JABHandler.py

# -*- coding: UTF-8 -*-
# A part of NonVisual Desktop Access (NVDA)
# Copyright (C) 2007-2019 NV Access Limited, Peter Vágner, Renaud Paquay, Babbage B.V.
# This file is covered by the GNU General Public License.
# See the file COPYING for more details.

import os
import queue
from ctypes import (
	c_short,
	c_long,
	c_int,
	c_int64,
	c_bool,
	c_float,
	c_char,
	c_wchar,
	c_wchar_p,
	c_void_p,
	Structure,
	POINTER,
	byref,
	cdll,
	windll,
	CFUNCTYPE,
	WinError,
	create_string_buffer,
	create_unicode_buffer
)
from ctypes.wintypes import BOOL, HWND, WCHAR
import time
import queueHandler
from logHandler import log
import winUser
import api
import eventHandler
import controlTypes
import NVDAObjects.JAB
import core
import textUtils
import NVDAHelper
import config
import globalVars

#: The path to the user's .accessibility.properties file, used
#: to enable JAB.
A11Y_PROPS_PATH = os.path.expanduser(r"~\.accessibility.properties")
#: The content of ".accessibility.properties" when JAB is enabled.
A11Y_PROPS_CONTENT = (
	"assistive_technologies=com.sun.java.accessibility.AccessBridge\n"
	"screen_magnifier_present=true\n"
)

#Some utility functions to help with function defines

def _errcheck(res, func, args):
	if not res:
		raise RuntimeError("Result %s" % res)
	return res

def _fixBridgeFunc(restype,name,*argtypes,**kwargs):
	try:
		func=getattr(bridgeDll,name)
	except AttributeError:
		log.warning("%s not found in Java Access Bridge dll"%name)
		return
	func.restype=restype
	func.argtypes=argtypes
	if kwargs.get('errcheck'):
		func.errcheck=_errcheck


bridgeDll = None

#Definitions of access bridge types, structs and prototypes

jchar=c_wchar
jint=c_int
jfloat=c_float
jboolean=c_bool


class JOBJECT64(c_int64):
	pass
AccessibleTable=JOBJECT64

MAX_STRING_SIZE=1024
SHORT_STRING_SIZE=256

class AccessBridgeVersionInfo(Structure):
	_fields_=[
		('VMVersion',WCHAR*SHORT_STRING_SIZE),
		('bridgeJavaClassVersion',WCHAR*SHORT_STRING_SIZE),
		('bridgeJavaDLLVersion',WCHAR*SHORT_STRING_SIZE),
		('bridgeWinDLLVersion',WCHAR*SHORT_STRING_SIZE),
	]

class AccessibleContextInfo(Structure):
	_fields_=[
		('name',WCHAR*MAX_STRING_SIZE),
		('description',WCHAR*MAX_STRING_SIZE),
		('role',WCHAR*SHORT_STRING_SIZE),
		('role_en_US',WCHAR*SHORT_STRING_SIZE),
		('states',WCHAR*SHORT_STRING_SIZE),
		('states_en_US',WCHAR*SHORT_STRING_SIZE),
		('indexInParent',jint),
		('childrenCount',jint),
		('x',jint),
		('y',jint),
		('width',jint),
		('height',jint),
		('accessibleComponent',BOOL),
		('accessibleAction',BOOL),
		('accessibleSelection',BOOL),
		('accessibleText',BOOL),
		('accessibleValue',BOOL),
	]

class AccessibleTextInfo(Structure):
	_fields_=[
		('charCount',jint),
		('caretIndex',jint),
		('indexAtPoint',jint),
	]

class AccessibleTextItemsInfo(Structure):
	_fields_=[
		('letter',WCHAR),
		('word',WCHAR*SHORT_STRING_SIZE),
		('sentence',WCHAR*MAX_STRING_SIZE),
	]

class AccessibleTextSelectionInfo(Structure):
	_fields_=[
		('selectionStartIndex',jint),
		('selectionEndIndex',jint),
		('selectedText',WCHAR*MAX_STRING_SIZE),
	]

class AccessibleTextRectInfo(Structure):
	_fields_=[
		('x',jint),
		('y',jint),
		('width',jint),
		('height',jint),
	]

class AccessibleTextAttributesInfo(Structure):
	_fields_=[
		('bold',BOOL),
		('italic',BOOL),
		('underline',BOOL),
		('strikethrough',BOOL),
		('superscript',BOOL),
		('subscript',BOOL),
		('backgroundColor',WCHAR*SHORT_STRING_SIZE),
		('foregroundColor',WCHAR*SHORT_STRING_SIZE),
		('fontFamily',WCHAR*SHORT_STRING_SIZE),
		('fontSize',jint),
		('alignment',jint),
		('bidiLevel',jint),
		('firstLineIndent',jfloat),
		('LeftIndent',jfloat),
		('rightIndent',jfloat),
		('lineSpacing',jfloat),
		('spaceAbove',jfloat),
		('spaceBelow',jfloat),
		('fullAttributesString',WCHAR*MAX_STRING_SIZE),
	]

