Print2eDoc
Convert any document to PDF, BMP, TIFF, JPEG, PNG...

Compatibility

Windows Vista Windows XP Windows 2000

Home » Newsletter » June 2008

By Mallika

In Version 1.05, Print2eDoc introduced support for Windows messages.

Or, rather the Print2eDoc application generated certain Windows messages that were broadcast to all applications and a programmer could create an application in Delphi, VB, or VC++ to track these messages.

By tracking these messages, the application would be able to know the status of Print2eDoc printer at any moment in time.

Print2eDoc sends the following messages:

1. PRINT2EDOC_BEGINDOC - when a conversion job begins
2. PRINT2EDOC_PROCESSPAGE - when a page is about to be rendered in the output document
3. PRINT2EDOC_PRINTPAGE - when a page is being rendered in the output document
4. PRINT2EDOC_ENDDOC - when a particular conversion job has ended
5. PRINT2EDOC_ABORT - when a particular conversion job is aborted

If an application needs to monitor these messages, it must call the Windows API RegisterWindowMessage() function. This function returns the unique ID that was generated when Print2eDoc registered the messages.

UINT RegisterWindowMessage(
  LPCTSTR lpString   // message string
);

Then, the application should call the function IsDialogMessage() in a loop to check if the messages it receives are from Print2eDoc.

BOOL IsDialogMessage(
  HWND hDlg,   // handle to dialog box
  LPMSG lpMsg  // message to be checked
);

The lpMsg argument is a pointer to a MSG structure that will contain the message details.

typedef struct tagMSG {
  HWND   hwnd; 
  UINT   message; 
  WPARAM wParam; 
  LPARAM lParam; 
  DWORD  time; 
  POINT  pt; 
} MSG, *PMSG;

The message member of the MSG structure can be compared with message identifier returned by RegisterWindowMessage() to see if the message processed by IsDialogMessage() comes from Print2eDoc.

With the PRINT2EDOC_PROCESSPAGE message, the page number is sent with the wParam parameter. With the PRINT2EDOC_PRINTPAGE message, the page number is sent with the wParam parameter and the total page count with the lParam. With the PRINT2EDOC_ENDDOC message, the total page count is again sent with the lParam parameter.

In Delphi, you can use the function AllocateHWnd(Method: TWndMethod) to specify a form procedure that will process all messages.

Application.ProcessMessages;
FMessageWndHandle := AllocateHWnd(WinProc);

The specified procedure then needs to check if its TMessage argument is equal to any of the message identifiers provided by the RegisterWindowMessage() function.

WM_PRINT2EDOC_BEGINDOC := 
  RegisterWindowMessage('PRINT2EDOC_BEGINDOC');
WM_PRINT2EDOC_PROCESSPAGE := 
  RegisterWindowMessage('PRINT2EDOC_PROCESSPAGE');
WM_PRINT2EDOC_ENDDOC := 
  RegisterWindowMessage('PRINT2EDOC_ENDDOC');
WM_PRINT2EDOC_PRINTPAGE := 
  RegisterWindowMessage('PRINT2EDOC_PRINTPAGE');
WM_PRINT2EDOC_ABORT := 
  RegisterWindowMessage('PRINT2EDOC_ABORT');

...
// This procedure checks if the message it receives
// comes from Print2eDoc and if it is from 
// Print2eDoc, then it adds more information obtained 
// from the message to a list box.
procedure TfrmEventDemo.WinProc(var Mssg: TMessage);
begin
  try
    with Mssg do
    begin
      // Check if the message was sent by Print2eDoc
      if Msg = WM_PRINT2EDOC_BEGINDOC then
      begin
        SetLength(str, MAX_PATH);
        Length := 
           GlobalGetAtomName(wParam, PAnsiChar(str), MAX_PATH);
        SetLength(str, Length);
        lstStatus.Items.Add('Beginning to print ' + str );
      end
      else if Msg = WM_PRINT2EDOC_ENDDOC then
      begin
        lstStatus.Items.Add('Finished printing ' + str);
      end
      else if Msg = WM_PRINT2EDOC_PRINTPAGE then
      begin
        lstStatus.Items.Add(
                'Printing '+ 
                IntToStr(WParam) + 
                ' of '+ IntToStr(LParam) + 
                ' pages of ' + 
                str);
      end
    end;
  except on E:Exception do;
end

In Version 1.1, we added support for using the GlobalGetAtomName() for retrieving the name of the output file.

---o0O0o---

Downloads:

• Sample project in Delphi