Initial revision

git-svn-id: file:///fltk/svn/fltk/trunk@2 ea41ed52-d2ee-0310-a9c1-e6b18d33e121

1 files changed, 50 insertions, 0 deletions

diff --git a/src/fl_arc.cxx b/src/fl_arc.cxx
new file mode 100644
index 000000000..756c2a4bb
--- /dev/null
+++ b/src/fl_arc.cxx
@@ -0,0 +1,50 @@
+// fl_arc.C
+
+// 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.C
+void fl_circle(double x,double y,double r) {
+  _fl_arc(x, y, r, r, 0, 360);
+}
+#endif