Optimize ExecutionEngine::metaTypeToJS()

We almost never need to construct a QVariant to do this. Constructing a
QVariant is excessively expensive if you have something simple like an
integer. This also fixes the unexpected "unwrapping" of variants when we
pass them through QJSValue.

[ChangeLog][QtQml][Important Behavior Changes] If you create a QJSValue
from a nested QVariant (that is, a QVariant containing another
QVariant), then, when retrieving its contents again, the outer variant
is not unwrapped anymore. Rather, you get exactly the value you've
passed in.

Change-Id: I8c16eed4f13e8cfdeced0756eef593b3b8e84dd1
Reviewed-by: Fabian Kosmale <fabian.kosmale@qt.io>

1 files changed, 10 insertions, 5 deletions

diff --git a/src/qml/jsruntime/qv4sequenceobject.cpp b/src/qml/jsruntime/qv4sequenceobject.cpp
index 73fa2385fd..95ba210753 100644
--- a/src/qml/jsruntime/qv4sequenceobject.cpp
+++ b/src/qml/jsruntime/qv4sequenceobject.cpp
@@ -627,8 +627,14 @@ ReturnedValue SequencePrototype::newSequence(QV4::ExecutionEngine *engine, int s
     return Encode::undefined();
 }
 
-ReturnedValue SequencePrototype::fromVariant(QV4::ExecutionEngine *engine, const QVariant &v,
-                                             bool *succeeded)
+ReturnedValue SequencePrototype::fromVariant(
+        QV4::ExecutionEngine *engine, const QVariant &v, bool *succeeded)
+{
+    return fromData(engine, v.metaType(), v.constData(), succeeded);
+}
+
+ReturnedValue SequencePrototype::fromData(
+        ExecutionEngine *engine, const QMetaType &type, const void *data, bool *succeeded)
 {
     QV4::Scope scope(engine);
     // This function is called when assigning a sequence value to a normal JS var
@@ -637,11 +643,10 @@ ReturnedValue SequencePrototype::fromVariant(QV4::ExecutionEngine *engine, const
     // QObject property.
 
     const QQmlType qmlType = QQmlMetaType::qmlType(
-                v.userType(), QQmlMetaType::TypeIdCategory::MetaType);
+                type.id(), QQmlMetaType::TypeIdCategory::MetaType);
     if (qmlType.isSequentialContainer()) {
         *succeeded = true;
-        QV4::ScopedObject obj(scope, engine->memoryManager->allocate<QV4Sequence>(
-                                  qmlType, v.data()));
+        QV4::ScopedObject obj(scope, engine->memoryManager->allocate<QV4Sequence>(qmlType, data));
         return obj.asReturnedValue();
     }