How does delphi determine if the application is not responding?

Today, I saw two articles in the core discussion group of MSN, discussing whether the application did not respond. The original Article is as follows:

> How is it possible to determine a process is "not responding" like nt task
> Manager Do?
The heuristic works only for GUI processes, and consists of calling
Sendmessagetimeout () with smto_abortifhung.

> There is any API call to do the job, or this status is simply a deduction
> Based on Process counters, like that 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. of course, I also have an unmarshented function here, which is another solution. nt and 9x have a user32.dll function, ishungappwindow (NT) and ishungthread (9x ). easy to use. the prototype is given below.
Bool ishungappwindow (
Hwnd, // handle to main app's window
);

Bool ishungthread (
DWORD dwthreadid, // The thread's identifier of the main app's window
);
With the prototype, you don't need any explanation. It's too bad. :) However, you need to call the function in getprocaddress. The Library does not have this function.
****************************************
Check whether an application (window) is not responding?

{1. The specified ented way}

{
An application can check if a window is responding to messages
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 unencrypted ented 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
Determine if the target application is responding but CILS
Uninitialized ented functions from the user32.dll.

--> For 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)
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
User32.lib for these functions, so we shoshould load them dynamically using
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 ('recorct 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;