Register Qt 4.7 import on-demand, instead of at startup.

This is a slightly less awkward approach (keeps backwards-compatibility) while
speeding up startup for applications that don't use the old import path.

Also prints a warning to let developers know they should migrate their code when
possible. Completely disabling the Qt 4.7 import is still possible by setting
QT_NO_IMPORT_QT47_QML.

This takes around 10-15ms off a very simple "hello world" on my macbook.

As an added bonus, forward-port a similar approach to 4.8's
a26f545d8e25af74fb43d16c9afa79f6e04463e7 and don't register graphical types in a
non-graphical application as someone (very naughtily) apparently forgot to get
it integrated to Qt 5 first.

Change-Id: I7821523750b3ab6770f367788725d0da70c5ec1f
Reviewed-by: Thomas McGuire <thomas.mcguire@kdab.com>
Reviewed-by: Alan Alpert <416365416c@gmail.com>

5 files changed, 37 insertions, 6 deletions

diff --git a/src/declarative/qml/qdeclarativeengine.cpp b/src/declarative/qml/qdeclarativeengine.cpp
index bbf2b6be..b38a4991 100644
--- a/src/declarative/qml/qdeclarativeengine.cpp
+++ b/src/declarative/qml/qdeclarativeengine.cpp
@@ -188,13 +188,16 @@ void QDeclarativeEnginePrivate::defineModule()
     qmlRegisterType<QObject>("QtQuick",1,0,"QtObject");
     qmlRegisterType<QDeclarativeWorkerScript>("QtQuick",1,0,"WorkerScript");
 
+    qmlRegisterType<QDeclarativeBinding>();
+}
+
+void QDeclarativeEnginePrivate::defineModuleCompat()
+{
 #ifndef QT_NO_IMPORT_QT47_QML
     qmlRegisterType<QDeclarativeComponent>("Qt",4,7,"Component");
     qmlRegisterType<QObject>("Qt",4,7,"QtObject");
     qmlRegisterType<QDeclarativeWorkerScript>("Qt",4,7,"WorkerScript");
 #endif
-
-    qmlRegisterType<QDeclarativeBinding>();
 }
 
 /*!
@@ -356,10 +359,10 @@ QDeclarativeEnginePrivate::QDeclarativeEnginePrivate(QDeclarativeEngine *e)
 {
     if (!qt_QmlQtModule_registered) {
         qt_QmlQtModule_registered = true;
-        QDeclarativeItemModule::defineModule();
-        QDeclarativeUtilModule::defineModule();
         QDeclarativeEnginePrivate::defineModule();
+        QDeclarativeItemModule::defineModule();
         QDeclarativeValueTypeFactory::registerValueTypes();
+        QDeclarativeUtilModule::defineModule();
     }
     globalClass = new QDeclarativeGlobalScriptClass(&scriptEngine);
 }
diff --git a/src/declarative/qml/qdeclarativeengine_p.h b/src/declarative/qml/qdeclarativeengine_p.h
index c4b55156..d5659878 100644
--- a/src/declarative/qml/qdeclarativeengine_p.h
+++ b/src/declarative/qml/qdeclarativeengine_p.h
@@ -324,6 +324,7 @@ public:
     static QString urlToLocalFileOrQrc(const QUrl& url);
 
     static void defineModule();
+    static void defineModuleCompat();
 
     static bool qml_debugging_enabled;
 };
diff --git a/src/declarative/qml/qdeclarativemetatype.cpp b/src/declarative/qml/qdeclarativemetatype.cpp
index 7786bea4..a045623d 100644
--- a/src/declarative/qml/qdeclarativemetatype.cpp
+++ b/src/declarative/qml/qdeclarativemetatype.cpp
@@ -45,6 +45,9 @@
 #include "private/qdeclarativeproxymetaobject_p.h"
 #include "private/qdeclarativecustomparser_p.h"
 #include "private/qdeclarativeguard_p.h"
+#include "private/qdeclarativeengine_p.h"
+#include "private/qdeclarativeitemsmodule_p.h"
+#include "private/qdeclarativeutilmodule_p.h"
 
