//// "$Id: fl_arc.cxx,v 1.1.1.1 2003/08/07 21:18:40 jasonk Exp $"//// Arc functions for the Fast Light Tool Kit (FLTK).//// Copyright 1998-1999 by Bill Spitzak and others.//// This library is free software; you can redistribute it and/or// modify it under the terms of the GNU Library General Public// License as published by the Free Software Foundation; either// version 2 of the License, or (at your option) any later version.//// This library 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// Library General Public License for more details.//// You should have received a copy of the GNU Library General Public// License along with this library; if not, write to the Free Software// Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307// USA.//// Please report all bugs and problems to "fltk-bugs@easysw.com".//// Utility for drawing arcs and circles.  They are added to// the current fl_begin/fl_vertex/fl_end path.// Incremental math implementation:#include <FL/fl_draw.H>#include <FL/math.h>void fl_arc(double x, double y, double r, double start, double end) {  // draw start point accurately:  double A = start*(M_PI/180);  double X = r*cos(A);  double Y = -r*sin(A);  fl_vertex(x+X,y+Y);  // number of segments per radian:  int n; {    double x1 = fl_transform_dx(r,0);    double y1 = fl_transform_dy(r,0);    double r1 = x1*x1+y1*y1;    x1 = fl_transform_dx(0,r);    y1 = fl_transform_dy(0,r);    double r2 = x1*x1+y1*y1;    if (r2 < r1) r1 = r2;    n = int(sqrt(r1)*.841471);    if (n < 2) n = 2;  }  double epsilon = 1.0/n;  double E = end*(M_PI/180);  int i = int((E-A)*n);  if (i < 0) {i = -i; epsilon = -epsilon;}  double epsilon2 = epsilon/2;  for (; i>1; i--) {    X += epsilon*Y;    Y -= epsilon2*X;    fl_vertex(x+X,y+Y);    Y -= epsilon2*X;  }  // draw the end point accurately:  fl_vertex(x+r*cos(E), y-r*sin(E));}#if 0 // portable version.  X-specific one in fl_vertex.Cvoid fl_circle(double x,double y,double r) {  _fl_arc(x, y, r, r, 0, 360);}#endif//// End of "$Id: fl_arc.cxx,v 1.1.1.1 2003/08/07 21:18:40 jasonk Exp $".//