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Annotation of 41BSD/cmd/cifplot/clip.c, revision 1.1

1.1     ! root        1: /*******************************************************************
        !             2: *                                                                  *
        !             3: *    File: CIFPLOT/clip.c                                          *
        !             4: *    Written by Dan Fitzpatrick                                    *
        !             5: *    copyright 1980 -- Regents of the University of California     *
        !             6: *                                                                  *
        !             7: ********************************************************************/
        !             8: 
        !             9: #include <stdio.h>
        !            10: #include "defs.h"
        !            11: #include "globals.h"
        !            12: #include "parser_defs.h"
        !            13: #include "structs.h"
        !            14: #include "out_structs.h"
        !            15: #include "alloc.h"
        !            16: 
        !            17: #define YINTERCEPT(y)  (x2 + ((x1 - x2)*((y) - y2))/(y1 - y2))
        !            18: 
        !            19: Clip(e)
        !            20: iedge *e;
        !            21: /* Clip edge and send to queue */
        !            22: {
        !            23:     register int x1,y1,x2,y2;  /* edges go from (x1,y1) to (x2,y2) */
        !            24:     int x;                     /* x is a temporary */
        !            25: 
        !            26:     x1 = e->x1; y1 = e->y1;
        !            27:     x2 = e->x2; y2 = e->y2;
        !            28:     /* If totally out of range return */
        !            29:     if((x1 >= Top) || (x2 <= Bottom)) {
        !            30:        return;
        !            31:        }
        !            32:     /* Clip against xmin */
        !            33:     if(x1 < Bottom) {
        !            34:        y1 = y2 + ((y1 - y2)*(Bottom - x2))/(x1 - x2);
        !            35:        x1 = Bottom;
        !            36:        }
        !            37:     
        !            38:     /* Clip against xmax */
        !            39:     if(x2 > Top) {
        !            40:        y2 = y1 + ((y2 - y1)*(Top - x1))/(x2 - x1);
        !            41:        x2 = Top;
        !            42:        }
        !            43: 
        !            44:     /* Determine slope of line and branch */
        !            45:     if(y1 > y2) {
        !            46:        /* Check that an end point is in a valid area */
        !            47:        if(y1 < 0) y1 = y2 = 0;
        !            48:        if(y2 > NoPixcels) y1 = y2 = NoPixcels;
        !            49: 
        !            50:        /* Clip against ymax */
        !            51:        if(y1 > NoPixcels) {
        !            52:                x = YINTERCEPT(NoPixcels);
        !            53:                if(x1 != x2) {
        !            54:                    if(x1 <= e->x1)
        !            55:                        SendEdge(x1,NoPixcels,x,NoPixcels,e->dir,e->poly);
        !            56:                      else
        !            57:                        DupEdge(x1,NoPixcels,x,NoPixcels,e->dir,e->poly);
        !            58:                    }
        !            59:                x1 = x; y1 = NoPixcels;
        !            60:                }
        !            61:        /* Clip against ymin */
        !            62:        if(y2 < 0) {
        !            63:                x = YINTERCEPT(0);
        !            64:                if(x1 != x2) {
        !            65:                    if(x <= e->x1)
        !            66:                        SendEdge(x,0,x2,0,e->dir,e->poly);
        !            67:                      else
        !            68:                        DupEdge(x,0,x2,0,e->dir,e->poly);
        !            69:                    }
        !            70:                x2 = x; y2 = 0;
        !            71:                }
        !            72:        }
        !            73:     if(y1 < y2) {
        !            74:        /* Check that an end point is in a valid area */
        !            75:        if(y2 < 0) y1 = y2 = 0;
        !            76:        if(y1 > NoPixcels) y1 = y2 = NoPixcels;
        !            77: 
        !            78:        /* Clip against ymin */
        !            79:        if(y1 < 0) {
