...how will I know...?

I need to recieve data dragged from another application into my program in the form of Clipboard data. Question: how will I know when the user has dropped the data "in" (my app will already be running)? I will use a thread, presumably, but I just don't know when to initiate the transfer. I thougt maybe windows sends my app a message, but of the possible ones, none seemed conspicuous. Nonetheless, I'll try those first, but if anyone here knows, I'd appreciate the tip!

Aargh! One more thing. Windows won't let me drag anything onto my app anyway! How do I tell it to do so?

Ok, here's a little class that will take care of the implementation.
Just be sure to place the Allow() function under your WM_DROPFILES handler, and pass it your WPARAM.
Enjoy.

Code:

class DragDrop {
 public:

 int file_count;
 String * files;

 void Allow(HWND hwnd) {
   DragAcceptFiles(hwnd, TRUE);
  }

 bool Accept(WPARAM wp) {
   if( files ){
    delete [] files;
   }
   iter = 0;
   data = (HDROP)wp;
   file_count =  DragQueryFile(data, 0xFFFFFFFF, NULL, 0);
   files = new String[ file_count ];
     if( files == NULL ){
      return false;
      }
   while(iter < file_count) {
    DragQueryFile(data, iter, buffer, 256);
    files[iter++] = buffer;
   }
  DragFinish(data);
  return true;
 }

 DragDrop()
 :files(NULL) {
  /* */
 }

 ~DragDrop() {
   if( files ){
    delete [] files;
   }
 }
 private:

  HDROP data;
  int iter;
  char buffer[256];

};

I've had this in my favorites for a while, I hope it's of use to you: http://cprogramming.com/cboard/showt...&threadid=7829

...or can register your wnd as a drop target by giving it the WS_EX_ACCEPTFILES extended style. Presumably that's what DragAcceptFiles does: calls SetWindowLong with the GWL_EXSTYLE flag to set the extended style bit.