/*
 * synergy -- mouse and keyboard sharing utility
 * Copyright (C) 2012-2016 Symless Ltd.
 * Copyright (C) 2011 Chris Schoeneman
 * 
 * This package is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * found in the file LICENSE that should have accompanied this file.
 * 
 * This package is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */

#include "platform/MSWindowsHook.h"
#include "synergy/protocol_types.h"
#include "synergy/XScreen.h"
#include "base/Log.h"

static const char* g_name = "synwinhk";

static DWORD            g_processID       = 0;
static DWORD            g_threadID        = 0;
static HHOOK            g_getMessage      = NULL;
static HHOOK            g_keyboardLL      = NULL;
static HHOOK            g_mouseLL         = NULL;
static bool                g_screenSaver     = false;
static EHookMode        g_mode            = kHOOK_DISABLE;
static UInt32            g_zoneSides       = 0;
static SInt32            g_zoneSize        = 0;
static SInt32            g_xScreen         = 0;
static SInt32            g_yScreen         = 0;
static SInt32            g_wScreen         = 0;
static SInt32            g_hScreen         = 0;
static WPARAM            g_deadVirtKey     = 0;
static WPARAM            g_deadRelease     = 0;
static LPARAM            g_deadLParam      = 0;
static BYTE                g_deadKeyState[256] = { 0 };
static BYTE                g_keyState[256]   = { 0 };
static DWORD            g_hookThread      = 0;
static bool                g_fakeServerInput       = false;
static BOOL				g_isPrimary = TRUE;

MSWindowsHook::MSWindowsHook()
{
}

MSWindowsHook::~MSWindowsHook()
{
    cleanup();

    if (g_processID == GetCurrentProcessId()) {
        uninstall();
        uninstallScreenSaver();
        g_processID = 0;
    }
}

void
MSWindowsHook::loadLibrary()
{
    if (g_processID == 0) {
        g_processID = GetCurrentProcessId();
    }

    // initialize library
    if (init(GetCurrentThreadId()) == 0) {
        LOG((CLOG_ERR "failed to init %s.dll, another program may be using it", g_name));
        LOG((CLOG_INFO "restarting your computer may solve this error"));
        throw XScreenOpenFailure();
    }
}

int
MSWindowsHook::init(DWORD threadID)
{
    // try to open process that last called init() to see if it's
    // still running or if it died without cleaning up.
    if (g_processID != 0 && g_processID != GetCurrentProcessId()) {
        HANDLE process = OpenProcess(STANDARD_RIGHTS_REQUIRED,
                                FALSE, g_processID);
        if (process != NULL) {
            // old process (probably) still exists so refuse to
            // reinitialize this DLL (and thus steal it from the
            // old process).
            int result = CloseHandle(process);
            if (result == false) {
                return 0;
            }
        }

        // clean up after old process.  the system should've already
        // removed the hooks so we just need to reset our state.
        g_processID       = GetCurrentProcessId();
        g_threadID        = 0;
        g_getMessage      = NULL;
        g_keyboardLL      = NULL;
        g_mouseLL         = NULL;
        g_screenSaver     = false;
    }

    // save thread id.  we'll post messages to this thread's
    // message queue.
    g_threadID  = threadID;

    // set defaults
    g_mode      = kHOOK_DISABLE;
    g_zoneSides = 0;
    g_zoneSize  = 0;
    g_xScreen   = 0;
    g_yScreen   = 0;
    g_wScreen   = 0;
    g_hScreen   = 0;

    return 1;
}

int
MSWindowsHook::cleanup()
{
    if (g_processID == GetCurrentProcessId()) {
        g_threadID = 0;
    }

    return 1;
}

void
MSWindowsHook::setSides(UInt32 sides)
{
    g_zoneSides = sides;
}

void
MSWindowsHook::setZone(SInt32 x, SInt32 y, SInt32 w, SInt32 h, SInt32 jumpZoneSize)
{
    g_zoneSize = jumpZoneSize;
    g_xScreen  = x;
    g_yScreen  = y;
    g_wScreen  = w;
    g_hScreen  = h;
}

void
MSWindowsHook::setMode(EHookMode mode)
{
    if (mode == g_mode) {
        // no change
        return;
    }
    g_mode = mode;
}

static
void
keyboardGetState(BYTE keys[256], DWORD vkCode, bool kf_up)
{
    // we have to use GetAsyncKeyState() rather than GetKeyState() because
    // we don't pass through most keys so the event synchronous state
    // doesn't get updated.  we do that because certain modifier keys have
    // side effects, like alt and the windows key.
    if (vkCode < 0 || vkCode >= 256) {
        return;
    }

