/*
 *  ReactOS W32 Subsystem
 *  Copyright (C) 1998, 1999, 2000, 2001, 2002, 2003, 2004 ReactOS Team
 *
 *  This program is free software; you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License as published by
 *  the Free Software Foundation; either version 2 of the License, or
 *  (at your option) any later version.
 *
 *  This program 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, write to the Free Software Foundation, Inc.,
 *  51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 *  COPYRIGHT:        See COPYING in the top level directory
 *  PROJECT:          ReactOS kernel
 *  PURPOSE:          Monitor support
 *  FILE:             subsys/win32k/ntuser/monitor.c
 *  PROGRAMER:        Anich Gregor (blight@blight.eu.org)
 *  REVISION HISTORY:
 *       26-02-2004  Created
 */

/* INCLUDES ******************************************************************/

#include <win32k.h>

/* FIXME: find include file for these */
#define MONITORINFOF_PRIMARY      1
#define MONITOR_DEFAULTTONULL     0
#define MONITOR_DEFAULTTOPRIMARY  1
#define MONITOR_DEFAULTTONEAREST  2

#define NDEBUG
#include <debug.h>

/* GLOBALS *******************************************************************/

/* list of monitors */
static PMONITOR gMonitorList = NULL;

/* INITALIZATION FUNCTIONS ****************************************************/

NTSTATUS
InitMonitorImpl()
{
   DPRINT("Initializing monitor implementation...\n");

   return STATUS_SUCCESS;
}

NTSTATUS
CleanupMonitorImpl()
{
   DPRINT("Cleaning up monitor implementation...\n");
   /* FIXME: Destroy monitor objects? */

   return STATUS_SUCCESS;
}

/* PRIVATE FUNCTIONS **********************************************************/

#ifndef MIN
# define MIN(a, b) ((a) < (b) ? (a) : (b))
#endif
#ifndef MAX
# define MAX(a, b) ((a) > (b) ? (a) : (b))
#endif
#ifndef ABS
# define ABS(a) ((a) < (0) ? (-(a)) : (a))
#endif

/* IntCreateMonitorObject
 *
 * Creates a MONITOR
 *
 * Return value
 *   If the function succeeds a pointer to a MONITOR is returned. On failure
 *   NULL is returned.
 */
static
PMONITOR
IntCreateMonitorObject()
{
   HANDLE Handle;
   PMONITOR Monitor;

   Monitor = UserCreateObject(gHandleTable, NULL, &Handle, otMonitor, sizeof (MONITOR));
   if (Monitor == NULL)
   {
      return NULL;
   }

   ExInitializeFastMutex(&Monitor->Lock);

   return Monitor;
}

/* IntDestroyMonitorObject
 *
 * Destroys a MONITOR
 * You have to be the owner of the monitors lock to safely destroy it.
 *
 * Arguments
 *
 *   pMonitor
 *      Pointer to the MONITOR which shall be deleted
 */
static
void
IntDestroyMonitorObject(IN PMONITOR pMonitor)
{
   RtlFreeUnicodeString(&pMonitor->DeviceName);
   UserDereferenceObject(pMonitor);
}


PMONITOR FASTCALL
UserGetMonitorObject(IN HMONITOR hMonitor)
{
   PMONITOR Monitor;

   if (!hMonitor)
   {
      SetLastWin32Error(ERROR_INVALID_MONITOR_HANDLE);
      return NULL;
   }


   Monitor = (PMONITOR)UserGetObject(gHandleTable, hMonitor, otMonitor);
   if (!Monitor)
   {
      SetLastWin32Error(ERROR_INVALID_MONITOR_HANDLE);
      return NULL;
   }

   ASSERT(Monitor->head.cLockObj >= 0);

   return Monitor;
}


/* IntAttachMonitor
 *
 * Creates a new MONITOR and appends it to the list of monitors.
 *
 * Arguments
 *
 *   pGdiDevice     Pointer to the PDEVOBJ onto which the monitor was attached
 *   DisplayNumber  Display Number (starting with 0)
 *
 * Return value
 *   Returns a NTSTATUS
 */
NTSTATUS
IntAttachMonitor(IN PDEVOBJ *pGdiDevice,
                 IN ULONG DisplayNumber)
{
   PMONITOR Monitor;
   WCHAR Buffer[CCHDEVICENAME];

