How do I paint the background of TStringGrid - delphi

Question

I do custom drawing of a Delphi TStringGrid using the OnDrawCell event.
There is no problem with the area covered by cells, but how do I paint the background right of the rightmost column and below the last row ?
(Edit)
Painting is not really necessary, I just want to set the color used for background.
I am using XE2 and investigating VCL styles.
Even in default drawing, setting Colors in a stringgrid, seams to have no effect at all.
TIA

Answer 1

This is some code I found with google (It is not from me, I could not find the name of the author, maybe it comes from StackExchange on some way...). It defines a descendant from TStringGrid and implements a new background drawing. (The example uses a bitmap, but you easily can change that...)
type
TStringGrid = class(Grids.TStringGrid)
private
FGraphic: TGraphic;
FStretched: Boolean;
function BackgroundVisible(var ClipRect: TRect): Boolean;
procedure PaintBackground;
protected
procedure Paint; override;
procedure Resize; override;
procedure TopLeftChanged; override;
public
property BackgroundGraphic: TGraphic read FGraphic write FGraphic;
property BackgroundStretched: Boolean read FStretched write FStretched;
end;
TForm1 = class(TForm)
StringGrid: TStringGrid;
Image: TImage;
procedure FormCreate(Sender: TObject);
end;
var
Form1: TForm1;
implementation
{$R *.dfm}
{ TStringGrid }
function TStringGrid.BackgroundVisible(var ClipRect: TRect): Boolean;
var
Info: TGridDrawInfo;
R: TRect;
begin
CalcDrawInfo(Info);
SetRect(ClipRect, 0, 0, Info.Horz.GridBoundary, Info.Vert.GridBoundary);
R := ClientRect;
Result := (ClipRect.Right < R.Right) or (ClipRect.Bottom < R.Bottom);
end;
procedure TStringGrid.Paint;
begin
inherited Paint;
PaintBackground;
end;
procedure TStringGrid.PaintBackground;
var
R: TRect;
begin
if (FGraphic <> nil) and BackgroundVisible(R) then
begin
with R do
ExcludeClipRect(Canvas.Handle, Left, Top, Right, Bottom);
if FStretched then
Canvas.StretchDraw(ClientRect, FGraphic)
else
Canvas.Draw(0, 0, FGraphic);
end;
end;
procedure TStringGrid.Resize;
begin
inherited Resize;
PaintBackground;
end;
procedure TStringGrid.TopLeftChanged;
begin
inherited TopLeftChanged;
PaintBackground;
end;
{ TForm1 }
procedure TForm1.FormCreate(Sender: TObject);
begin
// Usage:
StringGrid.BackgroundGraphic := Image.Picture.Graphic;
StringGrid.BackgroundStretched := True;
end;