def shouldAcceptEvent(eventName, windowHandle=None):
	"""Check whether an event should be accepted from a platform API.
	Creating NVDAObjects and executing events can be expensive
	and might block the main thread noticeably if the object is slow to respond.
	Therefore, this should be used before NVDAObject creation to filter out any unnecessary events.
	A platform API handler may do its own filtering before this.
	"""
	if not windowHandle:
		# We can't filter without a window handle.
		return True
	key = (eventName,
		winUser.getWindowThreadProcessID(windowHandle)[0],
		winUser.getClassName(windowHandle))
	if key in _acceptEvents:
		return True
	if eventName == "valueChange" and config.conf["presentation"]["progressBarUpdates"]["reportBackgroundProgressBars"]:
		return True
	if eventName == "show":
		# Only accept 'show' events for specific cases, as otherwise we get flooded.
		return winUser.getClassName(windowHandle) in (
			"Frame Notification Bar", # notification bars
			"tooltips_class32", # tooltips
			"mscandui21.candidate", "mscandui40.candidate", "MSCandUIWindow_Candidate", # IMM candidates
			"TTrayAlert", # 5405: Skype
		)
	if eventName == "reorder":
		# Prevent another flood risk.
		return winUser.getClassName(windowHandle) == "TTrayAlert" # #4841: Skype
	if eventName == "alert" and winUser.getClassName(winUser.getAncestor(windowHandle, winUser.GA_PARENT)) == "ToastChildWindowClass":
		# Toast notifications.
		return True
	if eventName in ("menuEnd", "switchEnd", "desktopSwitch"):
		# #5302, #5462: These events can be fired on the desktop window
		# or windows that would otherwise be blocked.
		# Platform API handlers will translate these events to focus events anyway,
		# so we must allow them here.
		return True
	if windowHandle == winUser.getDesktopWindow():
		# #5595: Events for the cursor get mapped to the desktop window.
		return True

	fg = winUser.getForegroundWindow()
	if (winUser.isDescendantWindow(fg, windowHandle)
			# #3899, #3905: Covers cases such as the Firefox Page Bookmarked window and OpenOffice/LibreOffice context menus.
			or winUser.isDescendantWindow(fg, winUser.getAncestor(windowHandle, winUser.GA_ROOTOWNER))):
		# This is for the foreground application.
		return True
	if (winUser.user32.GetWindowLongW(windowHandle, winUser.GWL_EXSTYLE) & winUser.WS_EX_TOPMOST
			or winUser.user32.GetWindowLongW(winUser.getAncestor(windowHandle, winUser.GA_ROOT), winUser.GWL_EXSTYLE) & winUser.WS_EX_TOPMOST):
		# This window or its root is a topmost window.
		# This includes menus, combo box pop-ups and the task switching list.
		return True
	return False

	def _get_parent(self):
		parentHandle=winUser.getAncestor(self.windowHandle,winUser.GA_PARENT)
		if parentHandle:
			#Because we, we need to get the APIclass manually need to  set the relation as parent
			kwargs=dict(windowHandle=parentHandle)
			APIClass=Window.findBestAPIClass(kwargs,relation="parent")
			return APIClass(**kwargs) if APIClass else None

	def event_NVDAObject_init(self, obj):
		windowClass = obj.windowClassName
		role = obj.role

		if windowClass == "ToolbarWindow32" and role == controlTypes.ROLE_POPUPMENU:
			parent = obj.parent
			if parent and parent.windowClassName == "SysPager" and not (obj.windowStyle & 0x80):
				# This is the menu for a group of icons on the task bar, which Windows stupidly names "Application".
				obj.name = None
			return

		if windowClass == "#32768":
			# Standard menu.
			parent = obj.parent
			if parent and not parent.parent:
				# Context menu.
				# We don't trust the names that Explorer gives to context menus, so better to have no name at all.
				obj.name = None
			return

		if windowClass == "DV2ControlHost" and role == controlTypes.ROLE_PANE:
			# Windows Vista/7 start menu.
			obj.presentationType=obj.presType_content
			obj.isPresentableFocusAncestor = True
			# In Windows 7, the description of this pane is extremely verbose help text, so nuke it.
			obj.description = None
			return

