Add QQuickItemParticle give() method body

The current version of QQuickItemParticle give() method was not
implemented and a simple TODO comment was present instead.
I added a working body and add also a reparent feature when an
added item is released.

Fixes: QTBUG-76827
Change-Id: Ib7d289cad2ff0cd166e766eb7f07e92437e7681b
Reviewed-by: Shawn Rutledge <shawn.rutledge@qt.io>

src/particles/qquickitemparticle.cpp

@@ -159,8 +159,15 @@ void QQuickItemParticle::take(QQuickItem *item, bool prioritize)
 
 void QQuickItemParticle::give(QQuickItem *item)
 {
-    //TODO: This
-    Q_UNUSED(item);
+    for (auto groupId : groupIds()) {
+        for (QQuickParticleData* data : qAsConst(m_system->groupData[groupId]->data)) {
+            if (data->delegate == item){
+                m_deletables << item;
+                data->delegate = nullptr;
+                return;
+            }
+        }
+    }
 }
 
 void QQuickItemParticle::initialize(int gIdx, int pIdx)
@@ -179,8 +186,11 @@ void QQuickItemParticle::processDeletables()
             item->setOpacity(0.);
         item->setVisible(false);
         QQuickItemParticleAttached* mpa;
-        if ((mpa = qobject_cast<QQuickItemParticleAttached*>(qmlAttachedPropertiesObject<QQuickItemParticle>(item))))
-            mpa->detach();//reparent as well?
+        if ((mpa = qobject_cast<QQuickItemParticleAttached*>(qmlAttachedPropertiesObject<QQuickItemParticle>(item)))) {
+            if (mpa->m_parentItem != nullptr)
+                item->setParentItem(mpa->m_parentItem);
+            mpa->detach();
+        }
         int idx = -1;
         if ((idx = m_managed.indexOf(item)) != -1) {
             m_managed.takeAt(idx);
@@ -205,9 +215,12 @@ void QQuickItemParticle::tick(int time)
             m_deletables << d->delegate;
             d->delegate = nullptr;
         }
+        QQuickItem* parentItem = nullptr;
         if (!m_pendingItems.isEmpty()){
-            d->delegate = m_pendingItems.front();
+            QQuickItem *item = m_pendingItems.front();
             m_pendingItems.pop_front();
+            parentItem = item->parentItem();
+            d->delegate = item;
         }else if (m_delegate){
             d->delegate = qobject_cast<QQuickItem*>(m_delegate->create(qmlContext(this)));
             if (d->delegate)
@@ -218,6 +231,7 @@ void QQuickItemParticle::tick(int time)
             d->delegate->setY(d->curY(m_system) - d->delegate->height() / 2);
             QQuickItemParticleAttached* mpa = qobject_cast<QQuickItemParticleAttached*>(qmlAttachedPropertiesObject<QQuickItemParticle>(d->delegate));
             if (mpa){
+                mpa->m_parentItem = parentItem;
                 mpa->m_mp = this;
                 mpa->attach();
             }

src/particles/qquickitemparticle_p.h

@@ -130,13 +130,14 @@ class QQuickItemParticleAttached : public QObject
     Q_PROPERTY(QQuickItemParticle* particle READ particle CONSTANT);
 public:
     QQuickItemParticleAttached(QObject* parent)
-        : QObject(parent), m_mp(0)
+        : QObject(parent), m_mp(0), m_parentItem(nullptr)
     {;}
     QQuickItemParticle* particle() const { return m_mp; }
     void detach(){Q_EMIT detached();}
     void attach(){Q_EMIT attached();}
 private:
     QQuickItemParticle* m_mp;
+    QPointer<QQuickItem> m_parentItem;
     friend class QQuickItemParticle;
 Q_SIGNALS:
     void detached();

tests/auto/particles/qquickitemparticle/data/takeGive.qml

@@ -0,0 +1,74 @@
+/****************************************************************************
+**
+** Copyright (C) 2020 The Qt Company Ltd.
+** Contact: https://www.qt.io/licensing/
+**
+** This file is part of the test suite 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.
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+import QtQuick 2.0
+import QtQuick.Particles 2.0
+
+Rectangle {
+    id: testTakeGive
+    color: "black"
+    width: 320
+    height: 320
+
+    function takeItems()
+    {
+        for(var i = 0; i < imgList.count; i++) ip.take(imgList.itemAt(i));
+    }
+    function giveItems()
+    {
+        for(var i = 0; i < imgList.count; i++) ip.give(imgList.itemAt(i));
+    }
+
+    Repeater {
+        id: imgList
+        model: 100
+        delegate: Image {
+            ItemParticle.onAttached: sys.acc = sys.acc + 1
+            ItemParticle.onDetached: sys.acc = sys.acc - 1;
+            source: "../../shared/star.png"
+        }
+    }
+
+    ParticleSystem {
+        id: sys
+        objectName: "system"
+        anchors.fill: parent
+        property int acc: 0
+
+        ItemParticle {
+            id: ip
+        }
+
+        Emitter{
+            //0,0 position
+            size: 32
+            emitRate: 1000
+            lifeSpan: Emitter.InfiniteLife
+        }
+    }
+}

tests/auto/particles/qquickitemparticle/tst_qquickitemparticle.cpp

@@ -45,6 +45,7 @@ private slots:
     void test_basic();
     void test_deletion();
     void test_noDeletion();
+    void test_takeGive();
 };
 
 void tst_qquickitemparticle::initTestCase()
@@ -107,6 +108,18 @@ void tst_qquickitemparticle::test_noDeletion()
     delete view;
 }
 
+void tst_qquickitemparticle::test_takeGive()
+{
+    QQuickView* view = createView(testFileUrl("takeGive.qml"), 500);
+    QQuickParticleSystem* system = view->rootObject()->findChild<QQuickParticleSystem*>("system");
+    QMetaObject::invokeMethod(view->rootObject(), "takeItems");
+    ensureAnimTime(1000, system->m_animation);
+    QVERIFY(system->property("acc").toInt() == 100);
+    QMetaObject::invokeMethod(view->rootObject(), "giveItems");
+    QTRY_VERIFY(system->property("acc").toInt() == 0);
+    delete view;
+}
+
 QTEST_MAIN(tst_qquickitemparticle);
 
 #include "tst_qquickitemparticle.moc"