   DPRINT("Attaching monitor...\n");

   /* create new monitor object */
   Monitor = IntCreateMonitorObject();
   if (Monitor == NULL)
   {
      DPRINT("Couldnt create monitor object\n");
      return STATUS_INSUFFICIENT_RESOURCES;
   }

   _snwprintf(Buffer, CCHDEVICENAME, L"\\\\.\\DISPLAY%d", DisplayNumber + 1);
   if (!RtlCreateUnicodeString(&Monitor->DeviceName, Buffer))
   {
      DPRINT("Couldn't duplicate monitor name!\n");
      UserDereferenceObject(Monitor);
      UserDeleteObject(UserHMGetHandle(Monitor), otMonitor);
      return STATUS_INSUFFICIENT_RESOURCES;
   }

   Monitor->GdiDevice = pGdiDevice;
   Monitor->rcMonitor.left  = 0;
   Monitor->rcMonitor.top   = 0;
   Monitor->rcMonitor.right  = Monitor->rcMonitor.left + pGdiDevice->gdiinfo.ulHorzRes;
   Monitor->rcMonitor.bottom = Monitor->rcMonitor.top + pGdiDevice->gdiinfo.ulVertRes;
   Monitor->rcWork = Monitor->rcMonitor;
   Monitor->cWndStack = 0;

   Monitor->hrgnMonitor = IntSysCreateRectRgnIndirect( &Monitor->rcMonitor );

   IntGdiSetRegionOwner(Monitor->hrgnMonitor, GDI_OBJ_HMGR_PUBLIC);

   if (gMonitorList == NULL)
   {
      DPRINT("Primary monitor is beeing attached\n");
      Monitor->IsPrimary = TRUE;
      gMonitorList = Monitor;
   }
   else
   {
      PMONITOR p;
      DPRINT("Additional monitor is beeing attached\n");
      for (p = gMonitorList; p->Next != NULL; p = p->Next)
      {
         p->Next = Monitor;
      }
      Monitor->Prev = p;
   }

   return STATUS_SUCCESS;
}

/* IntDetachMonitor
 *
 * Deletes a MONITOR and removes it from the list of monitors.
 *
 * Arguments
 *
 *   pGdiDevice  Pointer to the PDEVOBJ from which the monitor was detached
 *
 * Return value
 *   Returns a NTSTATUS
 */
NTSTATUS
IntDetachMonitor(IN PDEVOBJ *pGdiDevice)
{
   PMONITOR Monitor;

   for (Monitor = gMonitorList; Monitor != NULL; Monitor = Monitor->Next)
   {
      if (Monitor->GdiDevice == pGdiDevice)
         break;
   }

   if (Monitor == NULL)
   {
      /* no monitor for given device found */
      return STATUS_INVALID_PARAMETER;
   }

   if (Monitor->IsPrimary && (Monitor->Next != NULL || Monitor->Prev != NULL))
   {
      PMONITOR NewPrimaryMonitor = (Monitor->Prev != NULL) ? (Monitor->Prev) : (Monitor->Next);

      ExEnterCriticalRegionAndAcquireFastMutexUnsafe(&NewPrimaryMonitor->Lock);
      NewPrimaryMonitor->IsPrimary = TRUE;
      ExReleaseFastMutexUnsafeAndLeaveCriticalRegion(&NewPrimaryMonitor->Lock);
   }

   if (gMonitorList == Monitor)
   {
      gMonitorList = Monitor->Next;
      if (Monitor->Next != NULL)
         Monitor->Next->Prev = NULL;
   }
   else
   {
      Monitor->Prev->Next = Monitor->Next;
      if (Monitor->Next != NULL)
         Monitor->Next->Prev = Monitor->Prev;
   }

   if (Monitor->hrgnMonitor)
      REGION_FreeRgnByHandle(Monitor->hrgnMonitor);

