Draft: added functions to edit tangent or symmetric bezier curves

       changed icon Draft_BezTanNode
       bugfix in Draft BezCurve modifytangentpole
       move poles with knots for Bezier Curves with Degree >=3
       make bezier curves symmetric/tangent when clicking on poles by
           keeping the coordinates of the selected pole

src/Mod/Draft/Draft.py

@@ -4005,25 +4005,45 @@ def createGeometry(self,fp):
             fp.Shape = w
         fp.Placement = plm
 
-    @staticmethod
-    def symmetricpoles(knot, p1, p2):
+    @classmethod
+    def symmetricpoles(cls,knot, p1, p2):
         """make two poles symmetric respective to the knot"""
         p1h=FreeCAD.Vector(p1)
         p2h=FreeCAD.Vector(p2)
         p1h.multiply(0.5)
         p2h.multiply(0.5)
-        return ( knot+p1-p2 , knot+p2-p1)
+        return ( knot+p1h-p2h , knot+p2h-p1h)
 
-    @staticmethod
-    def tangentpoles(knot, p1, p2):
+    @classmethod
+    def tangentpoles(cls,knot, p1, p2,allowsameside=False):
         """make two poles have the same tangent at knot"""
         p12n=p2.sub(p1)
         p12n.normalize()
         p1k=knot-p1
+        p2k=knot-p2
         p1k_= FreeCAD.Vector(p12n)
-        p1k_.multiply(p1k*p12n)
-        pk_k=knot-p1-p1k_
-        return (p1+pk_k,p2+pk_k)
+        kon12=(p1k*p12n)
+        if allowsameside or not (kon12 < 0 or p2k*p12n > 0):# instead of moving
+            p1k_.multiply(kon12)
+            pk_k=knot-p1-p1k_
+            return (p1+pk_k,p2+pk_k)
+        else:
+            return cls.symmetricpoles(knot, p1, p2)
+
+    @staticmethod
+    def modifysymmetricpole(knot,p1):
+        """calculate the coordinates of the opposite pole
+        of a symmetric knot"""
+        return knot+knot-p1
+
+    @staticmethod
+    def modifytangentpole(knot,p1,oldp2):
+        """calculate the coordinates of the opposite pole
+        of a tangent knot"""
+        pn=knot-p1
+        pn.normalize()
+        pn.multiply((knot-oldp2).Length)
+        return pn+knot
 
 # for compatibility with older versions ???????
 _ViewProviderBezCurve = _ViewProviderWire

src/Mod/Draft/DraftTools.py

@@ -3354,6 +3354,14 @@ def update(self,v):
                 self.obj.Closed = True
             # DNC: fix error message if edited point coinsides with one of the existing points
             if ( editPnt in pts ) == False:
+                if Draft.getType(self.obj) in ["BezCurve"] and self.obj.Degree >=3 and \
+                    (self.editing % self.obj.Degree) == 0: #it's a knot
+                    if self.editing >= 1: #move left pole
+                        pts[self.editing-1] = pts[self.editing-1] + editPnt - pts[self.editing] 
+                        self.trackers[self.editing-1].set(pts[self.editing-1])
+                    if self.editing < len(pts)-1: #move right pole
+                        pts[self.editing+1] = pts[self.editing+1] + editPnt - pts[self.editing] 
+                        self.trackers[self.editing+1].set(pts[self.editing+1])
                 pts[self.editing] = editPnt
                 self.obj.Points = pts
                 self.trackers[self.editing].set(v)
@@ -3511,18 +3519,38 @@ def smoothBezPoint(self,point, info=None, style='Symmetric'):
             return # didn't click control point
         pts = self.obj.Points
         deg = self.obj.Degree
-        if point not in range(0, len(pts), deg):
-            msg(translate("draft", "Selection is not a Node\n"),'warning')
-            return
-        if (point == 0) or (point == (len(pts)-1)):
+        if point % deg != 0:
+            if deg >=3: #allow to select poles
+                if point > 2 and point % deg == 1: #right pole
+                    knot = point -1
+                    keepp = point
+                    changep = point -2
+                elif point -3 < len(pts): #left pole
+                    knot = point +1
+                    keepp = point
+                    changep = point +2
+                else:
+                    msg(translate("draft", "Can't change Knot belonging to that pole\n"),'warning')
+                    return
+                if knot:
+                    if style == 'Tangent':
+                        pts[changep] = self.obj.Proxy.modifytangentpole(pts[knot],pts[keepp],\
+                            pts[changep])
+                    else:
+                        pts[changep] = self.obj.Proxy.modifysymmetricpole(pts[knot],pts[keepp])
+            else:
+                msg(translate("draft", "Selection is not a Pole\n"),'warning')
+                return
+        elif (point == 0) or (point == (len(pts)-1)):
             msg(translate("draft", "Endpoint of BezCurve can't be smoothed\n"),'warning')
             return
-        if style == 'Tangent':
-            prev, next = self.obj.Proxy.tangentpoles(pts[point],pts[point-1],pts[point+1])
         else:
-            prev, next = self.obj.Proxy.symmetricpoles(pts[point],pts[point-1],pts[point+1])
-        pts[point-1] = prev
-        pts[point+1] = next
+            if style == 'Tangent':
+                prev, next = self.obj.Proxy.tangentpoles(pts[point],pts[point-1],pts[point+1])
+            else:
+                prev, next = self.obj.Proxy.symmetricpoles(pts[point],pts[point-1],pts[point+1])
+            pts[point-1] = prev
+            pts[point+1] = next
         self.obj.Points = pts
         self.doc.openTransaction("Edit "+self.obj.Name)
         self.doc.commitTransaction()