Excel with UIA: announce merged cells

[LeonarddeR]

Link to issue number:

None

Summary of the issue:

When UIA is enabled for Excel, merged cells were not mentioned as such. Instead, only the first coordinates of the merged range were reported.

Description of how this pull request fixes the issue:

There is no way to fetch the last cell in the range from Excel itself. The UIA implementation in Excel also refuses to provide real row and column numbers. Therefore we have to convert the alphabetical column representation to a column number, then correct the column number for column span and convert it back to alphabetical representation.

Testing strategy:

Tested several merged cells on an empty Excel sheet.

Known issues with pull request:

1. Excel seems to expose only the visible part of the sheet to UIA. Therefore, if a merged cell spans more rows or columns than what's visible, the announcements are likely incorrect. Note that this also applies to selection.
2. Initiating selection from a merged cell is broken, because the selection pattern reveals a null pointer as the first selected value. This is definitely a bug in Excel.

Change log entries:

Changes

• When using UI Automation to access Microsoft Excel spreadsheet controls, NVDA is now able to report when a cell is merged. (Excel with UIA: announce merged cells #12843)

Code Review Checklist:

• Pull Request description is up to date.
• Unit tests.
• System (end to end) tests.
• Manual testing.
• API is compatible with existing addons.
• User Documentation.
• Change log entry.
• Context sensitive help for GUI changes.
• UX of all users considered:
  • Speech
  • Braille
  • Low Vision
  • Different web browsers

[feerrenrut]

@seanbudd Could you elaborate on why this must go into the 2021.3 release, there doesn't seem to be a justification provided.

[cary-rowen]

I am a frequent user of excel. I hope that this PR can be merged. Is there any problem that prevents this PR?

[seanbudd]

Thanks @LeonarddeR - do you know if MS is aware of the bug(s)?

[seanbudd]

Could this get a unit test with a couple of examples?

[seanbudd]

it appears that unittests cannot import from NVDAObjects.UIA.excel

======================================================================
ERROR: Failure: AttributeError ('NoneType' object has no attribute 'registerUIAProperty')
----------------------------------------------------------------------
Traceback (most recent call last):
  File "C:\Users\sean\projects\nvda\.venv\lib\site-packages\nose\failure.py", line 39, in runTest       
    raise self.exc_val.with_traceback(self.tb)
  File "C:\Users\sean\projects\nvda\.venv\lib\site-packages\nose\loader.py", line 418, in loadTestsFromName
    addr.filename, addr.module)
  File "C:\Users\sean\projects\nvda\.venv\lib\site-packages\nose\importer.py", line 47, in importFromPath
    return self.importFromDir(dir_path, fqname)
  File "C:\Users\sean\projects\nvda\.venv\lib\site-packages\nose\importer.py", line 94, in importFromDir
    mod = load_module(part_fqname, fh, filename, desc)
  File "C:\Users\sean\AppData\Local\Programs\Python\Python37-32\lib\imp.py", line 234, in load_module   
    return load_source(name, filename, file)
  File "C:\Users\sean\AppData\Local\Programs\Python\Python37-32\lib\imp.py", line 171, in load_source   
    module = _load(spec)
  File "<frozen importlib._bootstrap>", line 696, in _load
  File "<frozen importlib._bootstrap>", line 677, in _load_unlocked
  File "<frozen importlib._bootstrap_external>", line 728, in exec_module
  File "<frozen importlib._bootstrap>", line 219, in _call_with_frames_removed
  File "C:\Users\sean\projects\nvda\tests\unit\test_excel.py", line 11, in <module>
    from NVDAObjects.UIA.excel import ExcelCell
  File "C:\Users\sean\projects\nvda\source\NVDAObjects\UIA\__init__.py", line 928, in <module>
    class UIA(Window):
  File "C:\Users\sean\projects\nvda\source\NVDAObjects\UIA\__init__.py", line 929, in UIA
    _UIACustomProps = UIAHandler.customProps.CustomPropertiesCommon.get()
  File "C:\Users\sean\projects\nvda\source\UIAHandler\customProps.py", line 75, in get
    cls._instance = cls()
  File "C:\Users\sean\projects\nvda\source\UIAHandler\customProps.py", line 83, in __init__
    uiaType=UIAutomationType.INT,
  File "<string>", line 6, in __init__
  File "C:\Users\sean\projects\nvda\source\UIAHandler\customProps.py", line 54, in __post_init__        
    self.id = NVDAHelper.localLib.registerUIAProperty(
AttributeError: 'NoneType' object has no attribute 'registerUIAProperty'

[LeonarddeR]

Do you know if MS is aware of the bug(s)?

Nope. May be @michaelDCurran knows. I believe there's no such thing as a presentational row or column number like the ones implemented for IAccessible2. That would certainly help.