MAX_RELATION_TARGETS = 25
MAX_RELATIONS = 5

class AccessibleRelationInfo(Structure):
	_fields_ = [
		("key", WCHAR * SHORT_STRING_SIZE),
		("targetCount", jint),
		("targets", JOBJECT64 * MAX_RELATION_TARGETS),
	]

class AccessibleRelationSetInfo(Structure):
	_fields_ = [
		("relationCount", jint),
		("relations", AccessibleRelationInfo * MAX_RELATIONS),
	]

MAX_ACTION_INFO = 256
MAX_ACTIONS_TO_DO = 32

class AccessibleActionInfo(Structure):
	_fields_ = (
		("name", c_wchar * SHORT_STRING_SIZE),
	)

class AccessibleActions(Structure):
	_fields_ = (
		("actionsCount", jint),
		("actionInfo", AccessibleActionInfo * MAX_ACTION_INFO),
	)

class AccessibleActionsToDo(Structure):
	_fields_ = (
		("actionsCount", jint),
		("actions", AccessibleActionInfo * MAX_ACTIONS_TO_DO),
	)

class AccessibleTableInfo(Structure):
	_fields_=[
		('caption',JOBJECT64),
		('summary',JOBJECT64),
		('rowCount',jint),
		('columnCount',jint),
		('accessibleContext',JOBJECT64),
		('accessibleTable',JOBJECT64),
	]

class AccessibleTableCellInfo(Structure):
	_fields_=[
		('accessibleContext',JOBJECT64),
		('index',jint),
		('row',jint),
		('column',jint),
		('rowExtent',jint),
		('columnExtent',jint),
		('isSelected',jboolean),
	]

MAX_KEY_BINDINGS=50
ACCESSIBLE_SHIFT_KEYSTROKE=1
ACCESSIBLE_CONTROL_KEYSTROKE=2
ACCESSIBLE_META_KEYSTROKE=4
ACCESSIBLE_ALT_KEYSTROKE=8
ACCESSIBLE_ALT_GRAPH_KEYSTROKE=16
ACCESSIBLE_BUTTON1_KEYSTROKE=32
ACCESSIBLE_BUTTON2_KEYSTROKE=64
ACCESSIBLE_BUTTON3_KEYSTROKE=128

class AccessibleKeyBindingInfo(Structure):
	_fields_=[
		('character',jchar),
		('modifiers',jint),
	]

class AccessibleKeyBindings(Structure):
	_fields_=[
		('keyBindingsCount',c_int),
		('keyBindingInfo',AccessibleKeyBindingInfo*MAX_KEY_BINDINGS),
	]

AccessBridge_FocusGainedFP=CFUNCTYPE(None,c_long,JOBJECT64,JOBJECT64)
AccessBridge_PropertyNameChangeFP=CFUNCTYPE(None,c_long,JOBJECT64,JOBJECT64,c_wchar_p,c_wchar_p)
AccessBridge_PropertyDescriptionChangeFP=CFUNCTYPE(None,c_long,JOBJECT64,JOBJECT64,c_wchar_p,c_wchar_p)
AccessBridge_PropertyValueChangeFP=CFUNCTYPE(None,c_long,JOBJECT64,JOBJECT64,c_wchar_p,c_wchar_p)
AccessBridge_PropertyStateChangeFP=CFUNCTYPE(None,c_long,JOBJECT64,JOBJECT64,c_wchar_p,c_wchar_p)
AccessBridge_PropertyCaretChangeFP=CFUNCTYPE(None,c_long,JOBJECT64,JOBJECT64,c_int,c_int)
AccessBridge_PropertyActiveDescendentChangeFP=CFUNCTYPE(None,c_long,JOBJECT64,JOBJECT64,JOBJECT64,JOBJECT64)


