// a client has stopped listening for an event on object(s) in the specified window.
internal void AdviseEventRemoved(IntPtr hwnd, AutomationEvent eventId, AutomationProperty[] properties)
{
// note: we don't need to worry about removing entries from our tables when windows are destroyed
//(EVENT_OBJECT_DESTROY with OBJID_WINDOW) because UIA already watches for this event and calls AdviseEventRemoved.
// use a lock to update our tables in one atomic operation.
lock (this)
{
// we should have a 2-nd level table for this hwnd...
if (_hwndTable.ContainsKey(hwnd))
{
Hashtable eventTable = (Hashtable)(_hwndTable[hwnd]);
// for the single event or each of possibly multiple properties decrement the reference count.
foreach (AutomationIdentifier key in EventKeys(eventId, properties))
{
// we should have an entry in the 2-nd level table for this event or property...
if (eventTable.ContainsKey(key))
{
// decrement the reference count
int refcount = (int)eventTable[key] - 1;
Debug.Assert(refcount >= 0);
if (refcount > 0)
{
eventTable[key] = refcount;
}
else
{
// if the refcount has gone to zero then remove this entry from the 2-nd level table.
eventTable.Remove(key);
// if this window doesn't have any more advises then remove it's entry from the top-level table
if (eventTable.Count == 0)
{
_hwndTable.Remove(hwnd);
// if there are no more advises then we can stop listening for WinEvents
if (_hwndTable.Count == 0)
{
//Debug.WriteLine("Stop listening for WinEvents.", "NativeMsaaProxy");
WinEventTracker.GetCallbackQueue().PostSyncWorkItem(new QueueItem.MSAAWinEventItem(StopListening));
}
}
}
}
else
{
Debug.WriteLine(string.Format(CultureInfo.CurrentCulture, "ERROR: AdviseEventRemoved called for {0} and event/property {1} without matching AdviseEventAdded.", hwnd, key), "NativeMsaaProxy");
}
}
}
else
{
Debug.WriteLine(string.Format(CultureInfo.CurrentCulture, "ERROR: AdviseEventRemoved called for {0} without matching AdviseEventAdded.", hwnd), "NativeMsaaProxy");
}
}
}
// a client is listening for an event on object(s) in the specified window.
internal void AdviseEventAdded(IntPtr hwnd, AutomationEvent eventId, AutomationProperty[] properties)
{
// When you start listening for events you listen for all events and then
// when you get the event you filter by any hwnd that got advised. But you have enough
// information when you get advised to listen only for in process where that hwnd resides.
// The SetWinEventHook api takes a process id, you could get the process id from the hwnd
// and limit the number of event you have to process.
// we have a two-level table structure. the top-level table maps an hwnd to another table.
// the second-level table maps an event (or a property in the case of property-changed-event)
// in that hwnd to a reference count of the number of clients listening for that event.
// use a lock to update our tables in one atomic operation.
lock (this)
{
// if we aren't listening for WinEvents then start listening.
if (_hwndTable.Count == 0)
{
//Debug.WriteLine("Starting listening for WinEvents.", "NativeMsaaProxy");
// Posting an item to the queue to start listening for WinEvents. This makes sure it is done on the proper thread
// Notably the same thread WinEventTracker uses, which guarantees the thread that SetWinEventHook is called on is
// actively pumping messages, which is required for SetWinEventHook to function properly.
WinEventTracker.GetCallbackQueue().PostSyncWorkItem(new QueueItem.MSAAWinEventItem(StartListening));
}
// if we already have a 2-nd level table for this hwnd then simply update the 2nd-level table.
// otherwise we need to create a 2-nd level table.
Hashtable eventTable;
if (_hwndTable.ContainsKey(hwnd))
{
eventTable = (Hashtable)(_hwndTable[hwnd]);
}
else
{
eventTable = new Hashtable();
_hwndTable[hwnd] = eventTable;
}
// for the single event or each of possibly multiple properties increment the reference counter.
foreach (AutomationIdentifier key in EventKeys(eventId, properties))
{
eventTable[key] = eventTable.ContainsKey(key) ? (int)eventTable[key] + 1 : 1;
}
}
}