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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