Circumflex vs macron 

I keep coming across Tongan words spelled with circumflex accents over vowels. Notably in translation tables in the English Wiktionary.

I just want to check with experts here whether the circumflex was formerly an official way to denote a long vowel, or whether the macron has always held this role with the circumflex just being used as an ad-hoc replacement due to macrons not being available on English typewriters and computer keyboards. —