// // "$Id: fl_arc.cxx,v 1.4 1999/01/07 19:17:35 mike 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 #include 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.C void fl_circle(double x,double y,double r) { _fl_arc(x, y, r, r, 0, 360); } #endif // // End of "$Id: fl_arc.cxx,v 1.4 1999/01/07 19:17:35 mike Exp $". //