HP Secure Browser support (#16377): Amend browseMode dead document detection to cope with VT_EMPTY runtimeID.

[tomaszw]

Link to issue number:

#16377

Summary of the issue:

When enough websites are open in separate tabs, SB will suspend some of the virtual machines hosting the websites to disk. This can cause UIA documents representing these websites to become dead.

In this scenario querying UIA_RuntimeIdPropertyId of the dead document returns VT_EMPTY variant, causing uncaught exception raised from UIABrowseModeDocument.contains. This keeps repeating, preventing NVDA from working correctly, if at all.

Description of user facing changes

NVDA works correctly regardless of vm suspensions or other scenarios where UIA documents can become dead.

Description of development approach

UIABrowseModeDocument.contains already has code to detect dead documents, however it relies on COMError being reported from UIA_RuntimeIdPropertyId property query.

In my testing, even when the server side reports an error HRESULT from IRawElementProviderFragment::GetRuntimeID() uia method, UIA core appears to translate it into a successful property query, yet with a VT_EMPTY variant as the property value. It's possible this behaviour is different between various UIA core versions, my testing is primarily on Windows 11 build 22631.

We amend the detection such that both COMError and VT_EMPTY variant are detected and treated equally, causing the dead document codepath to execute.

Testing strategy:

Manual testing

Known issues with pull request:

N/A

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.