Refactor LiveText to use diff-match-patch

.gitmodules

@@ -43,3 +43,6 @@
 [submodule "include/javaAccessBridge32"]
 	path = include/javaAccessBridge32
 	url = https://github.com/nvaccess/javaAccessBridge32-bin.git
+[submodule "include/dmp"]
+	path = include/dmp
+	url = https://github.com/diff-match-patch-python/diff-match-patch

source/NVDAObjects/UIA/winConsoleUIA.py

@@ -1,4 +1,3 @@
-# NVDAObjects/UIA/winConsoleUIA.py
 # A part of NonVisual Desktop Access (NVDA)
 # This file is covered by the GNU General Public License.
 # See the file COPYING for more details.
@@ -366,13 +365,6 @@ def _get_TextInfo(self):
 		movement."""
 		return consoleUIATextInfo if self.is21H1Plus else consoleUIATextInfoPre21H1
 
-	def _getTextLines(self):
-		# This override of _getTextLines takes advantage of the fact that
-		# the console text contains linefeeds for every line
-		# Thus a simple string splitlines is much faster than splitting by unit line.
-		ti = self.makeTextInfo(textInfos.POSITION_ALL)
-		text = ti.text or ""
-		return text.splitlines()
 
 def findExtraOverlayClasses(obj, clsList):
 	if obj.UIAElement.cachedAutomationId == "Text Area":

source/NVDAObjects/behaviors.py

@@ -1,5 +1,4 @@
 # -*- coding: UTF-8 -*-
-# NVDAObjects/behaviors.py
 # A part of NonVisual Desktop Access (NVDA)
 # This file is covered by the GNU General Public License.
 # See the file COPYING for more details.
@@ -12,7 +11,7 @@
 import os
 import time
 import threading
-import difflib
+from diff_match_patch import diff_match_patch
 import tones
 import queueHandler
 import eventHandler
@@ -228,6 +227,7 @@ def initOverlayClass(self):
 		self._event = threading.Event()
 		self._monitorThread = None
 		self._keepMonitoring = False
+		self._dmp = diff_match_patch()
 
 	def startMonitoring(self):
 		"""Start monitoring for new text.
@@ -263,15 +263,18 @@ def event_textChange(self):
 		"""
 		self._event.set()
 
-	def _getTextLines(self):
-		"""Retrieve the text of this object in lines.
+	def _getText(self):
+		"""Retrieve the text of this object.
 		This will be used to determine the new text to speak.
 		The base implementation uses the L{TextInfo}.
 		However, subclasses should override this if there is a better way to retrieve the text.
-		@return: The current lines of text.
-		@rtype: list of str
+		@return: The current text ob the object.
+		@rtype: str
 		"""
-		return list(self.makeTextInfo(textInfos.POSITION_ALL).getTextInChunks(textInfos.UNIT_LINE))
+		if hasattr(self, "_getTextLines"):
+			log.warning("LiveText._getTextLines is deprecated, please override _getText instead.")
+			return '\n'.join(self._getTextLines())
+		return self.makeTextInfo(textInfos.POSITION_ALL).text
 
 	def _reportNewLines(self, lines):
 		"""
@@ -289,10 +292,10 @@ def _reportNewText(self, line):
 
 	def _monitor(self):
 		try:
-			oldLines = self._getTextLines()
+			oldText = self._getText()
 		except:
-			log.exception("Error getting initial lines")
-			oldLines = []
+			log.exception("Error getting initial text")
+			oldText = ""
 
 		while self._keepMonitoring:
 			self._event.wait()
@@ -307,59 +310,61 @@ def _monitor(self):
 			self._event.clear()
 
 			try:
-				newLines = self._getTextLines()
+				newText = self._getText()
 				if config.conf["presentation"]["reportDynamicContentChanges"]:
-					outLines = self._calculateNewText(newLines, oldLines)
+					outLines = self._calculateNewText(newText, oldText)
 					if len(outLines) == 1 and len(outLines[0].strip()) == 1:
 						# This is only a single character,
 						# which probably means it is just a typed character,
 						# so ignore it.
 						del outLines[0]
 					if outLines:
 						queueHandler.queueFunction(queueHandler.eventQueue, self._reportNewLines, outLines)
-				oldLines = newLines
+				oldText = newText
 			except:
-				log.exception("Error getting lines or calculating new text")
+				log.exception("Error getting or calculating new text")
 
-	def _calculateNewText(self, newLines, oldLines):
-		outLines = []
+	def _calculateNewText(self, newText, oldText):
+		(oldText, newText, linearray) = self._dmp.diff_linesToChars(oldText, newText)
+		diffs = self._dmp.diff_main(oldText, newText, checklines=False)
+		# Convert the diff back to original text.
+		self._dmp.diff_charsToLines(diffs, linearray)
+		# Eliminate freak matches (e.g. blank lines)
+		self._dmp.diff_cleanupSemantic(diffs)
 
