use screenBitmap

source/visionEnhancementProviders/screenCurtain.py

@@ -1,7 +1,7 @@
 # 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) 2018-2019 NV Access Limited, Babbage B.V., Leonard de Ruijter
+# Copyright (C) 2018-2021 NV Access Limited, Babbage B.V., Leonard de Ruijter
 
 """Screen curtain implementation based on the windows magnification API.
 The Magnification API has been marked by MS as unsupported for WOW64 applications such as NVDA. (#12491)
@@ -22,6 +22,8 @@
 from typing import Optional, Type
 import nvwave
 import globalVars
+from screenBitmap import ScreenBitmap
+from itertools import chain
 
 
 class MAGCOLOREFFECT(Structure):
@@ -302,35 +304,16 @@ def confirmInitWithUser(self) -> bool:
 
 def isScreenFullyBlack() -> bool:
 	"""
-	Uses wx to check that the screen is currently fully black by taking a screen capture and checking:
-	- there is only one colour used in the image
-	- the first pixel of the screen capture is black
+	Uses ScreenBitmap to check that the screen is currently fully black by taking a screen capture and
+	checking the colour of each pixel.
 	"""
 	screen = wx.ScreenDC()
 	screenSize = screen.GetSize()
-	bmp: wx.Bitmap = wx.Bitmap(screenSize[0], screenSize[1])
-	mem = wx.MemoryDC(bmp)
-	mem.Blit(0, 0, screenSize[0], screenSize[1], screen, 0, 0)  # copy screen over to bmp
-	del mem  # Release bitmap
-	img: wx.Image = bmp.ConvertToImage()
-	# https://docs.wxwidgets.org/3.0/classwx_image.html#a7c9d557cd7ad577ed76e4337b1fd843a
-	hist = wx.ImageHistogram()
-	numberOfColours = img.ComputeHistogram(hist)
-	# Due to wxImageHistogram not fully supported in wxPython, the histogram is not subscriptable,
-	# and thus the key value cannot be accessed for colours.
-	# https://github.com/wxWidgets/Phoenix/issues/1991
-	# This function could be improved in the future using the following logic:
-	# numberOfBlackPixelsKey = hist.MakeKey(255, 255, 255)
-	# numberOfBlackPixels = hist[numberOfBlackPixelsKey]
-	# numberOfDisplayPixels = screenSize[0] * screenSize[1]
-	# log.debug(f"""Screen Capture:
-	#  - number of colours: {numberOfColours}
-	#  - number of black pixels: {numberOfBlackPixels}
-	#  - number of total pixels: {numberOfDisplayPixels}
-	# """)
-	# return numberOfColours == 1 and numberOfBlackPixels == numberOfDisplayPixels
-	firstPixelIsBlack = img.GetRed(0, 0) == 0 and img.GetBlue(0, 0) == 0 and img.GetGreen(0, 0) == 0
-	return numberOfColours == 1 and firstPixelIsBlack
+	screenCapture = ScreenBitmap(screenSize[0], screenSize[1]).captureImage(0, 0, screenSize[0], screenSize[1])
+	for pixel in chain.from_iterable(screenCapture):
+		if not (pixel.rgbRed == 0 and pixel.rgbGreen == 0 and pixel.rgbBlue == 0):
+			return False
+	return True
 
 
 class ScreenCurtainInitializationError(RuntimeError):