John Barrat wrote:
> Steve – thanks for the input, however, I have implemented more
> or less what you suggest although not as a class.
>
> What I don’t understand is that it works in one application
> when it’s at Main form yet it won’t when it is a secondary form
> called up as a modal dialog.
>
> This is the code I have used:
>
> in the interface bit….
>
> public
> { Public declarations }
> procedure AcceptFiles( var msg : TMessage );
> message WM_DROPFILES;
>
> and in the implementation….
>
> procedure TfmAddLib.FormCreate(Sender: TObject);
> begin
> DragAcceptFiles(LstFiles.Handle, True);
> end;
>
> procedure TfmAddLib.AcceptFiles(var msg : TMessage);
> const
> cnMaxFileNameLen = 255;
> var
> i,
> nCount : integer;
> acFileName : array [0..cnMaxFileNameLen] of char;
> begin
> // find out how many files we're accepting
> nCount := DragQueryFile( msg.WParam,
> $FFFFFFFF,
> acFileName,
> cnMaxFileNameLen );
> // query Windows one at a time for the file name
> for i := 0 to nCount-1 do
> begin
> DragQueryFile( msg.WParam, i,
> acFileName, cnMaxFileNameLen );
> if CheckFileType(acFileName)
> And (lstFiles.Items.IndexOf(acFileName) = -1) then
> LstFiles.Items.Add(acFileName);
> end;
>
> // let Windows know that you're done
> DragFinish( msg.WParam );
> end;
>
> If I change my create procedure to use the form handle it
> works – yet this same code works on another application
> where the listbox is sitting on the Main Form.
That's because the WM_DROPFILES implementation you've provided is
a method of the FORM.
In the setup you've created, the our ListBox generates the "files
dropped" condition. As the initiating HWND, the ListBox receives
the WM_DROPFILES message back, but has no implementation for it.
The Form, has an implementation to handle it, but it doesn't
receive the WM_DROPFILES message because it was not the
initiating HWND.
Make sense?
Anyways, that's the intent of the "interposer" class
re-implementation of TListBox I sent, it makes the TListBox
responsible both for generating the dropped files condition as
well as handling the message when it arrives.
Stephen Posey
[EMAIL PROTECTED]
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