Subscribe to Vista Events in .NET (e.g. Window Opened) - events

Question

I am trying to build my own little toolbox for Vista.
One of the features is a "window placeing tool" which places the windows at saved position. Another tool I could imagine are extensions to firefox or thunderbird...
For these tools to work, I need them to be able to capture "Events" in Vista.
To give you a concrete example:
Explorer Opened New Window
User started Firefox
Mouse moved
For the mouse case, there are some examples for C#.
I also know about the directory watcher, nice little helper.
Want I now need is the "new window opened event"
Any idea how to monitor this, without iterating the current window list every 5 seconds (I already know how to get Windows using the DLLImports, and getting Processes using managed code. But I have no Event when the explorer process opens a new windows)
Thanks for your help,
Chris

Answer 1

What you're talking about doing is not simple by any stretch.
You're going to need to register a hook, and you're going to have to build a callback procedure that gets called within another process's execution context -- this is not going to be .NET code (probably C instead), and will have to be in a DLL. That callback procedure will get called every time a certain class of events happens. It will examine the events it receives and filter out the ones you're interested, then send your application the notifications you want (probably via PostMessage). You'll then tap in to your application's main message loop to intercept those messages, and from there you can fire a .NET Event, or whatever you want.
Writing hook callbacks is tricky stuff because the code gets run within another process, not your own, and the memory management and concurrency issues take a bit of forethought. For that same reason, it's not going to be done in C#. Ideally, though, this callback code will be very small and very fast, since it's going to get called so often.
Also note that while perfectly "legal" in Win32, these system hooks have an immense amount of power and are commonly used by malware to change the way your system works. For that reason, you may run afoul of antivirus software if you attempt to do this sort of thing on a customer's computer.
Also note that the far-reaching effects of system hooks also means that simple programming mistakes can take down your whole system, which you will probably discover for yourself at some point while debugging; so save everything before you hit "run".
Good luck!
EDIT
Did a bit more search to see if there's any way to write the hook proc in C#, and came up with this:
How to set a Windows hook in Visual C# .NET
This is almost what you're looking for, but not quite. Hook procedures can either be global (which means that they run on every application) or thread (only runs within your application). The document states that:
Global hooks are not supported in the .NET Framework
Except for the
WH_KEYBOARD_LL low-level hook and the
WH_MOUSE_LL low-level hook, you cannot
implement global hooks in the
Microsoft .NET Framework. To install a
global hook, a hook must have a native
DLL export to inject itself in another
process that requires a valid,
consistent function to call into. This
behavior requires a DLL export. The
.NET Framework does not support DLL
exports. Managed code has no concept
of a consistent value for a function
pointer because these function
pointers are proxies that are built
dynamically.
Which means, again, to monitor things that go on outside your application's view, you need to set a global hook, which can't be written in .NET.

Answer 2

I have exactly the same issue as this, and I think I have a workable solution. Initially I looked into a similar option to the one mentioned by 'tylerl'. In my case however, instead of using 'SetWindowsHookEx', I attempted to use the similar function 'RegisterShellHookWindows'.
Unfortunately, this only succeeded in providing me with notifications of when a subset of windows are created/destroyed. The only windows which it provided notifications for are those shown on the taskbar.
Since I didn't fancy hacking into other processes, or writing the native code which would be required for SetWindowHookEx, I tried digging into the .NET automation APIs introduced in .NET 4.0, and I think this has the answer to your problem (at least as far as detecting when windows are opened / closed).
Here's a code snippet for using this API to detect windows being opened/closed:
using System.Windows.Automation;
private void StartMonitoringForWindowEvents()
{
Task.Factory.StartNew(() =>
{
AutomationEventHandler windowOpenedHandler = new AutomationEventHandler(OnWindowOpened);
System.Windows.Automation.Automation.AddAutomationEventHandler(
WindowPattern.WindowOpenedEvent, AutomationElement.RootElement,
TreeScope.Descendants, windowOpenedHandler);
});
}
private void OnWindowOpened(object source, AutomationEventArgs eventArgs)
{
try
{
AutomationElement sourceElement = (AutomationElement)source;
string message = string.Format(
"Automation.WindowOpened PID: {0}, Handle: {1}, Name:{2}",
sourceElement.Current.ProcessId,
sourceElement.Current.NativeWindowHandle,
sourceElement.Current.Name);
Debug.WriteLine(message);
// for each created window, register to watch for it being closed
RegisterForClosedWindowEvent(sourceElement);
}
catch
{
}
}
private void RegisterForClosedWindowEvent(AutomationElement element)
{
try
{
string elementName = element.Current.Name;
int processId = element.Current.ProcessId;
int nativeHandle = element.Current.NativeWindowHandle;
AutomationEventHandler windowClosedHandler = new AutomationEventHandler(
(ignoreSource, ignoreArgs) => OnWindowClosed(nativeHandle, processId, elementName));
System.Windows.Automation.Automation.AddAutomationEventHandler(
WindowPattern.WindowClosedEvent, element,
TreeScope.Element, windowClosedHandler);
}
catch
{
}
}
private void OnWindowClosed(int nativeHandle, int processId, string elementName)
{
string message = string.Format(
"Automation.WindowClosed PID: {0}, Handle: {1}, Name:{2}",
processId,
nativeHandle,
elementName);
Debug.WriteLine(message);
}
You will need to add a reference to the assemblies 'UIAutomationClient' and 'UIAutomationClientTypes'.
Here's a link to the MSDN documentation (you'll probably particularly want to take a look at the information on events):
http://msdn.microsoft.com/en-us/library/ms747327.aspx
Important implementation Notes:
1.) Notice that in the sample, I used a task factory to register for reception of the automation events. It's particularly important to avoid using the UI thread when registering for automation events or generally interacting with the automation APIs. Doing so can (and usually quickly does) result in a deadlock. Therefore, I use the task factory to ensure registration is done via the thread pool.
This also means, that the events will be received on the thread pool... So, if you need to perform any UI updates, you will have to marshal these across to the UI thread.
2.) You'll also note, that I capture any needed information on the element which may be closed, at the time of registration (using a closure). This is because, once the element is closed, we will no longer have access to this information - since the element has been destroyed.
Phil

Answer 3

The answer is not C# (or .Net) specific. You'll need to call SetWindowsHookEx( WH_CBT, ... ). This will allows to know when a window is created, destroyed, moved, sized, etc. You'll also need to get the relevant information from the window to identify if its one you need to do something about. Perhaps GetClassInfo, GetWindowLong, and GetWindowText.
The problem with the SetWindowsHookEx is that in order to get events from every window you need to have a separate win32 dll with the function in question exported. Although you might have success with the procedure outlined here.

Answer 4

To expand upon Joel Lucsy's answer, you need to use the Win32 API. However, there's a nice library, the Managed Windows API, that provides an object-oriented wrapper over common APIs. It may have what you need.