/*
 * Window painting functions
 *
 * Copyright 1993, 1994, 1995, 2001, 2004 Alexandre Julliard
 * Copyright 1999 Alex Korobka
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * This library 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
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA
 */

#include "config.h"
#include "wine/port.h"

#include <stdarg.h>
#include <string.h>

#include "ntstatus.h"
#define WIN32_NO_STATUS
#include "windef.h"
#include "winbase.h"
#include "wingdi.h"
#include "winuser.h"
#include "wine/server.h"
#include "win.h"
#include "user_private.h"
#include "wine/debug.h"

WINE_DEFAULT_DEBUG_CHANNEL(win);


/***********************************************************************
 *           dump_rdw_flags
 */
static void dump_rdw_flags(UINT flags)
{
    TRACE("flags:");
    if (flags & RDW_INVALIDATE) TRACE(" RDW_INVALIDATE");
    if (flags & RDW_INTERNALPAINT) TRACE(" RDW_INTERNALPAINT");
    if (flags & RDW_ERASE) TRACE(" RDW_ERASE");
    if (flags & RDW_VALIDATE) TRACE(" RDW_VALIDATE");
    if (flags & RDW_NOINTERNALPAINT) TRACE(" RDW_NOINTERNALPAINT");
    if (flags & RDW_NOERASE) TRACE(" RDW_NOERASE");
    if (flags & RDW_NOCHILDREN) TRACE(" RDW_NOCHILDREN");
    if (flags & RDW_ALLCHILDREN) TRACE(" RDW_ALLCHILDREN");
    if (flags & RDW_UPDATENOW) TRACE(" RDW_UPDATENOW");
    if (flags & RDW_ERASENOW) TRACE(" RDW_ERASENOW");
    if (flags & RDW_FRAME) TRACE(" RDW_FRAME");
    if (flags & RDW_NOFRAME) TRACE(" RDW_NOFRAME");

#define RDW_FLAGS \
    (RDW_INVALIDATE | \
    RDW_INTERNALPAINT | \
    RDW_ERASE | \
    RDW_VALIDATE | \
    RDW_NOINTERNALPAINT | \
    RDW_NOERASE | \
    RDW_NOCHILDREN | \
    RDW_ALLCHILDREN | \
    RDW_UPDATENOW | \
    RDW_ERASENOW | \
    RDW_FRAME | \
    RDW_NOFRAME)

    if (flags & ~RDW_FLAGS) TRACE(" %04x", flags & ~RDW_FLAGS);
    TRACE("\n");
#undef RDW_FLAGS
}


/***********************************************************************
 *           get_update_region
 *
 * Return update region (in screen coordinates) for a window.
 */
static HRGN get_update_region( HWND hwnd, UINT *flags, HWND *child )
{
    HRGN hrgn = 0;
    NTSTATUS status;
    RGNDATA *data;
    size_t size = 256;

    do
    {
        if (!(data = HeapAlloc( GetProcessHeap(), 0, sizeof(*data) + size - 1 )))
        {
            SetLastError( ERROR_OUTOFMEMORY );
            return 0;
        }

        SERVER_START_REQ( get_update_region )
        {
            req->window     = hwnd;
            req->from_child = child ? *child : 0;
            req->flags      = *flags;
            wine_server_set_reply( req, data->Buffer, size );
            if (!(status = wine_server_call( req )))
            {
                size_t reply_size = wine_server_reply_size( reply );
                data->rdh.dwSize   = sizeof(data->rdh);
                data->rdh.iType    = RDH_RECTANGLES;
                data->rdh.nCount   = reply_size / sizeof(RECT);
                data->rdh.nRgnSize = reply_size;
                hrgn = ExtCreateRegion( NULL, size, data );
                if (child) *child = reply->child;
                *flags = reply->flags;
            }
            else size = reply->total_size;
        }
        SERVER_END_REQ;
        HeapFree( GetProcessHeap(), 0, data );
    } while (status == STATUS_BUFFER_OVERFLOW);

    if (status) SetLastError( RtlNtStatusToDosError(status) );
    return hrgn;
}


/***********************************************************************
 *           get_update_flags
 *
 * Get only the update flags, not the update region.
 */
static BOOL get_update_flags( HWND hwnd, HWND *child, UINT *flags )
{
    BOOL ret;

