index != -1) {
+        QObject *factoryObject = loader->instance(index);
+        if (FactoryInterface *factory = qobject_cast<FactoryInterface *>(factoryObject))
+            if (PluginInterface *result = factory->create(key, std::forward<Args>(args)...))
+                return result;
+    }
+    return nullptr;
+}
+
+#else
+
 template <class PluginInterface, class FactoryInterface>
     PluginInterface *qLoadPlugin(const QFactoryLoader *loader, const QString &key)
 {
@@ -98,21 +115,57 @@ template <class PluginInterface, class FactoryInterface>
     return 0;
 }
 
-template <class PluginInterface, class FactoryInterface, class Parameter1>
-PluginInterface *qLoadPlugin1(const QFactoryLoader *loader,
+template <class PluginInterface, class FactoryInterface, class P1>
+PluginInterface *qLoadPlugin(const QFactoryLoader *loader,
                               const QString &key,
-                              const Parameter1 &parameter1)
+                              P1 &&p1)
 {
     const int index = loader->indexOf(key);
     if (index != -1) {
         QObject *factoryObject = loader->instance(index);
         if (FactoryInterface *factory = qobject_cast<FactoryInterface *>(factoryObject))
-            if (PluginInterface *result = factory->create(key, parameter1))
+            if (PluginInterface *result = factory->create(key, std::forward<P1>(p1)))
                 return result;
     }
     return 0;
 }
 
+template <class PluginInterface, class FactoryInterface, class P1, class P2>
+PluginInterface *qLoadPlugin(const QFactoryLoader *loader,
+                              const QString &key,
+                              P1 &&p1, P2 &&p2)
+{
+    const int index = loader->indexOf(key);
+    if (index != -1) {
+        QObject *factoryObject = loader->instance(index);
+        if (FactoryInterface *factory = qobject_cast<FactoryInterface *>(factoryObject))
+            if (PluginInterface *result = factory->create(key, std::forward<P1>(p1), std::forward<P2>(p2)))
+                return result;
+    }
+    return 0;
+}
+
+template <class PluginInterface, class FactoryInterface, class P1, class P2, class P3>
+PluginInterface *qLoadPlugin(const QFactoryLoader *loader,
+                              const QString &key,
+                              P1 &&p1, P2 &&p2, P3 &&p3)
+{
+    const int index = loader->indexOf(key);
+    if (index != -1) {
+        QObject *factoryObject = loader->instance(index);
+        if (FactoryInterface *factory = qobject_cast<FactoryInterface *>(factoryObject))
+            if (PluginInterface *result = factory->create(key, std::forward<P1>(p1), std::forward<P2>(p2), std::forward<P3>(p3)))
+                return result;
+    }
+    return 0;
+}
+
+#endif
+
+template <class PluginInterface, class FactoryInterface, typename Arg>
+Q_DECL_DEPRECATED PluginInterface *qLoadPlugin1(const QFactoryLoader *loader, const QString &key, Arg &&arg)
+{ return qLoadPlugin(loader, key, std::forward<Arg>(arg)); }
+
 QT_END_NAMESPACE
 
 #endif // QT_NO_QOBJECT

src/gui/kernel/qgenericpluginfactory.cpp

@@ -71,7 +71,7 @@ QObject *QGenericPluginFactory::create(const QString& key, const QString &specif
 {
 #if (!defined(Q_OS_WIN32) || defined(QT_SHARED)) && !defined(QT_NO_LIBRARY)
     const QString driver = key.toLower();
-    if (QObject *object = qLoadPlugin1<QObject, QGenericPlugin>(loader(), driver, specification))
+    if (QObject *object = qLoadPlugin<QObject, QGenericPlugin>(loader(), driver, specification))
         return object;
 #else // (!Q_OS_WIN32 || QT_SHARED) && !QT_NO_LIBRARY
     Q_UNUSED(key)

src/gui/kernel/qplatforminputcontextfactory.cpp

@@ -69,7 +69,7 @@ QPlatformInputContext *QPlatformInputContextFactory::create(const QString& key)
         QStringList paramList = key.split(QLatin1Char(':'));
         const QString platform = paramList.takeFirst().toLower();
 
