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, 71 insertions, 0 deletions

diff --git a/tests/auto/quick/qquickmousearea/data/mouseAreasOverlapped.qml b/tests/auto/quick/qquickmousearea/data/mouseAreasOverlapped.qml
new file mode 100644
index 0000000000..aba574283b
--- /dev/null
+++ b/tests/auto/quick/qquickmousearea/data/mouseAreasOverlapped.qml
@@ -0,0 +1,37 @@
+
+import QtQuick 2.0
+
+Item {
+    width: 300
+    height:200
+    property var clicks: []
+    
+    Rectangle {
+        x: 75
+        y: 75
+        width: 200
+        height: 100
+        color: "salmon"
+
+        MouseArea {
+            objectName: "parentMouseArea"
+            anchors.fill: parent
+            onClicked: clicks.push(objectName)
+        }
+        
+        Rectangle {
+            x: 25
+            y: 25
+            width: 200
+            height: 100
+            color: "lightsteelblue"
+
+            MouseArea {
+                id: mouseArea
+                objectName: "childMouseArea"
+                anchors.fill: parent
+                onClicked: clicks.push(objectName)
+            }
+        }
+    }
+}
diff --git a/tests/auto/quick/qquickmousearea/tst_qquickmousearea.cpp b/tests/auto/quick/qquickmousearea/tst_qquickmousearea.cpp
index c38ab72a7b..7bf9660978 100644
--- a/tests/auto/quick/qquickmousearea/tst_qquickmousearea.cpp
+++ b/tests/auto/quick/qquickmousearea/tst_qquickmousearea.cpp
@@ -158,6 +158,7 @@ private slots:
     void mask();
     void nestedEventDelivery();
     void settingHiddenInPressUngrabs();
+    void negativeZStackingOrder();
 
 private:
     int startDragDistance() const {
@@ -2438,6 +2439,39 @@ void tst_QQuickMouseArea::settingHiddenInPressUngrabs()
     QVERIFY(!mouseArea->pressed());
 }
 
+void tst_QQuickMouseArea::negativeZStackingOrder() // QTBUG-83114
+{
+    QQuickView window;
+    QByteArray errorMessage;
+    QVERIFY2(QQuickTest::initView(window, testFileUrl("mouseAreasOverlapped.qml"), true, &errorMessage), errorMessage.constData());
+    window.show();
+    QVERIFY(QTest::qWaitForWindowExposed(&window));
+    QVERIFY(window.rootObject() != nullptr);
+    QQuickItem *root = window.rootObject();
+
+    QQuickMouseArea *parentMouseArea = root->findChild<QQuickMouseArea*>("parentMouseArea");
+    QVERIFY(parentMouseArea != nullptr);
+    QSignalSpy clickSpyParent(parentMouseArea, &QQuickMouseArea::clicked);
+    QQuickMouseArea *childMouseArea = root->findChild<QQuickMouseArea*>("childMouseArea");
+    QVERIFY(childMouseArea != nullptr);
+    QSignalSpy clickSpyChild(childMouseArea, &QQuickMouseArea::clicked);
+
+    QTest::mouseClick(&window, Qt::LeftButton, Qt::NoModifier, QPoint(150, 100));
+    QCOMPARE(clickSpyChild.count(), 1);
+    QCOMPARE(clickSpyParent.count(), 0);
+    auto order = root->property("clicks").toList();
+    QVERIFY(order.at(0) == "childMouseArea");
+
+    // Now change stacking order and try again.
+    childMouseArea->parentItem()->setZ(-1);
+    root->setProperty("clicks", QVariantList());
+    QTest::mouseClick(&window, Qt::LeftButton, Qt::NoModifier, QPoint(150, 100));
+    QCOMPARE(clickSpyChild.count(), 1);
+    QCOMPARE(clickSpyParent.count(), 1);
+    order = root->property("clicks").toList();
+    QVERIFY(order.at(0) == "parentMouseArea");
+}
+
 QTEST_MAIN(tst_QQuickMouseArea)
 
 #include "tst_qquickmousearea.moc"