    // Keep track of key state on our own in case GetAsyncKeyState() fails
    g_keyState[vkCode] = kf_up ? 0 : 0x80;
    g_keyState[VK_SHIFT] = g_keyState[VK_LSHIFT] | g_keyState[VK_RSHIFT];

    SHORT key;
    // Test whether GetAsyncKeyState() is being honest with us
    key = GetAsyncKeyState(vkCode);

    if (key & 0x80) {
        // The only time we know for sure that GetAsyncKeyState() is working
        // is when it tells us that the current key is down.
        // In this case, update g_keyState to reflect what GetAsyncKeyState()
        // is telling us, just in case we have gotten out of sync

        for (int i = 0; i < 256; ++i) {
            key = GetAsyncKeyState(i);
            g_keyState[i] = (BYTE)((key < 0) ? 0x80u : 0);
        }
    }

    // copy g_keyState to keys
    for (int i = 0; i < 256; ++i) {
        keys[i] = g_keyState[i];
    }

    key = GetKeyState(VK_CAPITAL);
    keys[VK_CAPITAL] = (BYTE)(((key < 0) ? 0x80 : 0) | (key & 1));
}

static
WPARAM
makeKeyMsg(UINT virtKey, char c, bool noAltGr)
{
    return MAKEWPARAM(MAKEWORD(virtKey & 0xff, (BYTE)c), noAltGr ? 1 : 0);
}

static
bool
keyboardHookHandler(WPARAM wParam, LPARAM lParam)
{
    DWORD vkCode = static_cast<DWORD>(wParam);
    bool kf_up = (lParam & (KF_UP << 16)) != 0;

    // check for special events indicating if we should start or stop
    // passing events through and not report them to the server.  this
    // is used to allow the server to synthesize events locally but
    // not pick them up as user events.
    if (wParam == SYNERGY_HOOK_FAKE_INPUT_VIRTUAL_KEY &&
        ((lParam >> 16) & 0xffu) == SYNERGY_HOOK_FAKE_INPUT_SCANCODE) {
        // update flag
        g_fakeServerInput = ((lParam & 0x80000000u) == 0);
        PostThreadMessage(g_threadID, SYNERGY_MSG_DEBUG,
                                0xff000000u | wParam, lParam);

        // discard event
        return true;
    }

    // if we're expecting fake input then just pass the event through
    // and do not forward to the server
    if (g_fakeServerInput) {
        PostThreadMessage(g_threadID, SYNERGY_MSG_DEBUG,
                                0xfe000000u | wParam, lParam);
        return false;
    }

    // VK_RSHIFT may be sent with an extended scan code but right shift
    // is not an extended key so we reset that bit.
    if (wParam == VK_RSHIFT) {
        lParam &= ~0x01000000u;
    }

    // tell server about event
    PostThreadMessage(g_threadID, SYNERGY_MSG_DEBUG, wParam, lParam);

    // ignore dead key release
    if ((g_deadVirtKey == wParam || g_deadRelease == wParam) &&
        (lParam & 0x80000000u) != 0) {
        g_deadRelease = 0;
        PostThreadMessage(g_threadID, SYNERGY_MSG_DEBUG,
                        wParam | 0x04000000, lParam);
        return false;
    }

    // we need the keyboard state for ToAscii()
    BYTE keys[256];
    keyboardGetState(keys, vkCode, kf_up);

    // ToAscii() maps ctrl+letter to the corresponding control code
    // and ctrl+backspace to delete.  we don't want those translations
    // so clear the control modifier state.  however, if we want to
    // simulate AltGr (which is ctrl+alt) then we must not clear it.
    UINT control = keys[VK_CONTROL] | keys[VK_LCONTROL] | keys[VK_RCONTROL];
    UINT menu    = keys[VK_MENU] | keys[VK_LMENU] | keys[VK_RMENU];
    if ((control & 0x80) == 0 || (menu & 0x80) == 0) {
        keys[VK_LCONTROL] = 0;
        keys[VK_RCONTROL] = 0;
        keys[VK_CONTROL]  = 0;
    }
    else {
        keys[VK_LCONTROL] = 0x80;
        keys[VK_RCONTROL] = 0x80;
        keys[VK_CONTROL]  = 0x80;
        keys[VK_LMENU]    = 0x80;
        keys[VK_RMENU]    = 0x80;
        keys[VK_MENU]     = 0x80;
    }

