Add support for binding directly to QProperty instances

Avoid going through externally managed bindings and instead allocate a
more lightweight property binding. It's basically a
QQmlJavaScriptExpression and one pointer plus the overhead of
QPropertyBindingPrivate.

Change-Id: I1530330926d351b61f2b3bbad39301c628a8bef1
Reviewed-by: Fabian Kosmale <fabian.kosmale@qt.io>

8 files changed, 207 insertions, 6 deletions

diff --git a/src/qml/.prev_CMakeLists.txt b/src/qml/.prev_CMakeLists.txt
index 0f25337573..147419711f 100644
--- a/src/qml/.prev_CMakeLists.txt
+++ b/src/qml/.prev_CMakeLists.txt
@@ -229,6 +229,7 @@ qt_add_module(Qml
         qml/qqmlplatform.cpp qml/qqmlplatform_p.h
         qml/qqmlprivate.h
         qml/qqmlproperty.cpp qml/qqmlproperty.h qml/qqmlproperty_p.h
+        qml/qqmlpropertybinding.cpp qml/qqmlpropertybinding_p.h
         qml/qqmlpropertycache.cpp qml/qqmlpropertycache_p.h
         qml/qqmlpropertycachecreator.cpp qml/qqmlpropertycachecreator_p.h
         qml/qqmlpropertycachemethodarguments_p.h
diff --git a/src/qml/CMakeLists.txt b/src/qml/CMakeLists.txt
index f6ab914b9a..cb49452a26 100644
--- a/src/qml/CMakeLists.txt
+++ b/src/qml/CMakeLists.txt
@@ -231,6 +231,7 @@ qt_add_module(Qml
         qml/qqmlplatform.cpp qml/qqmlplatform_p.h
         qml/qqmlprivate.h
         qml/qqmlproperty.cpp qml/qqmlproperty.h qml/qqmlproperty_p.h
+        qml/qqmlpropertybinding.cpp qml/qqmlpropertybinding_p.h
         qml/qqmlpropertycache.cpp qml/qqmlpropertycache_p.h
         qml/qqmlpropertycachecreator.cpp qml/qqmlpropertycachecreator_p.h
         qml/qqmlpropertycachemethodarguments_p.h
diff --git a/src/qml/qml/qml.pri b/src/qml/qml/qml.pri
index f937d4d0b3..6cca897e08 100644
--- a/src/qml/qml/qml.pri
+++ b/src/qml/qml/qml.pri
@@ -54,6 +54,7 @@ SOURCES += \
     $$PWD/qqmlfile.cpp \
     $$PWD/qqmlplatform.cpp \
     $$PWD/qqmlbinding.cpp \
+    $$PWD/qqmlpropertybinding.cpp \
     $$PWD/qqmlabstracturlinterceptor.cpp \
     $$PWD/qqmlapplicationengine.cpp \
     $$PWD/qqmllistwrapper.cpp \
@@ -148,6 +149,7 @@ HEADERS += \
     $$PWD/qqmlfile.h \
     $$PWD/qqmlplatform_p.h \
     $$PWD/qqmlbinding_p.h \
+    $$PWD/qqmlpropertybinding_p.h \
     $$PWD/qqmlextensionplugin_p.h \
     $$PWD/qqmlabstracturlinterceptor.h \
     $$PWD/qqmlapplicationengine_p.h \
diff --git a/src/qml/qml/qqmlobjectcreator.cpp b/src/qml/qml/qqmlobjectcreator.cpp
index 213e15e173..2ee2969d43 100644
--- a/src/qml/qml/qqmlobjectcreator.cpp
+++ b/src/qml/qml/qqmlobjectcreator.cpp
@@ -60,6 +60,7 @@
 #include <private/qjsvalue_p.h>
 #include <private/qv4generatorobject_p.h>
 #include <private/qv4resolvedtypereference_p.h>
+#include <private/qqmlpropertybinding_p.h>
 
