Several fixes to native selection mode

[michaelDCurran]

Link to issue number:

Fixes #16064
Fixes #16097

Summary of the issue:

• Native selection mode can be enabled in unsupported Gecko, such as Thunderbird 115.x #16064: turning on native selection mode in thunderbird 115 would cause errors when moving with the arrow keys as IAccessibleTextSelectionContainer is unavailable.
• Wrong message reported when toggling native selection in Word #16097: NVDA is misleading in MS Word browse mode when it says that native selection mode is not supported when trying to toggle it on, as MS word Browse mode does move the caret / selection, thus it has always used native selection mode.. It is just you can't toggle it off.

Description of user facing changes

• In firefox, If NVDA fails to update the native selection when turning on native selection mode, it is now left off, and the user is
  notified that native selection mode is not supported. this stops errors when moving with the arrow keys in Thunderbird after turning on native selection mode.
• NVDA no longer incorrectly alerts the user that native selection mode is not supported in Microsoft Word. Rather, the message state that it canot be turned off.
• when copying text with control+c in Microsoft Word with Browse mode on, formatting is now also copied, fulfilling the expectation of a native selection mode.

Description of development approach

• Gecko virtualBuffer's updateAppSelection method: if the selection is collapsed, don't try fetching information for the selection, instead just clear the app selection. This error was previously silently ignored.
• In UIA Browse mode documents, _nativeAppSelectionMode is now set to True, as this correctly reflects that UIA browse mode documents move the native selection.
• BrowseMode document's toggleNativeSelectionMode script:
  • Tailor the message reported if native selection mode is not supported (by looking at _nativeSelectionMode). If _nativeSelectionMode is True, then the message is changed to state it can't be turned off.
  • If updateappSelection fails when turning on native selection mode, log the error, turn it off, and alert the user that it is not supported.
• In MS word, suppress the "copy" UIA notification, if in MS word Browse mode. Otherwise there would be double speaking along with the message in cursorManager's copyToclipboard script when doing a native copy.

Testing strategy:

• Opened a page in Firefox. Turned on native selection mode. Selected some text, copied, and pasted in to MS Word to confirm that the text was formatted.
• Tried togling native sleection mode in MS word browse mode. Confirmed that NvDA reported that it could not be toggled off.
• Temporarily caused Gecko virtualbuffer's updateAppSelection method to raise NotImplementedError, Opened a page in Firefox, and tried turning on native selection mode. Confirmed that NVDA reported it was not supported.

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.

[AppVeyorBot]

• PASS: Translation comments check.
• PASS: Unit tests.
• FAIL: Lint check. See test results for more information.
• PASS: System tests (tags: installer NVDA).
• Build (for testing PR): https://ci.appveyor.com/api/buildjobs/q6dh8ex9bqfq12g2/artifacts/output/nvda_snapshot_pr16129-30947,e8102767.exe
• CI timing (mins):
  INIT 0.0,
  INSTALL_START 1.0,
  INSTALL_END 0.9,
  BUILD_START 0.0,
  BUILD_END 28.7,
  TESTSETUP_START 0.0,
  TESTSETUP_END 0.4,
  TEST_START 0.0,
  TEST_END 2.3,
  FINISH_END 0.6

See test results for failed build of commit e81027670d

[CyrilleB79]

Please, also update the change log to indicate that native copy (i.e. with formatting) is now done in Word Browse Mode. Before, in Word Browse Mode, formatting was copied when using Object Model, but not when using UIA.
Thanks.

[CyrilleB79]

"browse mode document" -> "document"

My feeling is that, for users and translators, there is no need to specify here that the document is a browse mode document (no possible ambiguity). This way, the messages are lighter. Feel free to ignore this suggestion if you disagree with me though.

Suggested change

	# Translators: the message when native selection mode is not available in this browse mode document.
	ui.message(_("Native selection mode unsupported in this browse mode document"))
	else:
	# Translators: the message when native selection mode cannot be turned off in this browse mode document.
	ui.message(_("Native selection mode cannot be turned off in this browse mode document"))
	# Translators: the message when native selection mode is not available in this document.
	ui.message(_("Native selection mode unsupported in this document"))
	else:
	# Translators: the message when native selection mode cannot be turned off in this document.
	ui.message(_("Native selection mode cannot be turned off in this document"))