shapes.pas

《Kylix程序设计》一书中附带的例程源代码

unit Shapes;

interface

uses
  SysUtils, Classes, Types, QGraphics;

type
  TGeoShape = class( TObject )
  public
    procedure Draw( Canvas: TCanvas ); virtual; abstract;
  end;

  TGeoPoint = class( TGeoShape )
  protected
    FPoint: TPoint;
  public
    procedure SetValue( Point: TPoint );
    procedure Draw( Canvas: TCanvas ); override;
  end;

  TGeoLine = class( TGeoPoint )
  protected
    FToPoint: TPoint;
  public
    procedure SetValue( FromPoint, ToPoint: TPoint ); overload;
    procedure Draw( Canvas: TCanvas ); override;
  end;

  TGeoRect = class( TGeoShape )
  protected
    FRect: TRect;
  public
    procedure SetValue( Rect: TRect ); overload;
    procedure Draw( Canvas: TCanvas ); override;
  end;
{
var
  Shape: TGeoShape;
  Point: TGeoPoint;
  Line: TGeoLine;
  Rect: TGeoRect;
}
implementation

{ TGeoShape }
{
procedure TGeoShape.Draw(Canvas: TCanvas);
begin
  Canvas.TextOut( 200, 200, 'Do nothing.' );
end;
}
{ TGeoPoint }

procedure TGeoPoint.SetValue(Point: TPoint);
begin
  FPoint := Point;
end;

procedure TGeoPoint.Draw(Canvas: TCanvas);
begin
  Canvas.DrawPoint( FPoint );
end;

{ TGeoLine }

procedure TGeoLine.SetValue(FromPoint, ToPoint: TPoint);
begin
  FPoint := FromPoint;
  FToPoint := ToPoint;
end;

procedure TGeoLine.Draw(Canvas: TCanvas);
begin
  Canvas.MoveTo( FPoint.X, FPoint.Y );
  Canvas.LineTo( FToPoint.X, FToPoint.Y );
end;

{ TGeoRect }

procedure TGeoRect.Draw(Canvas: TCanvas);
begin
  Canvas.Rectangle( FRect );
end;

procedure TGeoRect.SetValue(Rect: TRect);
begin
  FRect := Rect;
end;

end.