    SERVER_START_REQ( get_update_region )
    {
        req->window     = hwnd;
        req->from_child = child ? *child : 0;
        req->flags      = *flags | UPDATE_NOREGION;
        if ((ret = !wine_server_call_err( req )))
        {
            if (child) *child = reply->child;
            *flags = reply->flags;
        }
    }
    SERVER_END_REQ;
    return ret;
}


/***********************************************************************
 *           redraw_window_rects
 *
 * Redraw part of a window.
 */
static BOOL redraw_window_rects( HWND hwnd, UINT flags, const RECT *rects, UINT count )
{
    BOOL ret;

    if (!(flags & (RDW_INVALIDATE|RDW_VALIDATE|RDW_INTERNALPAINT|RDW_NOINTERNALPAINT)))
        return TRUE;  /* nothing to do */

    SERVER_START_REQ( redraw_window )
    {
        req->window = hwnd;
        req->flags  = flags;
        wine_server_add_data( req, rects, count * sizeof(RECT) );
        ret = !wine_server_call_err( req );
    }
    SERVER_END_REQ;
    return ret;
}


/***********************************************************************
 *           send_ncpaint
 *
 * Send a WM_NCPAINT message if needed, and return the resulting update region (in screen coords).
 * Helper for erase_now and BeginPaint.
 */
static HRGN send_ncpaint( HWND hwnd, HWND *child, UINT *flags )
{
    HRGN whole_rgn = get_update_region( hwnd, flags, child );
    HRGN client_rgn = 0;

    if (child) hwnd = *child;

    if (whole_rgn)
    {
        RECT client, update;
        INT type;

        /* check if update rgn overlaps with nonclient area */
        type = GetRgnBox( whole_rgn, &update );
        GetClientRect( hwnd, &client );
        MapWindowPoints( hwnd, 0, (POINT *)&client, 2 );

        if ((*flags & UPDATE_NONCLIENT) ||
            update.left < client.left || update.top < client.top ||
            update.right > client.right || update.bottom > client.bottom)
        {
            client_rgn = CreateRectRgnIndirect( &client );
            CombineRgn( client_rgn, client_rgn, whole_rgn, RGN_AND );

            /* check if update rgn contains complete nonclient area */
            if (type == SIMPLEREGION)
            {
                RECT window;
                GetWindowRect( hwnd, &window );
                if (EqualRect( &window, &update ))
                {
                    DeleteObject( whole_rgn );
                    whole_rgn = (HRGN)1;
                }
            }
        }
        else
        {
            client_rgn = whole_rgn;
            whole_rgn = 0;
        }

        if (whole_rgn) /* NOTE: WM_NCPAINT allows wParam to be 1 */
        {
            if (*flags & UPDATE_NONCLIENT) SendMessageW( hwnd, WM_NCPAINT, (WPARAM)whole_rgn, 0 );
            if (whole_rgn > (HRGN)1) DeleteObject( whole_rgn );
        }
    }
    return client_rgn;
}


/***********************************************************************
 *           send_erase
 *
 * Send a WM_ERASEBKGND message if needed, and optionally return the DC for painting.
 * If a DC is requested, the region is selected into it. In all cases the region is deleted.
 * Helper for erase_now and BeginPaint.
 */
static BOOL send_erase( HWND hwnd, UINT flags, HRGN client_rgn,
                        RECT *clip_rect, HDC *hdc_ret )
{
    BOOL need_erase = (flags & UPDATE_DELAYED_ERASE) != 0;
    HDC hdc = 0;
    RECT dummy;

    if (!clip_rect) clip_rect = &dummy;
    if (hdc_ret || (flags & UPDATE_ERASE))
    {
        UINT dcx_flags = DCX_INTERSECTRGN | DCX_USESTYLE;
        if (IsIconic(hwnd)) dcx_flags |= DCX_WINDOW;

        if ((hdc = GetDCEx( hwnd, client_rgn, dcx_flags )))
        {
            INT type = GetClipBox( hdc, clip_rect );

            if (flags & UPDATE_ERASE)
            {
                /* don't erase if the clip box is empty */
                if (type != NULLREGION)
                    need_erase = !SendMessageW( hwnd, WM_ERASEBKGND, (WPARAM)hdc, 0 );
            }
            if (!hdc_ret) USER_Driver->pReleaseDC( hwnd, hdc, TRUE );
        }

        if (hdc_ret) *hdc_ret = hdc;
    }
    if (!hdc) DeleteObject( client_rgn );
    return need_erase;
}


