78 lines
2.2 KiB
C++
78 lines
2.2 KiB
C++
//
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// "$Id: fl_arc.cxx,v 1.4 1999/01/07 19:17:35 mike Exp $"
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//
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// Arc functions for the Fast Light Tool Kit (FLTK).
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//
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// Copyright 1998-1999 by Bill Spitzak and others.
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//
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// This library is free software; you can redistribute it and/or
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// modify it under the terms of the GNU Library General Public
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// License as published by the Free Software Foundation; either
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// version 2 of the License, or (at your option) any later version.
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//
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// This library is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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// Library General Public License for more details.
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//
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// You should have received a copy of the GNU Library General Public
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// License along with this library; if not, write to the Free Software
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// Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307
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// USA.
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//
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// Please report all bugs and problems to "fltk-bugs@easysw.com".
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//
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// Utility for drawing arcs and circles. They are added to
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// the current fl_begin/fl_vertex/fl_end path.
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// Incremental math implementation:
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#include <FL/fl_draw.H>
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#include <FL/math.h>
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void fl_arc(double x, double y, double r, double start, double end) {
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// draw start point accurately:
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double A = start*(M_PI/180);
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double X = r*cos(A);
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double Y = -r*sin(A);
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fl_vertex(x+X,y+Y);
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// number of segments per radian:
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int n; {
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double x1 = fl_transform_dx(r,0);
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double y1 = fl_transform_dy(r,0);
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double r1 = x1*x1+y1*y1;
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x1 = fl_transform_dx(0,r);
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y1 = fl_transform_dy(0,r);
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double r2 = x1*x1+y1*y1;
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if (r2 < r1) r1 = r2;
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n = int(sqrt(r1)*.841471);
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if (n < 2) n = 2;
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}
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double epsilon = 1.0/n;
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double E = end*(M_PI/180);
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int i = int((E-A)*n);
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if (i < 0) {i = -i; epsilon = -epsilon;}
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double epsilon2 = epsilon/2;
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for (; i>1; i--) {
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X += epsilon*Y;
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Y -= epsilon2*X;
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fl_vertex(x+X,y+Y);
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Y -= epsilon2*X;
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}
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// draw the end point accurately:
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fl_vertex(x+r*cos(E), y-r*sin(E));
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}
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#if 0 // portable version. X-specific one in fl_vertex.C
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void fl_circle(double x,double y,double r) {
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_fl_arc(x, y, r, r, 0, 360);
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}
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#endif
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//
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// End of "$Id: fl_arc.cxx,v 1.4 1999/01/07 19:17:35 mike Exp $".
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//
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