 #include <QScopedValueRollback>
 
@@ -917,6 +918,12 @@ bool QQmlObjectCreator::setPropertyBinding(const QQmlPropertyData *bindingProper
                         _scopeObject, runtimeFunction, currentQmlContext());
 
             bs->takeExpression(expr);
+        } else if (bindingProperty->isQProperty()) {
+            // ### TODO: support binding->isTranslationBinding()
+            QV4::Function *runtimeFunction = compilationUnit->runtimeFunctions[binding->value.compiledScriptIndex];
+            auto qmlBinding = QQmlPropertyBinding::create(bindingProperty, runtimeFunction, _scopeObject, context, currentQmlContext());
+            void *argv[] = { &qmlBinding };
+            _bindingTarget->qt_metacall(QMetaObject::SetQPropertyBinding, bindingProperty->coreIndex(), argv);
         } else {
             // When writing bindings to grouped properties implemented as value types,
             // such as point.x: { someExpression; }, then the binding is installed on
diff --git a/src/qml/qml/qqmlpropertybinding.cpp b/src/qml/qml/qqmlpropertybinding.cpp
new file mode 100644
index 0000000000..ca64cf412a
--- /dev/null
+++ b/src/qml/qml/qqmlpropertybinding.cpp
@@ -0,0 +1,101 @@
+/****************************************************************************
+**
+** Copyright (C) 2020 The Qt Company Ltd.
+** Contact: https://www.qt.io/licensing/
+**
+** This file is part of the QtQml module of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:LGPL$
+** Commercial License Usage
+** Licensees holding valid commercial Qt licenses may use this file in
+** accordance with the commercial license agreement provided with the
+** Software or, alternatively, in accordance with the terms contained in
+** a written agreement between you and The Qt Company. For licensing terms
+** and conditions see https://www.qt.io/terms-conditions. For further
+** information use the contact form at https://www.qt.io/contact-us.
+**
+** GNU Lesser General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU Lesser
+** General Public License version 3 as published by the Free Software
+** Foundation and appearing in the file LICENSE.LGPL3 included in the
+** packaging of this file. Please review the following information to
+** ensure the GNU Lesser General Public License version 3 requirements
+** will be met: https://www.gnu.org/licenses/lgpl-3.0.html.
+**
+** GNU General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU
+** General Public License version 2.0 or (at your option) the GNU General
+** Public license version 3 or any later version approved by the KDE Free
+** Qt Foundation. The licenses are as published by the Free Software
+** Foundation and appearing in the file LICENSE.GPL2 and LICENSE.GPL3
+** included in the packaging of this file. Please review the following
+** information to ensure the GNU General Public License requirements will
+** be met: https://www.gnu.org/licenses/gpl-2.0.html and
+** https://www.gnu.org/licenses/gpl-3.0.html.
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+#include "qqmlpropertybinding_p.h"
+
+#include <private/qpropertybinding_p.h>
+
+QT_BEGIN_NAMESPACE
+
+QUntypedPropertyBinding QQmlPropertyBinding::create(const QQmlPropertyData *pd, QV4::Function *function,
+                                                    QObject *obj, const QQmlRefPointer<QQmlContextData> &ctxt,
+                                                    QV4::ExecutionContext *scope)
+{
+    auto binding = new QQmlPropertyBinding(QMetaType(pd->propType()));
+    binding->setNotifyOnValueChanged(true);
+    binding->setContext(ctxt);
+    binding->setScopeObject(obj);
+    binding->setupFunction(scope, function);
+    return QUntypedPropertyBinding(QPropertyBindingPrivatePtr(binding));
+}
+
+void QQmlPropertyBinding::expressionChanged()
+{
+    setDirty(true);
+}
+
+QQmlPropertyBinding::QQmlPropertyBinding(const QMetaType &mt)
+    : QPropertyBindingPrivate(mt,
+                              [this](const QMetaType &metaType, void *dataPtr) -> QUntypedPropertyBinding::BindingEvaluationResult {
+                                  return evaluateAndReturnTrueIfChanged(metaType, dataPtr);
+                              }, QPropertyBindingSourceLocation())
+{
+}
+
+QUntypedPropertyBinding::BindingEvaluationResult QQmlPropertyBinding::evaluateAndReturnTrueIfChanged(const QMetaType &metaType, void *dataPtr)
+{
+    QQmlEngine *engine = context()->engine();
+    QQmlEnginePrivate *ep = QQmlEnginePrivate::get(engine);
+    ep->referenceScarceResources();
+
+    bool isUndefined = false;
+
+    QV4::Scope scope(engine->handle());
