WinAPI: SetLayeredWindowAttributes – 設定視窗的透明

這是來賓 Dolby 在 http://www.cnblogs.com/del/archive/2008/03/08/1081295.html#1096814
詢問的問題.

//聲明:SetLayeredWindowAttributes(  Hwnd: THandle;   {視窗控制代碼}  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;        {是否成功設定}//舉例(控制外部程式的透明度, 用計算機舉了個例子):unit Unit1;interfaceuses  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}{設定計算機的 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;{設定計算機中的白色透明}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.