QtStateMachine QQmlListProperty bindables

The commit uses 'mutable' and 'const_cast' to able to serve
the bindable property without creating an additional copy (== avoid
additional memory usage). These are flagged with a comment
around them and in future we may be able to remove them as
the bindable support evolves.

Task-number: QTBUG-91375
Change-Id: I91f3c823eac1979628731853e20ed82a34636d99
Reviewed-by: Ulf Hermann <ulf.hermann@qt.io>
Reviewed-by: Fabian Kosmale <fabian.kosmale@qt.io>
Reviewed-by: Ivan Solovev <ivan.solovev@qt.io>

2 files changed, 162 insertions, 0 deletions

diff --git a/tests/auto/qml/qqmlstatemachine/tst_qqmlstatemachine.cpp b/tests/auto/qml/qqmlstatemachine/tst_qqmlstatemachine.cpp
index f4a16a1..d0b9445 100644
--- a/tests/auto/qml/qqmlstatemachine/tst_qqmlstatemachine.cpp
+++ b/tests/auto/qml/qqmlstatemachine/tst_qqmlstatemachine.cpp
@@ -31,11 +31,15 @@
 #include <QtQuick/QQuickItem>
 #include <QtStateMachineQml/private/signaltransition_p.h>
 #include <QtStateMachineQml/private/timeouttransition_p.h>
+#include <QtStateMachineQml/private/statemachine_p.h>
+#include <QtStateMachineQml/private/finalstate_p.h>
+#include <QtStateMachineQml/private/state_p.h>
 #include <QtQml/qqmlscriptstring.h>
 
 #include <QTest>
 #include "../../shared/util.h"
 #include "../../shared/bindableutils.h"
+#include "../../shared/bindableqmlutils.h"
 
 class tst_qqmlstatemachine : public QQmlDataTest
 {
@@ -145,6 +149,23 @@ void tst_qqmlstatemachine::tst_bindings()
     int timeout2{200};
     testWritableBindableBasics<TimeoutTransition, int>(
                 timeoutTransition, timeout1, timeout2, "timeout");
+
+    // -- FinalState::children
+    FinalState finalState;
+    QObject object1;
+    QObject object2;
+    testManipulableQmlListBasics<FinalState, QObject*>(
+                finalState, &object1, &object2, "children");
+
+    // -- State::children
+    State state;
+    testManipulableQmlListBasics<State, QObject*>(
+                state, &object1, &object2, "children");
+
+    // -- StateMachine::children
+    StateMachine stateMachine;
+    testManipulableQmlListBasics<StateMachine, QObject*>(
+                stateMachine, &object1, &object2, "children");
 }
 
