Unset mouseGrabberPopup if it's removed from children

The mouseGrabberPopup is supposed to be unset in handleRelease, however
when the exit transition of the mouseGrabberPopup (that closed itself on
button press) finishes before the release event is delivered, it
unparents itself from the overlay (see
QQuickPopupPrivate::finalizeExitTransition) and the overlay sets itself
invisible if there is nothing else visible in it. Because the overlay
is not visible it handles no events anymore and the release is missed
and the grabber is never unset. When opening another non-modal popup
the overlay then will continue forwarding the events to now invisible
popup.
So when the overlay loses the currently grabbing popup as a child we need
to reset mouseGrabberPopup.

Fixes: QTBUG-95259
Change-Id: I3c832d47f3cee216b81ef1b5cb7dd77bf4149991
Reviewed-by: Mitch Curtis <mitch.curtis@qt.io>
(adapted from commit d07ee1345acd8100fa5cbb7f05c0aaf5f87f4cae)

3 files changed, 110 insertions, 1 deletions

diff --git a/src/quicktemplates2/qquickoverlay.cpp b/src/quicktemplates2/qquickoverlay.cpp
index 982834d8..1325e62c 100644
--- a/src/quicktemplates2/qquickoverlay.cpp
+++ b/src/quicktemplates2/qquickoverlay.cpp
@@ -395,8 +395,11 @@ void QQuickOverlay::itemChange(ItemChange change, const ItemChangeData &data)
     Q_D(QQuickOverlay);
     QQuickItem::itemChange(change, data);
 
-    if (change == ItemChildAddedChange || change == ItemChildRemovedChange)
+    if (change == ItemChildAddedChange || change == ItemChildRemovedChange) {
         setVisible(!d->allDrawers.isEmpty() || !childItems().isEmpty());
+        if (data.item->parent() == d->mouseGrabberPopup)
+            d->setMouseGrabberPopup(nullptr);
+    }
 }
 
 void QQuickOverlay::geometryChange(const QRectF &newGeometry, const QRectF &oldGeometry)
diff --git a/tests/auto/qquickpopup/data/releaseAfterExitTransition.qml b/tests/auto/qquickpopup/data/releaseAfterExitTransition.qml
new file mode 100644
index 00000000..cfd9a947
--- /dev/null
+++ b/tests/auto/qquickpopup/data/releaseAfterExitTransition.qml
@@ -0,0 +1,78 @@
+/****************************************************************************
+**
+** Copyright (C) 2021 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
+import QtQuick.Controls
+
+ApplicationWindow {
+    id: window
+    width: 400
+    height: 400
+    title: "releaseAfterExitTransition"
+
+    property alias popup: popup
+    property alias modalPopup: modalPopup
+
+    Popup {
+        id: popup
+        y: parent.height - height
+        width: 50
+        height: 50
+    }
+
+    Popup {
+        id: modalPopup
+        modal: true
+        y: parent.height - height
+        width: 50
+        height: 50
+        exit:  Transition { PauseAnimation { duration: 100 } }
+    }
+}
diff --git a/tests/auto/qquickpopup/tst_qquickpopup.cpp b/tests/auto/qquickpopup/tst_qquickpopup.cpp
index 442b99fa..cb99a92e 100644
--- a/tests/auto/qquickpopup/tst_qquickpopup.cpp
+++ b/tests/auto/qquickpopup/tst_qquickpopup.cpp
@@ -101,6 +101,7 @@ private slots:
     void invisibleToolTipOpen();
     void centerInOverlayWithinStackViewItem();
     void destroyDuringExitTransition();
+    void releaseAfterExitTransition();
 };
 
 void tst_QQuickPopup::initTestCase()
@@ -1456,6 +1457,33 @@ void tst_QQuickPopup::destroyDuringExitTransition()
     QVERIFY(!button->isDown());
 }
 
+void tst_QQuickPopup::releaseAfterExitTransition()
+{
+    QQuickApplicationHelper helper(this, "releaseAfterExitTransition.qml");
+    QVERIFY2(helper.ready, helper.failureMessage());
+
+    QQuickWindow *window = helper.window;
+    window->show();
+    QVERIFY(QTest::qWaitForWindowActive(window));
+
+    QQuickOverlay *overlay = QQuickOverlay::overlay(window);
+    QQuickPopup *modalPopup = window->property("modalPopup").value<QQuickPopup *>();
+    QQuickPopup *popup = window->property("popup").value<QQuickPopup *>();
+
+    modalPopup->open();
+    QTRY_VERIFY(modalPopup->isOpened());
+
+    QTest::mousePress(window, Qt::LeftButton, Qt::NoModifier, QPoint(1, 1));
+    // wait until the transition is finished and the overlay hides itself
+    QTRY_VERIFY(!overlay->isVisible());
+    QTest::mouseRelease(window, Qt::LeftButton, Qt::NoModifier, QPoint(1, 1));
+
+    popup->open();
+    QTRY_VERIFY(popup->isOpened());
+    QTest::mouseClick(window, Qt::LeftButton, Qt::NoModifier, QPoint(1, 1));
+    QTRY_VERIFY(!popup->isOpened());
+}
+
 QTEST_QUICKCONTROLS_MAIN(tst_QQuickPopup)
 
 #include "tst_qquickpopup.moc"