Author: Tomas Rutkauskas

Does anyone have an example of using CopyFileEx with a CopyProgressRoutine? I have 
created a function that takes the same parameters as the CopyProgressRoutine, but 
when I pass it using @ or Addr() I get a Variable Required error message.

Answer:

Let's assume you call CopyFileEx and want the callback to update a progress bar. 
The callback cannot be an objects method but you can use the lpData parameter of 
CopyFileEx to pass any kind of data to the callback, e.g. a form reference. So, if 
you want to serve a progress form in the callback that would look like this 
(untested !):

1   type
2     TProgressForm = class(TForm)
3       AbortButton: TButton;
4       ProgressBar: TProgressBar;
5       procedure AbortButtonClick(Sender: TObject);
6     private
7       { Private declarations }
8     public
9       { Public declarations }
10      FCancel: BOOL;
11    end;
12    {form has fsStayOnTop formstyle!}
13  
14  implementation
15  
16  {$R *.DFM}
17  
18  procedure TProgressForm.AbortButtonClick(Sender: TObject);
19  begin
20    FCancel := True;
21  end;
22  
23  {Note: could use int64 instead of COMP, but that would make this D4 specific}
24  
25  function CopyCallback(TotalFileSize, TotalBytesTransferred, StreamSize,
26    StreamBytesTransferred: COMP; dwStreamNumber, dwCallbackReason: DWORD;
27    hSourceFile, hDestinationFile: THandle; progressform: TProgressForm): DWORD; 
28  stdcall;
29  var
30    newpos: Integer;
31  begin
32    Result := PROCESS_CONTINUE;
33    if dwCallbackReason = CALLBACK_CHUNK_FINISHED then
34    begin
35      newpos := Round(TotalBytesTransferred / TotalFileSize * 100);
36      with progressform.Progressbar do
37        if newpos <> Position then
38          Position := newpos;
39      Application.ProcessMessages;
40    end;
41  end;
42  
43  function DoFilecopy(const source, target: string): Boolean;
44  var
45    progressform: TProgressForm;
46  begin
47    progressform := TProgressform.Create;
48    try
49      progressform.Show;
50      Application.ProcessMessages;
51      Result := CopyFileEx(PChar(source), PChar(target), @CopyCallback,
52  		 Pointer(progressform), @progressform.FCancel, 0);
53    finally
54      progressform.Hide;
55      progressform.free;
56    end;
57  end;