def _fixBridgeFuncs():
	"""Appropriately set the return and argument types of all the access bridge dll functions
	"""
	_fixBridgeFunc(None,'Windows_run')
	_fixBridgeFunc(None,'setFocusGainedFP',c_void_p)
	_fixBridgeFunc(None,'setPropertyNameChangeFP',c_void_p)
	_fixBridgeFunc(None,'setPropertyDescriptionChangeFP',c_void_p)
	_fixBridgeFunc(None,'setPropertyValueChangeFP',c_void_p)
	_fixBridgeFunc(None,'setPropertyStateChangeFP',c_void_p)
	_fixBridgeFunc(None,'setPropertyCaretChangeFP',c_void_p)
	_fixBridgeFunc(None,'setPropertyActiveDescendentChangeFP',c_void_p)
	_fixBridgeFunc(None,'releaseJavaObject',c_long,JOBJECT64)
	_fixBridgeFunc(BOOL,'getVersionInfo',POINTER(AccessBridgeVersionInfo),errcheck=True)
	_fixBridgeFunc(BOOL,'isJavaWindow',HWND)
	_fixBridgeFunc(BOOL,'isSameObject',c_long,JOBJECT64,JOBJECT64)
	_fixBridgeFunc(BOOL,'getAccessibleContextFromHWND',HWND,POINTER(c_long),POINTER(JOBJECT64),errcheck=True)
	_fixBridgeFunc(HWND,'getHWNDFromAccessibleContext',c_long,JOBJECT64,errcheck=True)
	_fixBridgeFunc(BOOL,'getAccessibleContextAt',c_long,JOBJECT64,jint,jint,POINTER(JOBJECT64),errcheck=True)
	_fixBridgeFunc(BOOL,'getAccessibleContextWithFocus',HWND,POINTER(c_long),POINTER(JOBJECT64),errcheck=True)
	_fixBridgeFunc(BOOL,'getAccessibleContextInfo',c_long,JOBJECT64,POINTER(AccessibleContextInfo),errcheck=True)
	_fixBridgeFunc(JOBJECT64,'getAccessibleChildFromContext',c_long,JOBJECT64,jint,errcheck=True)
	_fixBridgeFunc(JOBJECT64,'getAccessibleParentFromContext',c_long,JOBJECT64)
	_fixBridgeFunc(JOBJECT64,'getParentWithRole',c_long,JOBJECT64,POINTER(c_wchar))
	_fixBridgeFunc(BOOL,'getAccessibleRelationSet',c_long,JOBJECT64,POINTER(AccessibleRelationSetInfo),errcheck=True)
	_fixBridgeFunc(BOOL,'getAccessibleTextInfo',c_long,JOBJECT64,POINTER(AccessibleTextInfo),jint,jint,errcheck=True)
	_fixBridgeFunc(BOOL,'getAccessibleTextItems',c_long,JOBJECT64,POINTER(AccessibleTextItemsInfo),jint,errcheck=True)
	_fixBridgeFunc(BOOL,'getAccessibleTextSelectionInfo',c_long,JOBJECT64,POINTER(AccessibleTextSelectionInfo),errcheck=True)
	_fixBridgeFunc(BOOL,'getAccessibleTextAttributes',c_long,JOBJECT64,jint,POINTER(AccessibleTextAttributesInfo),errcheck=True)
	_fixBridgeFunc(
		BOOL,
		'getAccessibleTextRect',
		c_long,
		JOBJECT64,
		POINTER(AccessibleTextRectInfo),
		jint,
		errcheck=True
	)
	_fixBridgeFunc(BOOL,'getAccessibleTextLineBounds',c_long,JOBJECT64,jint,POINTER(jint),POINTER(jint),errcheck=True)
	_fixBridgeFunc(BOOL,'getAccessibleTextRange',c_long,JOBJECT64,jint,jint,POINTER(c_char),c_short,errcheck=True)
	_fixBridgeFunc(BOOL,'getCurrentAccessibleValueFromContext',c_long,JOBJECT64,POINTER(c_wchar),c_short,errcheck=True)
	_fixBridgeFunc(BOOL,'selectTextRange',c_long,JOBJECT64,c_int,c_int,errcheck=True)
	_fixBridgeFunc(BOOL,'getTextAttributesInRange',c_long,JOBJECT64,c_int,c_int,POINTER(AccessibleTextAttributesInfo),POINTER(c_short),errcheck=True)
	_fixBridgeFunc(JOBJECT64,'getTopLevelObject',c_long,JOBJECT64,errcheck=True)
	_fixBridgeFunc(c_int,'getObjectDepth',c_long,JOBJECT64)
	_fixBridgeFunc(JOBJECT64,'getActiveDescendent',c_long,JOBJECT64)
	_fixBridgeFunc(BOOL,'requestFocus',c_long,JOBJECT64,errcheck=True)
	_fixBridgeFunc(BOOL,'setCaretPosition',c_long,JOBJECT64,c_int,errcheck=True)
	_fixBridgeFunc(BOOL,'getCaretLocation',c_long,JOBJECT64,POINTER(AccessibleTextRectInfo),jint,errcheck=True)
	_fixBridgeFunc(BOOL,'getAccessibleActions',c_long,JOBJECT64,POINTER(AccessibleActions),errcheck=True)
	_fixBridgeFunc(BOOL,'doAccessibleActions',c_long,JOBJECT64,POINTER(AccessibleActionsToDo),POINTER(jint),errcheck=True)
	_fixBridgeFunc(BOOL,'getAccessibleTableInfo',c_long,JOBJECT64,POINTER(AccessibleTableInfo))
	_fixBridgeFunc(BOOL,'getAccessibleTableCellInfo',c_long,AccessibleTable,jint,jint,POINTER(AccessibleTableCellInfo),errcheck=True)
	_fixBridgeFunc(BOOL,'getAccessibleTableRowHeader',c_long,JOBJECT64,POINTER(AccessibleTableInfo))
	_fixBridgeFunc(BOOL,'getAccessibleTableColumnHeader',c_long,JOBJECT64,POINTER(AccessibleTableInfo))
	_fixBridgeFunc(JOBJECT64,'getAccessibleTableRowDescription',c_long,JOBJECT64,jint)
	_fixBridgeFunc(JOBJECT64,'getAccessibleTableColumnDescription',c_long,JOBJECT64,jint)
	_fixBridgeFunc(jint,'getAccessibleTableRow',c_long,AccessibleTable,jint)
	_fixBridgeFunc(jint,'getAccessibleTableColumn',c_long,AccessibleTable,jint)
	_fixBridgeFunc(jint,'getAccessibleTableIndex',c_long,AccessibleTable,jint,jint)
	_fixBridgeFunc(BOOL,'getAccessibleKeyBindings',c_long,JOBJECT64,POINTER(AccessibleKeyBindings),errcheck=True)

