QQuickItemView: refill itself before populate transition

The view uses a visible items list, which is maintained by the refill()
method, to determine which items should be triggered to do the populate
transition.  The refill() was only invoked when component completed
before doing the populate transition; but if the size of the view
depends on the size of window (for example, using anchors.fill), more
delegates could become visible after component completed. In such a
case, part of visible items were not be triggered to do the transition.

[ChangeLog][QtQuick][Item Views] Item views such as ListView now properly
populate delegates with a populate transition when the view is resized
after componentComplete.

Fixes: QTBUG-76487
Change-Id: Id90c3f73d9911c8a1d6d8b1ea0c51f6c27d0ed5b
Reviewed-by: Shawn Rutledge <shawn.rutledge@qt.io>

3 files changed, 96 insertions, 0 deletions

diff --git a/src/quick/items/qquickitemview.cpp b/src/quick/items/qquickitemview.cpp
index d0715cdb7f..21d644dad5 100644
--- a/src/quick/items/qquickitemview.cpp
+++ b/src/quick/items/qquickitemview.cpp
@@ -1845,6 +1845,9 @@ void QQuickItemViewPrivate::layout()
     forceLayout = false;
 
     if (transitioner && transitioner->canTransition(QQuickItemViewTransitioner::PopulateTransition, true)) {
+        // Give the view one more chance to refill itself,
+        // in case its size is changed such that more delegates become visible after component completed
+        refill();
         for (FxViewItem *item : qAsConst(visibleItems)) {
             if (!item->transitionScheduledOrRunning())
                 item->transitionNextReposition(transitioner, QQuickItemViewTransitioner::PopulateTransition, true);
diff --git a/tests/auto/quick/qquicklistview/data/resizeAfterComponentComplete.qml b/tests/auto/quick/qquicklistview/data/resizeAfterComponentComplete.qml
new file mode 100644
index 0000000000..851d8f9a0c
--- /dev/null
+++ b/tests/auto/quick/qquicklistview/data/resizeAfterComponentComplete.qml
@@ -0,0 +1,77 @@
+/****************************************************************************
+**
+** Copyright (C) 2019 The Qt Company Ltd.
+** Contact: https://www.qt.io/licensing/
+**
+** This file is part of the test suite of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:BSD$
+** 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.
+**
+** BSD License Usage
+** Alternatively, you may use this file under the terms of the BSD license
+** as follows:
+**
+** "Redistribution and use in source and binary forms, with or without
+** modification, are permitted provided that the following conditions are
+** met:
+**   * Redistributions of source code must retain the above copyright
+**     notice, this list of conditions and the following disclaimer.
+**   * Redistributions in binary form must reproduce the above copyright
+**     notice, this list of conditions and the following disclaimer in
+**     the documentation and/or other materials provided with the
+**     distribution.
+**   * Neither the name of The Qt Company Ltd nor the names of its
+**     contributors may be used to endorse or promote products derived
+**     from this software without specific prior written permission.
+**
+**
+** THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+** "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+** LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+** A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+** OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+** SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+** LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+** DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+** THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+** (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+** OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE."
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+import QtQuick 2.12
+
+ListView {
+    id: listView
+    property var lastItem
+    anchors.fill: parent
+    model: 10
+    delegate: Rectangle {
+        width: parent.width
+        height: 40
+        border.color: "lightsteelblue"
+        Text {
+            text: "Item" + (index + 1)
+        }
+        Component.onCompleted: {
+            if (index == 9)
+                listView.lastItem = this
+        }
+    }
+
+    populate: Transition {
+        NumberAnimation {
+            properties: "x,y"
+            duration: 1000
+        }
+    }
+}
diff --git a/tests/auto/quick/qquicklistview/tst_qquicklistview.cpp b/tests/auto/quick/qquicklistview/tst_qquicklistview.cpp
index cfd740f33d..d956d89292 100644
--- a/tests/auto/quick/qquicklistview/tst_qquicklistview.cpp
+++ b/tests/auto/quick/qquicklistview/tst_qquicklistview.cpp
@@ -276,6 +276,7 @@ private slots:
     void addOnCompleted();
     void setPositionOnLayout();
     void touchCancel();
+    void resizeAfterComponentComplete();
 
 private:
     template <class T> void items(const QUrl &source);
@@ -8994,6 +8995,21 @@ void tst_QQuickListView::touchCancel() // QTBUG-74679
     QTRY_COMPARE(listview->contentY(), 500.0);
 }
 
+void tst_QQuickListView::resizeAfterComponentComplete()  // QTBUG-76487
+{
+    QScopedPointer<QQuickView> window(createView());
+    window->setSource(testFileUrl("resizeAfterComponentComplete.qml"));
+    window->resize(640, 480);
+    window->show();
+    QVERIFY(QTest::qWaitForWindowExposed(window.data()));
+
+    QObject *listView = window->rootObject();
+    QVERIFY(listView);
+
+    QObject *lastItem = qvariant_cast<QObject *>(listView->property("lastItem"));
+    QTRY_COMPARE(lastItem->property("y").toInt(), 9 * lastItem->property("height").toInt());
+}
+
 QTEST_MAIN(tst_QQuickListView)
 
 #include "tst_qquicklistview.moc"