    // ToAscii() needs to know if a menu is active for some reason.
    // we don't know and there doesn't appear to be any way to find
    // out.  so we'll just assume a menu is active if the menu key
    // is down.
    // FIXME -- figure out some way to check if a menu is active
    UINT flags = 0;
    if ((menu & 0x80) != 0)
        flags |= 1;

    // if we're on the server screen then just pass numpad keys with alt
    // key down as-is.  we won't pick up the resulting character but the
    // local app will.  if on a client screen then grab keys as usual;
    // if the client is a windows system it'll synthesize the expected
    // character.  if not then it'll probably just do nothing.
    if (g_mode != kHOOK_RELAY_EVENTS) {
        // we don't use virtual keys because we don't know what the
        // state of the numlock key is.  we'll hard code the scan codes
        // instead.  hopefully this works across all keyboards.
        UINT sc = (lParam & 0x01ff0000u) >> 16;
        if (menu &&
            (sc >= 0x47u && sc <= 0x52u && sc != 0x4au && sc != 0x4eu)) {
            return false;
        }
    }

    WORD c        = 0;

    // map the key event to a character.  we have to put the dead
    // key back first and this has the side effect of removing it.
    if (g_deadVirtKey != 0) {
        if (ToAscii((UINT)g_deadVirtKey, (g_deadLParam & 0x10ff0000u) >> 16,
                    g_deadKeyState, &c, flags) == 2)
        {
            // If ToAscii returned 2, it means that we accidentally removed
            // a double dead key instead of restoring it. Thus, we call
            // ToAscii again with the same parameters to restore the
            // internal dead key state.
            ToAscii((UINT)g_deadVirtKey, (g_deadLParam & 0x10ff0000u) >> 16,
                    g_deadKeyState, &c, flags);

            // We need to keep track of this because g_deadVirtKey will be
            // cleared later on; this would cause the dead key release to
            // incorrectly restore the dead key state.
            g_deadRelease = g_deadVirtKey;
        }
    }

    UINT scanCode = ((lParam & 0x10ff0000u) >> 16);
    int n         = ToAscii((UINT)wParam, scanCode, keys, &c, flags);

    // if mapping failed and ctrl and alt are pressed then try again
    // with both not pressed.  this handles the case where ctrl and
    // alt are being used as individual modifiers rather than AltGr.
    // we note that's the case in the message sent back to synergy
    // because there's no simple way to deduce it after the fact.
    // we have to put the dead key back first, if there was one.
    bool noAltGr = false;
    if (n == 0 && (control & 0x80) != 0 && (menu & 0x80) != 0) {
        noAltGr = true;
        PostThreadMessage(g_threadID, SYNERGY_MSG_DEBUG,
                            wParam | 0x05000000, lParam);
        if (g_deadVirtKey != 0) {
            if (ToAscii((UINT)g_deadVirtKey, (g_deadLParam & 0x10ff0000u) >> 16,
                            g_deadKeyState, &c, flags) == 2)
            {
                ToAscii((UINT)g_deadVirtKey, (g_deadLParam & 0x10ff0000u) >> 16,
                            g_deadKeyState, &c, flags);
                g_deadRelease = g_deadVirtKey;
            }
        }
        BYTE keys2[256];
        for (size_t i = 0; i < sizeof(keys) / sizeof(keys[0]); ++i) {
            keys2[i] = keys[i];
        }
        keys2[VK_LCONTROL] = 0;
        keys2[VK_RCONTROL] = 0;
        keys2[VK_CONTROL]  = 0;
        keys2[VK_LMENU]    = 0;
        keys2[VK_RMENU]    = 0;
        keys2[VK_MENU]     = 0;
        n = ToAscii((UINT)wParam, scanCode, keys2, &c, flags);
    }