		# The Address bar is embedded inside a progressbar, how strange.
		# Lets hide that
		if windowClass=="msctls_progress32" and winUser.getClassName(winUser.getAncestor(obj.windowHandle,winUser.GA_PARENT))=="Address Band Root":
			obj.presentationType=obj.presType_layout

	def _isUIAWindowHelper(self,hwnd):
		# UIA in NVDA's process freezes in Windows 7 and below
		processID=winUser.getWindowThreadProcessID(hwnd)[0]
		if windll.kernel32.GetCurrentProcessId()==processID:
			return False
		import NVDAObjects.window
		windowClass=NVDAObjects.window.Window.normalizeWindowClassName(winUser.getClassName(hwnd))
		# For certain window classes, we always want to use UIA.
		if windowClass in goodUIAWindowClassNames:
			return True
		# allow the appModule for the window to also choose if this window is good
		# An appModule should be able to override bad UIA class names as prescribed by core
		appModule=appModuleHandler.getAppModuleFromProcessID(processID)
		if appModule and appModule.isGoodUIAWindow(hwnd):
			return True
		# There are certain window classes that just had bad UIA implementations
		if windowClass in badUIAWindowClassNames:
			return False
		if windowClass=="NetUIHWND":
			parentHwnd=winUser.getAncestor(hwnd,winUser.GA_ROOT)
			# #2816: Outlook 2010 auto complete does not fire enough UIA events, IAccessible is better.
			# #4056: Combo boxes in Office 2010 Options dialogs don't expose a name via UIA, but do via MSAA.
			if winUser.getClassName(parentHwnd) in {"Net UI Tool Window","NUIDialog"}:
				return False
		# allow the appModule for the window to also choose if this window is bad
		if appModule and appModule.isBadUIAWindow(hwnd):
			return False
		# Ask the window if it supports UIA natively
		res=windll.UIAutomationCore.UiaHasServerSideProvider(hwnd)
		if res:
			# the window does support UIA natively, but
			# Microsoft Word should not use UIA unless we can't inject or the user explicitly chose to use UIA with Microsoft word
			if windowClass=="_WwG" and not (config.conf['UIA']['useInMSWordWhenAvailable'] or not appModule.helperLocalBindingHandle):
				return False
		return bool(res)

def winEventCallback(handle,eventID,window,objectID,childID,threadID,timestamp):
	try:
		#Ignore all object IDs from alert onwards (sound, nativeom etc) as we don't support them
		if objectID<=winUser.OBJID_ALERT: 
			return
		#Ignore all locationChange events except ones for the caret
		if eventID==winUser.EVENT_OBJECT_LOCATIONCHANGE and objectID!=winUser.OBJID_CARET:
			return
		if eventID==winUser.EVENT_OBJECT_DESTROY:
			processDestroyWinEvent(window,objectID,childID)
			return
		#Change window objIDs to client objIDs for better reporting of objects
		if (objectID==0) and (childID==0):
			objectID=winUser.OBJID_CLIENT
		#Ignore events with invalid window handles
		isWindow = winUser.isWindow(window) if window else 0
		if window==0 or (not isWindow and eventID in (winUser.EVENT_SYSTEM_SWITCHSTART,winUser.EVENT_SYSTEM_SWITCHEND,winUser.EVENT_SYSTEM_MENUEND,winUser.EVENT_SYSTEM_MENUPOPUPEND)):
			window=winUser.getDesktopWindow()
		elif not isWindow:
			return

		if childID<0:
			tempWindow=window
			while tempWindow and not winUser.getWindowStyle(tempWindow)&winUser.WS_POPUP and winUser.getClassName(tempWindow)=="MozillaWindowClass":
				tempWindow=winUser.getAncestor(tempWindow,winUser.GA_PARENT)
			if tempWindow and winUser.getClassName(tempWindow).startswith('Mozilla'):
				window=tempWindow

