xcb: Adapt QXcbWindow::startSystemResize() for touch events

Window managers typically grab the pointer after receiving
the _NET_WM_MOVERESIZE event. But they fail to do it for
touch sequences which have a receiver. So we should reject
the touch sequence before sending _NET_WM_MOVERESIZE event.

QSizeGrip calls startSystemResize() on MouseButtonPress event
which is synthesized by Qt on TouchBegin. We can find the id
of the touch point by comparing coordinates of the synthesized
MouseButtonPress event with coordinates of all TouchBegin events.
Then we use this id to reject the touch sequence (it's possible
only after receiving XI_TouchUpdate).

Change-Id: I26519840cd221e28b0be7854e4617c9aba4b0817
Task-number: QTBUG-51385
Reviewed-by: Shawn Rutledge <shawn.rutledge@qt.io>

src/plugins/platforms/xcb/qxcbconnection.h

@@ -504,6 +504,7 @@ public:
 #endif
 
 #ifdef XCB_USE_XINPUT22
+    bool startSystemResizeForTouchBegin(xcb_window_t window, const QPoint &point, Qt::Corner corner);
     bool xi2SetMouseGrabEnabled(xcb_window_t w, bool grab);
 #endif
     Qt::MouseButton xiToQtMouseButton(uint32_t b);
@@ -639,6 +640,14 @@ private:
     QXcbEventReader *m_reader;
 #if defined(XCB_USE_XINPUT2)
     QHash<int, XInput2TouchDeviceData*> m_touchDevices;
+#ifdef XCB_USE_XINPUT22
+    struct StartSystemResizeInfo {
+        xcb_window_t window;
+        uint16_t deviceid;
+        uint32_t pointid;
+        Qt::Corner corner;
+    } m_startSystemResizeInfo;
+#endif
 #endif
 #ifdef Q_XCB_DEBUG
     struct CallInfo {

src/plugins/platforms/xcb/qxcbconnection_xi2.cpp

@@ -61,9 +61,9 @@ struct XInput2TouchDeviceData {
     XIDeviceInfo *xiDeviceInfo;
     QTouchDevice *qtTouchDevice;
     QHash<int, QWindowSystemInterface::TouchPoint> touchPoints;
+    QHash<int, QPointF> pointPressedPosition; // in screen coordinates where each point was pressed
 
     // Stuff that is relevant only for touchpads
-    QHash<int, QPointF> pointPressedPosition; // in screen coordinates where each point was pressed
     QPointF firstPressedPosition;        // in screen coordinates where the first point was pressed
     QPointF firstPressedNormalPosition;  // device coordinates (0 to 1, 0 to 1) where the first point was pressed
     QSizeF size;                         // device size in mm
@@ -93,6 +93,7 @@ void QXcbConnection::initializeXInput2()
         if (m_xi2Enabled) {
 #ifdef XCB_USE_XINPUT22
             qCDebug(lcQpaXInputDevices, "XInput version %d.%d is available and Qt supports 2.2 or greater", xiMajor, m_xi2Minor);
+            m_startSystemResizeInfo.window = XCB_NONE;
 #else
             qCDebug(lcQpaXInputDevices, "XInput version %d.%d is available and Qt supports 2.0", xiMajor, m_xi2Minor);
 #endif
@@ -714,7 +715,21 @@ void QXcbConnection::xi2ProcessTouch(void *xiDevEvent, QXcbWindow *platformWindo
             touchPoint.state = Qt::TouchPointMoved;
         } else if (touchPoint.area.center() != QPoint(x, y)) {
             touchPoint.state = Qt::TouchPointMoved;
-            dev->pointPressedPosition[touchPoint.id] = QPointF(x, y);
+            if (dev->qtTouchDevice->type() == QTouchDevice::TouchPad)
+                dev->pointPressedPosition[touchPoint.id] = QPointF(x, y);
+        }
+
+        if (dev->qtTouchDevice->type() == QTouchDevice::TouchScreen &&
+            xiDeviceEvent->event == m_startSystemResizeInfo.window &&
+            xiDeviceEvent->sourceid == m_startSystemResizeInfo.deviceid &&
+            xiDeviceEvent->detail == m_startSystemResizeInfo.pointid) {
+            QXcbWindow *window = platformWindowFromId(m_startSystemResizeInfo.window);
+            if (window) {
+                XIAllowTouchEvents(static_cast<Display *>(m_xlib_display), xiDeviceEvent->deviceid,
+                                   xiDeviceEvent->detail, xiDeviceEvent->event, XIRejectTouch);
+                window->doStartSystemResize(QPoint(x, y), m_startSystemResizeInfo.corner);
+                m_startSystemResizeInfo.window = XCB_NONE;
+            }
         }
         break;
     case XI_TouchEnd:
@@ -745,6 +760,27 @@ void QXcbConnection::xi2ProcessTouch(void *xiDevEvent, QXcbWindow *platformWindo
         touchPoint.state = Qt::TouchPointStationary;
 }
 