   IntDestroyMonitorObject(Monitor);

   return STATUS_SUCCESS;
}

/* IntGetPrimaryMonitor
 *
 * Returns a PMONITOR for the primary monitor
 *
 * Return value
 *   PMONITOR
 */
PMONITOR
FASTCALL
IntGetPrimaryMonitor()
{
   PMONITOR Monitor;

   for (Monitor = gMonitorList; Monitor != NULL; Monitor = Monitor->Next)
   {
      /* FIXME: I guess locking the monitor is not neccessary to read 1 int */
      if (Monitor->IsPrimary)
         break;
   }

   return Monitor;
}

/* IntGetMonitorsFromRect
 *
 * Returns a list of monitor handles/rectangles. The rectangles in the list are
 * the areas of intersection with the monitors.
 *
 * Arguments
 *
 *   pRect
 *      Rectangle in desktop coordinates. If this is NULL all monitors are
 *      returned and the rect list is filled with the sizes of the monitors.
 *
 *   hMonitorList
 *      Pointer to an array of HMONITOR which is filled with monitor handles.
 *      Can be NULL
 *
 *   monitorRectList
 *      Pointer to an array of RECT which is filled with intersection rects in
 *      desktop coordinates.
 *      Can be NULL, will be ignored if no intersecting monitor is found and
 *      flags is MONITOR_DEFAULTTONEAREST
 *
 *   listSize
 *      Size of the hMonitorList and monitorRectList arguments. If this is zero
 *      hMonitorList and monitorRectList are ignored.
 *
 *   flags
 *      Either 0 or MONITOR_DEFAULTTONEAREST (ignored if rect is NULL)
 *
 * Returns
 *   The number of monitors which intersect the specified region.
 */
static
UINT
IntGetMonitorsFromRect(OPTIONAL IN LPCRECTL pRect,
                       OPTIONAL OUT HMONITOR *hMonitorList,
                       OPTIONAL OUT PRECTL monitorRectList,
                       OPTIONAL IN DWORD listSize,
                       OPTIONAL IN DWORD flags)
{
   PMONITOR Monitor, NearestMonitor = NULL, PrimaryMonitor = NULL;
   UINT iCount = 0;
   LONG iNearestDistanceX = 0x7fffffff, iNearestDistanceY = 0x7fffffff;

   /* find monitors which intersect the rectangle */
   for (Monitor = gMonitorList; Monitor != NULL; Monitor = Monitor->Next)
   {
      RECTL MonitorRect, IntersectionRect;

      ExEnterCriticalRegionAndAcquireFastMutexUnsafe(&Monitor->Lock);
      MonitorRect = Monitor->rcMonitor;
      ExReleaseFastMutexUnsafeAndLeaveCriticalRegion(&Monitor->Lock);

      DPRINT("MonitorRect: left = %d, top = %d, right = %d, bottom = %d\n",
             MonitorRect.left, MonitorRect.top, MonitorRect.right, MonitorRect.bottom);

      if (flags == MONITOR_DEFAULTTOPRIMARY && Monitor->IsPrimary)
      {
         PrimaryMonitor = Monitor;
      }

      if (pRect != NULL)
      {
         BOOL intersects = TRUE;

         /* check if the rect intersects the monitor */
         if ((pRect->right < MonitorRect.left) || (pRect->left > MonitorRect.right) ||
               (pRect->bottom < MonitorRect.top) || (pRect->top > MonitorRect.bottom))
         {
            intersects = FALSE;
         }

         if (flags == MONITOR_DEFAULTTONEAREST && !intersects)
         {
            INT distanceX, distanceY;

            distanceX = MIN(ABS(MonitorRect.left - pRect->right),
                            ABS(pRect->left - MonitorRect.right));
            distanceY = MIN(ABS(MonitorRect.top - pRect->bottom),
                            ABS(pRect->top - MonitorRect.bottom));

            if (((distanceX <  iNearestDistanceX) && (distanceY <= iNearestDistanceY)) ||
                  ((distanceX <= iNearestDistanceX) && (distanceY <  iNearestDistanceY)))
            {
               iNearestDistanceX = distanceX;
               iNearestDistanceY = distanceY;
               NearestMonitor = Monitor;
            }
         }

         if (!intersects)
            continue;