-        QPlatformInputContext *ic = qLoadPlugin1<QPlatformInputContext, QPlatformInputContextPlugin>
+        QPlatformInputContext *ic = qLoadPlugin<QPlatformInputContext, QPlatformInputContextPlugin>
                                                  (loader(), platform, paramList);
         if (ic && ic->isValid())
             return ic;

src/gui/kernel/qplatformintegrationfactory.cpp

@@ -50,30 +50,19 @@ Q_GLOBAL_STATIC_WITH_ARGS(QFactoryLoader, directLoader,
                           (QPlatformIntegrationFactoryInterface_iid, QLatin1String(""), Qt::CaseInsensitive))
 #endif // !QT_NO_LIBRARY
 
-static inline QPlatformIntegration *loadIntegration(QFactoryLoader *loader, const QString &key, const QStringList &parameters, int &argc, char ** argv)
-{
-    const int index = loader->indexOf(key);
-    if (index != -1) {
-        if (QPlatformIntegrationPlugin *factory = qobject_cast<QPlatformIntegrationPlugin *>(loader->instance(index)))
-            if (QPlatformIntegration *result = factory->create(key, parameters, argc, argv))
-                return result;
-    }
-    return 0;
-}
-
 QPlatformIntegration *QPlatformIntegrationFactory::create(const QString &platform, const QStringList &paramList, int &argc, char **argv, const QString &platformPluginPath)
 {
 #ifndef QT_NO_LIBRARY
     // Try loading the plugin from platformPluginPath first:
     if (!platformPluginPath.isEmpty()) {
         QCoreApplication::addLibraryPath(platformPluginPath);
-        if (QPlatformIntegration *ret = loadIntegration(directLoader(), platform, paramList, argc, argv))
+        if (QPlatformIntegration *ret = qLoadPlugin<QPlatformIntegration, QPlatformIntegrationPlugin>(directLoader(), platform, paramList, argc, argv))
             return ret;
     }
 #else
     Q_UNUSED(platformPluginPath);
 #endif
-    return loadIntegration(loader(), platform, paramList, argc, argv);
+    return qLoadPlugin<QPlatformIntegration, QPlatformIntegrationPlugin>(loader(), platform, paramList, argc, argv);
 }
 
 /*!

src/gui/kernel/qplatformthemefactory.cpp

@@ -51,23 +51,22 @@ Q_GLOBAL_STATIC_WITH_ARGS(QFactoryLoader, directLoader,
 
 QPlatformTheme *QPlatformThemeFactory::create(const QString& key, const QString &platformPluginPath)
 {
+#ifndef QT_NO_LIBRARY
     QStringList paramList = key.split(QLatin1Char(':'));
     const QString platform = paramList.takeFirst().toLower();
 
-#ifndef QT_NO_LIBRARY
     // Try loading the plugin from platformPluginPath first:
     if (!platformPluginPath.isEmpty()) {
         QCoreApplication::addLibraryPath(platformPluginPath);
-        if (QPlatformTheme *ret = qLoadPlugin1<QPlatformTheme, QPlatformThemePlugin>(directLoader(), platform, paramList))
+        if (QPlatformTheme *ret = qLoadPlugin<QPlatformTheme, QPlatformThemePlugin>(directLoader(), platform, paramList))
             return ret;
     }
-    if (QPlatformTheme *ret = qLoadPlugin1<QPlatformTheme, QPlatformThemePlugin>(loader(), platform, paramList))
-           return ret;
+    return qLoadPlugin<QPlatformTheme, QPlatformThemePlugin>(loader(), platform, paramList);
 #else
     Q_UNUSED(key);
     Q_UNUSED(platformPluginPath);
-#endif
     return 0;
+#endif
 }
 
 /*!