/***********************************************************************
 *           erase_now
 *
 * Implementation of RDW_ERASENOW behavior.
 */
void erase_now( HWND hwnd, UINT rdw_flags )
{
    HWND child = 0;
    HRGN hrgn;
    BOOL need_erase = FALSE;

    /* loop while we find a child to repaint */
    for (;;)
    {
        UINT flags = UPDATE_NONCLIENT | UPDATE_ERASE;

        if (rdw_flags & RDW_NOCHILDREN) flags |= UPDATE_NOCHILDREN;
        else if (rdw_flags & RDW_ALLCHILDREN) flags |= UPDATE_ALLCHILDREN;
        if (need_erase) flags |= UPDATE_DELAYED_ERASE;

        if (!(hrgn = send_ncpaint( hwnd, &child, &flags ))) break;
        need_erase = send_erase( child, flags, hrgn, NULL, NULL );

        if (!flags) break;  /* nothing more to do */
        if ((rdw_flags & RDW_NOCHILDREN) && !need_erase) break;
    }
}


/***********************************************************************
 *           update_now
 *
 * Implementation of RDW_UPDATENOW behavior.
 *
 * FIXME: Windows uses WM_SYNCPAINT to cut down the number of intertask
 * SendMessage() calls. This is a comment inside DefWindowProc() source
 * from 16-bit SDK:
 *
 *   This message avoids lots of inter-app message traffic
 *   by switching to the other task and continuing the
 *   recursion there.
 *
 * wParam         = flags
 * LOWORD(lParam) = hrgnClip
 * HIWORD(lParam) = hwndSkip  (not used; always NULL)
 *
 */
static void update_now( HWND hwnd, UINT rdw_flags )
{
    HWND child = 0;

    /* desktop window never gets WM_PAINT, only WM_ERASEBKGND */
    if (hwnd == GetDesktopWindow()) erase_now( hwnd, rdw_flags | RDW_NOCHILDREN );

    /* loop while we find a child to repaint */
    for (;;)
    {
        UINT flags = UPDATE_PAINT | UPDATE_INTERNALPAINT;

        if (rdw_flags & RDW_NOCHILDREN) flags |= UPDATE_NOCHILDREN;
        else if (rdw_flags & RDW_ALLCHILDREN) flags |= UPDATE_ALLCHILDREN;

        if (!get_update_flags( hwnd, &child, &flags )) break;
        if (!flags) break;  /* nothing more to do */

        SendMessageW( child, WM_PAINT, 0, 0 );
        if (rdw_flags & RDW_NOCHILDREN) break;
    }
}


/*************************************************************************
 *             fix_caret
 *
 * Helper for ScrollWindowEx:
 * If the return value is 0, no special caret handling is necessary.
 * Otherwise the return value is the handle of the window that owns the
 * caret. Its caret needs to be hidden during the scroll operation and
 * moved to new_caret_pos if move_caret is TRUE.
 */
static HWND fix_caret(HWND hWnd, const RECT *scroll_rect, INT dx, INT dy,
                     UINT flags, LPBOOL move_caret, LPPOINT new_caret_pos)
{
    GUITHREADINFO info;
    RECT rect, mapped_rcCaret;
    BOOL hide_caret = FALSE;

    if (!GetGUIThreadInfo( GetCurrentThreadId(), &info )) return 0;
    if (!info.hwndCaret) return 0;
    
    if (info.hwndCaret == hWnd)
    {
        /* Move the caret if it's (partially) in the source rectangle */
        if (IntersectRect(&rect, scroll_rect, &info.rcCaret))
        {
            *move_caret = TRUE;
            hide_caret = TRUE;
            new_caret_pos->x = info.rcCaret.left + dx;
            new_caret_pos->y = info.rcCaret.top + dy;
        }
        else
        {
            *move_caret = FALSE;
            
            /* Hide the caret if it's in the destination rectangle */
            rect = *scroll_rect;
            OffsetRect(&rect, dx, dy);
            hide_caret = IntersectRect(&rect, &rect, &info.rcCaret);
        }
    }
    else
    {
        if ((flags & SW_SCROLLCHILDREN) && IsChild(hWnd, info.hwndCaret))
        {
            *move_caret = FALSE;
            