+    QV4::ScopedValue result(scope, QQmlJavaScriptExpression::evaluate(&isUndefined));
+
+    ep->dereferenceScarceResources();
+
+    if (hasError()) {
+        QPropertyBindingError error(QPropertyBindingError::UnknownError);
+        error.setDescription(delayedError()->error().description());
+        return error;
+    }
+
+    QVariant resultVariant(scope.engine->toVariant(result, metaType.id()));
+
+    int compareResult = 0;
+    if (QMetaType::compare(dataPtr, resultVariant.constData(), metaType.id(), &compareResult)
+        && compareResult == 0)
+        return false;
+    QMetaType::destruct(metaType.id(), dataPtr);
+    QMetaType::construct(metaType.id(), dataPtr, resultVariant.constData());
+    return true;
+}
+
+QT_END_NAMESPACE
diff --git a/src/qml/qml/qqmlpropertybinding_p.h b/src/qml/qml/qqmlpropertybinding_p.h
new file mode 100644
index 0000000000..3bd6772413
--- /dev/null
+++ b/src/qml/qml/qqmlpropertybinding_p.h
@@ -0,0 +1,83 @@
+/****************************************************************************
+**
+** Copyright (C) 2020 The Qt Company Ltd.
+** Contact: https://www.qt.io/licensing/
+**
+** This file is part of the QtQml module of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:LGPL$
+** Commercial License Usage
+** Licensees holding valid commercial Qt licenses may use this file in
+** accordance with the commercial license agreement provided with the
+** Software or, alternatively, in accordance with the terms contained in
+** a written agreement between you and The Qt Company. For licensing terms
+** and conditions see https://www.qt.io/terms-conditions. For further
+** information use the contact form at https://www.qt.io/contact-us.
+**
+** GNU Lesser General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU Lesser
+** General Public License version 3 as published by the Free Software
+** Foundation and appearing in the file LICENSE.LGPL3 included in the
+** packaging of this file. Please review the following information to
+** ensure the GNU Lesser General Public License version 3 requirements
+** will be met: https://www.gnu.org/licenses/lgpl-3.0.html.
+**
+** GNU General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU
+** General Public License version 2.0 or (at your option) the GNU General
+** Public license version 3 or any later version approved by the KDE Free
+** Qt Foundation. The licenses are as published by the Free Software
+** Foundation and appearing in the file LICENSE.GPL2 and LICENSE.GPL3
+** included in the packaging of this file. Please review the following
+** information to ensure the GNU General Public License requirements will
+** be met: https://www.gnu.org/licenses/gpl-2.0.html and
+** https://www.gnu.org/licenses/gpl-3.0.html.
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+#ifndef QQMLPROPERTYBINDING_P_H
+#define QQMLPROPERTYBINDING_P_H
+
+//
+//  W A R N I N G
+//  -------------
+//
+// This file is not part of the Qt API.  It exists purely as an
+// implementation detail.  This header file may change from version to
+// version without notice, or even be removed.
+//
+// We mean it.
+//
+
+#include <QtCore/qproperty.h>
+#include <private/qpropertybinding_p.h>
+
+#include "qqmlpropertydata_p.h"
+#include "qqmljavascriptexpression_p.h"
+
+#include <memory>
+
+QT_BEGIN_NAMESPACE
+
+class QQmlPropertyBinding final : public QQmlJavaScriptExpression,
+                                  public QPropertyBindingPrivate
+{
+public:
+    static QUntypedPropertyBinding create(const QQmlPropertyData *pd, QV4::Function *function,
+                                          QObject *obj, const QQmlRefPointer<QQmlContextData> &ctxt,
+                                          QV4::ExecutionContext *scope);
+
+    virtual void expressionChanged();
+
+private:
+    QQmlPropertyBinding(const QMetaType &metaType);
+
+    QUntypedPropertyBinding::BindingEvaluationResult evaluateAndReturnTrueIfChanged(const QMetaType &metaType,
+                                                                                    void *dataPtr);
+};
+
+QT_END_NAMESPACE
+
+#endif // QQMLPROPERTYBINDING_P_H
diff --git a/src/qml/qml/qqmlpropertycache.cpp b/src/qml/qml/qqmlpropertycache.cpp
index 4b17760f8e..72226a452d 100644
--- a/src/qml/qml/qqmlpropertycache.cpp
+++ b/src/qml/qml/qqmlpropertycache.cpp
@@ -76,6 +76,7 @@ static QQmlPropertyData::Flags fastFlagsForProperty(const QMetaProperty &p)
     flags.setIsResettable(p.isResettable());
     flags.setIsFinal(p.isFinal());
     flags.setIsRequired(p.isRequired());
+    flags.setIsQProperty(p.isQProperty());
 
