为什么DrawText只打印字符串的前四个字符？

Question

我有Canvas DrawText的问题,我从我想要显示的文本中得到了前4个字符.

例如,我有文本'离线'它将显示'offl'.

这段代码有什么不对.

代码

procedure TStatusCombo.Paint ;
var DrawRect : TRect ;
    StatusColor : TColor ;
    iTextWidth : Integer ;
    r : TRect ;
begin
DrawRect := ClientRect ;

//colors
Canvas.Brush.Style := bsClear ; //transparent background
Canvas.Brush.Color := Tcolor($4D4D4D) ;
Canvas.Pen.Color :=  Tcolor($4D4D4D)   ;

Canvas.RoundRect(DrawRect.Left , DrawRect.Top ,
            DrawRect.Right , DrawRect.Bottom , 15, 15);

//Drawing
//SetRect(DrawRect, DrawRect.Left+3, DrawRect.Top+3, DrawRect.Right-3, DrawRect.Bottom-3);

case ChatStatus of
  sNormal: StatusColor  :=   TColor($00FF78) ;
  sOnline: StatusColor  :=   TColor($00FF78) ;
  sBusy: StatusColor  :=   TColor($00FF78) ;
  sAway: StatusColor  :=   TColor($00FF78) ;
  sOffline:StatusColor  :=   TColor($00FF78) ;
end;
Canvas.Brush.Color := StatusColor ;

Canvas.RoundRect(DrawRect.Right - 20 , DrawRect.Top +4 ,
            DrawRect.Right -10  , DrawRect.Bottom -4  , 5, 5);


FCaption := FStatusText[ChatStatus];
Canvas.Brush.Style := bsClear ;
Canvas.Font.Color := clWhite ;


DrawText(Canvas.Handle,pchar(FCaption) ,sizeof(FCaption),DrawRect ,DT_VCENTER  or DT_CENTER or DT_SINGLELINE);




end;

Answer 1

你必须使用Length(FCaption)而不是SizeOf(FCaption).

实际上,Length(FCaption)是字符串的长度FCaption,而SizeOf(FCaption)变量的大小FCaption.由于FCaption是一个字符串,它(技术上)是指针(指向实际字符),指针长度为四个字节(在32位应用程序中).因此,你只得到前四个字符.