         /* calculate intersection */
         IntersectionRect.left   = MAX(MonitorRect.left,   pRect->left);
         IntersectionRect.top    = MAX(MonitorRect.top,    pRect->top);
         IntersectionRect.right  = MIN(MonitorRect.right,  pRect->right);
         IntersectionRect.bottom = MIN(MonitorRect.bottom, pRect->bottom);
      }
      else
      {
         IntersectionRect = MonitorRect;
      }

      if (iCount < listSize)
      {
         if (hMonitorList != NULL)
            hMonitorList[iCount] = UserHMGetHandle(Monitor);
         if (monitorRectList != NULL)
            monitorRectList[iCount] = IntersectionRect;
      }
      iCount++;
   }

   if (iCount == 0 && flags == MONITOR_DEFAULTTONEAREST)
   {
      if (iCount < listSize)
      {
         if (hMonitorList != NULL)
            hMonitorList[iCount] = UserHMGetHandle(NearestMonitor);
      }
      iCount++;
   }
   else if (iCount == 0 && flags == MONITOR_DEFAULTTOPRIMARY)
   {
      if (iCount < listSize)
      {
         if (hMonitorList != NULL)
            hMonitorList[iCount] = UserHMGetHandle(PrimaryMonitor);
      }
      iCount++;
   }
   return iCount;
}

/* PUBLIC FUNCTIONS ***********************************************************/

/* NtUserEnumDisplayMonitors
 *
 * Enumerates display monitors which intersect the given HDC/cliprect
 *
 * Arguments
 *
 *   hDC
 *      Handle to a DC for which to enum intersecting monitors. If this is NULL
 *      it returns all monitors which are part of the current virtual screen.
 *
 *   pRect
 *      Clipping rectangle with coordinate system origin at the DCs origin if the
 *      given HDC is not NULL or in virtual screen coordinated if it is NULL.
 *      Can be NULL
 *
 *   hMonitorList
 *      Pointer to an array of HMONITOR which is filled with monitor handles.
 *      Can be NULL
 *
 *   monitorRectList
 *      Pointer to an array of RECT which is filled with intersection rectangles.
 *      Can be NULL
 *
 *   listSize
 *      Size of the hMonitorList and monitorRectList arguments. If this is zero
 *      hMonitorList and monitorRectList are ignored.
 *
 * Returns
 *   The number of monitors which intersect the specified region or -1 on failure.
 */
INT
APIENTRY
NtUserEnumDisplayMonitors(
   OPTIONAL IN HDC hDC,
   OPTIONAL IN LPCRECTL pRect,
   OPTIONAL OUT HMONITOR *hMonitorList,
   OPTIONAL OUT PRECTL monitorRectList,
   OPTIONAL IN DWORD listSize)
{
   INT numMonitors, i;
   HMONITOR *safeHMonitorList = NULL;
   PRECTL safeRectList = NULL;
   RECTL rect, *myRect;
   RECTL dcRect;
   NTSTATUS status;

   /* get rect */
   if (pRect != NULL)
   {
      status = MmCopyFromCaller(&rect, pRect, sizeof (RECT));
      if (!NT_SUCCESS(status))
      {
         DPRINT("MmCopyFromCaller() failed!\n");
         SetLastNtError(status);
         return -1;
      }
   }

   if (hDC != NULL)
   {
      PDC dc;
      HRGN dcVisRgn;
      INT regionType;

      /* get visible region bounding rect */
      dc = DC_LockDc(hDC);
      if (dc == NULL)
      {
         DPRINT("DC_LockDc() failed!\n");
         /* FIXME: setlasterror? */
         return -1;
      }
      dcVisRgn = dc->prgnVis->BaseObject.hHmgr;
      DC_UnlockDc(dc);

      regionType = NtGdiGetRgnBox(dcVisRgn, &dcRect);
      if (regionType == 0)
      {
         DPRINT("NtGdiGetRgnBox() failed!\n");
         return -1;
      }
      if (regionType == NULLREGION)
         return 0;
      if (regionType == COMPLEXREGION)
      { /* TODO: warning */
      }

