XCB: fix leaked QXcbScrollingDevicePrivate

==1585319== 1,112 (720 direct, 392 indirect) bytes in 2 blocks are definitely lost in loss record 110 of 123
==1585319==    at 0x483EF2F: operator new(unsigned long) (in /usr/libexec/valgrind/vgpreload_memcheck-amd64-linux.so)
==1585319==    by 0x7D01D6C: QXcbConnection::xi2SetupSlavePointerDevice(void*, bool, QPointingDevice*)::{lambda()#1}::operator()() const (qxcbconnection_xi2.cpp:262)
==1585319==    by 0x7D025C2: QXcbConnection::xi2SetupSlavePointerDevice(void*, bool, QPointingDevice*) (qxcbconnection_xi2.cpp:316)
==1585319==    by 0x7D03D2D: QXcbConnection::xi2SetupDevices() (qxcbconnection_xi2.cpp:499)
==1585319==    by 0x7CE81A3: QXcbConnection::QXcbConnection(QXcbNativeInterface*, bool, unsigned int, char const*) (qxcbconnection.cpp:105)
==1585319==    by 0x7D27BEA: QXcbIntegration::QXcbIntegration(QList<QString> const&, int&, char**) (qxcbintegration.cpp:199)
==1585319==    by 0x7C9D282: QXcbIntegrationPlugin::create(QString const&, QList<QString> const&, int&, char**) (qxcbmain.cpp:56)
==1585319==    by 0x4B516DE: QPlatformIntegration* qLoadPlugin<QPlatformIntegration, QPlatformIntegrationPlugin, QList<QString> const&, int&, char**&>(QFactoryLoader const*, QString const&, QList<QString> const&, int&, char**&) (qfactoryloader_p.h:108)
==1585319==    by 0x4B512A9: QPlatformIntegrationFactory::create(QString const&, QList<QString> const&, int&, char**, QString const&) (qplatformintegrationfactory.cpp:71)
==1585319==    by 0x4B074EC: init_platform(QString const&, QString const&, QString const&, int&, char**) (qguiapplication.cpp:1209)
==1585319==    by 0x4B0A646: QGuiApplicationPrivate::createPlatformIntegration() (qguiapplication.cpp:1491)
==1585319==    by 0x4B0A7C9: QGuiApplicationPrivate::createEventDispatcher() (qguiapplication.cpp:1508)
==1585319==    by 0x568853F: QCoreApplicationPrivate::init() (qcoreapplication.cpp:847)
==1585319==    by 0x4B0A89F: QGuiApplicationPrivate::init() (qguiapplication.cpp:1532)
==1585319==    by 0x4B05D16: QGuiApplication::QGuiApplication(int&, char**, int) (qguiapplication.cpp:653)
==1585319==    by 0x451613: main (tst_qmetatype.cpp:2141)

Fixes: QTBUG-95468
Pick-to: 6.3 6.2
Change-Id: I7e0b82c2d2fe464082d8fffd1696c0122c3b35b7
Reviewed-by: Shawn Rutledge <shawn.rutledge@qt.io>

