seanbudd · Feb 20, 2026 · Feb 17, 2026 · Feb 17, 2026 · Feb 17, 2026 · Feb 17, 2026
@@ -1,5 +1,5 @@
 # A part of NonVisual Desktop Access (NVDA)
-# Copyright (C) 2017-2025 NV Access Limited, Bram Duvigneau, Łukasz Golonka
+# Copyright (C) 2017-2026 NV Access Limited, Bram Duvigneau, Łukasz Golonka
 # This file is covered by the GNU General Public License.
 # See the file COPYING for more details.
 
@@ -70,10 +70,16 @@ def funcWrapper(filePath, *attributes):
 
 
 @_suspendWow64RedirectionForFileInfoRetrieval
-def getFileVersionInfo(name, *attributes):
-	"""Gets the specified file version info attributes from the provided file."""
-	if not isinstance(name, str):
-		raise TypeError("name must be an unicode string")
+def getFileVersionInfo(name: str, *attributes: str) -> dict[str, str | None]:
+	"""
+	Gets the specified file version info attributes from the provided file.
+	:param name: The path to the file to get version info from.
+	:param attributes: The list of attributes to get. E.g. "FileVersion", "ProductVersion"
+	:return: A dictionary mapping the provided attributes to their values.
+	If an attribute is not found or invalid, its value will be None.
+
+	:raises RuntimeError: If the file does not exist, has no version information, or has no codepage.
+	"""
 	if not os.path.exists(name):
 		raise RuntimeError("The file %s does not exist" % name)
 	fileVersionInfo = {}

@@ -16,6 +16,7 @@
 from winBindings import shell32
 import globalVars
 import installer
+from installer import ComparisonState
 from logHandler import log
 import gui
 from gui import guiHelper
@@ -55,12 +56,12 @@ def _canPortableConfigBeCopied() -> bool:
 
 
 def doInstall(
-	createDesktopShortcut=True,
-	startOnLogon=True,
-	isUpdate=False,
-	copyPortableConfig=False,
-	silent=False,
-	startAfterInstall=True,
+	createDesktopShortcut: bool = True,
+	startOnLogon: bool = False,
+	isUpdate: bool = False,
+	copyPortableConfig: bool = False,
+	silent: bool = False,
+	startAfterInstall: bool = True,
 ):
 	progressDialog = gui.IndeterminateProgressDialog(
 		gui.mainFrame,
@@ -180,14 +181,14 @@ def doSilentInstall(
 	copyPortableConfig=False,
 	startAfterInstall=True,
 ):
-	prevInstall = installer.comparePreviousInstall() is not None
+	freshInstall = installer._comparePreviousInstall() is ComparisonState.FRESH_INSTALL
 	startOnLogon = globalVars.appArgs.enableStartOnLogon
 	if startOnLogon is None:
-		startOnLogon = config.getStartOnLogonScreen() if prevInstall else True
+		startOnLogon = config.getStartOnLogonScreen() if not freshInstall else False
 	doInstall(
-		createDesktopShortcut=installer.isDesktopShortcutInstalled() if prevInstall else True,
+		createDesktopShortcut=installer.isDesktopShortcutInstalled() if not freshInstall else True,
 		startOnLogon=startOnLogon,
-		isUpdate=prevInstall,
+		isUpdate=not freshInstall,
 		copyPortableConfig=copyPortableConfig,
 		silent=True,
 		startAfterInstall=startAfterInstall,
@@ -262,7 +263,7 @@ def __init__(self, parent, isUpdate):
 		if globalVars.appArgs.enableStartOnLogon is not None:
 			self.startOnLogonCheckbox.Value = globalVars.appArgs.enableStartOnLogon
 		else:
-			self.startOnLogonCheckbox.Value = config.getStartOnLogonScreen() if self.isUpdate else True
+			self.startOnLogonCheckbox.Value = config.getStartOnLogonScreen() if self.isUpdate else False
 
 		shortcutIsPrevInstalled = installer.isDesktopShortcutInstalled()
 		if self.isUpdate and shortcutIsPrevInstalled:
@@ -349,6 +350,26 @@ class InstallingOverNewerVersionDialog(
 ):
 	helpId = "InstallingNVDA"
 