    PostThreadMessage(g_threadID, SYNERGY_MSG_DEBUG,
                            wParam | ((c & 0xff) << 8) |
                            ((n & 0xff) << 16) | 0x06000000,
                            lParam);
    WPARAM charAndVirtKey = 0;
    bool clearDeadKey = false;
    switch (n) {
    default:
        // key is a dead key

        if (lParam & 0x80000000u)
            // This handles the obscure situation where a key has been
            // pressed which is both a dead key and a normal character
            // depending on which modifiers have been pressed. We
            // break here to prevent it from being considered a dead
            // key.
            break;

        g_deadVirtKey = wParam;
        g_deadLParam  = lParam;
        for (size_t i = 0; i < sizeof(keys) / sizeof(keys[0]); ++i) {
            g_deadKeyState[i] = keys[i];
        }
        break;

    case 0:
        // key doesn't map to a character.  this can happen if
        // non-character keys are pressed after a dead key.
        charAndVirtKey = makeKeyMsg((UINT)wParam, (char)0, noAltGr);
        break;

    case 1:
        // key maps to a character composed with dead key
        charAndVirtKey = makeKeyMsg((UINT)wParam, (char)LOBYTE(c), noAltGr);
        clearDeadKey   = true;
        break;

    case 2: {
        // previous dead key not composed.  send a fake key press
        // and release for the dead key to our window.
        WPARAM deadCharAndVirtKey =
                            makeKeyMsg((UINT)g_deadVirtKey, (char)LOBYTE(c), noAltGr);
        PostThreadMessage(g_threadID, SYNERGY_MSG_KEY,
                            deadCharAndVirtKey, g_deadLParam & 0x7fffffffu);
        PostThreadMessage(g_threadID, SYNERGY_MSG_KEY,
                            deadCharAndVirtKey, g_deadLParam | 0x80000000u);

        // use uncomposed character
        charAndVirtKey = makeKeyMsg((UINT)wParam, (char)HIBYTE(c), noAltGr);
        clearDeadKey   = true;
        break;
    }
    }

    // put back the dead key, if any, for the application to use
    if (g_deadVirtKey != 0) {
        ToAscii((UINT)g_deadVirtKey, (g_deadLParam & 0x10ff0000u) >> 16,
                            g_deadKeyState, &c, flags);
    }

    // clear out old dead key state
    if (clearDeadKey) {
        g_deadVirtKey = 0;
        g_deadLParam  = 0;
    }

    // forward message to our window.  do this whether or not we're
    // forwarding events to clients because this'll keep our thread's
    // key state table up to date.  that's important for querying
    // the scroll lock toggle state.
    // XXX -- with hot keys for actions we may only need to do this when
    // forwarding.
    if (charAndVirtKey != 0) {
        PostThreadMessage(g_threadID, SYNERGY_MSG_DEBUG,
                            charAndVirtKey | 0x07000000, lParam);
        PostThreadMessage(g_threadID, SYNERGY_MSG_KEY, charAndVirtKey, lParam);
    }

    if (g_mode == kHOOK_RELAY_EVENTS) {
        // let certain keys pass through
        switch (wParam) {
        case VK_CAPITAL:
        case VK_NUMLOCK:
        case VK_SCROLL:
            // pass event on.  we want to let these through to
            // the window proc because otherwise the keyboard
            // lights may not stay synchronized.
            break;

        case VK_HANGUL:
            // pass these modifiers if using a low level hook, discard
            // them if not.
            if (g_hookThread == 0) {
                return true;
            }
            break;

        default:
            // discard
            return true;
        }
    }

    return false;
}


#if !NO_GRAB_KEYBOARD
static
LRESULT CALLBACK
keyboardLLHook(int code, WPARAM wParam, LPARAM lParam)
{
    if (code >= 0) {
        // decode the message
        KBDLLHOOKSTRUCT* info = reinterpret_cast<KBDLLHOOKSTRUCT*>(lParam);

        bool const injected = info->flags & LLKHF_INJECTED;
        if (!g_isPrimary && injected) {
            return CallNextHookEx (g_keyboardLL, code, wParam, lParam);
        }

        WPARAM wParam = info->vkCode;
        LPARAM lParam = 1;                            // repeat code
        lParam      |= (info->scanCode << 16);        // scan code
        if (info->flags & LLKHF_EXTENDED) {
            lParam  |= (1lu << 24);                    // extended key
        }
        if (info->flags & LLKHF_ALTDOWN) {
            lParam  |= (1lu << 29);                    // context code
        }
        if (info->flags & LLKHF_UP) {
            lParam  |= (1lu << 31);                    // transition
        }
        // FIXME -- bit 30 should be set if key was already down but
        // we don't know that info.  as a result we'll never generate
        // key repeat events.

