feat: support localehints hints when provided for textviews

[kikkia]

Intention

Moving to FUTO from gboard one of the features I miss the most is auto keyboard language switching. For example if I am in google translate and I am translating japanese -> english, when I click on the japanese input box the keyboard automatically pulls up my last used JP keyboard format. If I click the "swap language" button that flips it to english -> japanese, the keyboard layout swaps to english from japanese automatically.

Android allows preferred locales to be hinted at within textViews https://developer.android.com/reference/android/widget/TextView#setImeHintLocales(android.os.LocaleList) . This is up to the app to implement, so it is not guaranteed the app sets them. However when they are set, we may as well support them.

Implementation

I added a setting under a new Advanced Settings category in the language settings. If enabled this will allow the keyboard to swap to a preferred language locale IF one is supplied, AND the user has that locale enabled.
Default: false

When we start the keyboard we run a check on the inputAttribute hints, our current selected locale and all available. If our current locale is not in the provided hints AND we find a suitable on in our enabled locales we swap to that keyboard layout.

There were a few workarounds I had to do, each is explained with a comment in the code. I am not a regular android dev (only did a little back in the android 4.4/5 days) so if I am doing anything not in best practices please let me know and I will be happy to refactor.

Tests

The instrumentation tests seem to be broken. When I try to run them locally I was getting some errors around main thread execution of getService.onCreate(), and more around some XML when I updated to run onCreate() on the main thread. This may just be something I have setup incorrectly. If that is fixable please LMK.

Because of this, for now I added a unit test for parsing the hints into our inputAttributes.

Device testing

I built these changes in a debug APK and loaded it onto my personal phone. I verified that the intended automatic language switching in Translate did work as intended. I tried with several languages and language pairs.

AI Disclaimer

It is a hot topic right now in OSS about AI slop PRs. I feel like one good thing we can all do to respect maintainers time is give a disclaimer at the minimum. Since I am new to the codebase I used some locally running AI models to help me trace and search through the code and learn the relevant things I was touching. AI generated ~30% of the code in this PR, 100% of that was reviewed by me and understood before accepting.

Thanks for your time.

[futo-cla-pr-labler]

Please sign our contributor license agreement at https://cla.futo.org

[futo-cla-pr-labler]

Please sign our contributor license agreement at https://cla.futo.org