     if (p.isEnumType())
         flags.type = QQmlPropertyData::Flags::EnumType;
diff --git a/src/qml/qml/qqmlpropertydata_p.h b/src/qml/qml/qqmlpropertydata_p.h
index 9fa272bcdf..697c995706 100644
--- a/src/qml/qml/qqmlpropertydata_p.h
+++ b/src/qml/qml/qqmlpropertydata_p.h
@@ -97,7 +97,7 @@ public:
         // b when type equals FunctionType. For that reason, the semantic meaning of the bit is
         // overloaded, and the accessor functions are used to get the correct value
         //
-        // Moreover, isSignalHandler, isOverload and isCloned and isConstructor make only sense
+        // Moreover, isSignalHandler, isOverload and isCloned make only sense
         // for functions, too (and could at a later point be reused for flags that only make sense
         // for non-functions)
         //
@@ -111,7 +111,7 @@ public:
         unsigned isSignalHandler               : 1; // Function is a signal handler
         unsigned isOverload                    : 1; // Function is an overload of another function
         unsigned isRequiredORisCloned          : 1; // Has REQUIRED flag OR The function was marked as cloned
-        unsigned isConstructor                 : 1; // The function was marked is a constructor
+        unsigned isConstructorORisQProperty    : 1; // The function was marked is a constructor OR property is backed by QProperty<T>
         unsigned isDirect                      : 1; // Exists on a C++ QMetaObject
         unsigned isOverridden                  : 1; // Is overridden by a extension property
     public:
@@ -156,6 +156,10 @@ public:
             isOverridden = b;
         }
 
+        void setIsQProperty(bool b) {
+            isConstructorORisQProperty = b;
+        }
+
         void setIsDirect(bool b) {
             isDirect = b;
         }
@@ -204,7 +208,7 @@ public:
 
         void setIsConstructor(bool b) {
             Q_ASSERT(type == FunctionType);
-            isConstructor = b;
+            isConstructorORisQProperty = b;
         }
 
     };
@@ -249,7 +253,8 @@ public:
     bool isOverload() const { return m_flags.isOverload; }
     void setOverload(bool onoff) { m_flags.isOverload = onoff; }
     bool isCloned() const { return isFunction() && m_flags.isRequiredORisCloned; }
-    bool isConstructor() const { return m_flags.isConstructor; }
+    bool isConstructor() const { return m_flags.isConstructorORisQProperty; }
+    bool isQProperty() const { return m_flags.isConstructorORisQProperty; }
 
     bool hasOverride() const { return overrideIndex() >= 0; }
     bool hasRevision() const { return revision() != QTypeRevision::zero(); }
@@ -441,7 +446,7 @@ QQmlPropertyData::Flags::Flags()
     , isSignalHandler(false)
     , isOverload(false)
     , isRequiredORisCloned(false)
-    , isConstructor(false)
+    , isConstructorORisQProperty(false)
     , isOverridden(false)
     , type(OtherType)
     , notFullyResolved(false)
@@ -459,7 +464,7 @@ bool QQmlPropertyData::Flags::operator==(const QQmlPropertyData::Flags &other) c
             isSignalHandler == other.isSignalHandler &&
             isRequiredORisCloned == other.isRequiredORisCloned &&
             type == other.type &&
-            isConstructor == other.isConstructor &&
+            isConstructorORisQProperty == other.isConstructorORisQProperty &&
             notFullyResolved == other.notFullyResolved &&
             overrideIndexIsProperty == other.overrideIndexIsProperty;
 }