/*
 * MACDRV window/DC scrolling
 *
 * Copyright 1993  David W. Metcalfe
 * Copyright 1995, 1996 Alex Korobka
 * Copyright 2001 Alexandre Julliard
 * Copyright 2011, 2013 Ken Thomases for CodeWeavers Inc.
 *
 * 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 "macdrv.h"
#include "winuser.h"

WINE_DEFAULT_DEBUG_CHANNEL(scroll);


static void dump_region(const char *p, HRGN hrgn)
{
    DWORD i, size;
    RGNDATA *data = NULL;
    RECT *rect;

    if (!hrgn)
    {
        TRACE("%s null region\n", p);
        return;
    }
    if (!(size = GetRegionData(hrgn, 0, NULL)))
        return;
    if (!(data = HeapAlloc(GetProcessHeap(), 0, size))) return;
    GetRegionData(hrgn, size, data);
    TRACE("%s %d rects:", p, data->rdh.nCount);
    for (i = 0, rect = (RECT *)data->Buffer; i<20 && i < data->rdh.nCount; i++, rect++)
        TRACE(" %s", wine_dbgstr_rect(rect));
    TRACE("\n");
    HeapFree(GetProcessHeap(), 0, data);
}


/*************************************************************************
 *              ScrollDC   (MACDRV.@)
 */
BOOL CDECL macdrv_ScrollDC(HDC hdc, INT dx, INT dy, const RECT *lprcScroll,
                           const RECT *lprcClip, HRGN hrgnUpdate, LPRECT lprcUpdate)
{
    RECT rcSrc, rcClip, offset;
    INT dxdev, dydev, res;
    HRGN DstRgn, clipRgn, visrgn;

    TRACE("dx,dy %d,%d rcScroll %s rcClip %s hrgnUpdate %p lprcUpdate %p\n",
          dx, dy, wine_dbgstr_rect(lprcScroll), wine_dbgstr_rect(lprcClip),
          hrgnUpdate, lprcUpdate);

    /* get the visible region */
    visrgn = CreateRectRgn(0, 0, 0, 0);
    GetRandomRgn(hdc, visrgn, SYSRGN);
    if (!(GetVersion() & 0x80000000))
    {
        /* Window NT/2k/XP */
        POINT org;
        GetDCOrgEx(hdc, &org);
        OffsetRgn(visrgn, -org.x, -org.y);
    }

    /* intersect with the clipping Region if the DC has one */
    clipRgn = CreateRectRgn(0, 0, 0, 0);
    if (GetClipRgn(hdc, clipRgn) != 1)
    {
        DeleteObject(clipRgn);
        clipRgn = NULL;
    }
    else
        CombineRgn(visrgn, visrgn, clipRgn, RGN_AND);

    /* only those pixels in the scroll rectangle that remain in the clipping
     * rect are scrolled. */
    if (lprcClip)
        rcClip = *lprcClip;
    else
        GetClipBox(hdc, &rcClip);
    rcSrc = rcClip;
    OffsetRect(&rcClip, -dx, -dy);
    IntersectRect(&rcSrc, &rcSrc, &rcClip);

    /* if an scroll rectangle is specified, only the pixels within that
     * rectangle are scrolled */
    if (lprcScroll)
        IntersectRect(&rcSrc, &rcSrc, lprcScroll);

    /* now convert to device coordinates */
    LPtoDP(hdc, (LPPOINT)&rcSrc, 2);
    TRACE("source rect: %s\n", wine_dbgstr_rect(&rcSrc));

    /* also dx and dy */
    SetRect(&offset, 0, 0, dx, dy);
    LPtoDP(hdc, (LPPOINT)&offset, 2);
    dxdev = offset.right - offset.left;
    dydev = offset.bottom - offset.top;

    /* now intersect with the visible region to get the pixels that will
     * actually scroll */
    DstRgn = CreateRectRgnIndirect(&rcSrc);
    res = CombineRgn(DstRgn, DstRgn, visrgn, RGN_AND);

    /* and translate, giving the destination region */
    OffsetRgn(DstRgn, dxdev, dydev);
    if (TRACE_ON(scroll)) dump_region("Destination scroll region: ", DstRgn);

    /* if there are any, do it */
    if (res > NULLREGION)
    {
        RECT rect ;
        /* clip to the destination region, so we can BitBlt with a simple
         * bounding rectangle */
        if (clipRgn)
            ExtSelectClipRgn(hdc, DstRgn, RGN_AND);
        else
            SelectClipRgn(hdc, DstRgn);
        GetRgnBox(DstRgn, &rect);
        DPtoLP(hdc, (LPPOINT)&rect, 2);
        TRACE("destination rect: %s\n", wine_dbgstr_rect(&rect));

        BitBlt(hdc, rect.left, rect.top,
               rect.right - rect.left, rect.bottom - rect.top,
               hdc, rect.left - dx, rect.top - dy, SRCCOPY);
    }

    /* compute the update areas.  This is the combined clip rectangle
     * minus the scrolled region, and intersected with the visible
     * region. */
    if (hrgnUpdate || lprcUpdate)
    {
        HRGN hrgn = hrgnUpdate;

        /* Intersect clip and scroll rectangles, allowing NULL values */
        if (lprcScroll)
            if (lprcClip)
                IntersectRect(&rcClip, lprcClip, lprcScroll);
            else
                rcClip = *lprcScroll;
        else
            if (lprcClip)
                rcClip = *lprcClip;
            else
                GetClipBox(hdc, &rcClip);

        /* Convert the combined clip rectangle to device coordinates */
        LPtoDP(hdc, (LPPOINT)&rcClip, 2);
        if (hrgn)
            SetRectRgn(hrgn, rcClip.left, rcClip.top, rcClip.right, rcClip.bottom);
        else
            hrgn = CreateRectRgnIndirect(&rcClip);
        CombineRgn(hrgn, hrgn, visrgn, RGN_AND);
        CombineRgn(hrgn, hrgn, DstRgn, RGN_DIFF);
        if (TRACE_ON(scroll)) dump_region("Update region: ", hrgn);
        if (lprcUpdate)
        {
            GetRgnBox(hrgn, lprcUpdate);
            /* Put the lprcUpdate in logical coordinates */
            DPtoLP(hdc, (LPPOINT)lprcUpdate, 2);
            TRACE("returning lprcUpdate %s\n", wine_dbgstr_rect(lprcUpdate));
        }
        if (!hrgnUpdate)
            DeleteObject(hrgn);
    }

    /* restore original clipping region */
    SelectClipRgn(hdc, clipRgn);
    DeleteObject(visrgn);
    DeleteObject(DstRgn);
    if (clipRgn) DeleteObject(clipRgn);
    return TRUE;
}