在EXE中调用就可以,为什么在dll中调用Synchronize(Owner.NotifyStartDoc)就不行?这句到底起什么作用?(100分)

我正在用APRO控件写一个传真软件,由于在DLL中需把一些DOC或XLS文件等转换为APF格式文件,所以需用到虚拟打印机,并且在DLL中需指定输出文件路径.输出文件用ApdFaxDriverInterface1.FileName=OutFile指定.而ApdFaxDriverInterface在AdFaxCtl中定义.AdFaxCtl内容如下:
unit AdFaxCtl;
{- Controller component for printer drivers.}
interface

uses
WinTypes,
WinProcs,
Messages,
SysUtils,
Classes,
Graphics,
Controls,
Forms,
Dialogs,
OOMisc;

type
TApdFaxDriverInterface = class;

{Thread for monitoring messages from the NT driver}
TMonitorThread = class(TThread)
Owner : TApdFaxDriverInterface; {Link to component}
Pipe : THandle; {Connection with driver}
Overlapped : TOverlapped; {Used to control overlapped i/o}
Semaphore : THandle; {Used for sync. with driver}
Events : array[0..1] of THandle;
// Stop & Overlapped finished - array used for WaitForMultiple...
procedure Execute; override;
end;

TApdFaxDriverInterface = class(TApdBaseComponent)
private
fFileName,
fDocName : string;
fOnDocStart,
fOnDocEnd : TNotifyEvent;

MonitorThread : TMonitorThread;
SecDesc : TSecurityDescriptor;
SecAttr : TSecurityAttributes;

FWindowHandle : HWND;
protected
procedure WndProc(var Msg: TMessage);
procedure NotifyStartDoc; virtual;
procedure NotifyEndDoc; virtual;
public
constructor Create(AOwner : TComponent); override;
destructor Destroy; override;
property DocName : string read fDocName;
published
property FileName : string read fFileName write fFileName;
property OnDocStart: TNotifyEvent read fOnDocStart write fOnDocStart;
property OnDocEnd: TNotifyEvent read fOnDocEnd write fOnDocEnd;
end;

implementation

procedure TMonitorThread.Execute;
{- Monitor thread. Looks for "events" coming through the pipe from the driver.}
var
Wait, BytesRead, BytesWritten : DWord;
InBuffer,OutBuffer : TPipeEvent;
Res : Bool;
begin
repeat
fillchar(Overlapped,sizeof(Overlapped),0);
Overlapped.hEvent := Events[1];
ResetEvent(Events[1]);

ConnectNamedPipe(Pipe, @Overlapped); // wait for driver to send something

if GetLastError = ERROR_IO_PENDING then begin
Wait := WaitForMultipleObjects(2, @Events, FALSE, INFINITE);
if Wait <> WAIT_OBJECT_0+1 then // not overlapped i/o event - error occurred,
break; // or stop signaled
end;

fillchar(Overlapped,sizeof(Overlapped),0);
Overlapped.hEvent := Events[1];
ResetEvent(Events[1]);

Res := ReadFile(
Pipe,
InBuffer,
sizeof(InBuffer),
BytesRead,
@Overlapped);

if not Res and (GetLastError = ERROR_IO_PENDING) then
begin
Wait := WaitForMultipleObjects(2, @Events, False, Infinite);
if Wait <> WAIT_OBJECT_0+1 then // not overlapped i/o event - error occurred,
Break; // or stop signaled
GetOverlappedResult(Pipe,Overlapped,BytesRead,False);
end;

if BytesRead > 0 then begin
case InBuffer.Event of
eNull : ;
eStartDoc :
begin
Owner.fDocName := InBuffer.Data;
[red]Synchronize(Owner.NotifyStartDoc);[/red] end;
eEndDoc :
begin
[red][blue]Synchronize(Owner.NotifyEndDoc);[/blue][/red] end;
else
raise Exception.CreateFmt('Unknown incoming event encountered:%d',[InBuffer.Event]);
end;

case InBuffer.Event of
eStartDoc :
begin
fillchar(Overlapped,sizeof(Overlapped),0);
Overlapped.hEvent := Events[1];
ResetEvent(Events[1]);

