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Diffstat (limited to 'contrib/groff/src/libs/libgroff/geometry.cc')
| -rw-r--r-- | contrib/groff/src/libs/libgroff/geometry.cc | 286 |
1 files changed, 286 insertions, 0 deletions
diff --git a/contrib/groff/src/libs/libgroff/geometry.cc b/contrib/groff/src/libs/libgroff/geometry.cc new file mode 100644 index 0000000..58a94a4 --- /dev/null +++ b/contrib/groff/src/libs/libgroff/geometry.cc @@ -0,0 +1,286 @@ +// -*- C++ -*- +/* Copyright (C) 1989, 1990, 1991, 1992, 2000, 2001, 2002 + Free Software Foundation, Inc. + Written by Gaius Mulley <gaius@glam.ac.uk> + using adjust_arc_center() from printer.cc, written by James Clark. + +This file is part of groff. + +groff is free software; you can redistribute it and/or modify it under +the terms of the GNU General Public License as published by the Free +Software Foundation; either version 2, or (at your option) any later +version. + +groff is distributed in the hope that it will be useful, but WITHOUT ANY +WARRANTY; without even the implied warranty of MERCHANTABILITY or +FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License +for more details. + +You should have received a copy of the GNU General Public License along +with groff; see the file COPYING. If not, write to the Free Software +Foundation, 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. */ + + +#include <stdio.h> +#include <math.h> + +#undef MAX +#define MAX(a, b) (((a) > (b)) ? (a) : (b)) + +#undef MIN +#define MIN(a, b) (((a) < (b)) ? (a) : (b)) + + +// This utility function adjusts the specified center of the +// arc so that it is equidistant between the specified start +// and end points. (p[0], p[1]) is a vector from the current +// point to the center; (p[2], p[3]) is a vector from the +// center to the end point. If the center can be adjusted, +// a vector from the current point to the adjusted center is +// stored in c[0], c[1] and 1 is returned. Otherwise 0 is +// returned. + +#if 1 +int adjust_arc_center(const int *p, double *c) +{ + // We move the center along a line parallel to the line between + // the specified start point and end point so that the center + // is equidistant between the start and end point. + // It can be proved (using Lagrange multipliers) that this will + // give the point nearest to the specified center that is equidistant + // between the start and end point. + + double x = p[0] + p[2]; // (x, y) is the end point + double y = p[1] + p[3]; + double n = x*x + y*y; + if (n != 0) { + c[0]= double(p[0]); + c[1] = double(p[1]); + double k = .5 - (c[0]*x + c[1]*y)/n; + c[0] += k*x; + c[1] += k*y; + return 1; + } + else + return 0; +} +#else +int printer::adjust_arc_center(const int *p, double *c) +{ + int x = p[0] + p[2]; // (x, y) is the end point + int y = p[1] + p[3]; + // Start at the current point; go in the direction of the specified + // center point until we reach a point that is equidistant between + // the specified starting point and the specified end point. Place + // the center of the arc there. + double n = p[0]*double(x) + p[1]*double(y); + if (n > 0) { + double k = (double(x)*x + double(y)*y)/(2.0*n); + // (cx, cy) is our chosen center + c[0] = k*p[0]; + c[1] = k*p[1]; + return 1; + } + else { + // We would never reach such a point. So instead start at the + // specified end point of the arc. Go towards the specified + // center point until we reach a point that is equidistant between + // the specified start point and specified end point. Place + // the center of the arc there. + n = p[2]*double(x) + p[3]*double(y); + if (n > 0) { + double k = 1 - (double(x)*x + double(y)*y)/(2.0*n); + // (c[0], c[1]) is our chosen center + c[0] = p[0] + k*p[2]; + c[1] = p[1] + k*p[3]; + return 1; + } + else + return 0; + } +} +#endif + + +/* + * check_output_arc_limits - works out the smallest box that will