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// 1. The Documented way
 
{
  An application can check if a window is responding to messages by
  sending the WM_NULL message with the SendMessageTimeout function.
}
 
function AppIsResponding(ClassName: string): Boolean;
const
  { Specifies the duration, in milliseconds, of the time-out period }
  TIMEOUT = 50;
var
  Res: DWORD;
  h: HWND;
begin
  h := FindWindow(PChar(ClassName), nil);
  if h <> 0 then
    Result := SendMessageTimeOut(H,
      WM_NULL,
      0,
      0,
      SMTO_NORMAL or SMTO_ABORTIFHUNG,
      TIMEOUT,
      Res) <> 0
  else
    ShowMessage(Format('%s not found!', [ClassName]));
end;
 
procedure TForm1.Button1Click(Sender: TObject);
begin
  if AppIsResponding('OpusApp') then
    { OpusApp is the Class Name of WINWORD }
    ShowMessage('App. responding');
end;

// 2. The Undocumented way
 
{
  // Translated form C to Delphi by Thomas Stutz
  // Original Code:
  // (c)1999 Ashot Oganesyan K, SmartLine, Inc
  // mailto:ashot@aha.ru, http://www.protect-me.com, http://www.codepile.com
 
 The code doesn't use the Win32 API SendMessageTimout function to
 determine if the target application is responding but calls
 undocumented functions from the User32.dll.
 
 --> For NT/2000/XP the IsHungAppWindow() API:
 
 The function IsHungAppWindow retrieves the status (running or not responding)
 of the specified application
 
 IsHungAppWindow(Wnd: HWND): // handle to main app's window
 BOOL;
 
 --> For Windows 95/98/ME we call the IsHungThread() API
 
 The function IsHungThread retrieves the status (running or not responding) of
 the specified thread
 
 IsHungThread(DWORD dwThreadId): // The thread's identifier of the main app's window
 BOOL;
 
 Unfortunately, Microsoft doesn't provide us with the exports symbols in the
 User32.lib for these functions, so we should load them dynamically using the
 GetModuleHandle and GetProcAddress functions:
}
 
// For Win9X/ME
function IsAppRespondig9X(dwThreadId: DWORD): Boolean;
type
  TIsHungThread = function(dwThreadId: DWORD): BOOL; stdcall;
var
  hUser32: THandle;
  IsHungThread: TIsHungThread;
begin
  Result := True;
  hUser32 := GetModuleHandle('user32.dll');
  if (hUser32 > 0) then
  begin
    @IsHungThread := GetProcAddress(hUser32, 'IsHungThread');
    if Assigned(IsHungThread) then
    begin
      Result := not IsHungThread(dwThreadId);
    end;
  end;
end;
 
// For Win NT/2000/XP
function IsAppRespondigNT(wnd: HWND): Boolean;
type
  TIsHungAppWindow = function(wnd:hWnd): BOOL; stdcall;
var
  hUser32: THandle;
  IsHungAppWindow: TIsHungAppWindow;
begin
  Result := True;
  hUser32 := GetModuleHandle('user32.dll');
  if (hUser32 > 0) then
  begin
    @IsHungAppWindow := GetProcAddress(hUser32, 'IsHungAppWindow');
    if Assigned(IsHungAppWindow) then
    begin
      Result := not IsHungAppWindow(wnd);
    end;
  end;
end;
 
function IsAppRespondig(Wnd: HWND): Boolean;
begin
 if not IsWindow(Wnd) then
 begin
   ShowMessage('Incorrect window handle!');
   Exit;
 end;
 if Win32Platform = VER_PLATFORM_WIN32_NT then
   Result := IsAppRespondigNT(wnd)
 else
   Result := IsAppRespondig9X(GetWindowThreadProcessId(Wnd,nil));
end;
 
// Example: Check if Word is hung/responding
 
procedure TForm1.Button3Click(Sender: TObject);
var
  Res: DWORD;
  h: HWND;
begin
  // Find Winword by classname
  h := FindWindow(PChar('OpusApp'), nil);
  if h <> 0 then
  begin
    if IsAppRespondig(h) then
      ShowMessage('Word is responding!')
    else
      ShowMessage('Word is not responding!');
  end
  else
    ShowMessage('Word is not open!');
end;

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