How Delphi determines that the application is not responding

There are two articles on MSN's core discussion group today. The discussion is whether the application is unresponsive. The original text is as follows:

> How was it possible to determine a process was "not responding" like NT Task
> Manager do?
The heuristic works only for GUI processes, and consists of calling
SendMessageTimeout () with Smto_abortifhung.

>there is an any API for the job, or this status is simply a deduction
>based on process counters, like this returned from call to Getprocesstimes
>api function?

Use SendMessageTimeout with a value of wm_null. That's all Task
Manager does to determine this AFAIK.

--
Rational and rational. Of course, I have a undocumented function here, but other solutions, NT and 9X have a USER32.DLL function, Ishungappwindow (NT) and Ishungthread (9X). It's incredibly easy to use. The prototype is given below.
BOOL Ishungappwindow (
HWND hwnd,//Handle to main app ' s window
);

BOOL Ishungthread (
DWORD dwThreadID,//The thread ' s identifier of the main app ' s window
);
With prototypes, there's no need for explanations.:) However, the call requires GetProcAddress. The function is not in the library.
****************************************
Check whether an application (window) isn't responding?

{1. The documented-i}

{
An application can check if a window was 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. EXE}
ShowMessage (' App. Responding ');
End

{2. The undocumented-i}

{
Translated form C to Delphi by Thomas Stutz
Original Code:
(c) 1999 Ashot Oganesyan K, Smartline, INC
Mailto:[email protected], 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.

--Windows 95/98/me We call the Ishungthread () 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 NT/2000/XP the Ishungappwindow () 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 Word 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

How Delphi determines that the application is not responding