Оформил: DeeCo
Автор: http://www.swissdelphicenter.ch

{ 
  ** What is a Hook? ** 

  A hook is a point in the system message-handling mechanism where an 
  application can install a subroutine to monitor the message traffic in 
  the system and process certain types of messages before they reach the target window procedure. 

  To use the Windows hook mechanism, a program calls the SetWindowsHookEx() API function, 
  passing the address of a hook procedure that is notified when the specified 
  event takes place. SetWindowsHookEx() returns the address of the previously installed 
  hook procedure for the same event type. This address is important, 
  because hook procedures of the same type form a kind of chain. 
  Windows notifies the first procedure in the chain when an event occurs, 
  and each procedure is responsible for passing along the notification. 
  To do so, a hook procedure must call the CallNextHookEx() API function, 
  passing the previous hook procedure's address. 

  --> All system hooks must be located in a dynamic link library. 

  ** The type of Hook used in this Example Code: ** 

  The WH_GETMESSAGE hook enables an application to monitor/intercept messages 
  about to be returned by the GetMessage or PeekMessage function. 
}


 { 

** Hook Dll - WINHOOK.dll ** 
WINHOOK.dpr 
       |-----WHookInt.pas 

** Interface unit ** WHookDef.dpr 

}

 {********** Begin WHookDef.dpr **************}

 { Interface unit for use with WINHOOK.DLL }

 unit WHookDef;

 interface

 uses
   Windows;

 function SetHook(WinHandle: HWND; MsgToSend: Integer): Boolean; stdcall;
 function FreeHook: Boolean; stdcall;

 implementation

 function SetHook; external 'WINHOOK.DLL' Index 1;
 function FreeHook; external 'WINHOOK.DLL' Index 2;

 end.

 {********** End WHookDef.dpr **************}


 {********** Begin Winhook.dpr **************}

 { The project file }

 { WINHOOK.dll }
 library Winhook;

 uses
   WHookInt in 'Whookint.pas';

 exports
   SetHook index 1,
   FreeHook index 2;
 end.

 {********** End Winhook.dpr **************}


 {********** Begin WHookInt.pas **************}

 unit WHookInt;

 interface

 uses
   Windows, Messages, SysUtils;

 function SetHook(WinHandle: HWND; MsgToSend: Integer): Boolean; stdcall; export;
 function FreeHook: Boolean; stdcall; export;
 function MsgFilterFunc(Code: Integer; wParam, lParam: Longint): Longint stdcall; export;

 implementation


 // Memory map file stuff 

{ 
  The CreateFileMapping function creates unnamed file-mapping object 
  for the specified file. 
}

 function CreateMMF(Name: string; Size: Integer): THandle;
 begin
   Result := CreateFileMapping($FFFFFFFF, nil, PAGE_READWRITE, 0, Size, PChar(Name));
   if Result <> 0 then
   begin
     if GetLastError = ERROR_ALREADY_EXISTS then
     begin
       CloseHandle(Result);
       Result := 0;
     end;
   end;
 end;

 { The OpenFileMapping function opens a named file-mapping object. }

 function OpenMMF(Name: string): THandle;
 begin
   Result := OpenFileMapping(FILE_MAP_ALL_ACCESS, False, PChar(Name));
   // The return value is an open handle to the specified file-mapping object. 
end;

 { 
 The MapViewOfFile function maps a view of a file into 
 the address space of the calling process. 
}

 function MapMMF(MMFHandle: THandle): Pointer;
 begin
   Result := MapViewOfFile(MMFHandle, FILE_MAP_ALL_ACCESS, 0, 0, 0);
 end;

 { 
  The UnmapViewOfFile function unmaps a mapped view of a file 
  from the calling process's address space. 
}

 function UnMapMMF(P: Pointer): Boolean;
 begin
   Result := UnmapViewOfFile(P);
 end;

 function CloseMMF(MMFHandle: THandle): Boolean;
 begin
   Result := CloseHandle(MMFHandle);
 end;


 // Actual hook stuff 

type
   TPMsg = ^TMsg;

 const
   VK_D = $44;
   VK_E = $45;
   VK_F = $46;
   VK_M = $4D;
   VK_R = $52;

   MMFName = 'MsgFilterHookDemo';

 type
   PMMFData = ^TMMFData;
   TMMFData = record
     NextHook: HHOOK;
     WinHandle: HWND;
     MsgToSend: Integer;
   end;

   // global variables, only valid in the process which installs the hook. 
var
   MMFHandle: THandle;
   MMFData: PMMFData;

 function UnMapAndCloseMMF: Boolean;
 begin
   Result := False;
   if UnMapMMF(MMFData) then
   begin
     MMFData := nil;
     if CloseMMF(MMFHandle) then
     begin
       MMFHandle := 0;
       Result := True;
     end;
   end;
 end;

 { 
  The SetWindowsHookEx function installs an application-defined 
  hook procedure into a hook chain. 