#NVDA specific code

isRunning=False
# Cache of the last active window handle for a given JVM ID. In theory, this
# cache should not be needed, as it should always be possible to retrieve the
# window handle of a given accessible context by calling getTopLevelObject then
# getHWNDFromAccessibleContext. However, getTopLevelObject sometimes returns 
# accessible contexts that make getHWNDFromAccessibleContext fail. To workaround
# the issue, we use this cache as a fallback when either getTopLevelObject or
# getHWNDFromAccessibleContext fails.
vmIDsToWindowHandles={}
internalFunctionQueue=queue.Queue(1000)
internalFunctionQueue.__name__="JABHandler.internalFunctionQueue"

def internalQueueFunction(func,*args,**kwargs):
	internalFunctionQueue.put_nowait((func,args,kwargs))
	core.requestPump()

def internal_getWindowHandleFromAccContext(vmID,accContext):
	try:
		topAC=bridgeDll.getTopLevelObject(vmID,accContext)
		try:
			return bridgeDll.getHWNDFromAccessibleContext(vmID,topAC)
		finally:
			bridgeDll.releaseJavaObject(vmID,topAC)
	except:
		return None

def getWindowHandleFromAccContext(vmID,accContext):
	hwnd=internal_getWindowHandleFromAccContext(vmID,accContext)
	if hwnd:
		vmIDsToWindowHandles[vmID]=hwnd
		return hwnd
	else:
		return vmIDsToWindowHandles.get(vmID)

class JABContext(object):

	def __init__(self,hwnd=None,vmID=None,accContext=None):
		if hwnd and not vmID:
			vmID=c_long()
			accContext=JOBJECT64()
			bridgeDll.getAccessibleContextFromHWND(hwnd,byref(vmID),byref(accContext))
			#Record  this vm ID and window handle for later use with other objects
			vmID=vmID.value
			vmIDsToWindowHandles[vmID]=hwnd
		elif vmID and not hwnd:
			hwnd = getWindowHandleFromAccContext(vmID,accContext)
		self.hwnd=hwnd
		self.vmID=vmID
		self.accContext=accContext

	def __del__(self):
		if isRunning:
			try:
				bridgeDll.releaseJavaObject(self.vmID,self.accContext)
			except:
				log.debugWarning("Error releasing java object",exc_info=True)


	def __eq__(self,jabContext):
		if self.vmID==jabContext.vmID and bridgeDll.isSameObject(self.vmID,self.accContext,jabContext.accContext):
			return True
		else:
			return False

	# As __eq__ was defined on this class, we must provide __hash__ to remain hashable.
	# The default hash implementation is fine for  our purposes.
	def __hash__(self):
		return super().__hash__()

	def __ne__(self,jabContext):
		if self.vmID!=jabContext.vmID or not bridgeDll.isSameObject(self.vmID,self.accContext,jabContext.accContext):
			return True
		else:
			return False

	def getVersionInfo(self):
		info=AccessBridgeVersionInfo()
		bridgeDll.getVersionInfo(self.vmID,byref(info))
		return info

	def getObjectDepth(self):
		return bridgeDll.getObjectDepth(self.vmID,self.accContext)

	def getAccessibleContextInfo(self):
		info=AccessibleContextInfo()
		bridgeDll.getAccessibleContextInfo(self.vmID,self.accContext,byref(info))
		return info

	def getAccessibleTextInfo(self,x,y):
		textInfo=AccessibleTextInfo()
		bridgeDll.getAccessibleTextInfo(self.vmID,self.accContext,byref(textInfo),x,y)
		return textInfo

	def getAccessibleTextItems(self,index):
		textItemsInfo=AccessibleTextItemsInfo()
		bridgeDll.getAccessibleTextItems(self.vmID,self.accContext,byref(textItemsInfo),index)
		return textItemsInfo