      /* if hDC and pRect are given the area of interest is pRect with
         coordinate origin at the DC position */
      if (pRect != NULL)
      {
         rect.left += dcRect.left;
         rect.right += dcRect.left;
         rect.top += dcRect.top;
         rect.bottom += dcRect.top;
      }
      /* if hDC is given and pRect is not the area of interest is the
         bounding rect of hDC */
      else
      {
         rect = dcRect;
      }
   }

   if (hDC == NULL && pRect == NULL)
      myRect = NULL;
   else
      myRect = &rect;

   /* find intersecting monitors */
   numMonitors = IntGetMonitorsFromRect(myRect, NULL, NULL, 0, 0);
   if (numMonitors == 0 || listSize == 0 ||
         (hMonitorList == NULL && monitorRectList == NULL))
   {
      DPRINT("numMonitors = %d\n", numMonitors);
      return numMonitors;
   }

   if (hMonitorList != NULL && listSize != 0)
   {
      safeHMonitorList = ExAllocatePool(PagedPool, sizeof (HMONITOR) * listSize);
      if (safeHMonitorList == NULL)
      {
         /* FIXME: SetLastWin32Error? */
         return -1;
      }
   }
   if (monitorRectList != NULL && listSize != 0)
   {
      safeRectList = ExAllocatePool(PagedPool, sizeof (RECT) * listSize);
      if (safeRectList == NULL)
      {
         ExFreePool(safeHMonitorList);
         /* FIXME: SetLastWin32Error? */
         return -1;
      }
   }

   /* get intersecting monitors */
   numMonitors = IntGetMonitorsFromRect(myRect, safeHMonitorList, safeRectList,
                                        listSize, 0 );

   if (hDC != NULL && pRect != NULL && safeRectList != NULL)
      for (i = 0; i < numMonitors; i++)
      {
         safeRectList[i].left -= dcRect.left;
         safeRectList[i].right -= dcRect.left;
         safeRectList[i].top -= dcRect.top;
         safeRectList[i].bottom -= dcRect.top;
      }

   /* output result */
   if (hMonitorList != NULL && listSize != 0)
   {
      status = MmCopyToCaller(hMonitorList, safeHMonitorList, sizeof (HMONITOR) * listSize);
      ExFreePool(safeHMonitorList);
      if (!NT_SUCCESS(status))
      {
         ExFreePool(safeRectList);
         SetLastNtError(status);
         return -1;
      }
   }
   if (monitorRectList != NULL && listSize != 0)
   {
      status = MmCopyToCaller(monitorRectList, safeRectList, sizeof (RECT) * listSize);
      ExFreePool(safeRectList);
      if (!NT_SUCCESS(status))
      {
         SetLastNtError(status);
         return -1;
      }
   }

   return numMonitors;
}

/* NtUserGetMonitorInfo
 *
 * Retrieves information about a given monitor
 *
 * Arguments
 *
 *   hMonitor
 *      Handle to a monitor for which to get information
 *
 *   pMonitorInfo
 *      Pointer to a MONITORINFO struct which is filled with the information.
 *      The cbSize member must be set to sizeof(MONITORINFO) or
 *      sizeof(MONITORINFOEX). Even if set to sizeof(MONITORINFOEX) only parts
 *      from MONITORINFO will be filled.
 *
 *   pDevice
 *      Pointer to a UNICODE_STRING which will recieve the device's name. The
 *      length should be CCHDEVICENAME
 *      Can be NULL
 *
 * Return value
 *   TRUE on success; FALSE on failure (calls SetLastNtError())
 *
 */
BOOL
APIENTRY
NtUserGetMonitorInfo(
   IN HMONITOR hMonitor,
   OUT LPMONITORINFO pMonitorInfo)
{
   PMONITOR Monitor;
   MONITORINFOEXW MonitorInfo;
   NTSTATUS Status;
   DECLARE_RETURN(BOOL);

   DPRINT("Enter NtUserGetMonitorInfo\n");
   UserEnterShared();

   /* get monitor object */
   if (!(Monitor = UserGetMonitorObject(hMonitor)))
   {
      DPRINT("Couldnt find monitor 0x%lx\n", hMonitor);
      RETURN(FALSE);
   }

   if(pMonitorInfo == NULL)
   {
      SetLastNtError(STATUS_INVALID_PARAMETER);
      RETURN(FALSE);
   }