            /* Hide the caret if it's in the source or in the destination
               rectangle */
            mapped_rcCaret = info.rcCaret;
            MapWindowPoints(info.hwndCaret, hWnd, (LPPOINT)&mapped_rcCaret, 2);
            
            if (IntersectRect(&rect, scroll_rect, &mapped_rcCaret))
            {
                hide_caret = TRUE;
            }
            else
            {
                rect = *scroll_rect;
                OffsetRect(&rect, dx, dy);
                hide_caret = IntersectRect(&rect, &rect, &mapped_rcCaret);
            }
        }
        else
            return 0;
    }

    if (hide_caret)
    {    
        HideCaret(info.hwndCaret);
        return info.hwndCaret;
    }
    else
        return 0;
}


/***********************************************************************
 *		BeginPaint (USER32.@)
 */
HDC WINAPI BeginPaint( HWND hwnd, PAINTSTRUCT *lps )
{
    HWND full_handle;
    HRGN hrgn;
    UINT flags = UPDATE_NONCLIENT | UPDATE_ERASE | UPDATE_PAINT | UPDATE_INTERNALPAINT | UPDATE_NOCHILDREN;

    if (!lps) return 0;

    if (!(full_handle = WIN_IsCurrentThread( hwnd )))
    {
        if (IsWindow(hwnd))
            FIXME( "window %p belongs to other thread\n", hwnd );
        return 0;
    }
    hwnd = full_handle;

    HideCaret( hwnd );

    if (!(hrgn = send_ncpaint( hwnd, NULL, &flags ))) return 0;

    lps->fErase = send_erase( hwnd, flags, hrgn, &lps->rcPaint, &lps->hdc );

    TRACE("hdc = %p box = (%d,%d - %d,%d), fErase = %d\n",
          lps->hdc, lps->rcPaint.left, lps->rcPaint.top, lps->rcPaint.right, lps->rcPaint.bottom,
          lps->fErase);

    return lps->hdc;
}


/***********************************************************************
 *		EndPaint (USER32.@)
 */
BOOL WINAPI EndPaint( HWND hwnd, const PAINTSTRUCT *lps )
{
    if (!lps) return FALSE;
    USER_Driver->pReleaseDC( hwnd, lps->hdc, TRUE );
    ShowCaret( hwnd );
    return TRUE;
}


/***********************************************************************
 *		GetDCEx (USER32.@)
 */
HDC WINAPI GetDCEx( HWND hwnd, HRGN hrgnClip, DWORD flags )
{
    if (!hwnd) hwnd = GetDesktopWindow();
    else hwnd = WIN_GetFullHandle( hwnd );

    return USER_Driver->pGetDCEx( hwnd, hrgnClip, flags );
}


/***********************************************************************
 *		GetDC (USER32.@)
 *
 * Get a device context.
 *
 * RETURNS
 *	Success: Handle to the device context
 *	Failure: NULL.
 */
HDC WINAPI GetDC( HWND hwnd )
{
    if (!hwnd) return GetDCEx( 0, 0, DCX_CACHE | DCX_WINDOW );
    return GetDCEx( hwnd, 0, DCX_USESTYLE );
}


/***********************************************************************
 *		GetWindowDC (USER32.@)
 */
HDC WINAPI GetWindowDC( HWND hwnd )
{
    return GetDCEx( hwnd, 0, DCX_USESTYLE | DCX_WINDOW );
}


/***********************************************************************
 *		ReleaseDC (USER32.@)
 *
 * Release a device context.
 *
 * RETURNS
 *	Success: Non-zero. Resources used by hdc are released.
 *	Failure: 0.
 */
INT WINAPI ReleaseDC( HWND hwnd, HDC hdc )
{
    return USER_Driver->pReleaseDC( hwnd, hdc, FALSE );
}


/**********************************************************************
 *		WindowFromDC (USER32.@)
 */
HWND WINAPI WindowFromDC( HDC hDC )
{
    return USER_Driver->pWindowFromDC( hDC );
}


