use more permissive comparisons

Author: itzpr3d4t0r

src_c/collisions.c

@@ -605,7 +605,7 @@ pgIntersection_CircleCircle(pgCircleBase *A, pgCircleBase *B,
         return 0;
     }
 
-    if (d2 == 0 && A->r == B->r) {
+    if (double_compare(d2, 0) && double_compare(A->r, B->r)) {
         return 0;
     }
 
@@ -621,7 +621,7 @@ pgIntersection_CircleCircle(pgCircleBase *A, pgCircleBase *B,
     double xs2 = xm - h * (dy / d);
     double ys2 = ym + h * (dx / d);
 
-    if (d2 == r_sum2 || d2 == r_diff2) {
+    if (double_compare(d2, r_sum2) || double_compare(d2, r_diff2)) {
         intersections[0] = xs1;
         intersections[1] = ys1;
         return 1;

src_c/include/geometry.h

@@ -147,4 +147,12 @@ PG_FREEPOLY_COND(pgPolygonBase *poly, int was_sequence)
     }
 }
 
+static int
+double_compare(double a, double b)
+{
+    /* Uses both a fixed epsilon and an adaptive epsilon */
+    const double e = 1e-6;
+    return fabs(a - b) < e || fabs(a - b) <= e * MAX(fabs(a), fabs(b));
+}
+
 #endif /* ~_GEOMETRY_H */