用C++Builder开发Windows下的屏保

摘要：本文通过一个具体的程序演示了Windows下的屏幕保护程序的实现过程。
一． 引言
视窗系统下的屏幕保护程序是一个基于命令行（Command Line）的应用程序。当屏保程序被调用时操作系统就用具体的命令行执行该程序。本文组织和处理了所有的命令行，包括“/p”，“/s”，“/c”，“/a”，其中“/p”表示让屏保在预览窗口中显示；“/s”表示真正运行屏保；“/c”表示调用设置对话框；而“/a”表示调用密码设置对话框（WinNT中无效）。本程序尽可能简单地实现一个全功能的屏保，运行Windows的屏保设置程序时你既可以修改密码（WinNT中无效）又可以设置图片显示的频率并把频率数值保存到注册表里。当屏保运行时图片以你设置的频率改变显示位置。笔者还留了个作业给读者，请看图1中的选择图片文件夹这个项目，按下浏览按钮可以设置图片的路径，笔者已经实现了浏览按钮的功能并
把得到的路径也保存到注册表中，并让屏保启动时读picdir的值，picdir等于"no"时的代码笔者已实现了，picdir不等于"no"时的代码由读者实现。也就是让读者实现一个能把picdir目录里的图片轮流显示的屏保程序。

二． 实现方法
首先介绍几个API函数。
WinMain函数：
int WINAPI WinMain(
    HINSTANCE hInstance, // 当前实例句柄
    HINSTANCE hPrevInstance, // 前一个实例句柄
    LPSTR lpCmdLine, // 指向命令行参数的指针（本程序要利用的参数）
    int nCmdShow  // 窗口的状态
   );
GetWindowLong函数：得到指定窗口信息的函数
    LONG GetWindowLong(
         HWND hWnd, //窗/口句柄
         int nIndex  //指/定返回的信息
       );
SetWindowLong函数：改变窗口属性
    LONG SetWindowLong(
    HWND hWnd, //窗/口句柄
    int nIndex, // 指定要设定的值的信息
    LONG dwNewLong  // 新值
   );
SetParent函数：改变指定窗口的父窗口
   HWND SetParent(
    HWND hWndChild, //要/改变父窗体的窗口句柄
    HWND hWndNewParent  //新/的父窗体的句柄
   );
GetClientRect函数：得到窗口的客户区
    BOOL GetClientRect(
    HWND hWnd, // 窗口句柄
    LPRECT lpRect  //RECT/结构的地址
   );
SetWindowPos函数：改变窗口的大小，位置，顶级窗口等
BOOL SetWindowPos(
HWND hWnd, // 窗口句柄
    HWND hWndInsertAfter, // 布置窗口顺序的句柄（Z order）
    int X, // horizontal position
    int Y, // vertical position
    int cx, // width
    int cy, // height
    UINT uFlags  // 窗口位置等标记
   );
SystemParametersInfo函数：访问或设置系统级的参数
    BOOL SystemParametersInfo(
    UINT uiAction, // 指定要获取或设置的系统参数
    UINT uiParam, // depends on action to be taken
    PVOID pvParam, // depends on action to be taken
    UINT fWinIni  // 用户配置文件是否改变标记
   );
ShowCursor函数：显示或隐藏光标
int ShowCursor(
BOOL bShow  // 鼠标可见度标记  
   );
GetVersion函数：获取系统的版本信息
DWORD GetVersion(VOID)

以上API函数的具体信息可以查找有关MSSDK文档。了解了基本函数后笔者简述一下实现方法。
1． 新建一工程，增加两个窗体，将三个窗体分别取名为MainForm,FrmConfig,FrmControl。在MainForm和FrmControl窗体上各添加一个Timer控件和TImage控件，把两窗体的BorderStyle设为bsNone，背景色设为黑色。在两个窗体的TImage上各加一张图片，FrmControl大小设为：高130像素，宽160像素，Timage的Stretch属性设为真值。FrmConfig的样式如图1。
2． 保存工程文件为screensaver.cpp，其它单元分别存为Unitmain.cpp，
Unitcontrol.cpp，Unitconfig.cpp。
3． 编写代码，具体代码见第三部分的源程序。
4． 编译成可执行文件，并把文件扩展名改为scr。
5． 最后把屏保程序拷贝到windows目录下就可以测试了。如果一切正常的话你将会看
到图片在屏幕上以随机的位置显示。
                                    
