WinAPI: SetBkMode - 设置背景模式

本例效果图:

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代码文件:

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unit Unit1;



interface



uses

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

  Dialogs, StdCtrls, ExtCtrls;



type

  TForm1 = class(TForm)

    RadioGroup1: TRadioGroup;

    procedure FormPaint(Sender: TObject);

    procedure FormCreate(Sender: TObject);

    procedure RadioGroup1Click(Sender: TObject);

  end;



var

  Form1: TForm1;



implementation



{$R *.dfm}



procedure TForm1.FormCreate(Sender: TObject);

begin

  RadioGroup1.Items.CommaText := 'TRANSPARENT,OPAQUE';

  RadioGroup1.ItemIndex := 0;

  RadioGroup1.Columns := RadioGroup1.Items.Count;

end;



procedure TForm1.FormPaint(Sender: TObject);

const

  str = 'Delphi 2007';

var

  x,y: Integer;

begin

  Canvas.Font.Size := 36;

  Canvas.Font.Style := [fsBold];

  x := (ClientWidth - Canvas.TextWidth(str)) div 2;

  y := (ClientHeight - Canvas.TextHeight(str)) div 4;



  Canvas.Pen.Color := clRed;

  Canvas.Brush.Color := clWhite;



  case RadioGroup1.ItemIndex of

    0: SetBkMode(Canvas.Handle, TRANSPARENT); {透明模式}

    1: SetBkMode(Canvas.Handle, OPAQUE);      {非透明模式}

  end;



  {也可以用下面一句话代替上面的 case 语句}

  //SetBkMode(Canvas.Handle, RadioGroup1.ItemIndex + 1);



  BeginPath(Canvas.Handle);

  Canvas.TextOut(x, y, str);

  EndPath(Canvas.Handle);



  StrokeAndFillPath(Canvas.Handle);

end;



procedure TForm1.RadioGroup1Click(Sender: TObject);

begin

  Repaint;

end;



end.


 
   

窗体文件:

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object Form1: TForm1

  Left = 329

  Top = 269

  Caption = 'Form1'

  ClientHeight = 206

  ClientWidth = 339

  Color = clBtnFace

  Font.Charset = DEFAULT_CHARSET

  Font.Color = clWindowText

  Font.Height = -11

  Font.Name = 'Tahoma'

  Font.Style = []

  OldCreateOrder = False

  Position = poDesigned

  OnCreate = FormCreate

  OnPaint = FormPaint

  PixelsPerInch = 96

  TextHeight = 13

  object RadioGroup1: TRadioGroup

    Left = 40

    Top = 149

    Width = 257

    Height = 41

    Caption = 'RadioGroup1'

    TabOrder = 0

    OnClick = RadioGroup1Click

  end

end