   /* get size of pMonitorInfo */
   Status = MmCopyFromCaller(&MonitorInfo.cbSize, &pMonitorInfo->cbSize, sizeof (MonitorInfo.cbSize));
   if (!NT_SUCCESS(Status))
   {
      SetLastNtError(Status);
      RETURN(FALSE);
   }
   if ((MonitorInfo.cbSize != sizeof (MONITORINFO)) &&
         (MonitorInfo.cbSize != sizeof (MONITORINFOEXW)))
   {
      SetLastNtError(STATUS_INVALID_PARAMETER);
      RETURN(FALSE);
   }

   /* fill monitor info */
   MonitorInfo.rcMonitor = Monitor->rcMonitor;
   MonitorInfo.rcWork = Monitor->rcWork;
   MonitorInfo.dwFlags = 0;

   if (Monitor->IsPrimary)
      MonitorInfo.dwFlags |= MONITORINFOF_PRIMARY;

   /* fill device name */
   if (MonitorInfo.cbSize == sizeof (MONITORINFOEXW))
   {
      WCHAR nul = L'\0';
      INT len = Monitor->DeviceName.Length;
      if (len >= CCHDEVICENAME * sizeof (WCHAR))
         len = (CCHDEVICENAME - 1) * sizeof (WCHAR);

      memcpy(MonitorInfo.szDevice, Monitor->DeviceName.Buffer, len);
      memcpy(MonitorInfo.szDevice + (len / sizeof (WCHAR)), &nul, sizeof (WCHAR));
   }

   /* output data */
   Status = MmCopyToCaller(pMonitorInfo, &MonitorInfo, MonitorInfo.cbSize);
   if (!NT_SUCCESS(Status))
   {
      DPRINT("GetMonitorInfo: MmCopyToCaller failed\n");
      SetLastNtError(Status);
      RETURN(FALSE);
   }

   DPRINT("GetMonitorInfo: success\n");

   RETURN(TRUE);

CLEANUP:
   DPRINT("Leave NtUserGetMonitorInfo, ret=%i\n",_ret_);
   UserLeave();
   END_CLEANUP;
}

/* NtUserMonitorFromPoint
 *
 * Returns a handle to the monitor containing the given point.
 *
 * Arguments
 *
 *   point
 *     Point for which to find monitor
 *
 *   dwFlags
 *     Specifies the behaviour if the point isn't on any of the monitors.
 *
 * Return value
 *   If the point is found a handle to the monitor is returned; if not the
 *   return value depends on dwFlags
 */
HMONITOR
APIENTRY
NtUserMonitorFromPoint(
   IN POINT point,
   IN DWORD dwFlags)
{
   INT NumMonitors;
   RECTL InRect;
   HMONITOR hMonitor = NULL;

   /* fill inRect */
   InRect.left = InRect.right = point.x;
   InRect.top = InRect.bottom = point.y;

   /* find intersecting monitor */
   NumMonitors = IntGetMonitorsFromRect(&InRect, &hMonitor, NULL, 1, 0);
   if (NumMonitors < 0)
   {
      return (HMONITOR)NULL;
   }

   if (hMonitor == NULL)
   {
      if (dwFlags == MONITOR_DEFAULTTOPRIMARY)
      {
         PMONITOR MonitorObj = IntGetPrimaryMonitor();
         if (MonitorObj)
            hMonitor = UserHMGetHandle(MonitorObj);
      }
      else if (dwFlags == MONITOR_DEFAULTTONEAREST)
      {
         NumMonitors = IntGetMonitorsFromRect(&InRect, &hMonitor, NULL,
                                              1, MONITOR_DEFAULTTONEAREST);
         /*ASSERT( (numMonitors > 0) && (hMonitor != NULL) );*/
      }
      /* else flag is DEFAULTTONULL */
   }

   return hMonitor;
}

/* NtUserMonitorFromRect
 *
 * Returns a handle to the monitor having the largest intersection with a
 * given rectangle
 *
 * Arguments
 *
 *   pRect
 *     Pointer to a RECT for which to find monitor
 *
 *   dwFlags
 *     Specifies the behaviour if no monitor intersects the given rect
 *
 * Return value
 *   If a monitor intersects the rect a handle to it is returned; if not the
 *   return value depends on dwFlags
 */
HMONITOR
APIENTRY
NtUserMonitorFromRect(
   IN LPCRECTL pRect,
   IN DWORD dwFlags)
{
   INT numMonitors, iLargestArea = -1, i;
   PRECTL rectList;
   HMONITOR *hMonitorList;
   HMONITOR hMonitor = NULL;
   RECTL rect;
   NTSTATUS status;

