1 /* Libart_LGPL - library of basic graphic primitives
2 * Copyright (C) 1998-2000 Raph Levien
4 * This library is free software; you can redistribute it and/or
5 * modify it under the terms of the GNU Library General Public
6 * License as published by the Free Software Foundation; either
7 * version 2 of the License, or (at your option) any later version.
9 * This library is distributed in the hope that it will be useful,
10 * but WITHOUT ANY WARRANTY; without even the implied warranty of
11 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
12 * Library General Public License for more details.
14 * You should have received a copy of the GNU Library General Public
15 * License along with this library; if not, write to the
16 * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
17 * Boston, MA 02111-1307, USA.
23 #include "art_uta_ops.h"
26 #define MIN(a,b) ((a) < (b) ? (a) : (b))
30 #define MAX(a,b) ((a) > (b) ? (a) : (b))
34 * art_uta_union: Compute union of two uta's.
36 * @uta2: The other uta.
38 * Computes the union of @uta1 and @uta2. The union is approximate,
39 * but coverage is guaranteed over all pixels included in either of
40 * the arguments, ie more pixels may be covered than the "exact"
43 * Note: this routine is used in the Gnome Canvas to accumulate the
44 * region that needs to be repainted. However, since it copies over
45 * the entire uta (which might be largish) even when the update may be
46 * small, it can be a performance bottleneck. There are two approaches
47 * to this problem, both of which are probably worthwhile. First, the
48 * generated uta's should always be limited to the visible window,
49 * thus guaranteeing that uta's never become large. Second, there
50 * should be a new, destructive union operation that only touches a
51 * small part of the uta when the update is small.
53 * Return value: The new union uta.
56 art_uta_union (ArtUta *uta1, ArtUta *uta2)
62 ArtUtaBbox bb, bb1, bb2;
64 x0 = MIN(uta1->x0, uta2->x0);
65 y0 = MIN(uta1->y0, uta2->y0);
66 x1 = MAX(uta1->x0 + uta1->width, uta2->x0 + uta2->width);
67 y1 = MAX(uta1->y0 + uta1->height, uta2->y0 + uta2->height);
68 uta = art_uta_new (x0, y0, x1, y1);
70 /* could move the first two if/else statements out of the loop */
72 for (y = y0; y < y1; y++)
74 ix1 = (y - uta1->y0) * uta1->width + x0 - uta1->x0;
75 ix2 = (y - uta2->y0) * uta2->width + x0 - uta2->x0;
76 for (x = x0; x < x1; x++)
78 if (x < uta1->x0 || y < uta1->y0 ||
79 x >= uta1->x0 + uta1->width || y >= uta1->y0 + uta1->height)
82 bb1 = uta1->utiles[ix1];
84 if (x < uta2->x0 || y < uta2->y0 ||
85 x >= uta2->x0 + uta2->width || y >= uta2->y0 + uta2->height)
88 bb2 = uta2->utiles[ix2];
95 bb = ART_UTA_BBOX_CONS(MIN(ART_UTA_BBOX_X0(bb1),
96 ART_UTA_BBOX_X0(bb2)),
97 MIN(ART_UTA_BBOX_Y0(bb1),
98 ART_UTA_BBOX_Y0(bb2)),
99 MAX(ART_UTA_BBOX_X1(bb1),
100 ART_UTA_BBOX_X1(bb2)),
101 MAX(ART_UTA_BBOX_Y1(bb1),
102 ART_UTA_BBOX_Y1(bb2)));
103 uta->utiles[ix] = bb;