Draft : Added knots support for snapping (#26571)

* Draft : Added knots support for snapping

Signed-off-by: Yash Suthar <yashsuthar983@gmail.com>

* Use Special snap for knots and rename snapToBSpline to snapToBSplineKnots

---------

Signed-off-by: Yash Suthar <yashsuthar983@gmail.com>
Co-authored-by: Roy-043 <70520633+Roy-043@users.noreply.github.com>

src/Mod/Draft/draftguitools/gui_snapper.py

@@ -413,6 +413,8 @@ class Snapper:
                         elif et == "Ellipse":
                             # extra ellipse options
                             snaps.extend(self.snapToCenter(edge))
+                        elif et == "BSplineCurve":
+                            snaps.extend(self.snapToBSplineKnots(edge))
                 elif "Face" in comp:
                     # we are snapping to a face
                     if shape.ShapeType == "Face":
@@ -800,6 +802,17 @@ class Snapper:
                     snaps.append([mp, "midpoint", self.toWP(mp)])
         return snaps
 
+    def snapToBSplineKnots(self, edge):
+        """Return a list of knot snap locations for a BSpline."""
+        snaps = []
+        if self.isEnabled("Special"):
+            if hasattr(edge, "Curve") and isinstance(edge.Curve, Part.BSplineCurve):
+                knots = edge.Curve.getKnots()
+                for k in knots:
+                    p = edge.Curve.value(k)
+                    snaps.append([p, "special", self.toWP(p)])
+        return snaps
+
     def snapToNear(self, shape, point):
         """Return a list with a near snap location for an edge."""
         if self.isEnabled("Near") and point: