Link to issue number:

Fixes #15096

Summary of the issue:

When an active profile has the synthesizer set to silence, and a user switches profiles to a synthesizer which fails to load, NVDA fails back to the silence synthesizer.

This is because the default behaviour on failure is to roll back to the previous synthesizer, which is appropriate except for silence.

As this is an attempt to change from silence to speech, instead NVDA should fallback to the next synthesizer, rather than the previous synthesizer.

Description of user facing changes

NVDA falls back to the silence synthesizer when:

• a user is using the silence synthesizer,
• and attempts to switch synthesizers e.g. via a profile change
• and the synthesizer fails to load

Description of development approach

ensure the previous synthesizer we are switching back to is not silence.
Instead, the synth will switch to the next one, which may eventually reach silence if subsequent synthesizers fail to load.

Testing strategy:

Confirm with @fernando-jose-silva

Known issues with pull request:

It would be ideal for us to switch back to OneCore before cycling to the next synthesizer, however it's impossible to do this without additional synth history state tracking

Change log entries:

N/A small change

Code Review Checklist:

• Pull Request description:
  • description is up to date
  • change log entries
• Testing:
  • Unit tests
  • System (end to end) tests
  • Manual testing
• API is compatible with existing add-ons.
• Documentation:
  • User Documentation
  • Developer / Technical Documentation
  • Context sensitive help for GUI changes
• UX of all users considered:
  • Speech
  • Braille
  • Low Vision
  • Different web browsers
  • Localization in other languages / culture than English
• Security precautions taken.