	def getAccessibleTextSelectionInfo(self):
		textSelectionInfo=AccessibleTextSelectionInfo()
		bridgeDll.getAccessibleTextSelectionInfo(self.vmID,self.accContext,byref(textSelectionInfo))
		return textSelectionInfo

	def getAccessibleTextRange(self,start,end):
		length=((end+1)-start)
		if length<=0:
			return u""
		# Use a string buffer, as from an unicode buffer, we can't get the raw data.
		buf = create_string_buffer((length +1) * 2)
		bridgeDll.getAccessibleTextRange(self.vmID, self.accContext, start, end, buf, length)
		return textUtils.getTextFromRawBytes(buf.raw, numChars=length, encoding=textUtils.WCHAR_ENCODING)

	def getAccessibleTextLineBounds(self,index):
		index=max(index,0)
		log.debug("lineBounds: index %s"%index)
		#Java returns end as the last character, not end as past the last character
		startIndex=c_int()
		endIndex=c_int()
		bridgeDll.getAccessibleTextLineBounds(self.vmID,self.accContext,index,byref(startIndex),byref(endIndex))
		start=startIndex.value
		end=endIndex.value
		log.debug("line bounds: start %s, end %s"%(start,end))
		if end<start or start<0:
			# Invalid or empty line.
			return (0,-1)
		ok=False
		# OpenOffice sometimes returns offsets encompassing more than one line, so try to narrow them down.
		# Try to retract the end offset.
		while not ok:
			bridgeDll.getAccessibleTextLineBounds(self.vmID,self.accContext,end,byref(startIndex),byref(endIndex))
			tempStart=max(startIndex.value,0)
			tempEnd=max(endIndex.value,0)
			log.debug("line bounds: tempStart %s, tempEnd %s"%(tempStart,tempEnd))
			if tempStart>(index+1):
				# This line starts after the requested index, so set end to point at the line before.
				end=tempStart-1
			else:
				ok=True
		ok=False
		# Try to retract the start.
		while not ok:
			bridgeDll.getAccessibleTextLineBounds(self.vmID,self.accContext,start,byref(startIndex),byref(endIndex))
			tempStart=max(startIndex.value,0)
			tempEnd=max(endIndex.value,0)
			log.debug("line bounds: tempStart %s, tempEnd %s"%(tempStart,tempEnd))
			if tempEnd<(index-1):
				# This line ends before the requested index, so set start to point at the line after.
				start=tempEnd+1
			else:
				ok=True
		log.debug("line bounds: returning %s, %s"%(start,end))
		return (start,end)


	def getAccessibleParentFromContext(self):
		accContext=bridgeDll.getAccessibleParentFromContext(self.vmID,self.accContext)
		if accContext:
			return self.__class__(self.hwnd,self.vmID,accContext)
		else:
			return None

	def getAccessibleParentWithRole(self, role):
		accContext=bridgeDll.getParentWithRole(self.vmID,self.accContext, role)
		if accContext:
			return self.__class__(self.hwnd,self.vmID,accContext)
		else:
			return None

	def getAccessibleChildFromContext(self,index):
		accContext=bridgeDll.getAccessibleChildFromContext(self.vmID,self.accContext,index)
		if accContext:
			return self.__class__(self.hwnd,self.vmID,accContext)
		else:
			return None

	def getActiveDescendent(self):
		accContext=bridgeDll.getActiveDescendent(self.vmID,self.accContext)
		if accContext:
			return self.__class__(self.hwnd,self.vmID,accContext)
		else:
			return None

	def getAccessibleContextAt(self,x,y):
		newAccContext=JOBJECT64()
		res=bridgeDll.getAccessibleContextAt(self.vmID,self.accContext,x,y,byref(newAccContext))
		if not res or not newAccContext:
			return None
		if not bridgeDll.isSameObject(self.vmID,newAccContext,self.accContext):
			return self.__class__(self.hwnd,self.vmID,newAccContext)
		elif newAccContext!=self.accContext:
			bridgeDll.releaseJavaObject(self.vmID,newAccContext)
		return None

	def getCurrentAccessibleValueFromContext(self):
		buf=create_unicode_buffer(SHORT_STRING_SIZE+1)
		bridgeDll.getCurrentAccessibleValueFromContext(self.vmID,self.accContext,buf,SHORT_STRING_SIZE)
		return buf.value

	def selectTextRange(self,start,end):
		bridgeDll.selectTextRange(start,end)

	def setCaretPosition(self,offset):
		bridgeDll.setCaretPosition(self.vmID,self.accContext,offset)

	def getTextAttributesInRange(self, startIndex, endIndex):
		attributes = AccessibleTextAttributesInfo()
		length = c_short()
		bridgeDll.getTextAttributesInRange(self.vmID, self.accContext, startIndex, endIndex, byref(attributes), byref(length))
		return attributes, length.value