/***********************************************************************
 *		LockWindowUpdate (USER32.@)
 *
 * Enables or disables painting in the chosen window.
 *
 * PARAMS
 *  hwnd [I] handle to a window.
 *
 * RETURNS
 *  If successful, returns nonzero value. Otherwise,
 *  returns 0.
 *
 * NOTES
 *  You can lock only one window at a time.
 */
BOOL WINAPI LockWindowUpdate( HWND hwnd )
{
    static HWND lockedWnd;

    /* This function is fully implemented by the following patch:
     *
     * http://www.winehq.org/hypermail/wine-patches/2004/01/0142.html
     *
     * but in order to work properly, it needs the ability to invalidate
     * DCEs in other processes when the lock window is changed, which
     * isn't possible yet.
     * -mike
     */

    FIXME("(%p), partial stub!\n",hwnd);

    USER_Lock();
    if (lockedWnd)
    {
        if (!hwnd)
        {
            /* Unlock lockedWnd */
            /* FIXME: Do something */
        }
        else
        {
            /* Attempted to lock a second window */
            /* Return FALSE and do nothing */
            USER_Unlock();
            return FALSE;
        }
    }
    lockedWnd = hwnd;
    USER_Unlock();
    return TRUE;
}


/***********************************************************************
 *		RedrawWindow (USER32.@)
 */
BOOL WINAPI RedrawWindow( HWND hwnd, const RECT *rect, HRGN hrgn, UINT flags )
{
    static const RECT empty;
    BOOL ret;

    if (!hwnd) hwnd = GetDesktopWindow();

    if (TRACE_ON(win))
    {
        if (hrgn)
        {
            RECT r;
            GetRgnBox( hrgn, &r );
            TRACE( "%p region %p box %s ", hwnd, hrgn, wine_dbgstr_rect(&r) );
        }
        else if (rect)
            TRACE( "%p rect %s ", hwnd, wine_dbgstr_rect(rect) );
        else
            TRACE( "%p whole window ", hwnd );

        dump_rdw_flags(flags);
    }

    /* process pending expose events before painting */
    if (flags & RDW_UPDATENOW) USER_Driver->pMsgWaitForMultipleObjectsEx( 0, NULL, 0, QS_PAINT, 0 );

    if (rect && !hrgn)
    {
        if (IsRectEmpty( rect )) rect = &empty;
        ret = redraw_window_rects( hwnd, flags, rect, 1 );
    }
    else if (!hrgn)
    {
        ret = redraw_window_rects( hwnd, flags, NULL, 0 );
    }
    else  /* need to build a list of the region rectangles */
    {
        DWORD size;
        RGNDATA *data = NULL;

        if (!(size = GetRegionData( hrgn, 0, NULL ))) return FALSE;
        if (!(data = HeapAlloc( GetProcessHeap(), 0, size ))) return FALSE;
        GetRegionData( hrgn, size, data );
        if (!data->rdh.nCount)  /* empty region -> use a single all-zero rectangle */
            ret = redraw_window_rects( hwnd, flags, &empty, 1 );
        else
            ret = redraw_window_rects( hwnd, flags, (const RECT *)data->Buffer, data->rdh.nCount );
        HeapFree( GetProcessHeap(), 0, data );
    }

    if (flags & RDW_UPDATENOW) update_now( hwnd, flags );
    else if (flags & RDW_ERASENOW) erase_now( hwnd, flags );

    return ret;
}


/***********************************************************************
 *		UpdateWindow (USER32.@)
 */
BOOL WINAPI UpdateWindow( HWND hwnd )
{
    return RedrawWindow( hwnd, NULL, 0, RDW_UPDATENOW | RDW_ALLCHILDREN );
}


/***********************************************************************
 *		InvalidateRgn (USER32.@)
 */
BOOL WINAPI InvalidateRgn( HWND hwnd, HRGN hrgn, BOOL erase )
{
    if (!hwnd)
    {
        SetLastError( ERROR_INVALID_WINDOW_HANDLE );
        return FALSE;
    }

    return RedrawWindow(hwnd, NULL, hrgn, RDW_INVALIDATE | (erase ? RDW_ERASE : 0) );
}


