Excel with UIA: announce merged cells (#12843)

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.

source/NVDAObjects/UIA/excel.py

@@ -25,6 +25,7 @@
 import ui
 from logHandler import log
 from . import UIA
+import re
 
 
 class ExcelCustomProperties:
@@ -131,6 +132,8 @@ class ExcelObject(UIA):
 
 class ExcelCell(ExcelObject):
 
+	_coordinateRegEx = re.compile("([A-Z]+)([0-9]+)", re.IGNORECASE)
+
 	# selecting cells causes duplicate focus events
 	shouldAllowDuplicateUIAFocusEvent = True
 
@@ -411,6 +414,40 @@ def _get_states(self):
 					states.add(controlTypes.State.HASNOTE)
 		return states
 
+	@staticmethod
+	def _getColumnRepresentationForNumber(n: int) -> str:
+		"""
+		Convert a decimal number to its base alphabet representation.
+		See https://codereview.stackexchange.com/questions/182733/base-26-letters-and-base-10-using-recursion
+		for more details about the approach used.
+		"""
+		def modGenerator(x: int) -> Tuple[int, int]:
+			"""Generate digits from L{x} in base alphabet, least significants
+			bits first.
+
+			Since A is 1 rather than 0 in base alphabet, we are dealing with
+			L{x} - 1 at each iteration to be able to extract the proper digits.
+			"""
+			while x:
+				x, y = divmod(x - 1, 26)
+				yield y
+		return ''.join(
+			chr(ord("A") + i)
+			for i in modGenerator(n)
+		)[::-1]
+
+	@staticmethod
+	def _getNumberRepresentationForColumn(column: str) -> int:
+		"""
+		Convert an alphabet number to its decimal representation.
+		See https://codereview.stackexchange.com/questions/182733/base-26-letters-and-base-10-using-recursion
+		for more details about the approach used.
+		"""
+		return sum(
+			(ord(letter) - ord("A") + 1) * (26 ** i)
+			for i, letter in enumerate(reversed(column.upper()))
+		)
+
 	def _get_cellCoordsText(self):
 		if self._hasSelection():
 			sc = self._getUIACacheablePropertyValue(
@@ -423,7 +460,7 @@ def _get_cellCoordsText(self):
 
 			firstAddress = firstSelected.GetCurrentPropertyValue(
 				UIAHandler.UIA_NamePropertyId
-			).replace('"', '')
+			).replace('"', '').replace(' ', '')
 
 			firstValue = firstSelected.GetCurrentPropertyValue(
 				UIAHandler.UIA_ValueValuePropertyId
@@ -435,15 +472,15 @@ def _get_cellCoordsText(self):
 
 			lastAddress = lastSelected.GetCurrentPropertyValue(
 				UIAHandler.UIA_NamePropertyId
-			).replace('"', '')
+			).replace('"', '').replace(' ', '')
 
 			lastValue = lastSelected.GetCurrentPropertyValue(
 				UIAHandler.UIA_ValueValuePropertyId
 			)
 
 			cellCoordsTemplate = pgettext(
 				"excel-UIA",
-				# Translators: Excel, report range of cell coordinates
+				# Translators: Excel, report selected range of cell coordinates
 				"{firstAddress} {firstValue} through {lastAddress} {lastValue}"
 			)
 			return cellCoordsTemplate.format(
@@ -452,11 +489,33 @@ def _get_cellCoordsText(self):
 				lastAddress=lastAddress,
 				lastValue=lastValue
 			)
-		name = super().name
-		# Later builds of Excel 2016 quote the letter coordinate.
-		# We don't want the quotes.
-		name = name.replace('"', '')
-		return name
+		else:
+			name = super().name
+			# Later builds of Excel 2016 quote the letter coordinate.
+			# We don't want the quotes and also strip the space between column and row.
+			name = name.replace('"', '').replace(' ', '')
+			if self.rowSpan > 1 or self.columnSpan > 1:
+				# Excel does not offer information about merged cells
+				# but merges all merged cells into one UIA element named as the first cell in the merged range.
+				# We have to calculate the last address name manually.
+				firstAddress = name
+				firstColumn, firstRow = self._coordinateRegEx.match(firstAddress).groups()
+				firstRow = int(firstRow)
+				lastColumn = firstColumn if self.columnSpan == 1 else self._getColumnRepresentationForNumber(
+					self._getNumberRepresentationForColumn(firstColumn) + (self.columnSpan - 1)
+				)
+				lastRow = firstRow + (self.rowSpan - 1)
+				lastAddress = f"{lastColumn}{lastRow}"
+				cellCoordsTemplate = pgettext(
+					"excel-UIA",
+					# Translators: Excel, report merged range of cell coordinates
+					"{firstAddress} through {lastAddress}"
+				)
+				return cellCoordsTemplate.format(
+					firstAddress=firstAddress,
+					lastAddress=lastAddress,
+				)
+			return name
 
 	@script(
 		# Translators: the description  for a script for Excel

user_docs/en/changes.t2t

@@ -9,6 +9,8 @@ What's New in NVDA
 
 
 == Changes ==
+- When using UI Automation to access Microsoft Excel spreadsheet controls, NVDA is now able to report when a cell is merged. (#12843)
+-
 
 
 == Bug Fixes ==