Question

Well Sometimes I am typing and very rarely it happens that something steals focus, I read some solution (even a VB watch) but they don’t apply to me. Is there any windows-wide ‘handle’ which handles ANY focus changes?

It doesn’t matter in which language, C, C++, VB.NET, C#, Anything .NET or windows related, Batch, PoweShell, VBS Script… As Long as I am able to monitor every focus change and log it into a file/cmd window/visual window.

Something like:

   void event_OnWindowsFocusChange(int OldProcID, int NewProcID);

would be very usefull. Or maybe there are tools for this already (which I can’t find?)

Answer 1

One way would be to use the windows UI Automation API. It exposes a global focus changed event. Here is a quick sample I came up with (in C#). Note, you need to add references to UIAutomationClient and UIAutomationTypes.

using System.Windows.Automation;
using System.Diagnostics;

namespace FocusChanged
{
    class Program
    {
        static void Main(string[] args)
        {
            Automation.AddAutomationFocusChangedEventHandler(OnFocusChangedHandler);
            Console.WriteLine("Monitoring... Hit enter to end.");
            Console.ReadLine();
        }

        private static void OnFocusChangedHandler(object src, AutomationFocusChangedEventArgs args)
        {
            Console.WriteLine("Focus changed!");
            AutomationElement element = src as AutomationElement;
            if (element != null)
            {
                string name = element.Current.Name;
                string id = element.Current.AutomationId;
                int processId = element.Current.ProcessId;
                using (Process process = Process.GetProcessById(processId))
                {
                    Console.WriteLine("  Name: {0}, Id: {1}, Process: {2}", name, id, process.ProcessName);
                }
            }
        }
    }
}