三． 源代码
以下是本程序的所有的源代码，其中screensaver.cpp, Unitmain.cpp是核心代码。
/*{*******************************}*/
/*{***** screensaver.cpp  ****}*/
/*{*******************************}*/
//---------------------------------------------------------------------------/
#include
#pragma hdrstop
USERES("screensaver.res");
USEFORM("Unitmain.cpp", Frmmain);
USEFORM("Unitconfig.cpp", FrmConfig);
USEFORM("Unitcontrol.cpp", FrmControl);
//---------------------------------------------------------------------------/
WINAPI WinMain(HINSTANCE, HINSTANCE, LPSTR p, int)//“p"是指向命令行参数的指针
{ String StartType;
  AnsiString Command=p,temp;
  HWND CPWindow =NULL;
  if(Command=="")
   StartType = "/c";
  else
   StartType=Command.SubString(1,2);//获取命令行的前两个参数
        try
        {
                 Application->Initialize();
                 if(StartType=="/c")//启动设置窗口
                   Application->CreateForm(__classid(TFrmConfig), &FrmConfig);
                 else if(StartType=="/s")启动屏保
                   Application->CreateForm(__classid(TFrmmain), &Frmmain);
                 else if(StartType=="/p")//预览
                  {
                   Application->CreateForm(__classid(TFrmControl), &FrmControl);
                   temp=Command.SubString(3,Command.Length()-2);//获取命令行中的屏保预览窗口句柄的字符串形式
                   CPWindow =(long *)temp.ToInt();//将预览窗口句柄的字符串形式强制转换为长整形指针
                   RECT *lookrect;//建立一个RECT结构指针
                   Long style=GetWindowLong(Application->MainForm->Handle,GWL_STYLE);//获取FrmControl窗口的风格
                   style=styleWS_CHILD;
                   SetWindowLong(Application->MainForm->Handle,GWL_STYLE,style);//设置窗口为子窗口
                   SetParent(Application->MainForm->Handle,CPWindow);//设置屏保预览窗口为FrmControl的父窗口
                   GetClientRect(CPWindow,lookrect);//获取屏保预览窗口的客户区
                   SetWindowPos(Application->MainForm->Handle,HWND_TOP,0,0,lookrect->right,lookrect->bottom ,SW
P_NOZORDERSWP_NOACTIVATESWP_SHOWWINDOW);//将FrmControl的窗口覆盖屏保预览窗口的客户区，并显示它
                   }
                 else if(StartType=="/a")//启动密码设置窗口
                  {
                   temp=Command.SubString(3,Command.Length()-2);
                   CPWindow =(long *)temp.ToInt();//以下是动态调用mpr.dll里的PwdChangePasswordA函数的过程
                   typedef UINT(CALLBACK *FUN)(LPSTR,HWND,UINT,UINT);
                   HINSTANCE hDll=LoadLibrary("mpr.DLL");
                   FUN myfun;
                   if(hDll!=NULL)
                    {
                     myfun=(FUN)GetProcAddress(hDll,"PwdChangePasswordA");
                     if(!myfun)FreeLibrary(hDll);
                     else
                     myfun("SCRSAVE", CPWindow, 0, 0);//函数的调用
                    }
                  }
                 Application->Run();
        }
        catch (Exception &exception)
        {
                 Application->ShowException(&exception);
        }
        return 0;
}
//---------------------------------------------------------------------------/
/*{*******************************}*/
/*{*****   Unitmain.h     ****}*/
/*{*******************************}*/
//---------------------------------------------------------------------------/