		windowClassName=winUser.getClassName(window)
		#At the moment we can't handle show, hide or reorder events on Mozilla Firefox Location bar,as there are just too many of them
		#Ignore show, hide and reorder on MozillaDropShadowWindowClass windows.
		if windowClassName.startswith('Mozilla') and eventID in (winUser.EVENT_OBJECT_SHOW,winUser.EVENT_OBJECT_HIDE,winUser.EVENT_OBJECT_REORDER) and childID<0:
			#Mozilla Gecko can sometimes fire win events on a catch-all window which isn't really the real window
			#Move up the ancestry to find the real mozilla Window and use that
			if winUser.getClassName(window)=='MozillaDropShadowWindowClass':
				return
		if eventID==winUser.EVENT_SYSTEM_FOREGROUND:
			#We never want to see foreground events for the Program Manager or Shell (task bar) 
			if windowClassName in ("Progman","Shell_TrayWnd"):
				return
			# #3831: Event handling can be deferred if Windows takes a while to change the foreground window.
			# See pumpAll for details.
			global _deferUntilForegroundWindow,_foregroundDefers
			_deferUntilForegroundWindow=window
			_foregroundDefers=0
		if windowClassName=="MSNHiddenWindowClass":
			# HACK: Events get fired by this window in Windows Live Messenger 2009 when it starts.
			# If we send a WM_NULL to this window at this point (which happens in accessibleObjectFromEvent), Messenger will silently exit (#677).
			# Therefore, completely ignore these events, which is useless to us anyway.
			return
		if winEventLimiter.addEvent(eventID,window,objectID,childID,threadID):
			core.requestPump()
	except:
		log.error("winEventCallback", exc_info=True)

	def event_NVDAObject_init(self,obj):
		controlID=obj.windowControlID
		windowHandle=obj.windowHandle
		parentWindow=winUser.getAncestor(windowHandle,winUser.GA_PARENT)
		parentClassName=winUser.getClassName(parentWindow)
		#If this object is an email header field, and we have a custom label for it,
		#Then set the object's name to the label 
		if parentClassName=="OE_Envelope" and obj.IAccessibleChildID==0 and envelopeNames.has_key(controlID):
			obj.name=envelopeNames[controlID]
			obj.useITextDocumentSupport=True
			obj.editValueUnit=textInfos.UNIT_STORY

	def isBadUIAWindow(self,hwnd):
		windowClass=winUser.getClassName(hwnd)
		# #2816: Outlook versions before 2016 auto complete does not fire enough UIA events, IAccessible is better.
		if windowClass=="NetUIHWND":
			parentHwnd=winUser.getAncestor(hwnd,winUser.GA_ROOT)
			if winUser.getClassName(parentHwnd)=="Net UI Tool Window":
				versionMajor=int(self.productVersion.split('.')[0])
				if versionMajor<16:
					return True
		if windowClass in ("WeekViewWnd","DayViewWnd"):
			return True
		return False

	def event_NVDAObject_init(self, obj):
		if not isinstance(obj, Window):
			return
		role = obj.role
		if role == controlTypes.ROLE_WINDOW:
			return
		wclass = Window.normalizeWindowClassName(obj.windowClassName)

		if wclass == "Window.8" and role == controlTypes.ROLE_PANE:
			# optimisation: There are quite a lot of these, so let's not instantiate parent NVDAObjects unnecessarily.
			parentWindow = winUser.getAncestor(obj.windowHandle, winUser.GA_PARENT)
			if parentWindow and Window.normalizeWindowClassName(winUser.getClassName(parentWindow)) == "SysTabControl32":
				obj.role = controlTypes.ROLE_PROPERTYPAGE

