WinAPI: SetRect 及初始化矩形的几种办法

本例分别用五种办法初始化了同样的一个矩形, 运行效果图:

---

unit Unit1;



interface



uses

  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,

  Dialogs, StdCtrls;



type

  TForm1 = class(TForm)

    Button1: TButton;

    Button2: TButton;

    Button3: TButton;

    Button4: TButton;

    Button5: TButton;

    procedure Button1Click(Sender: TObject);

    procedure Button2Click(Sender: TObject);

    procedure Button3Click(Sender: TObject);

    procedure Button4Click(Sender: TObject);

    procedure Button5Click(Sender: TObject);

  end;



var

  Form1: TForm1;



implementation



{$R *.dfm}



//使用 API 函数: SetRect

procedure TForm1.Button1Click(Sender: TObject);

var

  R: TRect;

begin

  SetRect(R, 20, 20, 80, 80);

  Canvas.Pen.Color := clBlue;

  Canvas.Rectangle(R);

end;



//使用 Classes.Rect 函数

procedure TForm1.Button2Click(Sender: TObject);

var

  R: TRect;

begin

  R := Rect(20, 20, 80, 80);

  Canvas.Pen.Color := clFuchsia;

  Canvas.Rectangle(R);

end;



//使用 Classes.Rect 函数, 用两个点合成

procedure TForm1.Button3Click(Sender: TObject);

const

  pt1: TPoint = (x:20; y:20);

  pt2: TPoint = (x:80; y:80);

var

  R: TRect;

begin

  R := Rect(pt1, pt2);

  Canvas.Pen.Color := clSkyBlue;

  Canvas.Rectangle(R);

end;



//矩形常量

procedure TForm1.Button4Click(Sender: TObject);

const

  R: TRect = (Left:20; Top:20; Right:80; Bottom:80);

begin

  Canvas.Pen.Color := clTeal;

  Canvas.Rectangle(R);

end;



//使用 Classes.Bounds 函数, 我最喜欢这种办法

procedure TForm1.Button5Click(Sender: TObject);

var

  R: TRect;

begin

  R := Bounds(20, 20, 60, 60);

  Canvas.Pen.Color := clWhite;

  Canvas.Rectangle(R);

end;



end.