Draft: Allow to set the Working Plane from 3 selected vertices

src/Mod/Draft/DraftTools.py

@@ -356,6 +356,17 @@ class SelectPlane(DraftTool):
                             self.display(plane.axis)
                             self.finish()
                             return
+                    elif len(sel.SubElementNames) == 3:
+                        if ("Vertex" in sel.SubElementNames[0]) \
+                        and ("Vertex" in sel.SubElementNames[1]) \
+                        and ("Vertex" in sel.SubElementNames[2]):
+                            plane.alignTo3Points(sel.SubObjects[0].Point,
+                                                 sel.SubObjects[1].Point,
+                                                 sel.SubObjects[2].Point,
+                                                 self.offset)
+                            self.display(plane.axis)
+                            self.finish()
+                            return
             self.ui.selectPlaneUi()
             msg(translate("draft", "Pick a face to define the drawing plane\n"))
             if plane.alignToSelection(self.offset):

src/Mod/Draft/WorkingPlane.py

@@ -256,6 +256,12 @@ class plane:
         else:
             return False
 
+    def alignTo3Points(self,p1,p2,p3,offset=0):
+        import Part
+        w = Part.makePolygon([p1,p2,p3,p1])
+        f = Part.Face(w)
+        return self.alignToFace(f,offset)
+
     def alignToSelection(self, offset):
         '''If selection uniquely defines a plane, align working plane to it.  Return success (bool)'''
         import FreeCADGui