Author: Tomas Rutkauskas

How to draw on the frame of a TForm

Answer:

Create a message handler for the Windows Message WM_NCPAINT message. The following 
example paints a 1 pixel red border around the frame of the form.


1   type
2     TForm1 = class(TForm)
3     private
4       { Private declarations }
5       procedure WMNCPaint(var Msg: TWMNCPaint); message WM_NCPAINT;
6     public
7       { Public declarations }
8     end;
9   
10  var
11    Form1: TForm1;
12  
13  implementation
14  
15  {$R *.DFM}
16  
17  procedure TForm1.WMNCPaint(var Msg: TWMNCPaint);
18  var
19    dc: hDc;
20    Pen: hPen;
21    OldPen: hPen;
22    OldBrush: hBrush;
23  begin
24    inherited;
25    dc := GetWindowDC(Handle);
26    msg.Result := 1;
27    Pen := CreatePen(PS_SOLID, 1, RGB(255, 0, 0));
28    OldPen := SelectObject(dc, Pen);
29    OldBrush := SelectObject(dc, GetStockObject(NULL_BRUSH));
30    Rectangle(dc, 0, 0, Form1.Width, Form1.Height);
31    SelectObject(dc, OldBrush);
32    SelectObject(dc, OldPen);
33    DeleteObject(Pen);
34    ReleaseDC(Handle, Canvas.Handle);
35  end;