OutBuffer.Event := eSetFileName;
OutBuffer.Data := Owner.FileName;

Res := WriteFile(
Pipe,
OutBuffer,
sizeof(OutBuffer),
BytesWritten,
@Overlapped);

if not Res and (GetLastError() = ERROR_IO_PENDING) then begin
Wait := WaitForMultipleObjects(2, @Events, FALSE, INFINITE);
if Wait <> WAIT_OBJECT_0+1 then // not overlapped i/o event - error occurred,
Break; // or stop signaled
end;
end;
end;
end;

DisconnectNamedPipe(Pipe);
until false;
Suspend;
end;

function IsWinNT : Boolean;
{- Are we running under Windows NT}
var
Osi : TOSVersionInfo;
begin
Osi.dwOSVersionInfoSize := sizeof(Osi);
GetVersionEx(Osi);
Result := (Osi.dwPlatformID = Ver_Platform_Win32_NT);
end;

constructor TApdFaxDriverInterface.Create;
begin
inherited Create(AOwner);
fFileName := ApdDefFileName;
fDocName := '';
if csDesigning in ComponentState then exit;
if IsWinNT then
begin {32-bit (NT) driver communicates via a named pipe}
MonitorThread := TMonitorThread.Create(True); // Suspended
try
MonitorThread.Owner := Self;
with MonitorThread do begin
{Create security descriptor for pipe}
if not InitializeSecurityDescriptor(@SecDesc, 1) then
raise Exception.Create('Unable to initialize security descriptor');

if not SetSecurityDescriptorDacl(@SecDesc, True, nil, False) then
raise Exception.Create('Unable to set security DACL');

{Create security attributes record for the pipe}
SecAttr.nLength := sizeof(SecAttr);
SecAttr.lpSecurityDescriptor := @SecDesc;
SecAttr.bInheritHandle := True;

{Create pipe that the driver can communicate through}
Pipe := INVALID_HANDLE_VALUE;
Pipe := CreateNamedPipe(
ApdPipeName,
FILE_FLAG_OVERLAPPED or
PIPE_ACCESS_DUPLEX, // pipe open mode
PIPE_TYPE_MESSAGE or
PIPE_READMODE_MESSAGE or
PIPE_WAIT, // pipe IO type
1, // number of instances
sizeof(TPipeEvent), // size of outbuf (0 = allocate as necessary)
sizeof(TPipeEvent), // size of inbuf
ApdPipeTimeout, // default time-out value
@SecAttr); // security attributes

if (Pipe = INVALID_HANDLE_VALUE) or (Pipe = 0) then
raise Exception.CreateFmt('Unable to create named pipe. Error:%d',[GetLastError]);
try
{Create events to signal Overlapped i/o and Stop.}
Events[0] := CreateEvent(nil,true,False,nil);
if Events[0] = 0 then
raise Exception.Create('Unable to create event');
try
Events[1] := CreateEvent(nil,true,False,nil);
if Events[1] = 0 then
raise Exception.Create('Unable to create event');
try

{Start monitor thread}
Resume;

{Check if we were started by driver}
Semaphore := OpenSemaphore(EVENT_ALL_ACCESS, False, ApdSemaphoreName);
if Semaphore <> 0 then
begin
if not ReleaseSemaphore(Semaphore, 1, nil) then //tell driver to continue
raise Exception.Create('Unable to release semaphore');
end
else {No, so...}
{Block driver from auto-starting another instance of us}
Semaphore := CreateSemaphore(nil, 0, 1, ApdSemaphoreName);

except
CloseHandle(Events[1]);
raise;
end;
except
CloseHandle(Events[0]);
raise;
end;
except
CloseHandle(MonitorThread.Pipe);
raise;
end;
end;
except
raise;
end;
end
else
begin {16-bit driver communicates via messages}
FWindowHandle := AllocateHWnd(WndProc);
if FWindowHandle = 0 then
raise Exception.Create('Unable to create &quot;pipe&quot; window');
SetWindowText (FWindowHandle, ApdPipeName);
end;
end;

