Find the Current Windows Application

Question

I'm trying to write what I hope is a simple application tracker. That is, whenever a new application starts, or a running application becomes current, I want to note the event and start timing it's time "on top".

I have code that lists all the current applications that are running, and some code that tells me the top window (always my test console app, naturally).

What I think I'm missing is the Windows event stream to monitor or something.

I'm using .NET (C# preferred).

Any hints, tips or cheats available?

Thanks - Jonathan

Answer 1

I'm not sure if there's a way to hook a Windows event, but simply polling System.Diagnostics.Process.GetProcesses() at regular intervals (say, 100ms) and looking for new/removed processes (comparing by process ID) should do the job. Also, Process.StartTime will give you the time at which the process began.

Caveat: This method may be require a higher amount of processing compare an event-based method (none of which I am aware). Processes that start and end between each poll will not be observed, but this ought to be quite rare indeed for a reasonably high polling frequency (and perhaps you do not even care about these processes anyway). Saying this, these are minor detractions, and I would recommend you at least test this solution as it is fairly simple.

Answer 2

I think the best way to do this would be using windows "hooks" (i.e. SetWindowsHookEx). These allow you to hook in to windows core functionality, specifically there is one called WH_CALLWNDPROC which calls a user function any time any window in the system receives a message.

You could use this to globally listen for messages that bring a window to the foreground, and/or messages for user interaction (mouse, keyboard).

However, this is a raw Windows API function primarily meant for use in a C/C++ windows DLL. You can implement it in C#, but that is a can of worms you may not want to open. But opening it would probably be the best way of doing what you're asking.

Answer 3

This is increasingly a SO problem, the down-voted answer is the correct one. SetWindowsHookEx() is indeed required to be able to catch the WM_ACTIVATE message that the activated window gets. But that requires a WH_CALLWNDPROC or WH_SHELL hook, hooks that cannot be implemented in C#. Catching those requires injecting a DLL in every process, a managed assembly cannot be injected into another process. The CLR cannot be initialized.

+1 for Noldorin to get him back to 0, that's all I can do. The OP needs to write his code in unmanaged C/C++, creating a DLL and use a standard IPC mechanism like pipes or sockets to notify the host app. Or poll, much easier.

Answer 4

I once wrote a small app that did this to keep track of my own work habits. What I did was call GetForegroundWindow() periodically (every 5 seconds or something) and noted the application that is running. You can get a lot of information from the window handle, not just the title but all the way down to the actual process that created it.

Answer 5

This is what I did using Java's JNA:

final HWND child = User32Ext.INSTANCE.GetForegroundWindow();
final int length = User32.INSTANCE.GetWindowTextLength(child) * 2;
final byte[] buffer = new byte[length];
User32.INSTANCE.GetWindowText(child, buffer, length);
title = new String(buffer, Charset.forName("UTF-16LE"));

where User32Ext is an extension I did because User32 (in JNA's distribution) doesn't have the interface for:

LRESULT callback(int nCode, WPARAM wParam, LPARAM lParam);

I'm periodically polling the active window, since I couldn't use the HCBT_SETFOCUS hook as mentioned in http://msdn.microsoft.com/en-us/library/ms997537.aspx, and I'll be very interested if someone comes up with the solution.

Answer 6

Hulk's idea sounds great.

Hulk, please post a link to the documentation or name the specific function. Googling for "win32 creation notification" gives unrelated links (about windows non-genuine notification).

Thank you.