[qt6web] register custom root scheme already when load library

Same as in qt5web, reference on that object may be preserved
in the qt classes

gui/qt6webdisplay/rootqt6.cpp

@@ -14,7 +14,6 @@
 #include <QWebEngineView>
 #include <qtwebenginecoreglobal.h>
 #include <QWebEngineDownloadRequest>
-// #include <qtwebenginequickglobal.h>
 
 #include <QThread>
 #include <QWebEngineSettings>
@@ -40,6 +39,9 @@
 #include <ROOT/RWebDisplayHandle.hxx>
 #include <ROOT/RLogger.hxx>
 
+QWebEngineUrlScheme gRootScheme("rootscheme");
+
+
 /** \class TQt6Timer
 \ingroup qt6webdisplay
 */
@@ -101,12 +103,6 @@ class RQt6WebDisplayHandle : public RWebDisplayHandle {
             // initialize web engine only before creating QApplication
             // QtWebEngineQuick::initialize();
 
-            QWebEngineUrlScheme scheme("rootscheme");
-            scheme.setSyntax(QWebEngineUrlScheme::Syntax::HostAndPort);
-            scheme.setDefaultPort(2345);
-            scheme.setFlags(QWebEngineUrlScheme::SecureScheme);
-            QWebEngineUrlScheme::registerScheme(scheme);
-
             qargv[0] = gApplication->Argv(0);
             qargv[1] = nullptr;
 
@@ -246,7 +242,16 @@ class RQt6WebDisplayHandle : public RWebDisplayHandle {
 };
 
 struct RQt6CreatorReg {
-   RQt6CreatorReg() { RQt6WebDisplayHandle::AddCreator(); }
+   RQt6CreatorReg()
+   {
+      RQt6WebDisplayHandle::AddCreator();
+
+      gRootScheme.setSyntax(QWebEngineUrlScheme::Syntax::HostAndPort);
+      gRootScheme.setDefaultPort(2345);
+      gRootScheme.setFlags(QWebEngineUrlScheme::SecureScheme);
+      QWebEngineUrlScheme::registerScheme(gRootScheme);
+
+   }
 } newRQt6CreatorReg;
 
 }