		elif wclass == "SysTabControl32":
			obj.isPresentableFocusAncestor = False

def processFocusWinEvent(window,objectID,childID,force=False):
	"""checks to see if the focus win event is not the same as the existing focus, 
	then converts the win event to an NVDA event (instanciating an NVDA Object) then calls processFocusNVDAEvent. If all is ok it returns True.
	@type window: integer
	@param objectID: a win event's object ID
	@type objectID: integer
	@param childID: a win event's child ID
	@type childID: integer
	@param force: If True, the shouldAllowIAccessibleFocusEvent property of the object is ignored.
	@type force: boolean
	@returns: True if the focus is valid and was handled, False otherwise.
	@rtype: boolean
	"""
	windowClassName=winUser.getClassName(window)
	# Generally, we must ignore focus on child windows of SDM windows as we only want the SDM MSAA events.
	# However, we don't want to ignore focus if the child ID isn't 0,
	# as this is a child control and the SDM MSAA events don't handle child controls.
	if childID==0 and not windowClassName.startswith('bosa_sdm') and winUser.getClassName(winUser.getAncestor(window,winUser.GA_PARENT)).startswith('bosa_sdm'):
		return False
	rootWindow=winUser.getAncestor(window,winUser.GA_ROOT)
	# If this window is not within the foreground window and this window or its root window is not a popup window, and this window's root window is not the highest in the z-order
	if not winUser.isDescendantWindow(winUser.getForegroundWindow(),window) and not (winUser.getWindowStyle(window) & winUser.WS_POPUP or winUser.getWindowStyle(rootWindow)&winUser.WS_POPUP) and winUser.getPreviousWindow(rootWindow)!=0: 
		# This is a focus event from a background window, so ignore it.
		return False
	#Notify appModuleHandler of this new foreground window
	appModuleHandler.update(winUser.getWindowThreadProcessID(window)[0])
	#If Java access bridge is running, and this is a java window, then pass it to java and forget about it
	if JABHandler.isRunning and JABHandler.isJavaWindow(window):
		JABHandler.event_enterJavaWindow(window)
		return True
	#Convert the win event to an NVDA event
	NVDAEvent=winEventToNVDAEvent(winUser.EVENT_OBJECT_FOCUS,window,objectID,childID,useCache=False)
	if not NVDAEvent:
		return False
	eventName,obj=NVDAEvent
	if (childID==0 and obj.IAccessibleRole==oleacc.ROLE_SYSTEM_LIST) or (objectID==winUser.OBJID_CLIENT and "SysListView32" in obj.windowClassName):
		# Some controls incorrectly fire focus on child ID 0, even when there is a child with focus.
		try:
			realChildID=obj.IAccessibleObject.accFocus
		except:
			realChildID=None
		if isinstance(realChildID,int) and realChildID>0 and realChildID!=childID:
			realObj=NVDAObjects.IAccessible.IAccessible(IAccessibleObject=obj.IAccessibleObject,IAccessibleChildID=realChildID,event_windowHandle=window,event_objectID=objectID,event_childID=realChildID)
			if realObj:
				obj=realObj
	return processFocusNVDAEvent(obj,force=force)

	def _getDropdown(self):
		w=winUser.getAncestor(self.windowHandle,winUser.GA_ROOT)
		if not w:
			log.debugWarning("Could not get ancestor window (GA_ROOT)")
			return
		obj=Window(windowHandle=w,chooseBestAPI=False)
		if not obj:
			log.debugWarning("Could not instnaciate NVDAObject for ancestor window")
			return
		threadID=obj.windowThreadID
		while not eventHandler.isPendingEvents("gainFocus"):
			obj=obj.previous
			if not obj or not isinstance(obj,Window) or obj.windowThreadID!=threadID:
				log.debugWarning("Could not locate dropdown list in previous objects")
				return
			if obj.windowClassName=='EXCEL:':
				break
		return obj

