Enable lookups in QML

The main feature that needs to be implemented in order to enable lookups
in QML files is to respect that the QObject wrapper has its own storage
layer (meta-object properties). Lookups need to be able to index those
when the base is a QObject. This is done by caching the property data
and guarding the validity by comparing property cache pointers.

The same lookup logic is also implemented for value type wrappers.

OVerall there's more that can be done with lookups in meta-objects, for
constant properties for example.

For "global" lookups we have a safeguard in place that generates a
LoadName instruction for property access that should end up in the qml
context wrapper. So no changes are needed here at first, but the lookup
in the QML context can be optimized in the future.

The way of storing the property cache in the lookup itself trades
ugliness on destruction against the creation of less internal classes.
Another option would be to store the property cache in the internal
class and let QObjectWrapper always transition via the property cache.

Task-number: QTBUG-69898
Change-Id: I9c378c071acc6d7d4a34a2a76616f9594119d515
Reviewed-by: Ulf Hermann <ulf.hermann@qt.io>

2 files changed, 9 insertions, 0 deletions

diff --git a/src/qml/types/qqmllistmodel.cpp b/src/qml/types/qqmllistmodel.cpp
index debf14df97..006825cc93 100644
--- a/src/qml/types/qqmllistmodel.cpp
+++ b/src/qml/types/qqmllistmodel.cpp
@@ -52,6 +52,7 @@
 #include <private/qv4dateobject_p.h>
 #include <private/qv4objectiterator_p.h>
 #include <private/qv4alloca_p.h>
+#include <private/qv4lookup_p.h>
 
 #include <qqmlcontext.h>
 #include <qqmlinfo.h>
@@ -1613,6 +1614,12 @@ ReturnedValue ModelObject::virtualGet(const Managed *m, PropertyKey id, const Va
     return that->engine()->fromVariant(value);
 }
 
+ReturnedValue ModelObject::virtualResolveLookupGetter(const Object *object, ExecutionEngine *engine, Lookup *lookup)
+{
+    lookup->getter = Lookup::getterFallback;
+    return lookup->getter(lookup, engine, *object);
+}
+
 struct ModelObjectOwnPropertyKeyIterator : ObjectOwnPropertyKeyIterator
 {
     int roleNameIndex = 0;
diff --git a/src/qml/types/qqmllistmodel_p_p.h b/src/qml/types/qqmllistmodel_p_p.h
index ff52ee049f..2876c71de6 100644
--- a/src/qml/types/qqmllistmodel_p_p.h
+++ b/src/qml/types/qqmllistmodel_p_p.h
@@ -181,6 +181,8 @@ struct ModelObject : public QObjectWrapper
 protected:
     static bool virtualPut(Managed *m, PropertyKey id, const Value& value, Value *receiver);
     static ReturnedValue virtualGet(const Managed *m, PropertyKey id, const Value *receiver, bool *hasProperty);
+    static ReturnedValue virtualResolveLookupGetter(const Object *object, ExecutionEngine *engine, Lookup *lookup);
+    static ReturnedValue lookupGetter(Lookup *l, ExecutionEngine *engine, const Value &object);
     static OwnPropertyKeyIterator *virtualOwnPropertyKeys(const Object *m, Value *target);
 };