Use App's x11 rootWindow and connection in PointerInputRedirection::warpXcbOnSurfaceLeft

It was already partially using the x11Connection and partially the global
connection. In order to prepare for removal of the global connection and
rootWindow, it is better to use only the newer variant through kwinApp.

pointer_input.cpp

@@ -652,10 +652,11 @@ void PointerInputRedirection::warpXcbOnSurfaceLeft(KWayland::Server::SurfaceInte
         // No XWayland, no point in warping the x cursor
         return;
     }
-    if (!kwinApp()->x11Connection()) {
+    const auto c = kwinApp()->x11Connection();
+    if (!c) {
         return;
     }
-    static bool s_hasXWayland119 = xcb_get_setup(kwinApp()->x11Connection())->release_number >= 11900000;
+    static bool s_hasXWayland119 = xcb_get_setup(c)->release_number >= 11900000;
     if (s_hasXWayland119) {
         return;
     }
@@ -669,8 +670,8 @@ void PointerInputRedirection::warpXcbOnSurfaceLeft(KWayland::Server::SurfaceInte
         return;
     }
     // warp pointer to 0/0 to trigger leave events on previously focused X window
-    xcb_warp_pointer(connection(), XCB_WINDOW_NONE, rootWindow(), 0, 0, 0, 0, 0, 0),
-    xcb_flush(connection());
+    xcb_warp_pointer(c, XCB_WINDOW_NONE, kwinApp()->x11RootWindow(), 0, 0, 0, 0, 0, 0),
+    xcb_flush(c);
 }
 
 QPointF PointerInputRedirection::applyPointerConfinement(const QPointF &pos) const