 #include <QtCore/qdebug.h>
 #include <QtCore/qstringlist.h>
@@ -690,6 +693,23 @@ int QDeclarativePrivate::qmlregister(RegistrationType type, void *data)
 */
 bool QDeclarativeMetaType::isModule(const QByteArray &module, int versionMajor, int versionMinor)
 {
+#ifndef QT_NO_IMPORT_QT47_QML
+    // "import Qt 4.7" should have died off, but unfortunately, it was in a
+    // major release. We don't register 4.7 types by default, as it's a
+    // performance penalty. Instead, register them on-demand.
+    if (strcmp(module.constData(), "Qt") == 0 && versionMajor == 4 && versionMinor == 7) {
+        static bool qt47Registered = false;
+        if (!qt47Registered) {
+            qWarning() << Q_FUNC_INFO << "Qt 4.7 import detected; please note that Qt 4.7 is directly reusable as QtQuick 1.x with no code changes. Continuing, but startup time will be slower.";
+            qt47Registered = true;
+            QDeclarativeEnginePrivate::defineModuleCompat();
+            QDeclarativeItemModule::defineModuleCompat();
+            QDeclarativeValueTypeFactory::registerValueTypesCompat();
+            QDeclarativeUtilModule::defineModuleCompat();
+        }
+    }
+#endif
+
     QDeclarativeMetaTypeData *data = metaTypeData();
     QDeclarativeMetaTypeData::ModuleInfoHash::Iterator it = data->modules.find(module);
     return it != data->modules.end()
diff --git a/src/declarative/qml/qdeclarativevaluetype.cpp b/src/declarative/qml/qdeclarativevaluetype.cpp
index c18ea9d8..6a0eac98 100644
--- a/src/declarative/qml/qdeclarativevaluetype.cpp
+++ b/src/declarative/qml/qdeclarativevaluetype.cpp
@@ -44,6 +44,7 @@
 #include "private/qdeclarativemetatype_p.h"
 #include "private/qfont_p.h"
 
+#include <QtWidgets/qapplication.h>
 #include <QtCore/qdebug.h>
 
 QT_BEGIN_NAMESPACE
@@ -106,10 +107,15 @@ void QDeclarativeValueTypeFactory::registerValueTypes()
 {
     qmlRegisterValueTypeEnums<QDeclarativeEasingValueType>("QtQuick",1,0,"Easing");
     qmlRegisterValueTypeEnums<QDeclarativeFontValueType>("QtQuick",1,0,"Font");
-#ifndef QT_NO_IMPORT_QT47_QML
+}
+
+void QDeclarativeValueTypeFactory::registerValueTypesCompat()
+{
+    if (QApplication::type() == QApplication::Tty)
+        return;
+
     qmlRegisterValueTypeEnums<QDeclarativeEasingValueType>("Qt",4,7,"Easing");
     qmlRegisterValueTypeEnums<QDeclarativeFontValueType>("Qt",4,7,"Font");
-#endif
 }
 
 QDeclarativeValueType *QDeclarativeValueTypeFactory::valueType(int t)
diff --git a/src/declarative/qml/qdeclarativevaluetype_p.h b/src/declarative/qml/qdeclarativevaluetype_p.h
index 66afdf95..3fac009b 100644
--- a/src/declarative/qml/qdeclarativevaluetype_p.h
+++ b/src/declarative/qml/qdeclarativevaluetype_p.h
@@ -90,6 +90,7 @@ public:
     static QDeclarativeValueType *valueType(int);
 
     static void registerValueTypes();
+    static void registerValueTypesCompat();
 
     QDeclarativeValueType *operator[](int idx) const {
         if (idx >= (int)QVariant::UserType) return 0;