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 *     fill.h
31 *
32 *     Created by Brian Kelleher; Oct 1985
33 *
34 *     Include file for filled polygon routines.
35 *
36 *     These are the data structures needed to scan
37 *     convert regions.  Two different scan conversion
38 *     methods are available -- the even-odd method, and
39 *     the winding number method.
40 *     The even-odd rule states that a point is inside
41 *     the polygon if a ray drawn from that point in any
42 *     direction will pass through an odd number of
43 *     path segments.
44 *     By the winding number rule, a point is decided
45 *     to be inside the polygon if a ray drawn from that
46 *     point in any direction passes through a different
47 *     number of clockwise and counter-clockwise path
48 *     segments.
49 *
50 *     These data structures are adapted somewhat from
51 *     the algorithm in (Foley/Van Dam) for scan converting
52 *     polygons.
53 *     The basic algorithm is to start at the top (smallest y)
54 *     of the polygon, stepping down to the bottom of
55 *     the polygon by incrementing the y coordinate.  We
56 *     keep a list of edges which the current scanline crosses,
57 *     sorted by x.  This list is called the Active Edge Table (AET)
58 *     As we change the y-coordinate, we update each entry in
59 *     in the active edge table to reflect the edges new xcoord.
60 *     This list must be sorted at each scanline in case
61 *     two edges intersect.
62 *     We also keep a data structure known as the Edge Table (ET),
63 *     which keeps track of all the edges which the current
64 *     scanline has not yet reached.  The ET is basically a
65 *     list of ScanLineList structures containing a list of
66 *     edges which are entered at a given scanline.  There is one
67 *     ScanLineList per scanline at which an edge is entered.
68 *     When we enter a new edge, we move it from the ET to the AET.
69 *
70 *     From the AET, we can implement the even-odd rule as in
71 *     (Foley/Van Dam).
72 *     The winding number rule is a little trickier.  We also
73 *     keep the EdgeTableEntries in the AET linked by the
74 *     nextWETE (winding EdgeTableEntry) link.  This allows
75 *     the edges to be linked just as before for updating
76 *     purposes, but only uses the edges linked by the nextWETE
77 *     link as edges representing spans of the polygon to
78 *     drawn (as with the even-odd rule).
79 */
80
81/*
82 * for the winding number rule
83 */
84#define CLOCKWISE          1
85#define COUNTERCLOCKWISE  -1
86
87typedef struct _EdgeTableEntry {
88    int ymax;                   /* ycoord at which we exit this edge. */
89    BRESINFO bres;              /* Bresenham info to run the edge     */
90    struct _EdgeTableEntry *next;       /* next in the list     */
91    struct _EdgeTableEntry *back;       /* for insertion sort   */
92    struct _EdgeTableEntry *nextWETE;   /* for winding num rule */
93    int ClockWise;              /* flag for winding number rule       */
94} EdgeTableEntry;
95
96typedef struct _ScanLineList {
97    int scanline;               /* the scanline represented */
98    EdgeTableEntry *edgelist;   /* header node              */
99    struct _ScanLineList *next; /* next in the list       */
100} ScanLineList;
101
102typedef struct {
103    int ymax;                   /* ymax for the polygon     */
104    int ymin;                   /* ymin for the polygon     */
105    ScanLineList scanlines;     /* header node              */
106} EdgeTable;
107
108/*
109 * Here is a struct to help with storage allocation
110 * so we can allocate a big chunk at a time, and then take
111 * pieces from this heap when we need to.
112 */
113#define SLLSPERBLOCK 25
114
115typedef struct _ScanLineListBlock {
116    ScanLineList SLLs[SLLSPERBLOCK];
117    struct _ScanLineListBlock *next;
118} ScanLineListBlock;
119
120/*
121 * number of points to buffer before sending them off
122 * to scanlines() :  Must be an even number
123 */
124#define NUMPTSTOBUFFER 200
125
126/*
127 *
128 *     a few macros for the inner loops of the fill code where
129 *     performance considerations don't allow a procedure call.
130 *
131 *     Evaluate the given edge at the given scanline.
132 *     If the edge has expired, then we leave it and fix up
133 *     the active edge table; otherwise, we increment the
134 *     x value to be ready for the next scanline.
135 *     The winding number rule is in effect, so we must notify
136 *     the caller when the edge has been removed so he
137 *     can reorder the Winding Active Edge Table.
138 */
139#define EVALUATEEDGEWINDING(pAET, pPrevAET, y, fixWAET) { \
140   if (pAET->ymax == y) {          /* leaving this edge */ \
141      pPrevAET->next = pAET->next; \
142      pAET = pPrevAET->next; \
143      fixWAET = 1; \
144      if (pAET) \
145         pAET->back = pPrevAET; \
146   } \
147   else { \
148      BRESINCRPGONSTRUCT(pAET->bres); \
149      pPrevAET = pAET; \
150      pAET = pAET->next; \
151   } \
152}
153
154/*
155 *     Evaluate the given edge at the given scanline.
156 *     If the edge has expired, then we leave it and fix up
157 *     the active edge table; otherwise, we increment the
158 *     x value to be ready for the next scanline.
159 *     The even-odd rule is in effect.
160 */
161#define EVALUATEEDGEEVENODD(pAET, pPrevAET, y) { \
162   if (pAET->ymax == y) {          /* leaving this edge */ \
163      pPrevAET->next = pAET->next; \
164      pAET = pPrevAET->next; \
165      if (pAET) \
166         pAET->back = pPrevAET; \
167   } \
168   else { \
169      BRESINCRPGONSTRUCT(pAET->bres); \
170      pPrevAET = pAET; \
171      pAET = pAET->next; \
172   } \
173}
174