+	_DOWNGRADE_WARNING = _(
+		# Translators: A warning presented when the user attempts to downgrade NVDA
+		# to an older version.
+		"You are attempting to install an earlier version of NVDA "
+		"than the version currently installed. "
+		"If you really wish to revert to an earlier version, "
+		"you should first cancel this installation "
+		"and completely uninstall NVDA before installing the earlier version.",
+	)
+
+	_UNKNOWN_WARNING = _(
+		# Translators: A warning presented when the installer is unable to determine
+		# the state of the current NVDA installation.
+		"NVDA has detected that you have NVDA already installed, "
+		"but it is unable to determine the version. "
+		"If you are attempting to install an earlier version of NVDA "
+		"you should first cancel this installation "
+		"and completely uninstall NVDA before installing the earlier version.",
+	)
+
 	def __init__(self):
 		# Translators: The title of a warning dialog.
 		super().__init__(gui.mainFrame, title=_("Warning"))
@@ -357,15 +378,7 @@ def __init__(self):
 		contentSizer = guiHelper.BoxSizerHelper(self, orientation=wx.VERTICAL)
 		text = wx.StaticText(
 			self,
-			label=_(
-				# Translators: A warning presented when the user attempts to downgrade NVDA
-				# to an older version.
-				"You are attempting to install an earlier version of NVDA "
-				"than the version currently installed. "
-				"If you really wish to revert to an earlier version, "
-				"you should first cancel this installation "
-				"and completely uninstall NVDA before installing the earlier version.",
-			),
+			label=self._warningText,
 		)
 		text.Wrap(self.scaleSize(600))
 		contentSizer.addItem(text)
@@ -391,18 +404,25 @@ def __init__(self):
 		mainSizer.Fit(self)
 		self.CentreOnScreen()
 
+	@property
+	def _warningText(self) -> str:
+		if self._installState == ComparisonState.DOWNGRADE:
+			return self._DOWNGRADE_WARNING
+		if self._installState == ComparisonState.UNKNOWN:
+			return self._UNKNOWN_WARNING
+		raise ValueError("Invalid install state for warning dialog")
+
 
 def showInstallGui():
 	gui.mainFrame.prePopup()
-	previous = installer.comparePreviousInstall()
-	if previous is not None and previous > 0:
-		# The existing installation is newer, which means this will be a downgrade.
+	installState = installer._comparePreviousInstall()
+	if installState in (ComparisonState.DOWNGRADE, ComparisonState.UNKNOWN):
 		d = InstallingOverNewerVersionDialog()
 		with d:
 			if d.ShowModal() == wx.ID_CANCEL:
 				gui.mainFrame.postPopup()
 				return
-	InstallerDialog(gui.mainFrame, previous is not None).Show()
+	InstallerDialog(gui.mainFrame, installState is not ComparisonState.FRESH_INSTALL).Show()
 	gui.mainFrame.postPopup()
 
 

@@ -1,11 +1,12 @@
 # A part of NonVisual Desktop Access (NVDA)
 # This file is covered by the GNU General Public License.
 # See the file COPYING for more details.
-# Copyright (C) 2011-2025 NV Access Limited, Joseph Lee, Babbage B.V., Łukasz Golonka, Cyrille Bougot
+# Copyright (C) 2011-2026 NV Access Limited, Joseph Lee, Babbage B.V., Łukasz Golonka, Cyrille Bougot
 
 from collections.abc import Iterable
 import comtypes.client
 import ctypes
+from enum import auto, Enum
 import pathlib
 import winreg
 import time
@@ -18,6 +19,7 @@
 import languageHandler
 import config
 from config.registry import NVDA_ADDON_PROG_ID, RegistryKey, _deleteKeyAndSubkeys
+import fileUtils
 import versionInfo
 import buildVersion
 from logHandler import log
@@ -28,7 +30,7 @@
 import NVDAState
 from NVDAState import WritePaths
 from utils.tempFile import _createEmptyTempFileForDeletingFile
-from utils._deprecate import handleDeprecations, MovedSymbol
+from utils._deprecate import handleDeprecations, MovedSymbol, RemovedSymbol
 
 _wsh = None
 
@@ -45,6 +47,10 @@
 		"WritePaths",
 		"defaultInstallDir",
 	),
+	RemovedSymbol(
+		"comparePreviousInstall",
+		"_legacyComparePreviousInstall",
+	),
 )
 
 
@@ -93,37 +99,87 @@ def createShortcut(
 		short.Save()
 
