/* Copyright 2000 by Symantec Corporation--------------------------------------

 File : LowLevelKeyHook.cpp

 Purpose : Install a hook prior to the system window procedure to catch
 Alt+Tab, Shift+Alt+Tab, Alt+Esc, Ctrl+Esc

 Author: E. Feldl, July 2000
----------------------------------------------------------------------------- */

// Must be before stdafx.h. Necessary for compile. We later poll the OS to
// determine if we should run NT/2000 or 98 code.
#define _WIN32_WINNT  0x0400

#include <afxwin.h>        // AfxGetInstanceHandle();
#include <windows.h>
#include <winuser.h>

#include "lowlevelkeyhook.h"
#include "globdefs.h"      // #define TERMWINDOW_CLASS_NAME (LPSTR)"TERMWindow"

HHOOK CurrentHook  = NULL; // necessary for LowLevelKeyboardProc
int   MajorVersion = 0;

/* -----------------------------------------------------------------------------
Routine:    "PreSysWndProcKeyHook"

Purpose:    Install the windows hook and register the custom messages.

Parameter            Type           Description
---------            ----           -----------
NONE

Initializer          Type           Description
-----------          ----           -----------
m_Hook               HHOOK          Current Window Hook

Creation Date: July 2000, E. Feldl
----------------------------------------------------------------------------- */
PreSysWndProcKeyHook::PreSysWndProcKeyHook() : m_Hook(NULL)
{

    // Please note that WH_KEYBOARD_LL used in SetWindowsHookEx is only valid
    // on Windows NT 4.0 Service Pack 3 or greater. This also serves as a
    // placeholder were code for other operating systems can be added.
    IsNTVersion4OrHigher(MajorVersion);

    if((MajorVersion == 4 && GetServicePack() >= 3)|| MajorVersion >= 5)
    {
        // Please note that RegisterWindowsMessage can perform two functions.
        // It can return a new unique message id or it can look up and existing
        // id. Therefor registering the same call twice does not result in
        // multiple identifiers.
        RegisterWindowMessage(CTRL_ESC_MSG);
        RegisterWindowMessage(ALT_ESC_MSG);
        RegisterWindowMessage(BRINGUPTASKSWITCHER_MSG);
        RegisterWindowMessage(TABNEXTTASK_MSG);

        // Do not install the hook unless this is NT4 SP3.
        m_Hook = InstallWindowHook();

        // We should pass in our current hook into CallNextHookEx and since
        // LowLevelKeyboardProc must be a C function, we need this global
        // to store it's value.
        CurrentHook = m_Hook;

    }
}
/* -----------------------------------------------------------------------------
Routine:    "~PreSysWndProcKeyHook"

Purpose:    Uninstall the hook.

Parameter            Type           Description
---------            ----           -----------
NONE

Creation Date: July 2000, E. Feldl
----------------------------------------------------------------------------- */
PreSysWndProcKeyHook::~PreSysWndProcKeyHook()
{
    // No need to call UnhookWindowsHookEx unless we installed the Hook. This
    // also serves as a placeholder for code for other operating systems.
    if((MajorVersion == 4 && GetServicePack() >= 3)|| MajorVersion >= 5)
    {
        UnhookWindowsHookEx(m_Hook);
        CurrentHook = NULL;
    }

}
/* -----------------------------------------------------------------------------
Routine:    "InstallWindowHook"

Purpose:    Wrap SetWindowsHookEx with checking.

Parameter            Type           Description
---------            ----           -----------
NONE

Returns              Type           Description
---------            ----           -----------
hHook                HHOOK          Current Window Hook

Creation Date: July 2000, E. Feldl
----------------------------------------------------------------------------- */
HHOOK PreSysWndProcKeyHook::InstallWindowHook()
{
    HHOOK hHook = SetWindowsHookEx(WH_KEYBOARD_LL,
                                   LowLevelKeyboardProc,
                                   AfxGetInstanceHandle(),
                                   0);
    ASSERT(hHook != NULL);

    return hHook;
}
/* -----------------------------------------------------------------------------
Routine:    "IsNTVersion4OrHigher"

Purpose:

    Check to see if this is NT 4.0 or greater. WH_KEYBOARD_LL is only valid on
    these systems.

Parameter            Type                 Description
---------            ----                 -----------
version              integer reference    Used to return the major version number

Returns              Type                 Description
---------            ----                 -----------
                     BOOL                 True if NT4, False otherwise

Creation Date: July 2000, E. Feldl
----------------------------------------------------------------------------- */
BOOL PreSysWndProcKeyHook::IsNTVersion4OrHigher(int &version)
{
    OSVERSIONINFO os;
    os.dwOSVersionInfoSize = sizeof(OSVERSIONINFO);

    GetVersionEx(&os);

    if(os.dwPlatformId == VER_PLATFORM_WIN32_NT &&
       os.dwMajorVersion >= 4 )
    {
        version = os.dwMajorVersion;
        return TRUE;
    }
    else
    {
        version = 0;
        return FALSE;
    }
}
/* -----------------------------------------------------------------------------
Routine:    "LowLevelKeyboardProc"

Purpose:    The "C" hook function to install.

