Block touch input while the magnifier is running

source/_magnifier/magnifier.py

@@ -12,9 +12,11 @@
 from comtypes import COMError
 from logHandler import log
 import wx
+import gui
 import ui
 import speech
 import screenCurtain
+import touchHandler
 from winAPI import _displayTracking
 from winAPI._displayTracking import OrientationState, getPrimaryDisplayOrientation
 from .utils.types import (
@@ -184,6 +186,39 @@ def _startMagnifier(self) -> None:
 
 		self._isActive = True
 		self.currentCoordinates = self._focusManager.getCurrentFocusCoordinates()
+		if touchHandler.handler is not None:
+			# Touch events are already intercepted by NVDA; block gesture execution
+			# to prevent incorrect coordinates from the magnified view reaching the system.
+			touchHandler.blockTouchInput = True
+		elif touchHandler.touchSupported():
+			# Touch is supported but the handler is not running (user disabled it).
+			# We can't intercept inputs, so warn the user.
+			wx.CallAfter(
+				gui.messageBox,
+				pgettext(
+					"magnifier",
+					# Translators: Warning shown when the magnifier starts and touch input cannot be intercepted
+					"Touch screen input cannot be intercepted because NVDA touch support is disabled. "
+					"Touch inputs may not behave as expected while the magnifier is running.",
+				),
+				# Translators: Title of the warning dialog shown when touch cannot be intercepted
+				pgettext("magnifier", "Magnifier — Touch screen warning"),
+				wx.OK | wx.ICON_WARNING,
+			)
+		else:
+			# Portable copy, running from source, or no UI access: touch cannot be intercepted.
+			wx.CallAfter(
+				gui.messageBox,
+				pgettext(
+					"magnifier",
+					# Translators: Warning shown when the magnifier starts on a portable/source copy with a touchscreen
+					"Touch screen input cannot be intercepted on portable copies of NVDA or without UI Access. "
+					"Touch inputs may not behave as expected while the magnifier is running.",
+				),
+				# Translators: Title of the warning dialog shown when touch cannot be intercepted
+				pgettext("magnifier", "Magnifier — Touch screen warning"),
+				wx.OK | wx.ICON_WARNING,
+			)
 
 	def _updateMagnifier(self) -> None:
 		"""
@@ -254,6 +289,7 @@ def _stopMagnifier(self) -> None:
 			return
 		self._stopTimer()
 		self._isActive = False
+		touchHandler.blockTouchInput = False
 		# Unregister from display changes
 		_displayTracking.displayChanged.unregister(self._onDisplayChanged)
 

source/touchHandler.py

@@ -189,6 +189,7 @@ class POINTER_TOUCH_INFO(Structure):
 
 touchWindow = None
 touchThread = None
+blockTouchInput: bool = False
 
 
 class TouchInputGesture(inputCore.InputGesture):
@@ -391,6 +392,11 @@ def setMode(self, mode):
 
 	def pump(self):
 		for preheldTracker, tracker in self.trackerManager.emitTrackers():
+			if blockTouchInput:
+				import tones
+
+				tones.beep(200, 50)
+				continue
 			gesture = TouchInputGesture(preheldTracker, tracker, self._curTouchMode.value)
 			try:
 				inputCore.manager.executeGesture(gesture)

tests/unit/test_magnifier/test_magnifier.py

@@ -539,3 +539,57 @@ def testClampCoordinatesWithinBounds(self):
 			validCoords = Coordinates(centerX, centerY)
 			self.magnifier.currentCoordinates = validCoords
 			self.assertEqual(self.magnifier.currentCoordinates, validCoords)
+
+	def testStartMagnifierBlocksTouchOnInstalledCopy(self):
+		"""blockTouchInput is set to True when the magnifier starts with the touch handler active."""
+		focusCoords = Coordinates(self.screenWidth // 2, self.screenHeight // 2)
+		self.magnifier._focusManager.getCurrentFocusCoordinates = MagicMock(return_value=focusCoords)
+
+		with (
+			patch("touchHandler.handler", new=MagicMock()),
+			patch("touchHandler.blockTouchInput", False),
+		):
+			self.magnifier._startMagnifier()
+			import touchHandler
+
+			self.assertTrue(touchHandler.blockTouchInput)
+
+	def testStartMagnifierWarnsWhenTouchSupportedButHandlerInactive(self):
+		"""A warning dialog is shown when touch is supported but the handler is not running."""
+		focusCoords = Coordinates(self.screenWidth // 2, self.screenHeight // 2)
+		self.magnifier._focusManager.getCurrentFocusCoordinates = MagicMock(return_value=focusCoords)
+
+		with (
+			patch("touchHandler.handler", new=None),
+			patch("touchHandler.touchSupported", return_value=True),
+			patch("_magnifier.magnifier.wx.CallAfter") as mock_call_after,
+		):
+			self.magnifier._startMagnifier()
+
+		mock_call_after.assert_called_once()
+
+	def testStartMagnifierWarnsOnPortableCopy(self):
+		"""A warning dialog is shown on portable copies where touch cannot be intercepted."""
+		focusCoords = Coordinates(self.screenWidth // 2, self.screenHeight // 2)
+		self.magnifier._focusManager.getCurrentFocusCoordinates = MagicMock(return_value=focusCoords)
+
+		with (
+			patch("touchHandler.handler", new=None),
+			patch("touchHandler.touchSupported", return_value=False),
+			patch("_magnifier.magnifier.wx.CallAfter") as mock_call_after,
+		):
+			self.magnifier._startMagnifier()
+
+		mock_call_after.assert_called_once()
+
+	def testStopMagnifierUnblocksTouchInput(self):
+		"""blockTouchInput is reset to False unconditionally when the magnifier stops."""
+		import touchHandler
+
+		self.magnifier._stopTimer = MagicMock()
+		self.magnifier._isActive = True
+		touchHandler.blockTouchInput = True
+
+		self.magnifier._stopMagnifier()
+
+		self.assertFalse(touchHandler.blockTouchInput)