fix(web): allow to use file URLs on Android

[ermshiperete]

This change fixes the blank keyboard problem on Android which was caused by using the Fetch API fetch() function which doesn't support file:// URLs. This change now uses the XMLHttpRequest class instead and sets the necessary flags on the Android side.

For Keyman for Web nothing changes compared to earlier alpha versions, which means that file URLs shouldn't be used.

This change also deletes loadKeyboardHelper.ts which wasn't used anywhere.

Note that this PR only fixes things for Android, but not iOS where we have a similar problem, but which requires a slightly different solution.

Fixes: #16096
Build-bot: skip release:web,android

User Testing

TEST_ANDROID:

• Install Keyman for Android from this PR
• Verify that a keyboard properly shows

TEST_WEB:

• Open KeymanWeb test page, navigate to any test
• Select a keyboard and verify that it displays the OSK and that the console window doesn't show errors

[keymanapp-test-bot]

User Test Results

Test specification and instructions

• ✅ TEST_ANDROID (PASSED) (notes)
• ✅ TEST_WEB (PASSED) (notes)

Test Artifacts

• Android
  • Keyman for Android apk
  • FirstVoices Keyboards for Android apk
  • FirstVoices Keyboards for Android apk (old PRs)
  • KeyboardHarness apk
  • Keyman for Android apk (old PRs)
  • KMSample1 apk
  • KMSample2 apk
• Web
  • KeymanWeb Test Home

[mcdurdin]

Can confirm this fix does not currently work on iOS.

[Meng-Heng]

Test Results

• TEST_ANDROID (PASSED):

1. Launch Android Studio, Pixel 9 API 35 Emulator
2. Drag and drop keyman-19.0.248-alpha-test-16132
3. Launch Keyman within the Emulator
4. The Euro Latin (SIL) keyboard displays without any error messages
5. Predictive text and typing works as expected
6. Navigate to Settings -> Install Keyboard or Dictionary -> Install from keyman.com -> Install Khmer Angkor keyboard
7. The process of downloading the keyboard work as expected
8. Khmer Angkor keyboard displays and types without any error messages
9. Switching keyboards work as expected.

• TEST_WEB (PASSED):

1. Navigate to the Web Test page for Keymanweb_TestPullRequests/630412
2. View KeymanWeb use samples ->Example 1 - Toggle UI, all resources in same folder as page -> Keyboard switches and types
3. View Keymanweb website-oriented manual test pages -> Prediction - robust testing (prediction-mtnt) -> Keyboard switches and types + predictive text works as expected.

Note

The Test Artifacts link for Android does not work, instead I navigated to the apk through the Test checks links.

[mcdurdin]

This is definitely a straightforward patch; can we refactor it to be more object-oriented given our existing pattern with KeymanEngine: KeymanEngineBase?

Will we need to do similar work for fonts and lexical models?

[mcdurdin]

I would prefer to have this designed as a protected function in KeymanEngineBase which we override here, in KeymanEngineBase.ts it would be something like:

protected fetch(uri: string): Promise<Response> {
  throw new Error('not implemented');
}

and in browser/src/KeymanEngine.ts:

protected fetch(uri: string): Promise<Response> {
  return window.fetch(uri);
}

and then this would also be protected.

That moves the responsibility for defining what fetch does into the same place for both WebView and Browser components.

[ermshiperete]

done

[mcdurdin]

The Test Artifacts link for Android does not work, instead I navigated to the apk through the Test checks links.

Tracking this in #16137 -- we were planning for Android test PRs to include the full tag in the file name:

• keyman-19.0.248-alpha-test-16132.apk vs
• keyman-19.0.248.apk

Note that the 'Keyman for Android apk (old PRs)' link currently works in the Test Artifacts list.

[ermshiperete]

#16146 implements a different approach for Android.