Parameter            Type               Description
---------            ----               -----------
nCode                int                Hook code passed to hook procedure
wParam               WPARAM             Custom messages wParam == NULL
lParam               LPARAM             Custom messages lParam == NULL

Returns              Type               Description
---------            ----               -----------
                     LRESULT CALLBACK   Windows Callback Function

Creation Date: July 2000, E. Feldl
----------------------------------------------------------------------------- */
LRESULT CALLBACK PreSysWndProcKeyHook::LowLevelKeyboardProc(int nCode,
                                                            WPARAM wParam,
                                                            LPARAM lParam)
{
    // Allow us to disable CallNextHookEx
    BOOL   fEatKeystroke            = FALSE;
    // Handle to our terminal window
    HWND   hFindWnd                 = NULL;
    // Used to toggle Alt+Tab, Tab, Tab .... in task switcher
    static BOOL RanOnce             = FALSE;

    //  Is the scroll key toggled on?
    BOOL ScrollLocked = GetKeyState(VK_SCROLL) & 0x0001;

    // If Scroll not locked don't handle.
    if((nCode == HC_ACTION) && ScrollLocked)
    {
        // Stores the low level keyboard event information.
        PKBDLLHOOKSTRUCT pInfoLowLevelEvent = (PKBDLLHOOKSTRUCT)lParam;

        // hFindWnd must be correct or else PostMessage
        // won't go to correct window proc.
        hFindWnd = FindWindow(TERMWINDOW_CLASS_NAME,NULL);

        // If our window isn't the active one, we shouldn't capture keys.
        if(hFindWnd != GetForegroundWindow())
        {
            return CallNextHookEx(CurrentHook, nCode, wParam, lParam);
        }

        // We must have a window to send the messages to.
        ASSERT(hFindWnd != NULL);

        //if(wParam == WM_KEYDOWN || wParam == WM_SYSKEYDOWN)
        switch(wParam)
        {
            case WM_KEYDOWN: case WM_SYSKEYDOWN:
            // Yes we are interested in these keys

            // ALT-DOWN+TAB-DOWN
            if((pInfoLowLevelEvent->vkCode==VK_TAB)&&
               ((pInfoLowLevelEvent->flags&LLKHF_ALTDOWN)!=0))
            {

                if(RanOnce == FALSE)
                {
                   // We need to bring up the task switcher.
                   SendCustomMessage(hFindWnd,
                             RegisterWindowMessage(BRINGUPTASKSWITCHER_MSG));
                   fEatKeystroke = TRUE;
                   RanOnce =TRUE;
                }
                else
                {
                   // We need to tab through the task switcher.
                   SendCustomMessage(hFindWnd,
                             RegisterWindowMessage(TABNEXTTASK_MSG));
                   fEatKeystroke = TRUE;
                }
            }
            else
            {
                // We did something besides Alt+Tab so reset Alt+Tab mechanism.
                // This is required because Alt+Tab can perform two functions.
                // It can bring up the task switcher and it can tab through the
                // tasks in the task switcher. RanOnce determines the correct
                // mode of operation.
                RanOnce = FALSE;

                // Alt+Esc ------------------------------
                if((pInfoLowLevelEvent->vkCode==VK_ESCAPE)&&
                   ((pInfoLowLevelEvent->flags&LLKHF_ALTDOWN)!=0))
                {
                    SendCustomMessage(hFindWnd,
                              RegisterWindowMessage(ALT_ESC_MSG));
                    fEatKeystroke = TRUE;
                }
                // Ctrl+Esc ------------------------------
                else if((pInfoLowLevelEvent->vkCode==VK_ESCAPE)&&
                        ((GetKeyState(VK_CONTROL) & 0x8000) != 0))
                {
                    // Ctrl+Esc does not work on NT4, just 2000
                    if(MajorVersion >= 5)
                    {
                        SendCustomMessage(hFindWnd,
                                  RegisterWindowMessage(CTRL_ESC_MSG));
                        fEatKeystroke = TRUE;
                    }
                }

            } // end else

        }  // end switch wParam

    }  // end if nCode == HC_ACTION && ScrollLocked

    // Call the next hook or eat the key.
    if(fEatKeystroke)
    {
        return 1;
    }
    else
    {
        return CallNextHookEx(CurrentHook, nCode, wParam, lParam);
    }
}
/* -----------------------------------------------------------------------------
Routine:    "SendCustomMessage"

Purpose:    Sends the custom message to the window.

Parameter            Type               Description
---------            ----               -----------
hWnd                 HWND               Handle to our window that will receive the
                                        message.
MessageId            UINT               Custom messages

Returns              Type               Description
---------            ----               -----------
NONE

Creation Date: July 2000, E. Feldl
----------------------------------------------------------------------------- */
void PreSysWndProcKeyHook::SendCustomMessage(HWND hWnd, UINT MessageId)
{
    ASSERT(MessageId != 0);

    BOOL Status = PostMessage(hWnd, MessageId, NULL, NULL);

    ASSERT(Status == TRUE);
}
/* -----------------------------------------------------------------------------
Routine:    "GetServicePack"

Purpose:    Gets the NT Service Pack number.

Parameter            Type               Description
---------            ----               -----------
NONE

Returns              Type               Description
---------            ----               -----------
iRet                 int                The Service Pack number

Creation Date: July 2000, E. Feldl, M. Vanloon
----------------------------------------------------------------------------- */
int PreSysWndProcKeyHook::GetServicePack()
{
    OSVERSIONINFO os;
    int iRet=0;

    os.dwOSVersionInfoSize = sizeof(OSVERSIONINFO);
    GetVersionEx(&os);

    if (os.dwPlatformId == VER_PLATFORM_WIN32_NT)
    {
        if (os.szCSDVersion)
        {
            int pos = strcspn(os.szCSDVersion,"1234567890");
            iRet = atoi(os.szCSDVersion + pos);
        }
    }

    return iRet;
}

// End of File: LowLevelKeyHook.cpp -----------------------------------------------