        // handle the message
        if (keyboardHookHandler(wParam, lParam)) {
            return 1;
        }
    }

    return CallNextHookEx(g_keyboardLL, code, wParam, lParam);
}
#endif

//
// low-level mouse hook -- this allows us to capture and handle mouse
// events very early.  the earlier the better.
//

static
bool
mouseHookHandler(WPARAM wParam, SInt32 x, SInt32 y, SInt32 data)
{
    switch (wParam) {
    case WM_LBUTTONDOWN:
    case WM_MBUTTONDOWN:
    case WM_RBUTTONDOWN:
    case WM_XBUTTONDOWN:
    case WM_LBUTTONDBLCLK:
    case WM_MBUTTONDBLCLK:
    case WM_RBUTTONDBLCLK:
    case WM_XBUTTONDBLCLK:
    case WM_LBUTTONUP:
    case WM_MBUTTONUP:
    case WM_RBUTTONUP:
    case WM_XBUTTONUP:
    case WM_NCLBUTTONDOWN:
    case WM_NCMBUTTONDOWN:
    case WM_NCRBUTTONDOWN:
    case WM_NCXBUTTONDOWN:
    case WM_NCLBUTTONDBLCLK:
    case WM_NCMBUTTONDBLCLK:
    case WM_NCRBUTTONDBLCLK:
    case WM_NCXBUTTONDBLCLK:
    case WM_NCLBUTTONUP:
    case WM_NCMBUTTONUP:
    case WM_NCRBUTTONUP:
    case WM_NCXBUTTONUP:
        // always relay the event.  eat it if relaying.
        PostThreadMessage(g_threadID, SYNERGY_MSG_MOUSE_BUTTON, wParam, data);
        return (g_mode == kHOOK_RELAY_EVENTS);

    case WM_MOUSEWHEEL:
        if (g_mode == kHOOK_RELAY_EVENTS) {
            // relay event
            PostThreadMessage(g_threadID, SYNERGY_MSG_MOUSE_WHEEL, data, 0);
        }
        return (g_mode == kHOOK_RELAY_EVENTS);

    case WM_NCMOUSEMOVE:
    case WM_MOUSEMOVE:
        if (g_mode == kHOOK_RELAY_EVENTS) {
            // relay and eat event
            PostThreadMessage(g_threadID, SYNERGY_MSG_MOUSE_MOVE, x, y);
            return true;
        }
        else if (g_mode == kHOOK_WATCH_JUMP_ZONE) {
            // low level hooks can report bogus mouse positions that are
            // outside of the screen.  jeez.  naturally we end up getting
            // fake motion in the other direction to get the position back
            // on the screen, which plays havoc with switch on double tap.
            // Server deals with that.  we'll clamp positions onto the
            // screen.  also, if we discard events for positions outside
            // of the screen then the mouse appears to get a bit jerky
            // near the edge.  we can either accept that or pass the bogus
            // events.  we'll try passing the events.
            bool bogus = false;
            if (x < g_xScreen) {
                x     = g_xScreen;
                bogus = true;
            }
            else if (x >= g_xScreen + g_wScreen) {
                x     = g_xScreen + g_wScreen - 1;
                bogus = true;
            }
            if (y < g_yScreen) {
                y     = g_yScreen;
                bogus = true;
            }
            else if (y >= g_yScreen + g_hScreen) {
                y     = g_yScreen + g_hScreen - 1;
                bogus = true;
            }

            // check for mouse inside jump zone
            bool inside = false;
            if (!inside && (g_zoneSides & kLeftMask) != 0) {
                inside = (x < g_xScreen + g_zoneSize);
            }
            if (!inside && (g_zoneSides & kRightMask) != 0) {
                inside = (x >= g_xScreen + g_wScreen - g_zoneSize);
            }
            if (!inside && (g_zoneSides & kTopMask) != 0) {
                inside = (y < g_yScreen + g_zoneSize);
            }
            if (!inside && (g_zoneSides & kBottomMask) != 0) {
                inside = (y >= g_yScreen + g_hScreen - g_zoneSize);
            }

            // relay the event
            PostThreadMessage(g_threadID, SYNERGY_MSG_MOUSE_MOVE, x, y);

            // if inside and not bogus then eat the event
            return inside && !bogus;
        }
    }

