Delphi 的绘图功能[9] TextRect

//第一种重载的声明:
TextRect(
  Rect: TRect;       {矩形}
  X, Y: Integer;     {相对于窗体的位置}
  const Text: string {文本}
);

{如果要输出的文本超出指定的矩形将不被显示}


//第一种重载的举例:
procedure TForm1.Button1Click(Sender: TObject);
const
  R: TRect = (Left:0; Top:0; Right:60; Bottom:60);
  s = '万一的 Delphi 博客';
begin
  Canvas.Brush.Color := clWhite;
  Canvas.FillRect(R);

  Canvas.TextRect(R, 10, 10, s);
end;


//效果图:

---

//第二种重载的声明:
TextRect(
  var Rect: TRect;             {矩形范围}
  var Text: string;            {文本}
  TextFormat: TTextFormat = [] {选项; 集合类型, 默认值是个空的集合}
);

{参数三是 TTextFormat 类型的集合, 它定义如下:}
TTextFormat = set of TTextFormats;

{TTextFormats 是个枚举, 定义如下}
TTextFormats = (tfBottom, tfCalcRect, tfCenter, tfEditControl, tfEndEllipsis,
  tfPathEllipsis, tfExpandTabs, tfExternalLeading, tfLeft, tfModifyString,
  tfNoClip, tfNoPrefix, tfRight, tfRtlReading, tfSingleLine, tfTop,
  tfVerticalCenter, tfWordBreak);

{所以参数三可以是下列值之一或它们的组合}
tfBottom          
tfCalcRect
tfCenter
tfEditControl
tfEndEllipsis
tfPathEllipsis
tfExpandTabs
tfExternalLeading
tfLeft
tfModifyString
tfNoClip
tfNoPrefix
tfRight
tfRtlReading
tfSingleLine
tfTop
tfVerticalCenter
tfWordBreak

//这个函数是 API 函数 DrawTextEx 的简化, 可以参见: DrawTextEx


//第二种重载的举例1:

{默认是顶对齐、左对齐; 前两个参数都是传址的, 不能用常量}
procedure TForm1.FormPaint(Sender: TObject);
var
  R: TRect;
  S: string;
begin
  R := ClientRect;
  InflateRect(R,-10,-10); {把矩形缩小一圈}

  S := 'Delphi';
  Canvas.Brush.Color := clWhite;
  Canvas.FillRect(R);

  Canvas.TextRect(R, S);
end;


//效果图:

---

//第二种重载的举例2:

{单行文本、水平居中、垂直居中}
procedure TForm1.FormPaint(Sender: TObject);
var
  R: TRect;
  S: string;
begin
  R := ClientRect;
  InflateRect(R,-10,-10); {把矩形缩小一圈}

  S := 'Delphi';
  Canvas.Brush.Color := clWhite;
  Canvas.FillRect(R);

  Canvas.TextRect(R, S , [tfSingleLine, tfCenter, tfVerticalCenter]);
end;


//效果图:

---