/***********************************************************************
 *		InvalidateRect (USER32.@)
 *
 * MSDN: if hwnd parameter is NULL, InvalidateRect invalidates and redraws
 * all windows and sends WM_ERASEBKGND and WM_NCPAINT.
 */
BOOL WINAPI InvalidateRect( HWND hwnd, const RECT *rect, BOOL erase )
{
    UINT flags = RDW_INVALIDATE | (erase ? RDW_ERASE : 0);

    if (!hwnd)
    {
        flags = RDW_ALLCHILDREN | RDW_INVALIDATE | RDW_FRAME | RDW_ERASE | RDW_ERASENOW;
        rect = NULL;
    }

    return RedrawWindow( hwnd, rect, 0, flags );
}


/***********************************************************************
 *		ValidateRgn (USER32.@)
 */
BOOL WINAPI ValidateRgn( HWND hwnd, HRGN hrgn )
{
    if (!hwnd)
    {
        SetLastError( ERROR_INVALID_WINDOW_HANDLE );
        return FALSE;
    }

    return RedrawWindow( hwnd, NULL, hrgn, RDW_VALIDATE );
}


/***********************************************************************
 *		ValidateRect (USER32.@)
 *
 * MSDN: if hwnd parameter is NULL, ValidateRect invalidates and redraws
 * all windows and sends WM_ERASEBKGND and WM_NCPAINT.
 */
BOOL WINAPI ValidateRect( HWND hwnd, const RECT *rect )
{
    UINT flags = RDW_VALIDATE;

    if (!hwnd)
    {
        flags = RDW_ALLCHILDREN | RDW_INVALIDATE | RDW_FRAME | RDW_ERASE | RDW_ERASENOW;
        rect = NULL;
    }

    return RedrawWindow( hwnd, rect, 0, flags );
}


/***********************************************************************
 *		GetUpdateRgn (USER32.@)
 */
INT WINAPI GetUpdateRgn( HWND hwnd, HRGN hrgn, BOOL erase )
{
    INT retval = ERROR;
    UINT flags = UPDATE_NOCHILDREN;
    HRGN update_rgn;

    if (erase) flags |= UPDATE_NONCLIENT | UPDATE_ERASE;

    if ((update_rgn = send_ncpaint( hwnd, NULL, &flags )))
    {
        POINT offset;

        retval = CombineRgn( hrgn, update_rgn, 0, RGN_COPY );
        if (send_erase( hwnd, flags, update_rgn, NULL, NULL ))
        {
            flags = UPDATE_DELAYED_ERASE;
            get_update_flags( hwnd, NULL, &flags );
        }
        /* map region to client coordinates */
        offset.x = offset.y = 0;
        ScreenToClient( hwnd, &offset );
        OffsetRgn( hrgn, offset.x, offset.y );
    }
    return retval;
}


/***********************************************************************
 *		GetUpdateRect (USER32.@)
 */
BOOL WINAPI GetUpdateRect( HWND hwnd, LPRECT rect, BOOL erase )
{
    UINT flags = UPDATE_NOCHILDREN;
    HRGN update_rgn;
    BOOL need_erase;

    if (erase) flags |= UPDATE_NONCLIENT | UPDATE_ERASE;

    if (!(update_rgn = send_ncpaint( hwnd, NULL, &flags ))) return FALSE;

    if (rect)
    {
        if (GetRgnBox( update_rgn, rect ) != NULLREGION)
        {
            HDC hdc = GetDCEx( hwnd, 0, DCX_USESTYLE );
            MapWindowPoints( 0, hwnd, (LPPOINT)rect, 2 );
            DPtoLP( hdc, (LPPOINT)rect, 2 );
            ReleaseDC( hwnd, hdc );
        }
    }
    need_erase = send_erase( hwnd, flags, update_rgn, NULL, NULL );

    /* check if we still have an update region */
    flags = UPDATE_PAINT | UPDATE_NOCHILDREN;
    if (need_erase) flags |= UPDATE_DELAYED_ERASE;
    return (get_update_flags( hwnd, NULL, &flags ) && (flags & UPDATE_PAINT));
}


/***********************************************************************
 *		ExcludeUpdateRgn (USER32.@)
 */
INT WINAPI ExcludeUpdateRgn( HDC hdc, HWND hwnd )
{
    HRGN update_rgn = CreateRectRgn( 0, 0, 0, 0 );
    INT ret = GetUpdateRgn( hwnd, update_rgn, FALSE );

    if (ret != ERROR)
    {
        POINT pt;

