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