  WH_GETMESSAGE Installs a hook procedure that monitors messages 
  posted to a message queue. 
  For more information, see the GetMsgProc hook procedure. 
}

 function SetHook(WinHandle: HWND; MsgToSend: Integer): Boolean; stdcall;
 begin
   Result := False;
   if (MMFData = nil) and (MMFHandle = 0) then
   begin
     MMFHandle := CreateMMF(MMFName, SizeOf(TMMFData));
     if MMFHandle <> 0 then
     begin
       MMFData := MapMMF(MMFHandle);
       if MMFData <> nil then
       begin
         MMFData.WinHandle := WinHandle;
         MMFData.MsgToSend := MsgToSend;
         MMFData.NextHook := SetWindowsHookEx(WH_GETMESSAGE, MsgFilterFunc, HInstance, 0);

         if MMFData.NextHook = 0 then
           UnMapAndCloseMMF
         else
           Result := True;
       end
       else
       begin
         CloseMMF(MMFHandle);
         MMFHandle := 0;
       end;
     end;
   end;
 end;


 { 
  The UnhookWindowsHookEx function removes the hook procedure installed 
  in a hook chain by the SetWindowsHookEx function. 
}

 function FreeHook: Boolean; stdcall;
 begin
   Result := False;
   if (MMFData <> nil) and (MMFHandle <> 0) then
     if UnHookWindowsHookEx(MMFData^.NextHook) then
       Result := UnMapAndCloseMMF;
 end;



 (*
     GetMsgProc(
     nCode: Integer;  {the hook code}
     wParam: WPARAM;  {message removal flag}
     lParam: LPARAM  {a pointer to a TMsg structure}
     ): LRESULT;  {this function should always return zero}

     { See help on ==> GetMsgProc}
 *)

 function MsgFilterFunc(Code: Integer; wParam, lParam: Longint): Longint;
 var
   MMFHandle: THandle;
   MMFData: PMMFData;
   Kill: boolean;
 begin
   Result := 0;
   MMFHandle := OpenMMF(MMFName);
   if MMFHandle <> 0 then
   begin
     MMFData := MapMMF(MMFHandle);
     if MMFData <> nil then
     begin
       if (Code < 0) or (wParam = PM_NOREMOVE) then
         { 
          The CallNextHookEx function passes the hook information to the 
          next hook procedure in the current hook chain. 
        }
         Result := CallNextHookEx(MMFData.NextHook, Code, wParam, lParam)
       else
       begin
         Kill := False;

         { Examples }
         with TMsg(Pointer(lParam)^) do
         begin
           // Kill Numbers 
          if (wParam >= 48) and (wParam <= 57) then Kill := True;
           // Kill Tabulator 
          if (wParam = VK_TAB) then Kill := True;
         end;

         { Example to disable all the start-Key combinations }
         case TPMsg(lParam)^.message of
           WM_SYSCOMMAND: // The Win Start Key (or Ctrl+ESC) 
            if TPMsg(lParam)^.wParam = SC_TASKLIST then Kill := True;

           WM_HOTKEY:
             case ((TPMsg(lParam)^.lParam and $00FF0000) shr 16) of
               VK_D,      // Win+D        ==> Desktop 
              VK_E,      // Win+E        ==> Explorer 
              VK_F,      // Win+F+(Ctrl) ==> Find:All (and Find: Computer) 
              VK_M,      // Win+M        ==> Minimize all 
              VK_R,      // Win+R        ==> Run program. 
              VK_F1,     // Win+F1       ==> Windows Help 
              VK_PAUSE:  // Win+Pause    ==> Windows system properties 
                Kill := True;
             end;
         end;
         if Kill then TPMsg(lParam)^.message := WM_NULL;
         Result := CallNextHookEx(MMFData.NextHook, Code, wParam, lParam)
       end;
       UnMapMMF(MMFData);
     end;
     CloseMMF(MMFHandle);
   end;
 end;


 initialization
   begin
     MMFHandle := 0;
     MMFData   := nil;
   end;

 finalization
   FreeHook;
 end.

 {********** End WHookInt.pas **************}


 { *******************************************}
 { ***************** Demo   ******************}
 { *******************************************}

 { 

** HostApp.Exe ** 
HostApp.dpr 
       |-----FrmMainU.pas 

}

 {********** Begin HostApp.dpr **************}

 { Project file }

 program HostApp;

 uses
   Forms,
   FrmMainU in 'FrmMainU.pas' {FrmMain};

 {$R *.RES}

 begin
   Application.Initialize;
   Application.CreateForm(TFrmMain, FrmMain);
   Application.Run;
 end.

 {********** End HostApp.dpr **************}


 {********** Begin FrmMainU.pas **************}

 unit FrmMainU;

 interface

 uses
   Windows, Messages, SysUtils, Classes, Graphics, Controls, Forms, Dialogs,
   StdCtrls, ExtCtrls;

 const
   HookDemo = 'WINHOOK.dll';

 const
   WM_HOOKCREATE = WM_USER + 300;

 type
   TFrmMain = class(TForm)
     Panel1: TPanel;
     BtnSetHook: TButton;
     BtnClearHook: TButton;
     procedure BtnSetHookClick(Sender: TObject);
     procedure BtnClearHookClick(Sender: TObject);
     procedure FormCreate(Sender: TObject);
   private
     FHookSet: Boolean;
     procedure EnableButtons;
   public

   end;

 var
   FrmMain: TFrmMain;

 function SetHook(WinHandle: HWND; MsgToSend: Integer): Boolean; stdcall;
   external HookDemo;

 function FreeHook: Boolean; stdcall; external HookDemo;

 implementation

 {$R *.DFM}

 procedure TFrmMain.EnableButtons;
 begin
   BtnSetHook.Enabled   := not FHookSet;
   BtnClearHook.Enabled := FHookSet;
 end;

 // Start the Hook 
procedure TFrmMain.BtnSetHookClick(Sender: TObject);
 begin
   FHookSet := LongBool(SetHook(Handle, WM_HOOKCREATE));
   EnableButtons;
 end;

 // Stop the Hook 
procedure TFrmMain.BtnClearHookClick(Sender: TObject);
 begin
   FHookSet := FreeHook;
   EnableButtons;
   BtnClearHook.Enabled := False;
 end;

 procedure TFrmMain.FormCreate(Sender: TObject);
 begin
   EnableButtons;
 end;

 end.

 {********** End FrmMainU.pas **************}