        GetDCOrgEx( hdc, &pt );
        MapWindowPoints( 0, hwnd, &pt, 1 );
        OffsetRgn( update_rgn, -pt.x, -pt.y );
        ret = ExtSelectClipRgn( hdc, update_rgn, RGN_DIFF );
        DeleteObject( update_rgn );
    }
    return ret;
}


/*************************************************************************
 *		ScrollWindowEx (USER32.@)
 *
 * Note: contrary to what the doc says, pixels that are scrolled from the
 *      outside of clipRect to the inside are NOT painted.
 *
 */
INT WINAPI ScrollWindowEx( HWND hwnd, INT dx, INT dy,
                           const RECT *rect, const RECT *clipRect,
                           HRGN hrgnUpdate, LPRECT rcUpdate,
                           UINT flags )
{
    INT   retVal = NULLREGION;
    BOOL  bOwnRgn = TRUE;
    BOOL  bUpdate = (rcUpdate || hrgnUpdate || flags & (SW_INVALIDATE | SW_ERASE));
    int rdw_flags;
    HRGN  hrgnTemp;
    HRGN  hrgnWinupd = 0;
    HDC   hDC;
    RECT  rc, cliprc;
    HWND hwndCaret = NULL;
    BOOL moveCaret = FALSE;
    POINT newCaretPos;

    TRACE( "%p, %d,%d hrgnUpdate=%p rcUpdate = %p %s %04x\n",
           hwnd, dx, dy, hrgnUpdate, rcUpdate, wine_dbgstr_rect(rect), flags );
    TRACE( "clipRect = %s\n", wine_dbgstr_rect(clipRect));
    if( flags & ~( SW_SCROLLCHILDREN | SW_INVALIDATE | SW_ERASE))
        FIXME("some flags (%04x) are unhandled\n", flags);

    rdw_flags = (flags & SW_ERASE) && (flags & SW_INVALIDATE) ?
                                RDW_INVALIDATE | RDW_ERASE  : RDW_INVALIDATE ;

    if (!WIN_IsWindowDrawable( hwnd, TRUE )) return ERROR;
    hwnd = WIN_GetFullHandle( hwnd );

    GetClientRect(hwnd, &rc);
    if (rect) IntersectRect(&rc, &rc, rect);

    if (clipRect) IntersectRect(&cliprc,&rc,clipRect);
    else cliprc = rc;

    if( hrgnUpdate ) bOwnRgn = FALSE;
    else if( bUpdate ) hrgnUpdate = CreateRectRgn( 0, 0, 0, 0 );

    newCaretPos.x = newCaretPos.y = 0;

    if( !IsRectEmpty(&cliprc) && (dx || dy)) {
        DWORD dcxflags = DCX_CACHE;
        DWORD style = GetWindowLongW( hwnd, GWL_STYLE );

        hwndCaret = fix_caret(hwnd, &rc, dx, dy, flags, &moveCaret, &newCaretPos);

        if( style & WS_CLIPSIBLINGS) dcxflags |= DCX_CLIPSIBLINGS;
        if( GetClassLongW( hwnd, GCL_STYLE ) & CS_PARENTDC)
            dcxflags |= DCX_PARENTCLIP;
        if( !(flags & SW_SCROLLCHILDREN) && (style & WS_CLIPCHILDREN))
            dcxflags |= DCX_CLIPCHILDREN;
        hDC = GetDCEx( hwnd, 0, dcxflags);
        if (hDC)
        {
            ScrollDC( hDC, dx, dy, &rc, &cliprc, hrgnUpdate, rcUpdate );

            ReleaseDC( hwnd, hDC );

            if (!bUpdate)
                RedrawWindow( hwnd, NULL, hrgnUpdate, rdw_flags);
        }

        /* If the windows has an update region, this must be
         * scrolled as well. Keep a copy in hrgnWinupd
         * to be added to hrngUpdate at the end. */
        hrgnTemp = CreateRectRgn( 0, 0, 0, 0 );
        retVal = GetUpdateRgn( hwnd, hrgnTemp, FALSE );
        if (retVal != NULLREGION)
        {
            HRGN hrgnClip = CreateRectRgnIndirect(&cliprc);
            if( !bOwnRgn) {
                hrgnWinupd = CreateRectRgn( 0, 0, 0, 0);
                CombineRgn( hrgnWinupd, hrgnTemp, 0, RGN_COPY);
            }
            OffsetRgn( hrgnTemp, dx, dy );
            CombineRgn( hrgnTemp, hrgnTemp, hrgnClip, RGN_AND );
            if( !bOwnRgn)
                CombineRgn( hrgnWinupd, hrgnWinupd, hrgnTemp, RGN_OR );
            RedrawWindow( hwnd, NULL, hrgnTemp, rdw_flags);

