UIA with conhost / openconsole on Win 21H1 comError (PR nvaccess#11039)

Downgrade E_FAIL to debugWarning when comparing selection changes.

source/NVDAObjects/UIA/winConsoleUIA.py

@@ -11,7 +11,7 @@
 import UIAHandler
 
 from comtypes import COMError
-from UIAUtils import isTextRangeOffscreen
+from logHandler import log
 from . import UIATextInfo
 from ..behaviors import EnhancedTermTypedCharSupport, KeyboardHandlerBasedTypedCharSupport
 from ..window import Window
@@ -31,7 +31,6 @@ def __init__(self, obj, position, _rangeObj=None):
 				_rangeObj, collapseToEnd = self._getBoundingRange(obj, position)
 			except (COMError, RuntimeError):
 				# We couldn't bound the console.
-				from logHandler import log
 				log.warning("Couldn't get bounding range for console", exc_info=True)
 				# Fall back to presenting the entire buffer.
 				_rangeObj, collapseToEnd = None, None
@@ -374,6 +373,19 @@ def _getTextLines(self):
 		text = ti.text or ""
 		return text.splitlines()
 
+	def detectPossibleSelectionChange(self):
+		try:
+			return super().detectPossibleSelectionChange()
+		except COMError:
+			# microsoft/terminal#5399: when attempting to compare text ranges
+			# from the standard and alt mode buffers, E_FAIL is returned.
+			# Downgrade this to a debugWarning.
+			log.debugWarning((
+				"Exception raised when comparing selections, "
+				"probably due to a switch to/from the alt buffer."
+			), exc_info=True)
+
+
 def findExtraOverlayClasses(obj, clsList):
 	if obj.UIAElement.cachedAutomationId == "Text Area":
 		clsList.append(WinConsoleUIA)