Merge 01d9be5 into 1b68eba

seanbudd · web-flow · commit 282d87596505 · 2021-07-27T15:37:42.000+10:00
diff --git a/source/visionEnhancementProviders/screenCurtain.py b/source/visionEnhancementProviders/screenCurtain.py
@@ -4,7 +4,8 @@
 # Copyright (C) 2018-2019 NV Access Limited, Babbage B.V., Leonard de Ruijter
 
 """Screen curtain implementation based on the windows magnification API.
-This implementation only works on Windows 8 and above.
+The Magnification API has been marked by MS as unsupported for WOW64 applications such as NVDA. (#12491)
+This module has been tested on Windows versions specified by winVersion.isFullScreenMagnificationAvailable.
 """
 
 import os
@@ -29,8 +30,9 @@ class MAGCOLOREFFECT(Structure):
 
 # homogeneous matrix for a 4-space transformation (red, green, blue, opacity).
 # https://docs.microsoft.com/en-gb/windows/win32/gdiplus/-gdiplus-using-a-color-matrix-to-transform-a-single-color-use
-TRANSFORM_BLACK = MAGCOLOREFFECT()
-TRANSFORM_BLACK.transform[4][4] = 1.0
+TRANSFORM_BLACK = MAGCOLOREFFECT()  # empty transformation
+TRANSFORM_BLACK.transform[4][4] = 1.0  # retain as an affine transformation
+TRANSFORM_BLACK.transform[3][3] = 1.0  # retain opacity, while subtracting other colours (#12491)
 
 
 def _errCheck(result, func, args):
diff --git a/source/winVersion.py b/source/winVersion.py
@@ -217,5 +217,9 @@ def isUwpOcrAvailable():
 	}
 
 
-def isFullScreenMagnificationAvailable():
+def isFullScreenMagnificationAvailable() -> bool:
+	"""
+	Technically this is always False. The Magnification API has been marked by MS as unsupported for
+	WOW64 applications such as NVDA. For our usages, support has been added since Windows 8.
+	"""
 	return getWinVer() >= WIN8
diff --git a/user_docs/en/changes.t2t b/user_docs/en/changes.t2t
@@ -5,6 +5,17 @@ What's New in NVDA
 
 = 2021.2 =
 
+== Important notes ==
+- Screen Curtain on previous releases of NVDA is no longer compatible with versions of Windows newer than Windows 10 21H2 (10.0.19044).
+This includes Windows 10 Insiders and Windows 11.
+This is due to a change in the Windows Magnification API.
+This release prevents activating screen curtain on untested Windows versions.
+When using previous NVDA releases and Windows newer than Windows 10 21H2, screen curtain may fail to work without warning.
+To ensure security, confirm that screen curtain works properly with new or experimental versions of Windows.
+(#12491, #12684)
+-
+
+
 == New Features ==
 - Support for ARIA annotations:
   - adds a command to read a summary of details of an object with aria-details. (#12364)
@@ -39,6 +50,7 @@ This can be toggled in the Preferences dialog or with a new (unassigned) command
 - NVDA exits safely when a new process is started. (#12605)
 - Reselecting the Handy Tech braille display driver from the Select Braille Display dialog no longer causes errors. (#12618)
 - Windows version 10.0.22000 or later is recognized as Windows 11, not Windows 10. (#12626)
+- Screen curtain support has been fixed and tested for Windows versions up until 10.0.22000. (#12684)
 -
 
 
diff --git a/user_docs/en/userGuide.t2t b/user_docs/en/userGuide.t2t
@@ -795,6 +795,9 @@ 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.
 
+To ensure security, confirm that the screen curtain works properly with new or experimental versions of Windows.
+When using NVDA releases older than 2021.2 and Windows newer than Windows 10 21H2, screen curtain may fail to work without warning.
+
 + 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.

Original file line number	Diff line number	Diff line change
`@@ -217,5 +217,9 @@ def isUwpOcrAvailable():`
`217`	`217`	`}`
`218`	`218`
`219`	`219`
`220`		`-def isFullScreenMagnificationAvailable():`
	`220`	`+def isFullScreenMagnificationAvailable() -> bool:`
	`221`	`+ """`
	`222`	`+ Technically this is always False. The Magnification API has been marked by MS as unsupported for`
	`223`	`+ WOW64 applications such as NVDA. For our usages, support has been added since Windows 8.`
	`224`	`+ """`
`221`	`225`	`return getWinVer() >= WIN8`