WinAPI: SetLayeredWindowAttributes - 设置窗口的透明

这是来宾 Dolby 在 http://www.cnblogs.com/del/archive/2008/03/08/1081295.html#1096814 询问的问题.

---

//声明:

SetLayeredWindowAttributes(

  Hwnd: THandle;   {窗口句柄}

  crKey: COLORREF; {透明色}

  bAlpha: Byte;    {Alpha 值}

  dwFlags: DWORD   {LWA_COLORKEY(=1)表示使用透明色; LWA_ALPHA(=2)表示使用 Alpha 值}

): Boolean;        {是否成功设置}


 
   




//举例(控制外部程序的透明度, 用计算器举了个例子):

unit Unit1;



interface



uses

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

  Dialogs, StdCtrls;



type

  TForm1 = class(TForm)

    Button1: TButton;

    Button2: TButton;

    procedure Button1Click(Sender: TObject);

    procedure Button2Click(Sender: TObject);

  end;



var

  Form1: TForm1;



implementation



{$R *.dfm}



{设定计算器的 Alpha 透明}

procedure TForm1.Button1Click(Sender: TObject);

var

  h: HWND;

  FormStyle: Integer;

begin

  h := FindWindow('SciCalc', nil);

  FormStyle := GetWindowLong(h, GWL_EXSTYLE);

  SetWindowLong(h, GWL_EXSTYLE, FormStyle or WS_EX_LAYERED);

  SetLayeredWindowAttributes(h, 0, 128, LWA_ALPHA);

end;



{设定计算器中的白色透明}

procedure TForm1.Button2Click(Sender: TObject);

var

  h: HWND;

  FormStyle: Integer;

begin

  h := FindWindow('SciCalc', nil);

  FormStyle := GetWindowLong(h, GWL_EXSTYLE);

  SetWindowLong(h, GWL_EXSTYLE, FormStyle or WS_EX_LAYERED);

  SetLayeredWindowAttributes(h, clWhite, 255, LWA_COLORKEY);

end;



end.