Fix and arc creation error when linking IDF files. For negative angles we need to use the absolute value of the angle. Also simplify the formula for center distance calculation.

Author: phkahler

src/importidf.cpp

@@ -211,7 +211,7 @@ static Vector ArcCenter(Vector p0, Vector p1, double angle) {
 // indicates a circle centered at x1,y1 passing through x2,y2 and is a complete loop.
 static void CreateEntity(EntityList *el, int *id, hEntity h0, hEntity h1, hEntity hnorm,
                     Vector p0, Vector p1, double angle, bool keepout) {
-    if (angle == 0.0) {
+    if (fabs(angle) < 0.1) {
         //line
         if(p0.Equals(p1)) return;
 
@@ -228,16 +228,14 @@ static void CreateEntity(EntityList *el, int *id, hEntity h0, hEntity h1, hEntit
         if(angle < 0.0) {
             swap(p0,p1);
             swap(h0,h1);
+            angle = fabs(angle);
         }
         // locate the center of the arc
         Vector m = p0.Plus(p1).ScaledBy(0.5);
         Vector perp = Vector::From(p1.y-p0.y, p0.x-p1.x, 0.0).WithMagnitude(1.0);
-        double dist = 0;
-        if (angle != 180) {
-            dist = (p1.Minus(m).Magnitude())/tan(0.5*angle*3.141592653589793/180.0);
-        } else {
-            dist = 0.0;
-        }
+        // half angle in radians
+        double theta = 0.5*angle*PI/180.0;
+        double dist = (p1.Minus(m).Magnitude())*cos(theta)/sin(theta);
         Vector c = m.Minus(perp.ScaledBy(dist));
         hEntity hc = newPoint(el, id, c, /*visible=*/false);
         newArc(el, id, h0, h1, hc, hnorm, keepout);