Thank you for writing.
RadMarkupEditor is a UserControl and when you type in the text area, the text box is the one with the focus. Not sure what you want to achieve with the focus, but if you want to know whether the design or the html tab is selected, you can use the CommandTabSelected event of the ribbon control:
RadMarkupDialog dialog =
dialog.Editor.RibbonBar.CommandTabSelected += RibbonBar_CommandTabSelected;
sender, CommandTabEventArgs args)
"Selected Tab: "
I hope that you find this information useful. Should you have any other questions, do not hesitate to contact us.