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111 lines
3.7 KiB
C
111 lines
3.7 KiB
C
/* Libart_LGPL - library of basic graphic primitives
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* Copyright (C) 1998-2000 Raph Levien
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*
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* This library is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Library General Public
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* License as published by the Free Software Foundation; either
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* version 2 of the License, or (at your option) any later version.
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*
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* This library is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* Library General Public License for more details.
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*
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* You should have received a copy of the GNU Library General Public
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* License along with this library; if not, write to the
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* Free Software Foundation, Inc., 59 Temple Place - Suite 330,
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* Boston, MA 02111-1307, USA.
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*/
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#include <string.h>
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#include "art_misc.h"
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#include "art_uta.h"
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#include "art_uta_ops.h"
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#ifndef MIN
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#define MIN(a,b) ((a) < (b) ? (a) : (b))
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#endif
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#ifndef MAX
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#define MAX(a,b) ((a) > (b) ? (a) : (b))
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#endif
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/**
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* art_uta_union: Compute union of two uta's.
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* @uta1: One uta.
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* @uta2: The other uta.
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*
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* Computes the union of @uta1 and @uta2. The union is approximate,
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* but coverage is guaranteed over all pixels included in either of
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* the arguments, ie more pixels may be covered than the "exact"
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* union.
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*
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* Note: this routine is used in the Gnome Canvas to accumulate the
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* region that needs to be repainted. However, since it copies over
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* the entire uta (which might be largish) even when the update may be
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* small, it can be a performance bottleneck. There are two approaches
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* to this problem, both of which are probably worthwhile. First, the
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* generated uta's should always be limited to the visible window,
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* thus guaranteeing that uta's never become large. Second, there
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* should be a new, destructive union operation that only touches a
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* small part of the uta when the update is small.
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*
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* Return value: The new union uta.
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**/
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ArtUta *
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art_uta_union (ArtUta *uta1, ArtUta *uta2)
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{
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ArtUta *uta;
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int x0, y0, x1, y1;
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int x, y;
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int ix, ix1, ix2;
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ArtUtaBbox bb, bb1, bb2;
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x0 = MIN(uta1->x0, uta2->x0);
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y0 = MIN(uta1->y0, uta2->y0);
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x1 = MAX(uta1->x0 + uta1->width, uta2->x0 + uta2->width);
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y1 = MAX(uta1->y0 + uta1->height, uta2->y0 + uta2->height);
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uta = art_uta_new (x0, y0, x1, y1);
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/* could move the first two if/else statements out of the loop */
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ix = 0;
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for (y = y0; y < y1; y++)
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{
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ix1 = (y - uta1->y0) * uta1->width + x0 - uta1->x0;
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ix2 = (y - uta2->y0) * uta2->width + x0 - uta2->x0;
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for (x = x0; x < x1; x++)
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{
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if (x < uta1->x0 || y < uta1->y0 ||
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x >= uta1->x0 + uta1->width || y >= uta1->y0 + uta1->height)
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bb1 = 0;
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else
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bb1 = uta1->utiles[ix1];
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if (x < uta2->x0 || y < uta2->y0 ||
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x >= uta2->x0 + uta2->width || y >= uta2->y0 + uta2->height)
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bb2 = 0;
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else
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bb2 = uta2->utiles[ix2];
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if (bb1 == 0)
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bb = bb2;
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else if (bb2 == 0)
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bb = bb1;
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else
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bb = ART_UTA_BBOX_CONS(MIN(ART_UTA_BBOX_X0(bb1),
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ART_UTA_BBOX_X0(bb2)),
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MIN(ART_UTA_BBOX_Y0(bb1),
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ART_UTA_BBOX_Y0(bb2)),
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MAX(ART_UTA_BBOX_X1(bb1),
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ART_UTA_BBOX_X1(bb2)),
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MAX(ART_UTA_BBOX_Y1(bb1),
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ART_UTA_BBOX_Y1(bb2)));
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uta->utiles[ix] = bb;
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ix++;
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ix1++;
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ix2++;
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}
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}
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return uta;
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}
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