	def chooseNVDAObjectOverlayClasses(self, obj, clsList):
		if UIAWordDocument in clsList:
			# Overlay class for Outlook message viewer when UI Automation for MS Word is enabled.
			clsList.insert(0,OutlookUIAWordDocument)
		if isinstance(obj,UIA) and obj.UIAElement.cachedClassName in ("LeafRow","ThreadItem","ThreadHeader"):
			clsList.insert(0,UIAGridRow)
		role=obj.role
		windowClassName=obj.windowClassName
		# AutoComplete listItems.
		# This class is abstract enough to  support both UIA and MSAA
		if role==controlTypes.ROLE_LISTITEM and (windowClassName.startswith("REListBox") or windowClassName.startswith("NetUIHWND")):
			clsList.insert(0,AutoCompleteListItem)
		#  all   remaining classes are IAccessible
		if not isinstance(obj,IAccessible):
			return
		# Outlook uses dialogs for many forms such as appointment / meeting creation. In these cases, there is no sane dialog caption that can be calculated as the dialog inly contains controls.
		# Therefore remove the Dialog behavior for these imbedded dialog forms so as to not announce junk as the caption
		if Dialog in clsList:
			parentWindow=winUser.getAncestor(obj.windowHandle,winUser.GA_PARENT)
			if parentWindow and winUser.getClassName(parentWindow)=="AfxWndW":
				clsList.remove(Dialog)
		if WordDocument in clsList:
			clsList.insert(0,OutlookWordDocument)
		states=obj.states
		controlID=obj.windowControlID
		# Support the date picker in Outlook Meeting / Appointment creation forms 
		if controlID==4352 and role==controlTypes.ROLE_BUTTON:
			clsList.insert(0,DatePickerButton)
		elif role==controlTypes.ROLE_TABLECELL and windowClassName=="rctrl_renwnd32":
			clsList.insert(0,DatePickerCell)
		elif windowClassName=="REListBox20W" and role==controlTypes.ROLE_CHECKBOX:
			clsList.insert(0,REListBox20W_CheckBox)
		if role==controlTypes.ROLE_LISTITEM and windowClassName=="OUTEXVLB":
			clsList.insert(0, AddressBookEntry)
			return
		if (windowClassName=="SUPERGRID" and controlID==4704) or (windowClassName=="rctrl_renwnd32" and controlID==109):
			outlookVersion=self.outlookVersion
			if outlookVersion and outlookVersion<=9:
				clsList.insert(0, MessageList_pre2003)
			elif obj.event_objectID==winUser.OBJID_CLIENT and obj.event_childID==0:
				clsList.insert(0,SuperGridClient2010)
		if (windowClassName == "AfxWndW" and controlID==109) or (windowClassName in ("WeekViewWnd","DayViewWnd")):
			clsList.insert(0,CalendarView)

def getScreenPosition(obj):
	"""
	Fetches a TextInfo instance suitable for reviewing the screen, positioned at the given object's coordinates. 
	@param obj: the NVDAObject to review
	@type obj: L{NVDAObject}
	@return: the TextInfo instance and the Scriptable object the TextInfo instance is referencing, or None on error. 
	@rtype: (L{TextInfo},L{ScriptableObject})
	"""
	focus=api.getFocusObject()
	while focus and not isinstance(focus,Window):
		focus=focus.parent
	if not focus: return None
	w=winUser.getAncestor(focus.windowHandle,winUser.GA_ROOT) or focus.windowHandle
	s=Window(windowHandle=w)
	if s:
		s.redraw()
		try:
			pos=DisplayModelTextInfo(s,obj)
		except LookupError:
			pos=DisplayModelTextInfo(s,textInfos.POSITION_FIRST)
		return pos,pos.obj

	def _isUIAWindowHelper(self,hwnd):
		# UIA in NVDA's process freezes in Windows 7 and below
		processID=winUser.getWindowThreadProcessID(hwnd)[0]
		if windll.kernel32.GetCurrentProcessId()==processID:
			return False
		import NVDAObjects.window
		windowClass=NVDAObjects.window.Window.normalizeWindowClassName(winUser.getClassName(hwnd))
		# There are certain window classes that just had bad UIA implementations
		if windowClass in badUIAWindowClassNames:
			return False
		if windowClass=="NetUIHWND":
			parentHwnd=winUser.getAncestor(hwnd,winUser.GA_ROOT)
			# #2816: Outlook 2010 auto complete does not fire enough UIA events, IAccessible is better.
			if winUser.getClassName(parentHwnd)=="Net UI Tool Window":
				return False
		# allow the appModule for the window to also choose if this window is bad
		appModule=appModuleHandler.getAppModuleFromProcessID(processID)
		if appModule and appModule.isBadUIAWindow(hwnd):
			return False
		# Ask the window if it supports UIA natively
		return windll.UIAutomationCore.UiaHasServerSideProvider(hwnd)