encompass + * an arc defined by an origin (x, y) and two + * vectors (p0, p1) and (p2, p3). + * (x1, y1) -> start of arc + * (x1, y1) + (xv1, yv1) -> center of circle + * (x1, y1) + (xv1, yv1) + (xv2, yv2) -> end of arc + * + * Works out in which quadrant the arc starts and + * stops, and from this it determines the x, y + * max/min limits. The arc is drawn clockwise. + * + * [I'm sure there is a better way to do this, but + * I don't know how. Please can someone let me + * know or "improve" this function.] + */ + +void check_output_arc_limits(int x1, int y1, + int xv1, int yv1, + int xv2, int yv2, + double c0, double c1, + int *minx, int *maxx, + int *miny, int *maxy) +{ + int radius = (int)sqrt(c0*c0 + c1*c1); + int x2 = x1 + xv1 + xv2; // end of arc is (x2, y2) + int y2 = y1 + yv1 + yv2; + + // firstly lets use the `circle' limitation + *minx = x1 + xv1 - radius; + *maxx = x1 + xv1 + radius; + *miny = y1 + yv1 - radius; + *maxy = y1 + yv1 + radius; + + /* now to see which min/max can be reduced and increased for the limits of + * the arc + * + * Q2 | Q1 + * -----+----- + * Q3 | Q4 + * + * + * NB. (x1+xv1, y1+yv1) is at the origin + * + * below we ask a nested question + * (i) from which quadrant does the first vector start? + * (ii) into which quadrant does the second vector go? + * from the 16 possible answers we determine the limits of the arc + */ + if (xv1 > 0 && yv1 > 0) { + // first vector in Q3 + if (xv2 >= 0 && yv2 >= 0 ) { + // second in Q1 + *maxx = x2; + *miny = y1; + } + else if (xv2 < 0 && yv2 >= 0) { + // second in Q2 + *maxx = x2; + *miny = y1; + } + else if (xv2 >= 0 && yv2 < 0) { + // second in Q4 + *miny = MIN(y1, y2); + } + else if (xv2 < 0 && yv2 < 0) { + // second in Q3 + if (x1 >= x2) { + *minx = x2; + *maxx = x1; + *miny = MIN(y1, y2); + *maxy = MAX(y1, y2); + } + else { + // xv2, yv2 could all be zero? + } + } + } + else if (xv1 > 0 && yv1 < 0) { + // first vector in Q2 + if (xv2 >= 0 && yv2 >= 0) { + // second in Q1 + *maxx = MAX(x1, x2); + *minx = MIN(x1, x2); + *miny = y1; + } + else if (xv2 < 0 && yv2 >= 0) { + // second in Q2 + if (x1 < x2) { + *maxx = x2; + *minx = x1; + *miny = MIN(y1, y2); + *maxy = MAX(y1, y2); + } + else { + // otherwise almost full circle anyway + } + } + else if (xv2 >= 0 && yv2 < 0) { + // second in Q4 + *miny = y2; + *minx = x1; + } + else if (xv2 < 0 && yv2 < 0) { + // second in Q3 + *minx = MIN(x1, x2); + } + } + else if (xv1 <= 0 && yv1 <= 0) { + // first vector in Q1 + if (xv2 >= 0 && yv2 >= 0) { + // second in Q1 + if (x1 < x2) { + *minx = x1; + *maxx = x2; + *miny = MIN(y1, y2); + *maxy = MAX(y1, y2); + } + else { + // nearly full circle + } + } + else if (xv2 < 0 && yv2 >= 0) { + // second in Q2 + *maxy = MAX(y1, y2); + } + else if (xv2 >= 0 && yv2 < 0) { + // second in Q4 + *miny = MIN(y1, y2); + *maxy = MAX(y1, y2); + *minx = MIN(x1, x2); + } + else if (xv2 < 0 && yv2 < 0) { + // second in Q3 + *minx = x2; + *maxy = y1; + } + } + else if (xv1 <= 0 && yv1 > 0) { + // first vector in Q4 + if (xv2 >= 0 && yv2 >= 0) { + // second in Q1 + *maxx = MAX(x1, x2); + } + else if (xv2 < 0 && yv2 >= 0) { + // second in Q2 + *maxy = MAX(y1, y2); + *maxx = MAX(x1, x2); + } + else if (xv2 >= 0 && yv2 < 0) { + // second in Q4 + if (x1 >= x2) { + *miny = MIN(y1, y2); + *maxy = MAX(y1, y2); + *minx = MIN(x1, x2); + *maxx = MAX(x2, x2); + } + else { + // nearly full circle + } + } + else if (xv2 < 0 && yv2 < 0) { + // second in Q3 + *maxy = MAX(y1, y2); + *minx = MIN(x1, x2); + *maxx = MAX(x1, x2); + } + } + + // this should *never* happen but if it does it means a case above is wrong + // this code is only present for safety sake + if (*maxx < *minx) { + fprintf(stderr, "assert failed *minx > *maxx\n"); + fflush(stderr); + *maxx = *minx; + } + if (*maxy < *miny) { + fprintf(stderr, "assert failed *miny > *maxy\n"); + fflush(stderr); + *maxy = *miny; + } +} |