    // pass the event
    return false;
}


static
LRESULT CALLBACK
mouseLLHook(int code, WPARAM wParam, LPARAM lParam)
{
    if (code >= 0) {
        // decode the message
        MSLLHOOKSTRUCT* info = reinterpret_cast<MSLLHOOKSTRUCT*>(lParam);

        bool const injected = info->flags & LLMHF_INJECTED;
        if (!g_isPrimary && injected) {
            return CallNextHookEx(g_mouseLL, code, wParam, lParam);
        }

        SInt32 x = static_cast<SInt32>(info->pt.x);
        SInt32 y = static_cast<SInt32>(info->pt.y);
        SInt32 w = static_cast<SInt16>(HIWORD(info->mouseData));

        // handle the message
        if (mouseHookHandler(wParam, x, y, w)) {
            return 1;
        }
    }

    return CallNextHookEx(g_mouseLL, code, wParam, lParam);
}

EHookResult
MSWindowsHook::install()
{
    assert(g_getMessage == NULL || g_screenSaver);

    // must be initialized
    if (g_threadID == 0) {
        return kHOOK_FAILED;
    }

    // discard old dead keys
    g_deadVirtKey = 0;
    g_deadLParam  = 0;

    // reset fake input flag
    g_fakeServerInput = false;

    // install low-level hooks.  we require that they both get installed.
    g_mouseLL = SetWindowsHookEx(WH_MOUSE_LL,
                                &mouseLLHook,
                                NULL,
                                0);
#if !NO_GRAB_KEYBOARD
    g_keyboardLL = SetWindowsHookEx(WH_KEYBOARD_LL,
                                &keyboardLLHook,
                                NULL,
                                0);
    if (g_mouseLL == NULL || g_keyboardLL == NULL) {
        if (g_keyboardLL != NULL) {
            UnhookWindowsHookEx(g_keyboardLL);
            g_keyboardLL = NULL;
        }
        if (g_mouseLL != NULL) {
            UnhookWindowsHookEx(g_mouseLL);
            g_mouseLL = NULL;
        }
    }
#endif

    // check that we got all the hooks we wanted
    if ((g_mouseLL    == NULL) ||
#if !NO_GRAB_KEYBOARD
        (g_keyboardLL == NULL)
#endif
        ) {
        uninstall();
        return kHOOK_FAILED;
    }

    if (g_keyboardLL != NULL || g_mouseLL != NULL) {
        g_hookThread = GetCurrentThreadId();
        return kHOOK_OKAY_LL;
    }

    return kHOOK_OKAY;
}

int
MSWindowsHook::uninstall()
{
    // discard old dead keys
    g_deadVirtKey = 0;
    g_deadLParam  = 0;

    // uninstall hooks
    if (g_keyboardLL != NULL) {
        UnhookWindowsHookEx(g_keyboardLL);
        g_keyboardLL = NULL;
    }
    if (g_mouseLL != NULL) {
        UnhookWindowsHookEx(g_mouseLL);
        g_mouseLL = NULL;
    }
    if (g_getMessage != NULL && !g_screenSaver) {
        UnhookWindowsHookEx(g_getMessage);
        g_getMessage = NULL;
    }

    return 1;
}

static
LRESULT CALLBACK
getMessageHook(int code, WPARAM wParam, LPARAM lParam)
{
    if (code >= 0) {
        if (g_screenSaver) {
            MSG* msg = reinterpret_cast<MSG*>(lParam);
            if (msg->message == WM_SYSCOMMAND &&
                msg->wParam  == SC_SCREENSAVE) {
                // broadcast screen saver started message
                PostThreadMessage(g_threadID,
                                SYNERGY_MSG_SCREEN_SAVER, TRUE, 0);
            }
        }
    }

    return CallNextHookEx(g_getMessage, code, wParam, lParam);
}

int
MSWindowsHook::installScreenSaver()
{
    // must be initialized
    if (g_threadID == 0) {
        return 0;
    }

    // generate screen saver messages
    g_screenSaver = true;

    // install hook unless it's already installed
    if (g_getMessage == NULL) {
        g_getMessage = SetWindowsHookEx(WH_GETMESSAGE,
                                &getMessageHook,
                                NULL,
                                0);
    }

    return (g_getMessage != NULL) ? 1 : 0;
}

int
MSWindowsHook::uninstallScreenSaver()
{
    // uninstall hook unless the mouse wheel hook is installed
    if (g_getMessage != NULL) {
        UnhookWindowsHookEx(g_getMessage);
        g_getMessage = NULL;
    }

    // screen saver hook is no longer installed
    g_screenSaver = false;

    return 1;
}