This is a native iOS keyboard for Hong Kong Cantonese. It is an iOS frontend to the excellent Google Input Tools service.
The project is built on KeyboardKit. I would not have taken this project on without it.
Google Input Tools is extremely good at Cantonese input. It picks the Cantonese phrases intelligently based on context. It is a joy to use.
Unfortunately, the service is only available on Android, Chrome, or Windows. The iOS Gboard does support Cantonese input, but it is not in the same league as Google Input Tools. For example, when entering the phrase "neihoma" in Gboard, it suggests "你可馬", instead of what Google Input Tools would suggest correctly, which is "你好嗎".
I really wanted to be able to use Google Input Tools on my iOS device. So I wrote my own iOS frontend for it.
Hong Kong Keyboard makes a network call to Google Input Tools on every keystroke. It sends the English characters you have typed so far, and the Cantonese sentence you have typed in up to this point as context. The service returns a list of suggestions, you pick from the suggestions, and rinse and repeat.
The response from Google Input Tools is pretty fast. If the network is slow, you will observe delayed response. It is unavoidable.
Sorry, this is not available on the Apple AppStore. It is too much hassle to go through the review process. It is also unclear if the app could pass the review process.
To install it, build it in XCode and run "HongKongKeyboardApp" on your device. XCode 12 works fine.