xcb: allow to change XInput device properties at runtime

xinput list-props <device-id>
xinput set-prop <device-id> <atom-id> n n n

Example:

xinput list-props 9
  ..
  Evdev Scrolling Distance (274): 1, 1, 1
  ..
xinput set-prop 9 274 8 1 1

[ChangeLog][Platform Specific Changes][Linux] XInput device property
changes are now detected at runtime (no application restart required).

Change-Id: I4d2455eef70857bc2e35c27011a3808a78fa960f
Reviewed-by: Allan Sandfeld Jensen <allan.jensen@qt.io>

src/plugins/platforms/xcb/qxcbconnection.h

@@ -547,6 +547,7 @@ private:
     bool m_xi2Enabled = false;
     int m_xi2Minor = -1;
     void initializeXInput2();
+    void xi2SetupDevice(void *info, bool removeExisting = true);
     void xi2SetupDevices();
     struct TouchDeviceData {
         QTouchDevice *qtTouchDevice = nullptr;

src/plugins/platforms/xcb/qxcbconnection_xi2.cpp

@@ -93,28 +93,29 @@ void QXcbConnection::initializeXInput2()
     }
 }
 
-void QXcbConnection::xi2SetupDevices()
+void QXcbConnection::xi2SetupDevice(void *info, bool removeExisting)
 {
+    XIDeviceInfo *deviceInfo = reinterpret_cast<XIDeviceInfo *>(info);
+    if (removeExisting) {
 #if QT_CONFIG(tabletevent)
-    m_tabletData.clear();
+        for (int i = 0; i < m_tabletData.count(); ++i) {
+            if (m_tabletData.at(i).deviceId == deviceInfo->deviceid) {
+                m_tabletData.remove(i);
+                break;
+            }
+        }
 #endif
-    m_scrollingDevices.clear();
+        m_scrollingDevices.remove(deviceInfo->deviceid);
-    m_touchDevices.clear();
+        m_touchDevices.remove(deviceInfo->deviceid);
+    }
 
-    Display *xDisplay = static_cast<Display *>(m_xlib_display);
+    qCDebug(lcQpaXInputDevices) << "input device " << deviceInfo->name << "ID" << deviceInfo->deviceid;
-    int deviceCount = 0;
-    XIDeviceInfo *devices = XIQueryDevice(xDisplay, XIAllDevices, &deviceCount);
-    for (int i = 0; i < deviceCount; ++i) {
-        // Only non-master pointing devices are relevant here.
-        if (devices[i].use != XISlavePointer)
-            continue;
-        qCDebug(lcQpaXInputDevices) << "input device " << devices[i].name << "ID" << devices[i].deviceid;
 #if QT_CONFIG(tabletevent)
     TabletData tabletData;
 #endif
     ScrollingDevice scrollingDevice;
-        for (int c = 0; c < devices[i].num_classes; ++c) {
+    for (int c = 0; c < deviceInfo->num_classes; ++c) {
-            XIAnyClassInfo *classinfo = devices[i].classes[c];
+        XIAnyClassInfo *classinfo = deviceInfo->classes[c];
         switch (classinfo->type) {
         case XIValuatorClass: {
             XIValuatorClassInfo *vci = reinterpret_cast<XIValuatorClassInfo *>(classinfo);
@@ -193,7 +194,7 @@ void QXcbConnection::xi2SetupDevices()
         isTablet = true;
 
     // But we need to be careful not to take the touch and tablet-button devices as tablets.
-        QByteArray name = QByteArray(devices[i].name).toLower();
+    QByteArray name = QByteArray(deviceInfo->name).toLower();
     QString dbgType = QLatin1String("UNKNOWN");
     if (name.contains("eraser")) {
         isTablet = true;
@@ -231,7 +232,7 @@ void QXcbConnection::xi2SetupDevices()
     }
 
     if (isTablet) {
-            tabletData.deviceId = devices[i].deviceid;
+        tabletData.deviceId = deviceInfo->deviceid;
         m_tabletData.append(tabletData);
         qCDebug(lcQpaXInputDevices) << "   it's a tablet with pointer type" << dbgType;
     }
@@ -239,7 +240,7 @@ void QXcbConnection::xi2SetupDevices()
 
 #ifdef XCB_USE_XINPUT21
     if (scrollingDevice.orientations || scrollingDevice.legacyOrientations) {
-            scrollingDevice.deviceId = devices[i].deviceid;
+        scrollingDevice.deviceId = deviceInfo->deviceid;
         // Only use legacy wheel button events when we don't have real scroll valuators.
         scrollingDevice.legacyOrientations &= ~scrollingDevice.orientations;
         m_scrollingDevices.insert(scrollingDevice.deviceId, scrollingDevice);
@@ -248,7 +249,7 @@ void QXcbConnection::xi2SetupDevices()
 #endif
 
     if (!isTablet) {
-            TouchDeviceData *dev = populateTouchDevices(&devices[i]);
+        TouchDeviceData *dev = populateTouchDevices(deviceInfo);
         if (dev && lcQpaXInputDevices().isDebugEnabled()) {
             if (dev->qtTouchDevice->type() == QTouchDevice::TouchScreen)
                 qCDebug(lcQpaXInputDevices, "   it's a touchscreen with type %d capabilities 0x%X max touch points %d",
@@ -261,6 +262,25 @@ void QXcbConnection::xi2SetupDevices()
                         dev->size.width(), dev->size.height());
         }
     }
+
+}
+
+void QXcbConnection::xi2SetupDevices()
+{
+#if QT_CONFIG(tabletevent)
+    m_tabletData.clear();
+#endif
+    m_scrollingDevices.clear();
+    m_touchDevices.clear();
+
+    Display *xDisplay = static_cast<Display *>(m_xlib_display);
+    int deviceCount = 0;
+    XIDeviceInfo *devices = XIQueryDevice(xDisplay, XIAllDevices, &deviceCount);
+    for (int i = 0; i < deviceCount; ++i) {
+        // Only non-master pointing devices are relevant here.
+        if (devices[i].use != XISlavePointer)
+            continue;
+        xi2SetupDevice(&devices[i], false);
     }
     XIFreeDeviceInfo(devices);
 }
@@ -835,8 +855,16 @@ void QXcbConnection::xi2HandleDeviceChangedEvent(void *event)
 {
     xXIDeviceChangedEvent *xiEvent = reinterpret_cast<xXIDeviceChangedEvent *>(event);
     switch (xiEvent->reason) {
-    case XIDeviceChange:
+    case XIDeviceChange: {
+        int nrDevices = 0;
+        Display *dpy = static_cast<Display *>(m_xlib_display);
+        XIDeviceInfo* deviceInfo = XIQueryDevice(dpy, xiEvent->sourceid, &nrDevices);
+        if (nrDevices <= 0)
+            return;
+        xi2SetupDevice(deviceInfo);
+        XIFreeDeviceInfo(deviceInfo);
         break;
+    }
     case XISlaveSwitch: {
 #ifdef XCB_USE_XINPUT21
         if (ScrollingDevice *scrollingDevice = scrollingDeviceForId(xiEvent->sourceid))