Question

I have a form that accepts files to be dragged and dropped on, as well as a TWebBrowser control placed on a TPanel control on the same form.

The main thing is that, when I drop a file on the form, its path is added to a TEdit control. However, as the user drags and drops the file on the form, sometimes they might actually drop it on the TWebBrowser, which offers to save or run the file for the user, depending on its file type. This is what I actually don’t want to happen, I’d just want for the TWebBrowser to either ignore the dropped file or to process it as the form would do.

This is the code I’m using to treat the WM_DROPFILES message:

procedure TMainForm.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 );

    // do your thing with the acFileName
    //MessageBox( Handle, acFileName, '', MB_OK );
    Edit1.Text := acFileName;
  end;

  // let Windows know that you're done
  DragFinish( msg.WParam );
end;

Thank you in advance. Any clue would be much appreciated.

Answer 1

To Intercept the drag and drop operations in a TWebBrowser you must implement the IDropTarget and the IDocHostUIHandler interfaces. then you must use the GetDropTarget method to pass you own IDropTarget implementation.

For a sample delphi code try this article How to handle drag and drop in a TWebBrowser control