Moving a caption-less window by using a "drag area"

Question

I would like to have my own caption bar and therefore I am using basically a panel (Name: pnCaption) and remove the original caption bar in CreateParams. But the ability to move the window by MouseDown-MouseMove in the new panel is a problem.

Normally you would use the NCHITTEST message. BUT this isn't signaled if the mouse is over the panel (my own caption). See code ...

procedure TForm1.CreateParams(var params: TCreateParams);  
begin  
  inherited Createparams(Params);  
  with Params do  
    Style := (Style or WS_POPUP) and (not WS_DLGFRAME);  
end;  

procedure TForm1.WM_NCHitTest(var Msg: TWMNcHitTest);  
begin  
  inherited;  
  if PtInRect(pnCaption.BoundsRect, ScreenToClient(Point(Msg.XPos, Msg.YPos)))  
      then Msg.Result := HTCAPTION;  
end;  

I would appreciate any hints how to accomplish that task.

Christian

Answer 1

You can always drag a window by any control that has a mousedown event by using the "Magic" $F012 number with a WM_SYSCOMMAND message. It's something I picked up from Ray Kanopka (author of the excellent raize components), but I no longer remember how this was imparted to me.

It is also a neat and simple way of allowing users to move borderless forms by giving them a label of panel that looks like a caption. For example, I use it to allow users to move a borderless about dialog:

procedure TAbout_Dlg.LblTitleMouseDown(Sender: TObject;
  Button: TMouseButton; Shift: TShiftState; X, Y: Integer);
const
  sc_DragMove = $F012;
begin
  ReleaseCapture;
  Perform( wm_SysCommand, sc_DragMove, 0 );
end;