When entering a secure desktop, cancel speech (#14135)
Summary of the issue:
NVDA 2022.2 would cancel speech when handling the foreground event for entering a secure desktop.
The security patch for 2022.2.1 broke how the foreground event was handled, and subsequently #14105 opted to avoid the foreground event entirely.
This results in NVDA not correctly cancelling speech when entering a secure desktop.
Description of user facing changes
Speech is cancelled when entering a secure desktop
Description of development approach
Cancel speech just before enter sleep mode, when SecureDesktopNVDAObject handles it's gain focus event.