	def getAccessibleTextRect(self, index):
		rect = AccessibleTextRectInfo()
		bridgeDll.getAccessibleTextRect(self.vmID, self.accContext, byref(rect), index)
		return rect

	def getAccessibleRelationSet(self):
		relations = AccessibleRelationSetInfo()
		bridgeDll.getAccessibleRelationSet(self.vmID, self.accContext, byref(relations))
		return relations

	def getAccessibleTableInfo(self):
		info=AccessibleTableInfo()
		if bridgeDll.getAccessibleTableInfo(self.vmID,self.accContext,byref(info)):
			# #6992: Querying the hwnd for table related objects can cause the app to crash.
			# A table is almost certainly contained within a single hwnd,
			# so just pass the hwnd for the querying object.
			info.jabCaption=JABContext(hwnd=self.hwnd,vmID=self.vmID,accContext=info.caption) if info.caption else None
			info.jabSummary=JABContext(hwnd=self.hwnd,vmID=self.vmID,accContext=info.summary) if info.summary else None
			info.jabContext=JABContext(hwnd=self.hwnd,vmID=self.vmID,accContext=info.accessibleContext) if info.accessibleContext else None
			info.jabTable=JABContext(hwnd=self.hwnd,vmID=self.vmID,accContext=info.accessibleTable) if info.accessibleTable else None
			return info

	def getAccessibleTableCellInfo(self,row,col):
		info=AccessibleTableCellInfo()
		if bridgeDll.getAccessibleTableCellInfo(self.vmID,self.accContext,row,col,byref(info)):
			# #6992: Querying the hwnd for table related objects can cause the app to crash.
			# A table is almost certainly contained within a single hwnd,
			# so just pass the hwnd for the querying object.
			info.jabContext=JABContext(hwnd=self.hwnd,vmID=self.vmID,accContext=info.accessibleContext) if info.accessibleContext else None
			return info

	def getAccessibleTableRow(self,index):
		return bridgeDll.getAccessibleTableRow(self.vmID,self.accContext,index)

	def getAccessibleTableColumn(self,index):
		return bridgeDll.getAccessibleTableColumn(self.vmID,self.accContext,index)

	def getAccessibleTableRowHeader(self):
		info=AccessibleTableInfo()
		if bridgeDll.getAccessibleTableRowHeader(self.vmID,self.accContext,byref(info)):
			# #6992: Querying the hwnd for table related objects can cause the app to crash.
			# A table is almost certainly contained within a single hwnd,
			# so just pass the hwnd for the querying object.
			info.jabCaption=JABContext(hwnd=self.hwnd,vmID=self.vmID,accContext=info.caption) if info.caption else None
			info.jabSummary=JABContext(hwnd=self.hwnd,vmID=self.vmID,accContext=info.summary) if info.summary else None
			info.jabContext=JABContext(hwnd=self.hwnd,vmID=self.vmID,accContext=info.accessibleContext) if info.accessibleContext else None
			info.jabTable=JABContext(hwnd=self.hwnd,vmID=self.vmID,accContext=info.accessibleTable) if info.accessibleTable else None
			return info

	def getAccessibleTableRowDescription(self,row):
		accContext=bridgeDll.getAccessibleTableRowDescription(self.vmID,self.accContext,row)
		if accContext:
			# #6992: Querying the hwnd for table related objects can cause the app to crash.
			# A table is almost certainly contained within a single hwnd,
			# so just pass the hwnd for the querying object.
			return JABContext(hwnd=self.hwnd, vmID=self.vmID, accContext=accContext)

	def getAccessibleTableColumnHeader(self):
		info=AccessibleTableInfo()
		if bridgeDll.getAccessibleTableColumnHeader(self.vmID,self.accContext,byref(info)):
			# #6992: Querying the hwnd for table related objects can cause the app to crash.
			# A table is almost certainly contained within a single hwnd,
			# so just pass the hwnd for the querying object.
			info.jabCaption=JABContext(hwnd=self.hwnd,vmID=self.vmID,accContext=info.caption) if info.caption else None
			info.jabSummary=JABContext(hwnd=self.hwnd,vmID=self.vmID,accContext=info.summary) if info.summary else None
			info.jabContext=JABContext(hwnd=self.hwnd,vmID=self.vmID,accContext=info.accessibleContext) if info.accessibleContext else None
			info.jabTable=JABContext(hwnd=self.hwnd,vmID=self.vmID,accContext=info.accessibleTable) if info.accessibleTable else None
			return info

	def getAccessibleTableColumnDescription(self,column):
		accContext=bridgeDll.getAccessibleTableColumnDescription(self.vmID,self.accContext,column)
		if accContext:
			# #6992: Querying the hwnd for table related objects can cause the app to crash.
			# A table is almost certainly contained within a single hwnd,
			# so just pass the hwnd for the querying object.
			return JABContext(hwnd=self.hwnd, vmID=self.vmID, accContext=accContext)

	def getAccessibleKeyBindings(self):
		bindings=AccessibleKeyBindings()
		if bridgeDll.getAccessibleKeyBindings(self.vmID,self.accContext,byref(bindings)):
			return bindings