def shouldAcceptEvent(eventName, windowHandle=None):
	"""Check whether an event should be accepted from a platform API.
	Creating NVDAObjects and executing events can be expensive
	and might block the main thread noticeably if the object is slow to respond.
	Therefore, this should be used before NVDAObject creation to filter out any unnecessary events.
	A platform API handler may do its own filtering before this.
	"""
	if not windowHandle:
		# We can't filter without a window handle.
		return True
	wClass = winUser.getClassName(windowHandle)
	key = (eventName,
		winUser.getWindowThreadProcessID(windowHandle)[0],
		wClass)
	if key in _acceptEvents:
		return True
	if eventName == "valueChange" and config.conf["presentation"]["progressBarUpdates"]["reportBackgroundProgressBars"]:
		return True
	if eventName == "show":
		# Only accept 'show' events for specific cases, as otherwise we get flooded.
		return wClass in (
			"Frame Notification Bar", # notification bars
			"tooltips_class32", # tooltips
			"mscandui21.candidate", "mscandui40.candidate", "MSCandUIWindow_Candidate", # IMM candidates
			"TTrayAlert", # 5405: Skype
		)
	if eventName == "reorder":
		# Prevent another flood risk.
		return wClass == "TTrayAlert" # #4841: Skype
	if eventName == "alert" and winUser.getClassName(winUser.getAncestor(windowHandle, winUser.GA_PARENT)) == "ToastChildWindowClass":
		# Toast notifications.
		return True
	if eventName in ("menuEnd", "switchEnd", "desktopSwitch"):
		# #5302, #5462: These events can be fired on the desktop window
		# or windows that would otherwise be blocked.
		# Platform API handlers will translate these events to focus events anyway,
		# so we must allow them here.
		return True
	if windowHandle == winUser.getDesktopWindow():
		# #5595: Events for the cursor get mapped to the desktop window.
		return True

	# #6713: Edge (and soon all UWP apps) will no longer have windows as descendants of the foreground window.
	# However, it does look like they are always  equal to or descendants of the "active" window of the input thread. 
	if wClass.startswith('Windows.UI.Core'):
		gi=winUser.getGUIThreadInfo(0)
		if winUser.isDescendantWindow(gi.hwndActive,windowHandle):
			return True

	fg = winUser.getForegroundWindow()
	if wClass == "NetUIHWND" and winUser.getClassName(fg) == "Net UI Tool Window Layered":
		# #5504: In Office >= 2013 with the ribbon showing only tabs,
		# when a tab is expanded, the window we get from the focus object is incorrect.
		# This window isn't beneath the foreground window,
		# so our foreground application checks fail.
		# Just compare the root owners.
		if winUser.getAncestor(windowHandle, winUser.GA_ROOTOWNER) == winUser.getAncestor(fg, winUser.GA_ROOTOWNER):
			return True
	if (winUser.isDescendantWindow(fg, windowHandle)
			# #3899, #3905: Covers cases such as the Firefox Page Bookmarked window and OpenOffice/LibreOffice context menus.
			or winUser.isDescendantWindow(fg, winUser.getAncestor(windowHandle, winUser.GA_ROOTOWNER))):
		# This is for the foreground application.
		return True
	if (winUser.user32.GetWindowLongW(windowHandle, winUser.GWL_EXSTYLE) & winUser.WS_EX_TOPMOST
			or winUser.user32.GetWindowLongW(winUser.getAncestor(windowHandle, winUser.GA_ROOT), winUser.GWL_EXSTYLE) & winUser.WS_EX_TOPMOST):
		# This window or its root is a topmost window.
		# This includes menus, combo box pop-ups and the task switching list.
		return True
	return False