Fix logical error

It makes more sense to access position() if positionValid() returns true.


(cherry picked from commit d074b47a)

input.cpp

@@ -2788,7 +2788,7 @@ void InputDeviceHandler::update()
     Toplevel *toplevel = nullptr;
     QWindow *internalWindow = nullptr;
 
-    if (!positionValid()) {
+    if (positionValid()) {
         const auto pos = position().toPoint();
         internalWindow = findInternalWindow(pos);
         if (internalWindow) {

input.h

@@ -482,7 +482,7 @@ protected:
      * is resting on the surface (no touch point).
      */
     virtual bool positionValid() const {
-        return false;
+        return true;
     }
     virtual bool focusUpdatesBlocked() {
         return false;

touch_input.cpp

@@ -77,7 +77,7 @@ bool TouchInputRedirection::positionValid() const
 {
     Q_ASSERT(m_touches >= 0);
     // we can only determine a position with at least one touch point
-    return m_touches == 0;
+    return m_touches;
 }
 
 void TouchInputRedirection::focusUpdate(Toplevel *focusOld, Toplevel *focusNow)