   /* get rect */
   status = MmCopyFromCaller(&rect, pRect, sizeof (RECT));
   if (!NT_SUCCESS(status))
   {
      SetLastNtError(status);
      return (HMONITOR)NULL;
   }

   /* find intersecting monitors */
   numMonitors = IntGetMonitorsFromRect(&rect, NULL, NULL, 0, 0);
   if (numMonitors < 0)
   {
      return (HMONITOR)NULL;
   }

   if (numMonitors == 0)
   {
      if (dwFlags == MONITOR_DEFAULTTOPRIMARY)
      {
         PMONITOR monitorObj = IntGetPrimaryMonitor();
         if (monitorObj)
            return UserHMGetHandle(monitorObj);
      }
      else if (dwFlags == MONITOR_DEFAULTTONEAREST)
      {
         numMonitors = IntGetMonitorsFromRect(&rect, &hMonitor, NULL,
                                              1, MONITOR_DEFAULTTONEAREST);
         if (numMonitors <= 0)
         {
            /* error? */
            return (HMONITOR)NULL;
         }

         if (numMonitors > 0)
            return hMonitor;
      }
      /* else flag is DEFAULTTONULL */
      return (HMONITOR)NULL;
   }

   hMonitorList = ExAllocatePool(PagedPool, sizeof (HMONITOR) * numMonitors);
   if (hMonitorList == NULL)
   {
      /* FIXME: SetLastWin32Error? */
      return (HMONITOR)NULL;
   }
   rectList = ExAllocatePool(PagedPool, sizeof (RECT) * numMonitors);
   if (rectList == NULL)
   {
      ExFreePool(hMonitorList);
      /* FIXME: SetLastWin32Error? */
      return (HMONITOR)NULL;
   }

   /* get intersecting monitors */
   numMonitors = IntGetMonitorsFromRect(&rect, hMonitorList, rectList,
                                        numMonitors, 0);
   if (numMonitors <= 0)
   {
      ExFreePool(hMonitorList);
      ExFreePool(rectList);
      return (HMONITOR)NULL;
   }

   /* find largest intersection */
   for (i = 0; i < numMonitors; i++)
   {
      INT area = (rectList[i].right - rectList[i].left) *
                 (rectList[i].bottom - rectList[i].top);
      if (area > iLargestArea)
      {
         hMonitor = hMonitorList[i];
      }
   }

   ExFreePool(hMonitorList);
   ExFreePool(rectList);

   return hMonitor;
}


HMONITOR
APIENTRY
NtUserMonitorFromWindow(
   IN HWND hWnd,
   IN DWORD dwFlags)
{
   PWINDOW_OBJECT Window;
   HMONITOR hMonitor = NULL;
   RECTL Rect;
   DECLARE_RETURN(HMONITOR);

   DPRINT("Enter NtUserMonitorFromWindow\n");
   UserEnterShared();

   if (!(Window = UserGetWindowObject(hWnd)))
   {
      if (dwFlags == MONITOR_DEFAULTTONULL)
      {
         RETURN(hMonitor);
      }
      IntGetMonitorsFromRect(NULL, &hMonitor, NULL, 1, dwFlags);
      RETURN(hMonitor);
   }

   if (!Window->Wnd)
      RETURN(hMonitor);

   Rect.left = Rect.right = Window->Wnd->rcWindow.left;
   Rect.top = Rect.bottom = Window->Wnd->rcWindow.bottom;

   IntGetMonitorsFromRect(&Rect, &hMonitor, NULL, 1, dwFlags);

   RETURN(hMonitor);

CLEANUP:
   DPRINT("Leave NtUserMonitorFromWindow, ret=%i\n",_ret_);
   UserLeave();
   END_CLEANUP;
}