+		outLines = []
 		prevLine = None
-		for line in difflib.ndiff(oldLines, newLines):
-			if line[0] == "?":
-				# We're never interested in these.
-				continue
-			if line[0] != "+":
+		prevChange = None
+		for change, text in diffs:
+			if change != self._dmp.DIFF_INSERT:
 				# We're only interested in new lines.
-				prevLine = line
+				prevChange, prevLine = change, text
 				continue
-			text = line[2:]
 			if not text or text.isspace():
-				prevLine = line
+				prevChange, prevLine = change, text
 				continue
 
-			if prevLine and prevLine[0] == "-" and len(prevLine) > 2:
+			if prevLine and prevChange == self._dmp.DIFF_DELETE and not prevLine.isspace():
 				# It's possible that only a few characters have changed in this line.
 				# If so, we want to speak just the changed section, rather than the entire line.
-				prevText = prevLine[2:]
 				textLen = len(text)
-				prevTextLen = len(prevText)
+				prevLineLen = len(prevLine)
 				# Find the first character that differs between the two lines.
-				for pos in range(min(textLen, prevTextLen)):
-					if text[pos] != prevText[pos]:
+				for pos in range(min(textLen, prevLineLen)):
+					if text[pos] != prevLine[pos]:
 						start = pos
 						break
 				else:
 					# We haven't found a differing character so far and we've hit the end of one of the lines.
 					# This means that the differing text starts here.
 					start = pos + 1
 				# Find the end of the differing text.
-				if textLen != prevTextLen:
+				if textLen != prevLineLen:
 					# The lines are different lengths, so assume the rest of the line changed.
 					end = textLen
 				else:
 					for pos in range(textLen - 1, start - 1, -1):
-						if text[pos] != prevText[pos]:
+						if text[pos] != prevLine[pos]:
 							end = pos + 1
 							break
 
@@ -369,9 +374,10 @@ def _calculateNewText(self, newLines, oldLines):
 
 			if text and not text.isspace():
 				outLines.append(text)
-			prevLine = line
+			prevChange, prevLine = change, text
+
+		return [line for outLine in outLines for line in outLine.splitlines() if line and not line.isspace()]
 
-		return outLines
 
 class Terminal(LiveText, EditableText):
 	"""An object which both accepts text input and outputs text which should be reported automatically.

source/NVDAObjects/window/winConsole.py

@@ -1,8 +1,7 @@
-#NVDAObjects/WinConsole.py
-#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) 2007-2019 NV Access Limited, Bill Dengler
+# 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) 2007-2020 NV Access Limited, Bill Dengler
 
 import winConsoleHandler
 from . import Window
@@ -69,8 +68,8 @@ def event_loseFocus(self):
 	def event_nameChange(self):
 		pass
 
-	def _getTextLines(self):
-		return winConsoleHandler.getConsoleVisibleLines()
+	def _getText(self):
+		return winConsoleHandler.getConsoleVisibleText()
 
 	def script_caret_backspaceCharacter(self, gesture):
 		super(WinConsole, self).script_caret_backspaceCharacter(gesture)

source/sourceEnv.py

@@ -1,5 +1,5 @@
 # A part of NonVisual Desktop Access (NVDA)
-# Copyright (C) 2013-2020 NV Access Limited, Leonard de Ruijter
+# Copyright (C) 2013-2020 NV Access Limited, Leonard de Ruijter, Bill Dengler
 # This file is covered by the GNU General Public License.
 # See the file COPYING for more details.
 
@@ -18,6 +18,7 @@
 	os.path.join(TOP_DIR, "include", "configobj", "src"),
 	os.path.join(TOP_DIR, "include", "wxPython"),
 	os.path.join(TOP_DIR, "include", "py2exe"),
+	os.path.join(TOP_DIR, "include", "dmp", "diff_match_patch"),
 	os.path.join(TOP_DIR, "miscDeps", "python"),
 )
 

source/winConsoleHandler.py

@@ -1,8 +1,7 @@
-#winConsoleHandler.py
-#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) 2009-2018 NV Access Limited, Babbage B.V.
+# 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) 2009-2020 NV Access Limited, Babbage B.V., Bill Dengler
 
 import gui
 import winUser
@@ -123,14 +122,14 @@ def _checkDead():
 	except:
 		log.exception()
 
-def getConsoleVisibleLines():
+
+def getConsoleVisibleText():
 	consoleScreenBufferInfo=wincon.GetConsoleScreenBufferInfo(consoleOutputHandle)
 	topLine=consoleScreenBufferInfo.srWindow.Top
 	lineCount=(consoleScreenBufferInfo.srWindow.Bottom-topLine)+1
 	lineLength=consoleScreenBufferInfo.dwSize.x
 	text=wincon.ReadConsoleOutputCharacter(consoleOutputHandle,lineCount*lineLength,0,topLine)
-	newLines=[text[x:x+lineLength] for x in range(0,len(text),lineLength)]
-	return newLines
+	return text
 
 @winUser.WINEVENTPROC
 def consoleWinEventHook(handle,eventID,window,objectID,childID,threadID,timestamp):