Add Snapping methods for snapping high or low

Author: gregmeess

core/Snapping.cs

@@ -29,5 +29,31 @@ public static double SnapToNearbyIncrement(double fValue, double fIncrement, dou
             return fValue;
         }
 
+        private static double SnapToIncrementSigned(double fValue, double fIncrement, bool low)
+        {
+            if (!MathUtil.IsFinite(fValue))
+                return 0;
+            double sign = Math.Sign(fValue);
+            fValue = Math.Abs(fValue);
+            int nInc = (int)(fValue / fIncrement);
+
+            if (low && sign < 0)
+                ++nInc;
+            else if (!low && sign > 0)
+                ++nInc;
+
+            return sign * (double)nInc * fIncrement;
+
+        }
+
+        public static double SnapToIncrementLow(double fValue, double fIncrement)
+        {
+            return SnapToIncrementSigned(fValue, fIncrement, true);
+        }
+
+        public static double SnapToIncrementHigh(double fValue, double fIncrement)
+        {
+            return SnapToIncrementSigned(fValue, fIncrement, false);
+        }
     }
 }