Fix MathCAT pauses at rate 0 and with eSpeak rate boost on

[tareh7z]

Link to issue number:

Fixes #19894

Summary of the issue:

MathCAT scales the duration of its pauses by the synthesizer rate, but ignored rate boost, so pauses were as long with rate boost on as off.

With the speech rate at 0%, this also raised a division by zero error.

Description of user facing changes:

MathCAT no longer fails at a 0% speech rate, and its pauses are shorter when eSpeak rate boost is enabled.

Description of developer facing changes:

None.

Description of development approach:

The wpm value in convertSSMLTextForNVDA is multiplied by the synth's RATE_BOOST_MULTIPLIER when rate boost is on, and clamped to at least 2 so rate 0 behaves like rate 1.

Only eSpeak defines this multiplier, so other synths are unchanged.

Testing strategy:

Added unit tests for rate 0, for rate boost, and for a synth without a boost multiplier; they pass together with the rest of the unit test suite (1475 tests, 5 skipped).

Known issues with pull request:

Pauses are not adjusted for rate boost in OneCore and SAPI5, since they have no fixed boost factor.

Code Review Checklist:

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

[seanbudd]

This fixes #19894 right?

[tareh7z]

This fixes #19894 right?

Oh, yes! It fixes #19894, sorry for not linking it earlier. I have updated the PR to also cover the rate boost part.