standalone, dui or cui; panel when the page is in a panel that could not be told apart, unknown for a panel of an unrecognized kind.
Whether the page is in a DUI or CUI panel; false for the main window and popups.
Always true here; a failed call resolves with ApiFailure instead.
Id of the calling window: main for the main window, the popup's actual id, or the panel's id. A panel without an id reports panel; an unmatched caller reports main.
Successful response from
window.getMode.