destructor TApdFaxDriverInterface.Destroy;
begin
fFileName := '';
fDocName := '';
if not (csDesigning in ComponentState) then begin
if IsWinNT then
with MonitorThread do begin
if not Suspended then begin
SetEvent(Events[0]); // tell monitor thread to terminate
while not Suspended do; // wait for it to do so before we pull the carpet
end;
CloseHandle(Events[0]);
CloseHandle(Events[1]);
CloseHandle(MonitorThread.Pipe);
if Semaphore <> 0 then
CloseHandle(Semaphore);
Free;
end
else
DeallocateHWnd(FWindowHandle);
end;
inherited Destroy;
end;

procedure TApdFaxDriverInterface.NotifyStartDoc;
begin
if Assigned(fOnDocStart) then
fOnDocStart(Self);
end;

procedure TApdFaxDriverInterface.NotifyEndDoc;
begin
if Assigned(fOnDocEnd) then
fOnDocEnd(Self);
end;

procedure TApdFaxDriverInterface.WndProc(var Msg: TMessage);
{- Window procedure for the 16-bit driver comm. window}
var
JobNameBuffer : array[0..255] of char;
begin
with Msg do
if Msg = apw_BeginDoc then
try
GetWindowText(FWindowHandle,JobNameBuffer,sizeof(JobNameBuffer));
fDocName := StrPas(JobNameBuffer);
NotifyStartDoc;
fFileName[length(fFileName)+1] := #0;
SetWindowText(FWindowHandle,@fFileName[1]);
except
Application.HandleException(Self);
end
else
if Msg = apw_EndDoc then
try
NotifyEndDoc;
except
Application.HandleException(Self);
end
else
Result := DefWindowProc(FWindowHandle, Msg, wParam, lParam);
end;

end.
而我的当前DLL是调用一个Convert.dll文件来进行文件格式转换,调用代码如下:
function ConvertFiletoApf(InFile,OutFile:string):Boolean;
type
ConvDll=function (InFile,OutFile,AppPathchar;DelifExist:Boolean;PrintNamechar):Boolean;stdcall;
var
CfgFile:String;
ApdFaxDriverInterface1:TApdFaxDriverInterface;
Inifile:TInifile;
FreeAfterSec:integer;
begin
Result:=False;
DllHandle:=LoadLibrary('Convert.dll');
if DllHandle>32 then
begin
try
begin
CfgFile:=DllAppPath+'Config.ini';
frmNewMain.Caption:=CfgFile;
ApdFaxDriverInterface1:=TApdFaxDriverInterface.Create(Application);
ApdFaxDriverInterface1.FileName:=OutFile;
Dllfarproc:=GetProcAddress(DllHandle,'ConvertFiletoApf'); //获取函数入口
if DllfarProc<>Nil then
Result:=ConvDll(Dllfarproc)(Pchar(InFile),Pchar(OutFile),'F:/我的程序/传真系统/',True,'APF Fax Printer');
end;
finally
Inifile:=TInifile.Create(CfgFile);
FreeAfterSec:=Inifile.ReadInteger('ApdFaxDriverInterface','Free',30);
CountSec:=0;
frmNewMain.Timer1.Enabled :=True;
While CountSec<FreeAfterSec do
begin
frmNewMain.Caption :=InttoStr(CountSec);
Application.ProcessMessages;
end;
frmNewMain.Timer1.Enabled :=False;
ApdFaxDriverInterface1.Free; //每次执行到这步时就停止响应,经调试发现,执行到 AdFaxCtl单元的Synchronize(Owner.NotifyStartDoc);就停止响应.如果把这个调用过程放在EXE程序中,则一切运行正常.
Freelibrary(DllHandle);
end;
end
else
MessageDlg('调用Convert.Dll，请确定动态库文件是否存在！', mtError, [mbOK], 0);
end;
同样的调用DLL的过程,在EXE中就一切正常,而在DLL中调用就停止响应,Synchronize(Owner.NotifyStartDoc);在AdFaxCtl当中到底起什么作用,这种情况该如何修改?

内容太长,希望各位能耐心的帮我出出主意.谢谢各位了.