By design, a Delphi form's "Caption" property is drawn by Windows, on the Caption Bar of a window next to the system menu.
If you want to add some custom text on the caption bar of a form, without changing the Caption property of the form you need to handle one special Windows message: WM_NCPAINT.
The WM_NCPAINT message is sent to a window when it needs to repaint its frame. An application can intercept this message and paint its own custom window frame.
Note that you also need to handle the WM_NCACTIVATE message that is sent to a window when it gets activated or deactivated. Without handling the WM_NCACTIVATE the custom caption text would disappear when our form looses the focus.
type
TCustomCaptionForm = class(TForm)
private
procedure WMNCPaint(var Msg: TWMNCPaint) ; message WM_NCPAINT;
procedure WMNCACTIVATE(var Msg: TWMNCActivate) ; message WM_NCACTIVATE;
procedure DrawCaptionText() ;
end;
...
implementation
procedure TCustomCaptionForm .DrawCaptionText;
const
captionText = 'delphi.about.com';
var
canvas: TCanvas;
begin
canvas := TCanvas.Create;
try
canvas.Handle := GetWindowDC(Self.Handle) ;
with canvas do
begin
Brush.Style := bsClear;
Font.Color := clMaroon;
TextOut(Self.Width - 110, 6, captionText) ;
end;
finally
ReleaseDC(Self.Handle, canvas.Handle) ;
canvas.Free;
end;
end;
procedure TCustomCaptionForm.WMNCACTIVATE(var Msg: TWMNCActivate) ;
begin
inherited;
DrawCaptionText;
end;
procedure TCustomCaptionForm.WMNCPaint(var Msg: TWMNCPaint) ;
begin
inherited;
DrawCaptionText;
end;
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