        !            80:                x = YINTERCEPT(0);
        !            81:                if(x1 != x2) {
        !            82:                    if(x1 <= e->x1)
        !            83:                        SendEdge(x1,0,x,0,e->dir,e->poly);
        !            84:                      else
        !            85:                        DupEdge(x1,0,x,0,e->dir,e->poly);
        !            86:                    }
        !            87:                x1 = x; y1 = 0;
        !            88:                }
        !            89:        /* Clip against ymax */
        !            90:        if(y2 > NoPixcels) {
        !            91:                x = YINTERCEPT(NoPixcels);
        !            92:                if(x1 != x2) {
        !            93:                    if(x <= e->x1)
        !            94:                        SendEdge(x,NoPixcels,x2,NoPixcels,e->dir,e->poly);
        !            95:                      else
        !            96:                        DupEdge(x,NoPixcels,x2,NoPixcels,e->dir,e->poly);
        !            97:                    }
        !            98:                x2 = x; y2 = NoPixcels;
        !            99:                }
        !           100:        }
        !           101:     if(y1 == y2) {
        !           102:        /* y1 == y2 is treated seperately since it would cause
        !           103:         * divide by zero in YINTERCEPT */
        !           104:        if(y1 < 0) y1 = y2 = 0;
        !           105:        if(y2 > NoPixcels) y1 = y2 = NoPixcels;
        !           106:        }
        !           107: 
        !           108:     /* Send clipped edges to queue */
        !           109:     if(x1 <= e->x1)
        !           110:         SendEdge(x1,y1,x2,y2,e->dir,e->poly);
        !           111:       else
        !           112:        DupEdge(x1,y1,x2,y2,e->dir,e->poly);
        !           113:     return;
        !           114:     }
        !           115: 
        !           116: int LastA = -999999;
        !           117: SendEdge(a,b,c,d,dir,poly)
        !           118: int a,b,c,d,dir;
        !           119: PolyDesc *poly;
        !           120: /* put the edge (a,b) -- (c,d) into queue */
        !           121: {
        !           122:     edge *e;
        !           123: 
        !           124:     /* Clip */
        !           125:     if(a == c && poly->level != 0) return;
        !           126:     if(a<Bottom) a = Bottom;
        !           127:     if(c>Top)    c = Top;
        !           128:     if(b < 0 || d < 0 || b > NoPixcels || d > NoPixcels) {
        !           129:        Error("Out of range in SendEdge",INTERNAL);
        !           130:        }
        !           131: 
        !           132:     if(a < LastA) Error("Out of order edges",INTERNAL);
        !           133:     e = GetEdge();
        !           134:     e->ix = a;
        !           135:     e->ex = c;
        !           136:     e->iy = b;
        !           137:     if(c != a)
        !           138:        e->dy = ((real) (d-b))/((real) (c-a));
        !           139:       else
        !           140:        e->dy = 0.0;
        !           141:     e->dir = dir;
        !           142:     if(!((dir == 1) || (dir == -1)))
        !           143:        Error("bad direction vector in SendEdge",INTERNAL);
        !           144:     e->poly = poly;
        !           145:     (poly->refs)++;
        !           146:     if(!extractor)
        !           147:        PutQueue(e,&(EdgeQueue[poly->level]));
        !           148:       else /* if running extractor everything goes on same layer */
        !           149:        PutQueue(e,&(EdgeQueue[0]));
        !           150:     }
        !           151: 
        !           152: DupEdge(a,b,c,d,dir,poly)
        !           153: int a,b,c,d;
        !           154: PolyDesc *poly;
        !           155: {
        !           156:     iedge *e;
        !           157: 
        !           158:     e = GetIEdge();
        !           159:     e->type = EDGE;
        !           160:     e->poly = poly;
        !           161:     (e->poly->refs)++;
        !           162:     e->dir = dir;
        !           163:     e->min = a;
        !           164:     e->x1 = a; e->y1 = b;
        !           165:     e->x2 = c; e->y2 = d;
        !           166:     Selector(e);
        !           167:     }

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