Cannot focus GUI.Window in OnSceneGUI

Hello,

I'm beginning to play with windows to display in the scene view for custom Editor, however they don't seem to react to any mouse event.

When I click on a window, it disappears and the current GameObject deselects just as if the window was not there...

My code:

 public class ShapeEditorBase : Editor
 {
     protected void ProcessGUIOverlay()
     {
         Handles.BeginGUI();
 
         GUI.Window(0, new Rect(10, 10, 200, 200), ProcessGUIWindow, "wiwiwiwi");
 
         Handles.EndGUI();
     }
 
     private void ProcessGUIWindow(int id)
     {
 // Nothing yet... should I have something?
     }
 
     protected void OnSceneGUI()
     {
         ProcessGUIOverlay();
     }
 }