 QTEST_MAIN(tst_qqmlstatemachine)
diff --git a/tests/auto/shared/bindableqmlutils.h b/tests/auto/shared/bindableqmlutils.h
new file mode 100644
index 0000000..f622093
--- /dev/null
+++ b/tests/auto/shared/bindableqmlutils.h
@@ -0,0 +1,141 @@
+/****************************************************************************
+**
+** Copyright (C) 2021 The Qt Company Ltd.
+** Contact: https://www.qt.io/licensing/
+**
+** This file is part of the QtScxml module of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:GPL-EXCEPT$
+** 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 General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU
+** General Public License version 3 as published by the Free Software
+** Foundation with exceptions as appearing in the file LICENSE.GPL3-EXCEPT
+** 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-3.0.html.
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+#ifndef BINDABLEQMLUTILS_H
+#define BINDABLEQMLUTILS_H
+
+#include <QtQml/QQmlListReference>
+#include <QtQml/QQmlProperty>
+#include <QObject>
+#include <QtTest>
+
+// This is a helper function to test basics of typical bindable
+// and manipulable QQmlListProperty
+// "TestedClass" is the class type we are testing
+// "TestedData" is the data type that the list contains
+// "testedClass" is an instance of the class we are interested testing
+// "data1" is a value that can be set and removed from the list
+// "data2" is a value that can be set and removed from the list
+// "propertyName" is the name of the property we are interested in testing
+template<typename TestedClass, typename TestedData>
+void testManipulableQmlListBasics(TestedClass& testedClass,
+                                TestedData data1, TestedData data2,
+                                const char* propertyName)
+{
+    // Get the property we are testing
+    const QMetaObject *metaObject = testedClass.metaObject();
+    QMetaProperty metaProperty = metaObject->property(metaObject->indexOfProperty(propertyName));
+
+    // Generate a string to help identify failures (as this is a generic template)
+    QString id(metaObject->className());
+    id.append(QStringLiteral("::"));
+    id.append(propertyName);
+
+    // Fail gracefully if preconditions to use this helper function are not met:
+    QQmlListReference listRef(&testedClass, propertyName);
+    QVERIFY2(metaProperty.isBindable(), qPrintable(id));
+    QVERIFY2(listRef.isManipulable(), qPrintable(id));
+    QVERIFY2(data1 != data2, qPrintable(id));
+
+    // Create a signal spy for the property changed -signal if such exists
+    QScopedPointer<QSignalSpy> changedSpy(nullptr);
+    if (metaProperty.hasNotifySignal())
+        changedSpy.reset(new QSignalSpy(&testedClass, metaProperty.notifySignal()));
+
+    // Modify values without binding (verify property basics still work)
+    QVERIFY2(listRef.count() == 0, qPrintable(id));
+    listRef.append(data1);
+    QVERIFY2(listRef.count() == 1, qPrintable(id));
+    if (changedSpy)
+        QVERIFY2(changedSpy->count() == 1, qPrintable(id + ", actual: " + QString::number(changedSpy->count())));
+    QVERIFY2(listRef.at(0) == data1, qPrintable(id));
+    listRef.clear();
+    QVERIFY2(listRef.count() == 0, qPrintable(id));
+    if (changedSpy)
+        QVERIFY2(changedSpy->count() == 2, qPrintable(id + ", actual: " + QString::number(changedSpy->count())));
+
+    // Bind to the property and verify that the bindings reflect the listproperty changes
+    QProperty<bool> data1InList([&](){
+        QQmlListReference list(&testedClass, propertyName);
+        for (int i = 0; i < list.count(); i++) {
+            if (list.at(i) == data1)
+                return true;
+        }
+        return false;
+    });
+    QProperty<bool> data2InList([&](){
+        QQmlListReference list(&testedClass, propertyName);
+        for (int i = 0; i < list.count(); i++) {
+            if (list.at(i) == data2)
+                return true;
+        }
+        return false;
+    });
+
+    // initial state
+    QVERIFY2(!data1InList, qPrintable(id));
+    QVERIFY2(!data2InList, qPrintable(id));
+
+    listRef.append(data1);
+    if (changedSpy)
+        QVERIFY2(changedSpy->count() == 3, qPrintable(id + ", actual: " + QString::number(changedSpy->count())));
+    QVERIFY2(data1InList, qPrintable(id));
+    QVERIFY2(!data2InList, qPrintable(id));
+
+    listRef.append(data2);
+    if (changedSpy)
+        QVERIFY2(changedSpy->count() == 4, qPrintable(id + ", actual: " + QString::number(changedSpy->count())));
+    QVERIFY2(data1InList, qPrintable(id));
+    QVERIFY2(data2InList, qPrintable(id));
+    QVERIFY2(listRef.count() == 2, qPrintable(id + ", actual: " + QString::number(changedSpy->count())));
+
+    listRef.clear();
+    if (changedSpy)
+        QVERIFY2(changedSpy->count() == 5, qPrintable(id + ", actual: " + QString::number(changedSpy->count())));
+    QVERIFY2(!data1InList, qPrintable(id));
+    QVERIFY2(!data2InList, qPrintable(id));
+    QVERIFY2(listRef.count() == 0, qPrintable(id + ", actual: " + QString::number(changedSpy->count())));
+
+    listRef.append(data1);
+    listRef.replace(0, data2);
+    if (changedSpy)
+        QVERIFY2(changedSpy->count() == 7, qPrintable(id + ", actual: " + QString::number(changedSpy->count())));
+    QVERIFY2(!data1InList, qPrintable(id));
+    QVERIFY2(data2InList, qPrintable(id));
+    QVERIFY2(listRef.count() == 1, qPrintable(id + ", actual: " + QString::number(changedSpy->count())));
+
+    listRef.removeLast();
+    if (changedSpy)
+        QVERIFY2(changedSpy->count() == 8, qPrintable(id + ", actual: " + QString::number(changedSpy->count())));
+    QVERIFY2(!data1InList, qPrintable(id));
+    QVERIFY2(!data2InList, qPrintable(id));
+
+    QVERIFY2(listRef.count() == 0, qPrintable(id + ", actual: " + QString::number(listRef.count())));
+}
+
+#endif // BINDABLEQMLUTILS_H