 
-def comparePreviousInstall() -> int | None:
-	"""Returns 1 if the existing installation is newer than this running version,
-	0 if it is the same, -1 if it is older,
-	None if there is no existing installation.
+class ComparisonState(Enum):
+	FRESH_INSTALL = auto()
+	DOWNGRADE = auto()
+	REINSTALL = auto()
+	UPGRADE = auto()
+	UNKNOWN = auto()
+
+	@property
+	def _legacyValue(self) -> int | None:
+		"""Legacy value for comparison state."""
+		match self:
+			case ComparisonState.FRESH_INSTALL:
+				return None
+			case ComparisonState.DOWNGRADE:
+				return 1
+			case ComparisonState.REINSTALL:
+				return 0
+			case ComparisonState.UPGRADE:
+				return -1
+			case ComparisonState.UNKNOWN:
+				return None
+
+
+def _legacyComparePreviousInstall() -> int | None:
+	"""Legacy wrapper for _comparePreviousInstall"""
+	return _comparePreviousInstall()._legacyValue
+
+
+def _comparePreviousInstall() -> ComparisonState:
+	"""
+	Compares the version of the currently running NVDA with the version of a previous installation of NVDA on this system, if any.
+	:return:
+		- ComparisonState.FRESH_INSTALL if no previous installation is found
+		- ComparisonState.DOWNGRADE if the previous installation is newer than the current one
+		- ComparisonState.REINSTALL if they are the same version
+		- ComparisonState.UPGRADE if the previous installation is older than the current one
+		- ComparisonState.UNKNOWN if there was an error determining the version of either the current or previous installation
 	"""
 	pathX86 = WritePaths._installDirX86
 	pathX86Exists = pathX86 and os.path.isdir(pathX86)
 	path = WritePaths.installDir
 	pathExists = path and os.path.isdir(path)
-	oldTime = None
+
 	if not (pathExists or pathX86Exists):
-		return None
+		return ComparisonState.FRESH_INSTALL
+
 	if pathExists:
+		oldSlavePath = os.path.join(path, "nvda_slave.exe")
 		try:
-			oldTime = os.path.getmtime(os.path.join(path, "nvda_slave.exe"))
-		except OSError:
-			log.debug("Unable to get modification time of nvda_slave.exe in previous installation.")
-			return None
+			oldVersion = fileUtils.getFileVersionInfo(oldSlavePath, "FileVersion")
+		except (OSError, RuntimeError):
+			log.debug("Unable to get file version of nvda_slave.exe in previous installation.")
+			return ComparisonState.UNKNOWN
 	elif pathX86Exists:
+		oldSlavePath = os.path.join(pathX86, "nvda_slave.exe")
 		try:
-			oldTime = os.path.getmtime(os.path.join(pathX86, "nvda_slave.exe"))
-		except OSError:
-			log.debug("Unable to get modification time of nvda_slave.exe in previous installation (x86).")
-			return None
+			oldVersion = fileUtils.getFileVersionInfo(oldSlavePath, "FileVersion")
+		except (OSError, RuntimeError):
+			log.debug("Unable to get file version of nvda_slave.exe in previous installation (x86).")
+			return ComparisonState.UNKNOWN
+
 	try:
-		newTime = os.path.getmtime("nvda_slave.exe")
-	except OSError:
+		newVersion = fileUtils.getFileVersionInfo("nvda_slave.exe", "FileVersion")
+	except (OSError, RuntimeError):
 		# This should never happen.
-		log.error("Unable to get modification time of nvda_slave.exe in current process.")
-		return None
-	return (oldTime > newTime) - (oldTime < newTime)
+		log.exception("Unable to get file version of nvda_slave.exe in current process.")
+		return ComparisonState.UNKNOWN
+
+	try:
+		oldVersion = [int(x) for x in oldVersion["FileVersion"].split(".")]
+		newVersion = [int(x) for x in newVersion["FileVersion"].split(".")]
+	except (KeyError, AttributeError, ValueError, TypeError):
+		log.exception("Error parsing version information.")
+		return ComparisonState.UNKNOWN
+
+	if oldVersion > newVersion:
+		return ComparisonState.DOWNGRADE
+	elif oldVersion < newVersion:
+		return ComparisonState.UPGRADE
+	else:
+		return ComparisonState.REINSTALL
 
 
 def getDocFilePath(fileName: str, installDir: str):