From 0f4d512dc46cb9d24b58083efdc1fa4631bdbec4 Mon Sep 17 00:00:00 2001
From: Fabian Kosmale <fabian.kosmale@qt.io>
Date: Fri, 22 Jan 2021 11:06:52 +0100
Subject: [PATCH] Q(Untyped)Bindable: add takeBinding method

We missed takeBinding as a supported operation on Q(Untyped)Bindable.
To avoid adding version checks to code dealing with QBindableInterface,
we simply synthesize takeBinding as a combination of binding to retrieve
the binding and setBinding with a default-constructed
QUntypedPropertyBinding.

Change-Id: I43803a0dfe210353d0235f0373d2257f75ffe534
Reviewed-by: Lars Knoll <lars.knoll@qt.io>
---
 src/corelib/kernel/qproperty.cpp              | 21 +++++++++++++++++-
 src/corelib/kernel/qproperty.h                | 22 +++++++++++++++++++
 .../kernel/qproperty/tst_qproperty.cpp        | 18 +++++++++++++++
 3 files changed, 60 insertions(+), 1 deletion(-)

diff --git a/src/corelib/kernel/qproperty.cpp b/src/corelib/kernel/qproperty.cpp
index 342a3d34eb..90df159e88 100644
--- a/src/corelib/kernel/qproperty.cpp
+++ b/src/corelib/kernel/qproperty.cpp
@@ -787,11 +787,20 @@ QString QPropertyBindingError::description() const
   \sa hasBinding()
 */
 
+/*!
+  \fn QUntypedPropertyBinding QUntypedBindable::takeBinding()
+
+  Removes the currently set binding from the property and returns it.
+  Returns a default-constructed QUntypedPropertyBinding if no binding is set.
+
+  \since 6.1
+*/
+
 /*!
   \fn bool QUntypedBindable::setBinding(const QUntypedPropertyBinding &binding)
 
   Sets the underlying property's binding to \a binding. This does not have any effect
-  if the QUntypedBindable is read-only, invalid or if \a binding's type does match the
+  if the QUntypedBindable is read-only, null or if \a binding's type does match the
   underlying property's type.
 
   \sa QUntypedPropertyBinding::valueMetaType()
@@ -841,6 +850,16 @@ QString QPropertyBindingError::description() const
    \sa setBinding, QPropertyBinding<T>::isValid(), hasBinding
 */
 
+/*!
+  \fn template <typename T> QPropertyBinding<T> QBindable<T>::takeBinding()
+
+   Removes the currently set binding of the underlying property and returns it.
+   If the property does not have a binding, the returned \c QPropertyBinding<T> will be invalid.
+
+   \sa setBinding, getBinding, QPropertyBinding<T>::isValid(), hasBinding
+*/
+
+
 /*!
   \fn template <typename T> void QBindable<T>::setBinding(const QPropertyBinding<T> &binding)
 
diff --git a/src/corelib/kernel/qproperty.h b/src/corelib/kernel/qproperty.h
index f853eb8634..750d75c4a7 100644
--- a/src/corelib/kernel/qproperty.h
+++ b/src/corelib/kernel/qproperty.h
@@ -581,6 +581,22 @@ public:
     {
         return iface ? iface->makeBinding(data, location) : QUntypedPropertyBinding();
     }
+
+    QUntypedPropertyBinding takeBinding()
+    {
+        if (!iface)
+            return QUntypedPropertyBinding {};
+        // We do not have a dedicated takeBinding function pointer in the interface
+        // therefore we synthesize takeBinding by retrieving the binding with binding
+        // and calling setBinding with a default constructed QUntypedPropertyBinding
+        // afterwards.
+        if (!(iface->getBinding && iface->setBinding))
+            return QUntypedPropertyBinding {};
+        QUntypedPropertyBinding binding = iface->getBinding(data);
+        iface->setBinding(data, QUntypedPropertyBinding{});
+        return binding;
+    }
+
     void observe(QPropertyObserver *observer)
     {
         if (iface)
@@ -650,6 +666,12 @@ public:
     {
         return static_cast<QPropertyBinding<T> &&>(QUntypedBindable::binding());
     }
+
+    QPropertyBinding<T> takeBinding()
+    {
+        return static_cast<QPropertyBinding<T> &&>(QUntypedBindable::takeBinding());
+    }
+
     using QUntypedBindable::setBinding;
     QPropertyBinding<T> setBinding(const QPropertyBinding<T> &binding)
     {
diff --git a/tests/auto/corelib/kernel/qproperty/tst_qproperty.cpp b/tests/auto/corelib/kernel/qproperty/tst_qproperty.cpp
index 3b656dae25..31ed610b09 100644
--- a/tests/auto/corelib/kernel/qproperty/tst_qproperty.cpp
+++ b/tests/auto/corelib/kernel/qproperty/tst_qproperty.cpp
@@ -78,6 +78,7 @@ private slots:
     void notifiedProperty();
     void typeNoOperatorEqual();
     void bindingValueReplacement();
+    void quntypedBindableApi();
 
     void testNewStuff();
     void qobjectObservers();
@@ -1008,6 +1009,23 @@ void tst_QProperty::bindingValueReplacement()
 //    QCOMPARE(test.iconText.value(), 42);
 }
 
+void tst_QProperty::quntypedBindableApi()
+{
+    QProperty<int> iprop;
+    QUntypedBindable bindable(&iprop);
+    QVERIFY(!bindable.hasBinding());
+    QVERIFY(bindable.binding().isNull());
+    bindable.setBinding(Qt::makePropertyBinding([]() -> int {return 42;}));
+    QVERIFY(bindable.hasBinding());
+    QVERIFY(!bindable.binding().isNull());
+    QUntypedPropertyBinding binding = bindable.takeBinding();
+    QVERIFY(!bindable.hasBinding());
+    bindable.setBinding(binding);
+    QCOMPARE(iprop.value(), 42);
+    QUntypedBindable propLess;
+    QVERIFY(propLess.takeBinding().isNull());
+}
+
 class MyQObject : public QObject
 {
     Q_OBJECT