WinAPI: SetRectEmpty、IsRectEmpty

SetRectEmpty: 使矩形为空;

IsRectEmpty: 判断矩形是否为空;

所谓矩形为空就是矩形是无区域的, 或者说是 Right <= Left 或 Bottom <= Top 情形下的矩形.

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unit Unit1;

interface

uses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs;

type
  TForm1 = class(TForm)
    procedure FormCreate(Sender: TObject);
  end;

var
  Form1: TForm1;

implementation

{$R *.dfm}

procedure TForm1.FormCreate(Sender: TObject);
var
  R: TRect;
  buf: array[Byte] of Char;
begin
  R := Rect(10,20,-30,-40);
  ShowMessage(BoolToStr(IsRectEmpty(R), True)); {True; 是空矩形}

  R := Rect(10,20,30,40);
  ShowMessage(BoolToStr(IsRectEmpty(R), True)); {False}

  wvsprintf(buf, 'L:%d, T:%d, R:%d, B:%d', @R);
  ShowMessage(buf); {L:10, T:20, R:30, B:40}

  SetRectEmpty(R);

  ShowMessage(BoolToStr(IsRectEmpty(R), True)); {True}

  wvsprintf(buf, 'L:%d, T:%d, R:%d, B:%d', @R);
  ShowMessage(buf); {L:0, T:0, R:0, B:0}
end;

end.

关于 wvsprintf 函数请参见: http://www.cnblogs.com/del/archive/2008/04/18/1159045.html

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