#ifndef UnitmainH
#define UnitmainH
//---------------------------------------------------------------------------/
#include
#include
#include
#include
#include
#include
#include
//---------------------------------------------------------------------------/
class TFrmmain : public TForm
{
__published: // IDE-managed Components
        TTimer *Timer1;
        TImage *Image1;
        void __fastcall FormCreate(TObject *Sender);
        void __fastcall FormKeyDown(TObject *Sender, WORD &Key,
          TShiftState Shift);
        void __fastcall FormMouseDown(TObject *Sender, TMouseButton Button,
          TShiftState Shift, int X, int Y);
        void __fastcall FormCloseQuery(TObject *Sender, bool &CanClose);
        void __fastcall FormClose(TObject *Sender, TCloseAction &Action);
        void __fastcall Image1MouseDown(TObject *Sender,
          TMouseButton Button, TShiftState Shift, int X, int Y);
        void __fastcall Image1MouseMove(TObject *Sender, TShiftState Shift,
          int X, int Y);
        void __fastcall Timer1Timer(TObject *Sender);
private: // User declarations
       DWORD PWProtect;
       DWORD Version;
       String picdir;
       int frequence;
public: // User declarations
        __fastcall TFrmmain(TComponent* Owner);
};
//---------------------------------------------------------------------------/
extern PACKAGE TFrmmain *Frmmain;
//---------------------------------------------------------------------------/
#endif
//---------------------------------------------------------------------------/
/*{*******************************}*/
/*{*****  Unitmain.cpp   ****}*/
/*{*******************************}*/
//---------------------------------------------------------------------------/
#include
#pragma hdrstop
#include
#include "Unitmain.h"
#include
//---------------------------------------------------------------------------/
#pragma package(smart_init)
#pragma resource "*.dfm"
TFrmmain *Frmmain;
//---------------------------------------------------------------------------/
__fastcall TFrmmain::TFrmmain(TComponent* Owner)
        : TForm(Owner)
{
}
//---------------------------------------------------------------------------/
void __fastcall TFrmmain::FormCreate(TObject *Sender)
{
    //使窗口成为最顶层的窗口
    SetWindowPos(this->Handle, HWND_TOPMOST, 0, 0, 0, 0, SWP_NOMOVESWP_NOSIZE);
    //时窗口覆盖屏幕
    this->Width=Screen->Width;
    this->Height=Screen->Height;
    this->Top=0;
    this->Left=0;
    Version=GetVersion();
    TRegistry *Registry = new TRegistry;
  try
  {
    if(Version>0x80000000){
    Registry->RootKey =HKEY_CURRENT_USER;
    Registry->OpenKey("\Control Panel\Desktop",false);
    PWProtect=Registry->ReadInteger("ScreenSaveUsePassword");//检测是否密码保护
    Registry->CloseKey();}
    Registry->RootKey =HKEY_CURRENT_USER;
    Registry->OpenKey("\Software\CODEHUNTER", true);
    picdir=Registry->ReadString("PicDir");//得到图片目录
    frequence=Registry->ReadInteger("frequence");//得到图像显示的频率
    if(picdir=="")picdir="no";
    if(frequence<0frequence>6) frequence=2;
    Timer1->Interval=1000*frequence;设置定时器
  }
  __finally
  {
    delete Registry;
    picdir="no";
  }
    //检测是否运行于 NT下
    if(Version!=0)
    if(PWProtect&&Version>0x80000000)//如果系统要求密码保护并此系统为非NT那么把系统设为屏保状态使光标消失
      SystemParametersInfo(SPI_SCREENSAVERRUNNING, 1, 0, 0);
    while (!ShowCursor(false)< -5);
}

//---------------------------------------------------------------------------/
void __fastcall TFrmmain::FormKeyDown(TObject *Sender, WORD &Key,
      TShiftState Shift)
{
this->Close();
}
//---------------------------------------------------------------------------/
void __fastcall TFrmmain::FormMouseDown(TObject *Sender,
      TMouseButton Button, TShiftState Shift, int X, int Y)
{
this->Close();
}
//---------------------------------------------------------------------------/
void __fastcall TFrmmain::FormCloseQuery(TObject *Sender, bool &CanClose)
{
if (PWProtect && Version>0x80000000)
      {
        bool PassChck;
       //显/示光标，并调用密码对话框
        while(!ShowCursor(True) > 5);
       //以/下是VerifyScreenSavePwd函数的动态调用
        typedef UINT(CALLBACK *FUN)(HWND);
                   HINSTANCE hDll=LoadLibrary("password.cpl");
                   FUN myfun;
                   if(hDll!=NULL)
                    {
                     myfun=(FUN)GetProcAddress(hDll,"VerifyScreenSavePwd");
                     if(!myfun)FreeLibrary(hDll);
                     else
                     PassChck=myfun(this->Handle);
                    }
        if(PassChck == false)
          {
            while(!ShowCursor(False) < -5);
            CanClose = false;
           }
      }
}
//---------------------------------------------------------------------------/