@AccessBridge_FocusGainedFP
def internal_event_focusGained(vmID, event,source):
	hwnd=getWindowHandleFromAccContext(vmID,source)
	internalQueueFunction(event_gainFocus,vmID,source,hwnd)
	bridgeDll.releaseJavaObject(vmID,event)

def event_gainFocus(vmID,accContext,hwnd):
	jabContext=JABContext(hwnd=hwnd,vmID=vmID,accContext=accContext)
	if not winUser.isDescendantWindow(winUser.getForegroundWindow(),jabContext.hwnd):
		return
	focus=eventHandler.lastQueuedFocusObject
	if (isinstance(focus,NVDAObjects.JAB.JAB) and focus.jabContext==jabContext):
		return 
	obj=NVDAObjects.JAB.JAB(jabContext=jabContext)
	if obj.role==controlTypes.Role.UNKNOWN:
		return
	eventHandler.queueEvent("gainFocus",obj)

@AccessBridge_PropertyActiveDescendentChangeFP
def internal_event_activeDescendantChange(vmID, event, source, oldDescendant, newDescendant):
	hwnd = getWindowHandleFromAccContext(vmID, source)
	sourceContext = JABContext(hwnd=hwnd, vmID=vmID, accContext=source)
	if internal_hasFocus(sourceContext):
		internalQueueFunction(event_gainFocus, vmID, newDescendant, hwnd)
	for accContext in [event, oldDescendant]:
		bridgeDll.releaseJavaObject(vmID, accContext)


def internal_hasFocus(sourceContext):
	focus = api.getFocusObject()
	if isinstance(focus, NVDAObjects.JAB.JAB) and focus.jabContext == sourceContext:
		return True
	ancestors = api.getFocusAncestors()
	for ancestor in reversed(ancestors):
		if isinstance(ancestor, NVDAObjects.JAB.JAB) and ancestor.jabContext == sourceContext:
			return True
	return False


@AccessBridge_PropertyNameChangeFP
def event_nameChange(vmID,event,source,oldVal,newVal):
	jabContext=JABContext(vmID=vmID,accContext=source)
	focus=api.getFocusObject()
	if isinstance(focus, NVDAObjects.JAB.JAB) and focus.jabContext == jabContext:
		obj = focus
	else:
		obj = NVDAObjects.JAB.JAB(jabContext=jabContext)
	if obj:
		eventHandler.queueEvent("nameChange", obj)
	bridgeDll.releaseJavaObject(vmID,event)

@AccessBridge_PropertyDescriptionChangeFP
def event_descriptionChange(vmID,event,source,oldVal,newVal):
	jabContext=JABContext(vmID=vmID,accContext=source)
	focus=api.getFocusObject()
	if isinstance(focus, NVDAObjects.JAB.JAB) and focus.jabContext == jabContext:
		obj = focus
	else:
		obj = NVDAObjects.JAB.JAB(jabContext=jabContext)
	if obj:
		eventHandler.queueEvent("descriptionChange", obj)
	bridgeDll.releaseJavaObject(vmID,event)

@AccessBridge_PropertyValueChangeFP
def event_valueChange(vmID,event,source,oldVal,newVal):
	jabContext=JABContext(vmID=vmID,accContext=source)
	focus=api.getFocusObject()
	if isinstance(focus, NVDAObjects.JAB.JAB) and focus.jabContext == jabContext:
		obj = focus
	else:
		obj = NVDAObjects.JAB.JAB(jabContext=jabContext)
	if obj:
		eventHandler.queueEvent("valueChange", obj)
	bridgeDll.releaseJavaObject(vmID,event)

@AccessBridge_PropertyStateChangeFP
def internal_event_stateChange(vmID,event,source,oldState,newState):
	internalQueueFunction(event_stateChange,vmID,source,oldState,newState)
	bridgeDll.releaseJavaObject(vmID,event)

def event_stateChange(vmID,accContext,oldState,newState):
	jabContext=JABContext(vmID=vmID,accContext=accContext)
	focus=api.getFocusObject()
	#For broken tabs and menus, we need to watch for things being selected and pretend its a focus change
	stateList=newState.split(',')
	if "focused" in stateList or "selected" in stateList:
		obj=NVDAObjects.JAB.JAB(jabContext=jabContext)
		if not obj:
			return
		if focus!=obj and eventHandler.lastQueuedFocusObject!=obj and obj.role in (controlTypes.Role.MENUITEM,controlTypes.Role.TAB,controlTypes.Role.MENU):
			eventHandler.queueEvent("gainFocus",obj)
			return
	if isinstance(focus,NVDAObjects.JAB.JAB) and focus.jabContext==jabContext:
		obj=focus
	else:
		obj=NVDAObjects.JAB.JAB(jabContext=jabContext)
		if not obj:
			return
	eventHandler.queueEvent("stateChange",obj)

