Fix TextInfo.moveToCodepointOffset() in PoEdit

source/NVDAObjects/window/edit.py

@@ -6,6 +6,7 @@
 from typing import (
 	Dict,
 	Optional,
+	Self,
 	Union,
 )
 
@@ -842,6 +843,18 @@ def updateSelection(self):
 		self.obj.ITextSelectionObject.start=self._rangeObj.start
 		self.obj.ITextSelectionObject.end=self._rangeObj.end
 
+	def getTextInfoForCodepointMovement(self) -> Self:
+		# # In PoEdit ITextDocumentTextInfo sometimes cannot access the last character when that character is
+		# a newline. In this case collapse(True) takes us not to the end of textInfo, but right before
+		# trailing newline character, which causes adverse side effects in moveToCodepointOffset() function.
+		# Trimming trailing newline character here to work around.
+		info = self.copy()
+		collapsedInfo = info.copy()
+		collapsedInfo.collapse(end=True)
+		if collapsedInfo.compareEndPoints(info, "endToEnd") < 0:
+			info.setEndPoint(collapsedInfo, "endToEnd")
+		return info
+
 
 class EditBase(Window):
 	""""Base class for Edit and Rich Edit controls, shared by legacy and UIA implementations."""

source/textInfos/__init__.py

@@ -655,7 +655,10 @@ def getMathMl(self, field):
 		@raise LookupError: If MathML can't be retrieved for this field.
 		"""
 		raise NotImplementedError
-
+
+	def getTextInfoForCodepointMovement(self) -> Self:
+		return self.copy()
+
 	def moveToCodepointOffset(
 			self,
 			codepointOffset: int,
@@ -748,15 +751,15 @@ def moveToCodepointOffset(
 				we reduce the count of characters in order to make sure
 				the algorithm makes some progress on each iteration.
 		"""
-		text = self.text
+		info = self.getTextInfoForCodepointMovement()
+		text = info.text
 		if codepointOffset < 0 or codepointOffset > len(text):
 			raise ValueError
 		if codepointOffset == 0 or codepointOffset == len(text):
-			result = self.copy()
+			result = info.copy()
 			result.collapse(end=codepointOffset > 0)
 			return result
 
-		info = self.copy()
 		# Total codepoint Length represents length in python characters of Current TextInfo we're workoing with.
 		# We start with self, and then gradually divide and conquer in order to find desired offset.
 		totalCodepointOffset = len(text)