void __fastcall TFrmmain::FormClose(TObject *Sender, TCloseAction &Action)
{
while(!ShowCursor(True) > 5);
    if(PWProtect&&Version>0x80000000)
        SystemParametersInfo(SPI_SCREENSAVERRUNNING, 0, 0, 0);//退出屏保状态
}
//---------------------------------------------------------------------------/
void __fastcall TFrmmain::Image1MouseDown(TObject *Sender,
      TMouseButton Button, TShiftState Shift, int X, int Y)
{
this->Close();
}
//---------------------------------------------------------------------------/
void __fastcall TFrmmain::Image1MouseMove(TObject *Sender,
      TShiftState Shift, int X, int Y)
{   static int MouseMoves=0;
    MouseMoves = MouseMoves + 1;
    if(MouseMoves >4)
     {
     this->Close();
     MouseMoves = 0 ;
     }
}
//---------------------------------------------------------------------------/
void __fastcall TFrmmain::Timer1Timer(TObject *Sender)
{
if(picdir=="no")
{
int i ;
randomize();
i=rand()%2;
if(i==0)
i=-1;
else
i=1;
Image1->Top=i*(rand()%this->Height);
Image1->Left=i*(rand()%this->Width);
}
}
//---------------------------------------------------------------------------/
/*{*******************************}*/
/*{*****   Unitcontrol.h   ****}*/
/*{*******************************}*/
//---------------------------------------------------------------------------/
#ifndef UnitcontrolH
#define UnitcontrolH
//---------------------------------------------------------------------------/
#include
#include
#include
#include
#include
#include
#include
//---------------------------------------------------------------------------/
class TFrmControl : public TForm
{
__published: // IDE-managed Components
        TImage *Image1;
        TTimer *Timer1;
        void __fastcall Timer1Timer(TObject *Sender);
        void __fastcall FormCreate(TObject *Sender);
private: // User declarations
public: // User declarations
        __fastcall TFrmControl(TComponent* Owner);
};
//---------------------------------------------------------------------------/
extern PACKAGE TFrmControl *FrmControl;
//---------------------------------------------------------------------------/
#endif
//---------------------------------------------------------------------------/
/*{*******************************}*/
/*{*****   Unitcontrol.cpp ****}*/
/*{*******************************}*/
//---------------------------------------------------------------------------/
#include
#pragma hdrstop
#include "Unitcontrol.h"
//---------------------------------------------------------------------------/
#pragma package(smart_init)
#pragma resource "*.dfm"
TFrmControl *FrmControl;
//---------------------------------------------------------------------------/
__fastcall TFrmControl::TFrmControl(TComponent* Owner)
        : TForm(Owner)
{
}
//---------------------------------------------------------------------------/
void __fastcall TFrmControl::Timer1Timer(TObject *Sender)
{
int i ;
randomize();
i=rand()%2;
if(i==0)
i=-1;
else
i=1;
Image1->Top=i*(rand()%this->Height);
Image1->Left=i*(rand()%this->Width);
}
//---------------------------------------------------------------------------/
void __fastcall TFrmControl::FormCreate(TObject *Sender)
{
Image1->Top=0;
Image1->Left=0;
Image1->Height=this->Height ;
Image1->Width=this->Width ;
}
//---------------------------------------------------------------------------/
/*{*******************************}*/
/*{*****    Unitconfig.h   ****}*/
/*{*******************************}*/
//---------------------------------------------------------------------------/
#ifndef UnitconfigH
#define UnitconfigH
//---------------------------------------------------------------------------/
#include
#include
#include
#include
#include
#include
#include
#include
//---------------------------------------------------------------------------/
class TFrmConfig : public TForm
{
__published: // IDE-managed Components
        TPanel *Panel1;
        TButton *Button1;
        TPanel *Panel2;
        TLabel *Label1;
        TTrackBar *TrackBar1;
        TLabel *Label2;
        TLabel *Label3;
        TLabel *Label4;
        TButton *Button2;
        void __fastcall Button1Click(TObject *Sender);
        void __fastcall Button2Click(TObject *Sender);
private: // User declarations
  AnsiString picdir;
  int frequence;
public: // User declarations
        __fastcall TFrmConfig(TComponent* Owner);
};
//---------------------------------------------------------------------------/
extern PACKAGE TFrmConfig *FrmConfig;
//---------------------------------------------------------------------------/
#endif
//---------------------------------------------------------------------------/
/*{*******************************}*/
/*{*****   Unitconfig.cpp  ****}*/
/*{*******************************}*/
//---------------------------------------------------------------------------/
#include
#pragma hdrstop
#include "Unitconfig.h"
//---------------------------------------------------------------------------/
#pragma package(smart_init)
#pragma resource "*.dfm"
TFrmConfig *FrmConfig;
//---------------------------------------------------------------------------/
__fastcall TFrmConfig::TFrmConfig(TComponent* Owner)
        : TForm(Owner)
{
}
//---------------------------------------------------------------------------/
void __fastcall TFrmConfig::Button1Click(TObject *Sender)
{
if(SelectDirectory("Select Picture Dir","",picdir))
   Panel2->Caption=picdir;
}
//---------------------------------------------------------------------------/
void __fastcall TFrmConfig::Button2Click(TObject *Sender)
{
//把信息写入注册表
if(picdir=="") picdir="no";
this->frequence=TrackBar1->Position;
TRegistry *Reg = new TRegistry;
  try
   {
    Reg->RootKey = HKEY_CURRENT_USER;
    if (Reg->OpenKey("\Software\CODEHUNTER", true))
    {
      Reg->WriteString("PicDir",picdir);
      Reg->WriteInteger("frequence",frequence);
      Reg->CloseKey();
    }
  }
  __finally
  {
    delete Reg;
  }
this->Close();
}
//---------------------------------------------------------------------------/