Fix virtual buffer creation when object IDs are None

[cary-rowen]

Link to issue number:

Fixes #20356

Summary of the issue:

In Foxit PDF Editor, NVDA could fail to create a virtual buffer for PDF content. When this happened, arrow keys scrolled the PDF instead of reading it.

Some virtual buffer backends can return None for part of an object identifier. This used to be accepted as 0 by ctypes, but the typed 64-bit VBuf calls now reject None for integer arguments.

Description of user facing changes:

PDF content in Foxit PDF Editor can be read with browse mode again when an object identifier contains None.

Description of developer facing changes:

Virtual buffer object identifiers are normalized before being passed to VBuf helper functions.

Description of development approach:

Added a small helper to convert None values in virtual buffer identifiers to 0.

This is handled in the shared virtual buffer code so buffer creation and related object lookup paths use the same behavior.

Testing strategy:

Manual testing.

Known issues with pull request:

None known.

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.

[cary-rowen]

Hi @prakashgomathi1-ui,
Just letting you know that I've opened a PR for the fix here. Although @lantianbaiyun2002 has already verified it works, it would be awesome if we could get some additional testing!