Author: Dmitri Papichev

How to remove system caption bar (title bar) or replace it by my own?

Answer:

Below you can find the source code of a unit that performs the task (note that it 
is not a form). All you need is to inherit your form from TDPCCForm instead of 
TForm. Property CaptionControl is accessible at run time and defines the control 
(TGraphicControl) which acts as a caption bar. Usually you assign CaptionControl 
once in OnCreate event handler of you form, but nothing prevents you from further 
changes of CaptionControl at run time. If you leave CaptionControl unassigned, the 
form will have no caption functionality at all. 

1   unit DPCCForms;
2   
3   interface
4   
5   uses
6     Windows, Messages, Classes, Controls, Forms;
7   
8   type
9     TDPCCForm = class(TForm)
10    private
11      { Private declarations }
12      FCaptionControl: TGraphicControl;
13      procedure WMNCHitTest(var AMessage: TWMNCHitTest); message WM_NCHITTEST;
14    protected
15      procedure CreateParams(var Params: TCreateParams); override;
16    public
17      { Public declarations }
18      property CaptionControl: TGraphicControl
19        read FCaptionControl write FCaptionControl default nil;
20    end;
21  
22    {===============================================================}
23  implementation
24  
25  {---------------------------------------------------------------}
26  
27  procedure TDPCCForm.CreateParams(var Params: TCreateParams);
28  begin
29    inherited CreateParams(Params);
30    with Params do
31    begin
32      Style := (Style or WS_POPUP) and (not WS_DLGFRAME);
33    end; {with}
34  end {--TDPCCForm.CreateParams--};
35  
36  {---------------------------------------------------------------}
37  
38  procedure TDPCCForm.WMNCHitTest(var AMessage: TWMNCHitTest);
39  begin
40    inherited;
41    if ((AMessage.Result = HTCLIENT) and
42      Assigned(CaptionControl) and
43      PtInRect(CaptionControl.BoundsRect,
44      ScreenToClient(Point(AMessage.XPos,
45      AMessage.YPos)))) then
46    begin
47      AMessage.Result := HTCAPTION;
48    end; {if}
49  end; {--TDPCCForm.WMNCHitTest--}
50  
51  end.