Правое выравнивание ячеек TStringGrid

Вариант 1:

Source: DelphiWorld 6.0 https://delphiworld.narod.ru/

procedure TForm1.GridSumaDrawCell(Sender: TObject; ACol, ARow: Longint;
  ARect: TRect; State: TGridDrawState);
var
  dx: integer;
begin
  with (Sender as TStringGrid).Canvas do
  begin
    Font := GridSuma.Font;
    Pen.Color := clBlack;
    if (ACol = 0) or (ARow = 0) then
    begin
      { Рисуем заголовок }
      Brush.Color := clBtnFace;
      FillRect(ARect);
      TextOut(ARect.Left, ARect.Top, GridSuma.Cells[ACol, ARow])
    end
    else
    begin
      { Рисуем ячейку с правым выравниванием }
      Brush.Color := clWhite;
      FillRect(ARect);
      dx := TextWidth(GridSuma.Cells[ACol, ARow]) + 2;
      TextOut(ARect.Right - dx, ARect.Top, GridSuma.Cells[ACol, ARow])
    end
  end
end;

Вариант 2:

Source: https://www.swissdelphicenter.ch

procedure TForm1.StringGrid1DrawCell(Sender: TObject; ACol, ARow: Integer;
  Rect: TRect; State: TGridDrawState);

procedure WriteText(StringGrid: TStringGrid; ACanvas: TCanvas; const ARect: TRect;
  const Text: string; Format: Word);
const
  DX = 2;
  DY = 2;
var
  S: array[0..255] of Char;
  B, R: TRect;
begin
  with Stringgrid, ACanvas, ARect do
  begin
    case Format of
      DT_LEFT: ExtTextOut(Handle, Left + DX, Top + DY,
          ETO_OPAQUE or ETO_CLIPPED, @ARect, StrPCopy(S, Text), Length(Text), nil);

      DT_RIGHT: ExtTextOut(Handle, Right - TextWidth(Text) - 3, Top + DY,
          ETO_OPAQUE or ETO_CLIPPED, @ARect, StrPCopy(S, Text),
          Length(Text), nil);

      DT_CENTER: ExtTextOut(Handle, Left + (Right - Left - TextWidth(Text)) div 2,
          Top + DY, ETO_OPAQUE or ETO_CLIPPED, @ARect,
          StrPCopy(S, Text), Length(Text), nil);
    end;
  end;
end;

procedure Display(StringGrid: TStringGrid; const S: string; Alignment: TAlignment);
const
  Formats: array[TAlignment] of Word = (DT_LEFT, DT_RIGHT, DT_CENTER);
begin
  WriteText(StringGrid, StringGrid.Canvas, Rect, S, Formats[Alignment]);
end;

begin
  // Right-justify columns 0-2 
  // Spalten 0-2 rechts ausrichten. 
  if ACol in [0..2] then
    Display(StringGrid1, StringGrid1.Cells[ACol, ARow], taRightJustify)

  // Center the first row 
  // Erste zeile zentrieren 
  if ARow = 0 then
    Display(StringGrid1, StringGrid1.Cells[ACol, ARow], taCenter)
end;