+bool QXcbConnection::startSystemResizeForTouchBegin(xcb_window_t window, const QPoint &point, Qt::Corner corner)
+{
+    QHash<int, XInput2TouchDeviceData*>::const_iterator devIt = m_touchDevices.constBegin();
+    for (; devIt != m_touchDevices.constEnd(); ++devIt) {
+        XInput2TouchDeviceData *deviceData = devIt.value();
+        if (deviceData->qtTouchDevice->type() == QTouchDevice::TouchScreen) {
+            QHash<int, QPointF>::const_iterator pointIt = deviceData->pointPressedPosition.constBegin();
+            for (; pointIt != deviceData->pointPressedPosition.constEnd(); ++pointIt) {
+                if (pointIt.value().toPoint() == point) {
+                    m_startSystemResizeInfo.window = window;
+                    m_startSystemResizeInfo.deviceid = devIt.key();
+                    m_startSystemResizeInfo.pointid = pointIt.key();
+                    m_startSystemResizeInfo.corner = corner;
+                    return true;
+                }
+            }
+        }
+    }
+    return false;
+}
+
 bool QXcbConnection::xi2SetMouseGrabEnabled(xcb_window_t w, bool grab)
 {
     if (grab && !canGrab())

src/plugins/platforms/xcb/qxcbwindow.cpp

@@ -2738,13 +2738,23 @@ bool QXcbWindow::startSystemResize(const QPoint &pos, Qt::Corner corner)
     const xcb_atom_t moveResize = connection()->atom(QXcbAtom::_NET_WM_MOVERESIZE);
     if (!connection()->wmSupport()->isSupportedByWM(moveResize))
         return false;
+    const QPoint globalPos = window()->mapToGlobal(pos);
+#ifdef XCB_USE_XINPUT22
+    if (connection()->startSystemResizeForTouchBegin(m_window, globalPos, corner))
+        return true;
+#endif
+    return doStartSystemResize(globalPos, corner);
+}
+
+bool QXcbWindow::doStartSystemResize(const QPoint &globalPos, Qt::Corner corner)
+{
+    const xcb_atom_t moveResize = connection()->atom(QXcbAtom::_NET_WM_MOVERESIZE);
     xcb_client_message_event_t xev;
     xev.response_type = XCB_CLIENT_MESSAGE;
     xev.type = moveResize;
     xev.sequence = 0;
     xev.window = xcb_window();
     xev.format = 32;
-    const QPoint globalPos = window()->mapToGlobal(pos);
     xev.data.data32[0] = globalPos.x();
     xev.data.data32[1] = globalPos.y();
     const bool bottom = corner == Qt::BottomRightCorner || corner == Qt::BottomLeftCorner;

src/plugins/platforms/xcb/qxcbwindow.h

@@ -178,6 +178,8 @@ public:
 
     QXcbScreen *xcbScreen() const;
 
+    bool doStartSystemResize(const QPoint &globalPos, Qt::Corner corner);
+
     virtual void create();
     virtual void destroy();