2 files changed, 11 insertions, 3 deletions

diff --git a/src/plugins/platforms/xcb/qxcbconnection.h b/src/plugins/platforms/xcb/qxcbconnection.h
index 943f380d5c..8eb6008425 100644
--- a/src/plugins/platforms/xcb/qxcbconnection.h
+++ b/src/plugins/platforms/xcb/qxcbconnection.h
@@ -296,7 +296,7 @@ private:
         QSizeF size;                         // device size in mm
         bool providesTouchOrientation = false;
     };
-    TouchDeviceData *populateTouchDevices(void *info, QXcbScrollingDevicePrivate *scrollingDeviceP);
+    TouchDeviceData *populateTouchDevices(void *info, QXcbScrollingDevicePrivate *scrollingDeviceP, bool *used = nullptr);
     TouchDeviceData *touchDeviceForId(int id);
     void xi2HandleEvent(xcb_ge_event_t *event);
     void xi2HandleGesturePinchEvent(void *event);
diff --git a/src/plugins/platforms/xcb/qxcbconnection_xi2.cpp b/src/plugins/platforms/xcb/qxcbconnection_xi2.cpp
index c9e45e623a..d775a7ebb5 100644
--- a/src/plugins/platforms/xcb/qxcbconnection_xi2.cpp
+++ b/src/plugins/platforms/xcb/qxcbconnection_xi2.cpp
@@ -280,6 +280,7 @@ void QXcbConnection::xi2SetupSlavePointerDevice(void *info, bool removeExisting,
     TabletData tabletData;
 #endif
     QXcbScrollingDevicePrivate *scrollingDeviceP = nullptr;
+    bool used = false;
     auto scrollingDevice = [&]() {
         if (!scrollingDeviceP)
             scrollingDeviceP = new QXcbScrollingDevicePrivate(name, deviceInfo->deviceid,
@@ -439,7 +440,7 @@ void QXcbConnection::xi2SetupSlavePointerDevice(void *info, bool removeExisting,
     }
 
     if (!isTablet) {
-        TouchDeviceData *dev = populateTouchDevices(deviceInfo, scrollingDeviceP);
+        TouchDeviceData *dev = populateTouchDevices(deviceInfo, scrollingDeviceP, &used);
         if (dev && lcQpaXInputDevices().isDebugEnabled()) {
             if (dev->qtTouchDevice->type() == QInputDevice::DeviceType::TouchScreen)
                 qCDebug(lcQpaXInputDevices, "   it's a touchscreen with type %d capabilities 0x%X max touch points %d",
@@ -462,6 +463,7 @@ void QXcbConnection::xi2SetupSlavePointerDevice(void *info, bool removeExisting,
             if (master)
                 scrollingDeviceP->seatName = master->seatName();
             QWindowSystemInterface::registerInputDevice(new QXcbScrollingDevice(*scrollingDeviceP, master));
+            used = true;
         } else {
             QWindowSystemInterface::registerInputDevice(new QPointingDevice(
                     name, deviceInfo->deviceid,
@@ -469,6 +471,11 @@ void QXcbConnection::xi2SetupSlavePointerDevice(void *info, bool removeExisting,
                     caps, 1, buttonCount, (master ? master->seatName() : QString()), QPointingDeviceUniqueId(), master));
         }
     }
+
+    if (!used && scrollingDeviceP) {
+        QXcbScrollingDevice *holder = new QXcbScrollingDevice(*scrollingDeviceP, master);
+        holder->deleteLater();
+    }
 }
 
 void QXcbConnection::xi2SetupDevices()
@@ -549,7 +556,7 @@ QXcbConnection::TouchDeviceData *QXcbConnection::touchDeviceForId(int id)
     return dev;
 }
 
-QXcbConnection::TouchDeviceData *QXcbConnection::populateTouchDevices(void *info, QXcbScrollingDevicePrivate *scrollingDeviceP)
+QXcbConnection::TouchDeviceData *QXcbConnection::populateTouchDevices(void *info, QXcbScrollingDevicePrivate *scrollingDeviceP, bool *used)
 {
     auto *deviceInfo = reinterpret_cast<xcb_input_xi_device_info_t *>(info);
     QPointingDevice::Capabilities caps;
@@ -654,6 +661,7 @@ QXcbConnection::TouchDeviceData *QXcbConnection::populateTouchDevices(void *info
             dev.qtTouchDevice = new QXcbScrollingDevice(*scrollingDeviceP, master);
             if (Q_UNLIKELY(!caps.testFlag(QInputDevice::Capability::Scroll)))
                 qCDebug(lcQpaXInputDevices) << "unexpectedly missing RelVert/HorizWheel atoms for touchpad with scroll capability" << dev.qtTouchDevice;
+            *used = true;
         } else {
             dev.qtTouchDevice = new QPointingDevice(QString::fromUtf8(xcb_input_xi_device_info_name(deviceInfo),
                                                                       xcb_input_xi_device_info_name_length(deviceInfo)),