@AccessBridge_PropertyCaretChangeFP
def internal_event_caretChange(vmID, event,source,oldPos,newPos):
	hwnd=getWindowHandleFromAccContext(vmID,source)
	if oldPos<0 and newPos>=0:
		internalQueueFunction(event_gainFocus,vmID,source,hwnd)
	else:
		internalQueueFunction(event_caret,vmID,source,hwnd)
	bridgeDll.releaseJavaObject(vmID,event)

def event_caret(vmID, accContext, hwnd):
	jabContext = JABContext(hwnd=hwnd, vmID=vmID, accContext=accContext)
	focus = api.getFocusObject()
	if isinstance(focus, NVDAObjects.JAB.JAB) and focus.jabContext == jabContext:
		obj = focus
	else:
		obj = NVDAObjects.JAB.JAB(jabContext=jabContext)
		if not obj:
			return
	eventHandler.queueEvent("caret", obj)

def event_enterJavaWindow(hwnd):
	internalQueueFunction(enterJavaWindow_helper,hwnd)

def enterJavaWindow_helper(hwnd):
	vmID=c_long()
	accContext=JOBJECT64()
	timeout=time.time()+0.2
	while time.time()<timeout and not eventHandler.isPendingEvents("gainFocus"):
		try:
			bridgeDll.getAccessibleContextWithFocus(hwnd,byref(vmID),byref(accContext))
		except:
			pass
		if vmID and accContext:
			break
		time.sleep(0.01)
	if not vmID or not accContext: 
		try:
			bridgeDll.getAccessibleContextFromHWND(hwnd,byref(vmID),byref(accContext))
		except:
			return
	vmID=vmID.value
	vmIDsToWindowHandles[vmID]=hwnd
	lastFocus=eventHandler.lastQueuedFocusObject
	if isinstance(lastFocus,NVDAObjects.JAB.JAB) and lastFocus.windowHandle==hwnd:
		return
	event_gainFocus(vmID,accContext,hwnd)

def isJavaWindow(hwnd):
	if not bridgeDll or not isRunning:
		return False
	return bridgeDll.isJavaWindow(hwnd)


def isBridgeEnabled():
	try:
		data = open(A11Y_PROPS_PATH, "rt").read()
	except OSError:
		return False
	return data == A11Y_PROPS_CONTENT


def enableBridge():
	try:
		props = open(A11Y_PROPS_PATH, "wt")
		props.write(A11Y_PROPS_CONTENT)
		log.info("Enabled Java Access Bridge for user")
	except OSError:
		log.warning("Couldn't enable Java Access Bridge for user", exc_info=True)


def initialize():
	global bridgeDll, isRunning
	try:
		bridgeDll = cdll.LoadLibrary(
			os.path.join(NVDAHelper.versionedLibPath, "windowsaccessbridge-32.dll"))
	except WindowsError:
		raise NotImplementedError("dll not available")
	_fixBridgeFuncs()
	if (
		not globalVars.appArgs.secure and config.isInstalledCopy()
		and not isBridgeEnabled()
	):
		enableBridge()
	# Accept wm_copydata and any wm_user messages from other processes even if running with higher privileges
	if not windll.user32.ChangeWindowMessageFilter(winUser.WM_COPYDATA, winUser.MSGFLT.ALLOW):
		raise WinError()
	for msg in range(winUser.WM_USER + 1, 0xffff):
		if not windll.user32.ChangeWindowMessageFilter(msg, winUser.MSGFLT.ALLOW):
			raise WinError()
	bridgeDll.Windows_run()
	# Register java events
	bridgeDll.setFocusGainedFP(internal_event_focusGained)
	bridgeDll.setPropertyActiveDescendentChangeFP(internal_event_activeDescendantChange)
	bridgeDll.setPropertyNameChangeFP(event_nameChange)
	bridgeDll.setPropertyDescriptionChangeFP(event_descriptionChange)
	bridgeDll.setPropertyValueChangeFP(event_valueChange)
	bridgeDll.setPropertyStateChangeFP(internal_event_stateChange)
	bridgeDll.setPropertyCaretChangeFP(internal_event_caretChange)
	isRunning=True

def pumpAll():
	if isRunning: 
		queueHandler.flushQueue(internalFunctionQueue)

def terminate():
	global isRunning, bridgeDll
	if not bridgeDll or not isRunning:
		return
	bridgeDll.setFocusGainedFP(None)
	bridgeDll.setPropertyActiveDescendentChangeFP(None)
	bridgeDll.setPropertyStateChangeFP(None)
	bridgeDll.setPropertyCaretChangeFP(None)
	h=bridgeDll._handle
	bridgeDll=None
	windll.kernel32.FreeLibrary(h)
	isRunning=False