Screen reader accessibility issues

[tmiw]

These are some issues I discovered while testing FreeDV 1.8.12 with NV Access:

General Issues

• ~Space button should not control PTT when the main window is not in focus. This causes use of the Space key to check checkboxes to not work.~

Main window

• ~The title bar reads "FreeDV January 8 12" instead of "FreeDV version 1 point 8 point 12".~ (Partially fixed.)
• ~The Squelch slider reads "Squelch 85" / "Checkbox checked". At minimum this should read the printed value for squelch instead (e.g. "Squelch -2").~
• ~Similar for TX Attenuation (example: "TX Attenuation 10" is read for -3.0 dB).~

Audio Config

• ~"Rec 2s" / "Play 2s" should say "Record 2 seconds" / "Play 2 seconds" not e.g. "Record 2 s".~

Options

Reporting

• ~Grid Square/Locator should come immediately after callsign in tab order.~

Modems

• ~"(secs)" should be expanded to "(in seconds)".~

Debugging

• ~The required tab order is as follows: Windows group->FIFO->app options.~

Filter

• ~All sliders reading internal values instead of printed values (similar to main window sliders)~

Note: all items ~struck out~ are currently fixed in #481.

[tmiw]

The Easy Setup section in the original issue wasn't actually accessibility related, just garden variety UI bugs. Those have been split out into another issue (#482) for handling in a separate PR.

[tmiw]

PR merged, closing issue.