update changes and user guide

mro.py

@@ -0,0 +1,35 @@
+# MRO example used from
+# https://stackoverflow.com/questions/66415093/how-do-i-use-the-windows-magnification-api-in-python-to-invert-the-screen
+from ctypes import c_float, c_long, c_bool, c_int, CDLL, Structure, POINTER
+
+
+class RECT(Structure):
+	_fields_ = [
+		('left', c_long),
+		('top', c_long),
+		('right', c_long),
+		('bottom', c_long),
+	]
+
+
+magnification_api = CDLL('magnification.dll')
+
+# declare types
+BOOL = c_bool
+FLOAT = c_float
+INT = c_int
+LPRECT = LPRECT = POINTER(RECT)
+PBOOL = PBOOL = POINTER(c_bool)
+PMAGCOLOREFFECT = c_float * 25
+MAGCOLOREFFECT = MAGCOLOREFFECT = POINTER(PMAGCOLOREFFECT)
+
+# MagInitialize
+magnification_api.MagInitialize.restype = BOOL
+# MagUninitialize
+magnification_api.MagUninitialize.restype = BOOL
+# MagSetFullscreenColorEffect
+magnification_api.MagSetFullscreenColorEffect.restype = BOOL
+magnification_api.MagSetFullscreenColorEffect.argtypes = (MAGCOLOREFFECT,)
+magnification_api.MagInitialize()  # initialize the API
+magnification_api.MagSetFullscreenColorEffect((c_float * 25)(-1, 0, 0, 0, 0, 0, -1, 0, 0,  0, 0,  0, -1, 0, 0, 0, 0, 0, 1, 0, 1, 1, 1, 0, 1)) # invert the screen
+magnification_api.MagUninitialize()  # use this to reset

user_docs/en/changes.t2t

@@ -6,11 +6,14 @@ What's New in NVDA
 = 2021.2 =
 
 == Important notes ==
-- NVDA Screen Curtain does not work on newer (unreleased) versions of Windows, such as Windows 11.
+- NVDA Screen Curtain is not supported on builds of Windows later than Windows 10 21H2.
+This includes Windows 10 Insiders and Windows 11.
+This is due to a breaking change in the Windows Magnification API.
 This release prevents activating screen curtain on untested Windows versions.
-Please be aware when using older NVDA releases and newer Windows versions.
+When using previous NVDA releases and Windows later than Windows 10 21H2, screen curtain may fail to work without warning.
 Screen Curtain support for newer versions of Windows is a high priority for NV Access.
 (#12491, #12684)
+-
 
 
 == New Features ==

user_docs/en/userGuide.t2t

@@ -795,6 +795,12 @@ You can enable the Screen Curtain in the [vision category #VisionSettings] of th
 
 When the screen curtain is active some tasks directly based on what appears on the screen such as performing [OCR #Win10Ocr] or taking a screenshot cannot be achieved.
 
+NVDA Screen Curtain is not supported on builds of Windows later than Windows 10 21H2.
+This includes Windows 10 Insiders and Windows 11.
+This is due to a breaking change in the Windows Magnification API.
+When using NVDA releases older than 2021.2 and Windows later than Windows 10 21H2, screen curtain may fail to work without warning.
+Screen Curtain support for newer versions of Windows is a high priority for NV Access.
+
 + Content Recognition +[ContentRecognition]
 When authors don't provide sufficient information for a screen reader user to determine the content of something, various tools can be used to attempt to recognize the content from an image.
 NVDA supports the optical character recognition (OCR) functionality built into Windows 10 to recognize text from images.