           /* Catch the case where the scolling amount exceeds the size of the
            * original window. This generated a second update area that is the
            * location where the original scrolled content would end up.
            * This second region is not returned by the ScrollDC and sets
            * ScrollWindowEx apart from just a ScrollDC.
            *
            * This has been verified with testing on windows.
            */
            if (abs(dx) > abs(rc.right - rc.left) ||
                abs(dy) > abs(rc.bottom - rc.top))
            {
                SetRectRgn( hrgnTemp, rc.left + dx, rc.top + dy, rc.right+dx, rc.bottom + dy);
                CombineRgn( hrgnTemp, hrgnTemp, hrgnClip, RGN_AND );
                CombineRgn( hrgnUpdate, hrgnUpdate, hrgnTemp, RGN_OR );

                if( !bOwnRgn)
                    CombineRgn( hrgnWinupd, hrgnWinupd, hrgnTemp, RGN_OR );
            }
            DeleteObject( hrgnClip );
        }
        DeleteObject( hrgnTemp );
    } else {
        /* nothing was scrolled */
        if( !bOwnRgn)
            SetRectRgn( hrgnUpdate, 0, 0, 0, 0 );
        SetRectEmpty( rcUpdate);
    }

    if( flags & SW_SCROLLCHILDREN )
    {
        HWND *list = WIN_ListChildren( hwnd );
        if (list)
        {
            int i;
            RECT r, dummy;
            for (i = 0; list[i]; i++)
            {
                GetWindowRect( list[i], &r );
                MapWindowPoints( 0, hwnd, (POINT *)&r, 2 );
                if (!rect || IntersectRect(&dummy, &r, rect))
                    SetWindowPos( list[i], 0, r.left + dx, r.top  + dy, 0, 0,
                                  SWP_NOZORDER | SWP_NOSIZE | SWP_NOACTIVATE |
                                  SWP_NOREDRAW | SWP_DEFERERASE );
            }
            HeapFree( GetProcessHeap(), 0, list );
        }
    }

    if( flags & (SW_INVALIDATE | SW_ERASE) )
        RedrawWindow( hwnd, NULL, hrgnUpdate, rdw_flags |
                      ((flags & SW_SCROLLCHILDREN) ? RDW_ALLCHILDREN : 0 ) );

    if( hrgnWinupd) {
        CombineRgn( hrgnUpdate, hrgnUpdate, hrgnWinupd, RGN_OR);
        DeleteObject( hrgnWinupd);
    }

    if( hwndCaret ) {
        if ( moveCaret ) SetCaretPos( newCaretPos.x, newCaretPos.y );
        ShowCaret(hwndCaret);
    }

    if( bOwnRgn && hrgnUpdate ) DeleteObject( hrgnUpdate );

    return retVal;
}


/*************************************************************************
 *		ScrollWindow (USER32.@)
 *
 */
BOOL WINAPI ScrollWindow( HWND hwnd, INT dx, INT dy,
                          const RECT *rect, const RECT *clipRect )
{
    return (ERROR != ScrollWindowEx( hwnd, dx, dy, rect, clipRect, 0, NULL,
                                     (rect ? 0 : SW_SCROLLCHILDREN) |
                                     SW_INVALIDATE | SW_ERASE ));
}


/*************************************************************************
 *		ScrollDC (USER32.@)
 *
 * dx, dy, lprcScroll and lprcClip are all in logical coordinates (msdn is
 * wrong) hrgnUpdate is returned in device coordinates with rcUpdate in
 * logical coordinates.
 */
BOOL WINAPI ScrollDC( HDC hdc, INT dx, INT dy, const RECT *lprcScroll,
                      const RECT *lprcClip, HRGN hrgnUpdate, LPRECT lprcUpdate )

{
    return USER_Driver->pScrollDC( hdc, dx, dy, lprcScroll, lprcClip, hrgnUpdate, lprcUpdate );
}