Or, in powershell

src/tools/scratch/focus-logger.ps1

@@ -0,0 +1,55 @@
+Add-Type @"
+  using System;
+  using System.Runtime.InteropServices;
+  public class Win32 {
+    [DllImport("user32.dll")]
+    public static extern IntPtr GetForegroundWindow();
+    [DllImport("user32.dll")]
+    public static extern uint GetWindowThreadProcessId(IntPtr hWnd, out uint lpdwProcessId);
+  }
+"@
+
+function Get-ForegroundWindow {
+  [System.IntPtr]$handle = [Win32]::GetForegroundWindow()
+  return $handle
+}
+
+function Get-ProcessFromWindowHandle {
+  param(
+    [System.IntPtr]$hwnd
+  )
+
+  $p = 0
+  [Win32]::GetWindowThreadProcessId($hwnd, [ref]$p)
+  if ($p -ne 0) {
+    $process = Get-Process -Id $p -ErrorAction SilentlyContinue
+    if ($process) {
+      return $process
+    }
+  }
+
+  return $null
+}
+
+$processId = (Get-Process -Id $pid).Id
+$processName = (Get-Process -Id $pid).ProcessName
+Write-Host "Current process: $processName"
+$hwnd = 0;
+
+while ($true) {
+
+  $hwndNew = Get-ForegroundWindow;
+
+
+  if ($hwndNew -ne $hwnd) {
+    $hwnd = $hwndNew
+    $processIdNew = (Get-ProcessFromWindowHandle $hwnd).Id
+
+    if ($processIdNew -ne $processId) {
+      $processId = $processIdNew
+      $processName = (Get-Process -Id $processId -FileVersionInfo).FileName
+      Write-Host "Current process: $processName"
+    }
+  }
+  Start-Sleep -Milliseconds 100
+}

src/tools/scratch/main.cpp

@@ -2,9 +2,66 @@
 // Licensed under the MIT license.
 
 #include <windows.h>
+#include <iostream>
+#include <string>
+#include <psapi.h>
 
 // This wmain exists for help in writing scratch programs while debugging.
 int __cdecl wmain(int /*argc*/, WCHAR* /*argv[]*/)
 {
+    HWND hwnd = GetForegroundWindow();
+    DWORD pid;
+    GetWindowThreadProcessId(hwnd, &pid);
+
+    HANDLE hProcess = OpenProcess(PROCESS_QUERY_INFORMATION | PROCESS_VM_READ, FALSE, pid);
+    if (hProcess == NULL)
+    {
+        std::cerr << "Failed to open process." << std::endl;
+        return 1;
+    }
+
+    wchar_t processName[MAX_PATH];
+    if (GetModuleFileNameExW(hProcess, NULL, processName, MAX_PATH) == 0)
+    {
+        std::cerr << "Failed to get module file name." << std::endl;
+        CloseHandle(hProcess);
+        return 1;
+    }
+
+    wprintf(L"Current process: %s\n", processName);
+    while (true)
+    {
+        HWND hwndNew = GetForegroundWindow();
+        if (hwndNew != hwnd)
+        {
+            hwnd = hwndNew;
+            DWORD pidNew;
+            GetWindowThreadProcessId(hwnd, &pidNew);
+
+            if (pidNew != pid)
+            {
+                pid = pidNew;
+                CloseHandle(hProcess);
+                hProcess = OpenProcess(PROCESS_QUERY_INFORMATION | PROCESS_VM_READ, FALSE, pid);
+                if (hProcess == NULL)
+                {
+                    std::cerr << "Failed to open process." << std::endl;
+                    return 1;
+                }
+
+                if (GetModuleFileNameExW(hProcess, NULL, processName, MAX_PATH) == 0)
+                {
+                    std::cerr << "Failed to get module file name." << std::endl;
+                    CloseHandle(hProcess);
+                    return 1;
+                }
+
+                wprintf(L"Current process: %s\n", processName);
+            }
+        }
+        Sleep(100);
+    }
+
+    CloseHandle(hProcess);
     return 0;
 }