QQuickWindow: Consider z-order of children when delivering pointer events

When creating a target item list for handling pointer events, put
children after the parent item if they have negative z-order value.
This fixes an issue where an item does not receive a pointer event if
there is a child item that accepts the event even when that child item
is shown under the parent item as per the stacking order.

Fixes: QTBUG-83114
Pick-to: 5.15
Change-Id: I711faa22516f5c2396b1138dc507bcaa4ba22241
Reviewed-by: Shawn Rutledge <shawn.rutledge@qt.io>

2 files changed, 93 insertions, 0 deletions

diff --git a/tests/auto/quick/pointerhandlers/qquicktaphandler/data/tapHandlersOverlapped.qml b/tests/auto/quick/pointerhandlers/qquicktaphandler/data/tapHandlersOverlapped.qml
new file mode 100644
index 0000000000..8d2e36d921
--- /dev/null
+++ b/tests/auto/quick/pointerhandlers/qquicktaphandler/data/tapHandlersOverlapped.qml
@@ -0,0 +1,60 @@
+/****************************************************************************
+**
+** 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 2.12
+
+Item {
+    width: 300
+    height: 200
+    property var taps: []
+
+    Rectangle {
+        x: 25
+        y: 25
+        width: 200
+        height: 100
+        color: "salmon"
+
+        TapHandler {
+            objectName: "parentTapHandler"
+            onTapped: taps.push(objectName)
+        }
+
+        Rectangle {
+            x: 25
+            y: 25
+            width: 200
+            height: 100
+            color: "lightsteelblue"
+
+            TapHandler {
+                objectName: "childTapHandler"
+                onTapped: taps.push(objectName)
+            }
+        }
+    }
+}
diff --git a/tests/auto/quick/pointerhandlers/qquicktaphandler/tst_qquicktaphandler.cpp b/tests/auto/quick/pointerhandlers/qquicktaphandler/tst_qquicktaphandler.cpp
index 32a68293c2..89de571abd 100644
--- a/tests/auto/quick/pointerhandlers/qquicktaphandler/tst_qquicktaphandler.cpp
+++ b/tests/auto/quick/pointerhandlers/qquicktaphandler/tst_qquicktaphandler.cpp
@@ -70,6 +70,7 @@ private slots:
     void buttonsMultiTouch();
     void componentUserBehavioralOverride();
     void rightLongPressIgnoreWheel();
+    void negativeZStackingOrder();
 
 private:
     void createView(QScopedPointer<QQuickView> &window, const char *fileName);
@@ -744,6 +745,38 @@ void tst_TapHandler::rightLongPressIgnoreWheel()
     QCOMPARE(tappedSpy.count(), 0);
 }
 
+void tst_TapHandler::negativeZStackingOrder() // QTBUG-83114
+{
+    QScopedPointer<QQuickView> windowPtr;
+    createView(windowPtr, "tapHandlersOverlapped.qml");
+    QQuickView *window = windowPtr.data();
+    QQuickItem *root = window->rootObject();
+
+    QQuickTapHandler *parentTapHandler = window->rootObject()->findChild<QQuickTapHandler*>("parentTapHandler");
+    QVERIFY(parentTapHandler != nullptr);
+    QSignalSpy clickSpyParent(parentTapHandler, &QQuickTapHandler::tapped);
+    QQuickTapHandler *childTapHandler = window->rootObject()->findChild<QQuickTapHandler*>("childTapHandler");
+    QVERIFY(childTapHandler != nullptr);
+    QSignalSpy clickSpyChild(childTapHandler, &QQuickTapHandler::tapped);
+
+    QTest::mouseClick(window, Qt::LeftButton, Qt::NoModifier, QPoint(150, 100));
+    QCOMPARE(clickSpyChild.count(), 1);
+    QCOMPARE(clickSpyParent.count(), 1);
+    auto order = root->property("taps").toList();
+    QVERIFY(order.at(0) == "childTapHandler");
+    QVERIFY(order.at(1) == "parentTapHandler");
+
+    // Now change stacking order and try again.
+    childTapHandler->parentItem()->setZ(-1);
+    root->setProperty("taps", QVariantList());
+    QTest::mouseClick(window, Qt::LeftButton, Qt::NoModifier, QPoint(150, 100));
+    QCOMPARE(clickSpyChild.count(), 2);
+    QCOMPARE(clickSpyParent.count(), 2);
+    order = root->property("taps").toList();
+    QVERIFY(order.at(0) == "parentTapHandler");
+    QVERIFY(order.at(1) == "childTapHandler");
+}
+
 QTEST_MAIN(tst_TapHandler)
 
 #include "tst_qquicktaphandler.moc"