To distinguish between the view/edit modes, so as to set an appropriate page title, I normally set the default mode to 'edit' in the ad_page_contract and then check it:

if {[ad_form_new_p -key item_id]} {

    set page_title "Add a new project"

} else {

    if {[string equal $mode "edit"]} {

        set page_title "Edit project"

    } else {

        set page_title "View project"

    }

}

Remember to pass the mode parameter to ad_form and when calling the add/view/edit program to just view an item's data add the mode=display to its url.