GetCurrentEditorWindow

private static bool         initializeCurrentEditorWindowMetadata;
private static PropertyInfo current;
private static FieldInfo    m_ActualView;

public static EditorWindow  GetCurrentEditorWindow()
{
    if (Utility.initializeCurrentEditorWindowMetadata == false)
    {
        Utility.initializeCurrentEditorWindowMetadata = true;
        Utility.LazyInitializeCurrentEditorWindowMetadata();
    }

    if (Utility.current == null)
        return null;

    object  guiView = Utility.current.GetValue(null, null);

    if (guiView != null)
        return Utility.m_ActualView.GetValue(guiView) as EditorWindow;
    return null;
}

[AssemblyVerifier]
private static void LazyInitializeCurrentEditorWindowMetadata()
{
    Type    GUIViewType = AssemblyVerifier.TryGetType(typeof(Editor).Assembly, "UnityEditor.GUIView");
    if (GUIViewType != null)
    {
        Utility.current = AssemblyVerifier.TryGetProperty(GUIViewType, "current", BindingFlags.Public | BindingFlags.Static);

        Type    HostViewType = AssemblyVerifier.TryGetType(typeof(Editor).Assembly, "UnityEditor.HostView");
        if (HostViewType != null)
            Utility.m_ActualView = AssemblyVerifier.TryGetField(HostViewType, "m_ActualView", BindingFlags.NonPublic | BindingFlags.Instance);

        if (Utility.m_ActualView == null)
            Utility.current = null;
    }
}