1/*
2
3Copyright 1987, 1998  The Open Group
4
5Permission to use, copy, modify, distribute, and sell this software and its
6documentation for any purpose is hereby granted without fee, provided that
7the above copyright notice appear in all copies and that both that
8copyright notice and this permission notice appear in supporting
9documentation.
10
11The above copyright notice and this permission notice shall be included
12in all copies or substantial portions of the Software.
13
14THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
15OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
16MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
17IN NO EVENT SHALL THE OPEN GROUP BE LIABLE FOR ANY CLAIM, DAMAGES OR
18OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
19ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
20OTHER DEALINGS IN THE SOFTWARE.
21
22Except as contained in this notice, the name of The Open Group shall
23not be used in advertising or otherwise to promote the sale, use or
24other dealings in this Software without prior written authorization
25from The Open Group.
26
27*/
28
29
30#ifdef HAVE_DIX_CONFIG_H
31#include <dix-config.h>
32#endif
33
34#ifndef SCANFILLINCLUDED
35#define SCANFILLINCLUDED
36/*
37 *     scanfill.h
38 *
39 *     Written by Brian Kelleher; Jan 1985
40 *
41 *     This file contains a few macros to help track
42 *     the edge of a filled object.  The object is assumed
43 *     to be filled in scanline order, and thus the
44 *     algorithm used is an extension of Bresenham's line
45 *     drawing algorithm which assumes that y is always the
46 *     major axis.
47 *     Since these pieces of code are the same for any filled shape,
48 *     it is more convenient to gather the library in one
49 *     place, but since these pieces of code are also in
50 *     the inner loops of output primitives, procedure call
51 *     overhead is out of the question.
52 *     See the author for a derivation if needed.
53 */
54
55
56/*
57 *  In scan converting polygons, we want to choose those pixels
58 *  which are inside the polygon.  Thus, we add .5 to the starting
59 *  x coordinate for both left and right edges.  Now we choose the
60 *  first pixel which is inside the pgon for the left edge and the
61 *  first pixel which is outside the pgon for the right edge.
62 *  Draw the left pixel, but not the right.
63 *
64 *  How to add .5 to the starting x coordinate:
65 *      If the edge is moving to the right, then subtract dy from the
66 *  error term from the general form of the algorithm.
67 *      If the edge is moving to the left, then add dy to the error term.
68 *
69 *  The reason for the difference between edges moving to the left
70 *  and edges moving to the right is simple:  If an edge is moving
71 *  to the right, then we want the algorithm to flip immediately.
72 *  If it is moving to the left, then we don't want it to flip until
73 *  we traverse an entire pixel.
74 */
75#define BRESINITPGON(dy, x1, x2, xStart, d, m, m1, incr1, incr2) { \
76    int dx;      /* local storage */ \
77\
78    /* \
79     *  if the edge is horizontal, then it is ignored \
80     *  and assumed not to be processed.  Otherwise, do this stuff. \
81     */ \
82    if ((dy) != 0) { \
83        xStart = (x1); \
84        dx = (x2) - xStart; \
85        if (dx < 0) { \
86            m = dx / (dy); \
87            m1 = m - 1; \
88            incr1 = -2 * dx + 2 * (dy) * m1; \
89            incr2 = -2 * dx + 2 * (dy) * m; \
90            d = 2 * m * (dy) - 2 * dx - 2 * (dy); \
91        } else { \
92            m = dx / (dy); \
93            m1 = m + 1; \
94            incr1 = 2 * dx - 2 * (dy) * m1; \
95            incr2 = 2 * dx - 2 * (dy) * m; \
96            d = -2 * m * (dy) + 2 * dx; \
97        } \
98    } \
99}
100
101#define BRESINCRPGON(d, minval, m, m1, incr1, incr2) { \
102    if (m1 > 0) { \
103        if (d > 0) { \
104            minval += m1; \
105            d += incr1; \
106        } \
107        else { \
108            minval += m; \
109            d += incr2; \
110        } \
111    } else {\
112        if (d >= 0) { \
113            minval += m1; \
114            d += incr1; \
115        } \
116        else { \
117            minval += m; \
118            d += incr2; \
119        } \
120    } \
121}
122
123
124/*
125 *     This structure contains all of the information needed
126 *     to run the bresenham algorithm.
127 *     The variables may be hardcoded into the declarations
128 *     instead of using this structure to make use of
129 *     register declarations.
130 */
131typedef struct {
132    int minor;         /* minor axis        */
133    int d;           /* decision variable */
134    int m, m1;       /* slope and slope+1 */
135    int incr1, incr2; /* error increments */
136} BRESINFO;
137
138
139#define BRESINITPGONSTRUCT(dmaj, min1, min2, bres) \
140	BRESINITPGON(dmaj, min1, min2, bres.minor, bres.d, \
141                     bres.m, bres.m1, bres.incr1, bres.incr2)
142
143#define BRESINCRPGONSTRUCT(bres) \
144        BRESINCRPGON(bres.d, bres.minor, bres.m, bres.m1, bres.incr1, bres.incr2)
145
146
147#endif
148