diff --git a/InitGui.py b/InitGui.py
index 456ff4a..6d3e303 100644
--- a/InitGui.py
+++ b/InitGui.py
@@ -5,23 +5,43 @@ class Assembly3Workbench(FreeCADGui.Workbench):
     MenuText = 'Assembly 3'
     Icon = asm3.utils.addIconToFCAD('AssemblyWorkbench.svg')
 
+    def __init__(self):
+        self.observer = None
+
     def Activated(self):
-        import asm3
-        asm3.constraint.Observer.attach()
+        self.observer.attach()
 
     def Deactivated(self):
-        import asm3
-        asm3.constraint.Observer.detach()
+        self.observer.detach()
 
     def Initialize(self):
         import asm3
-        cmds = asm3.gui.AsmCmdType.getInfo().TypeNames
+        cmdInfo = asm3.gui.AsmCmdType.getInfo()
+        cmds = cmdInfo.TypeNames
         asm3.utils.logger.debug(cmds)
         self.appendToolbar('asm3',cmds)
         self.appendMenu('&Assembly3', cmds)
         self.appendToolbar('asm3 Constraint',
-                    asm3.constraint.Constraint.CommandList)
+                asm3.constraint.Constraint.CommandList)
+        self.observer = asm3.gui.SelectionObserver(
+                cmdInfo.Types + asm3.constraint.Constraint.Commands)
         #  FreeCADGui.addPreferencePage(
         #          ':/assembly3/ui/assembly3_prefs.ui','Assembly3')
 
+    def ContextMenu(self, _recipient):
+        import asm3
+        cmds = []
+        for cmd in asm3.gui.AsmCmdType.getInfo().Types:
+            if cmd.IsActive:
+                cmds.append(cmd.getName())
+        if cmds:
+            self.appendContextMenu('Assembly',cmds)
+
+        cmds.clear()
+        for cmd in asm3.constraint.Constraint.Commands:
+            if cmd.IsActive:
+                cmds.append(cmd.getName())
+        if cmds:
+            self.appendContextMenu('Constraint',cmds)
+
 FreeCADGui.addWorkbench(Assembly3Workbench)
diff --git a/constraint.py b/constraint.py
index 09f60a5..98be56f 100644
--- a/constraint.py
+++ b/constraint.py
@@ -149,6 +149,9 @@ class ConstraintCommand:
     def __init__(self,tp):
         self.tp = tp
 
+    def getName(self):
+        return 'asm3Add'+self.tp.getName()
+
     def GetResources(self):
         return self.tp.GetResources()
 
@@ -159,49 +162,19 @@ class ConstraintCommand:
     def IsActive(self):
         return FreeCADGui.ActiveDocument and self.tp._active
 
-class SelectionObserver:
-    def __init__(self):
-        self._attached = False
-
-    def onChanged(self):
+    def checkActive(self):
         from asm3.assembly import AsmConstraint
-        for cls in Constraint._cmdTypes:
-            try:
-                AsmConstraint.getSelection()
-            except Exception as e:
-                logger.trace('selection "{}" exception: {}'.format(
-                    cls.getName(),e.message),frame=1)
-                cls._active = False
-            else:
-                cls._active = True
+        try:
+            AsmConstraint.getSelection(self.tp._id)
+        except Exception as e:
+            logger.trace('selection "{}" exception: {}'.format(
+                self.tp.getName(),e.message),frame=1)
+            self.tp._active = False
+        else:
+            self.tp._active = True
 
-    def addSelection(self,*_args):
-        self.onChanged()
-
-    def removeSelection(self,*_args):
-        self.onChanged()
-
-    def setSelection(self,*_args):
-        self.onChanged()
-
-    def clearSelection(self,*_args):
-        logger.trace('selection cleared')
-        for cls in Constraint._cmdTypes:
-            cls._active = False
-
-    def attach(self):
-        if not self._attached:
-            FreeCADGui.Selection.addObserver(self)
-            self._attached = True
-            self.onChanged()
-
-    def detach(self):
-        if self._attached:
-            FreeCADGui.Selection.removeObserver(self)
-            self._attached = False
-            self.clearSelection('')
-
-Observer = SelectionObserver()
+    def deactive(self):
+        self.tp._active = False
 
 class Constraint(ProxyType):
     'constraint meta class'
@@ -211,16 +184,17 @@ class Constraint(ProxyType):
     _disabled = 'Disabled'
 
     CommandList = []
-    _cmdTypes = []
+    Commands = []
 
     def register(cls):
         super(Constraint,cls).register()
         if cls._menuItem:
-            name = 'asm3Add'+cls.getName()
             mcs = cls.__class__
+            cmd = ConstraintCommand(cls)
+            name = cmd.getName()
             mcs.CommandList.append(name)
-            mcs._cmdTypes.append(cls)
-            FreeCADGui.addCommand(name,ConstraintCommand(cls))
+            mcs.Commands.append(cmd)
+            FreeCADGui.addCommand(name,cmd)
 
     @classmethod
     def attach(mcs,obj,checkType=True):
diff --git a/gui.py b/gui.py
index 532cde4..0162d4e 100644
--- a/gui.py
+++ b/gui.py
@@ -4,6 +4,41 @@ from asm3.utils import logger,objName,addIconToFCAD
 from asm3.assembly import Assembly,AsmConstraint
 from asm3.proxy import ProxyType
 
+class SelectionObserver:
+    def __init__(self, cmds):
+        self._attached = False
+        self.cmds = cmds
+
+    def onChanged(self):
+        for cmd in self.cmds:
+            cmd.checkActive()
+
+    def addSelection(self,*_args):
+        self.onChanged()
+
+    def removeSelection(self,*_args):
+        self.onChanged()
+
+    def setSelection(self,*_args):
+        self.onChanged()
+
+    def clearSelection(self,*_args):
+        for cmd in self.cmds:
+            cmd.deactive()
+
+    def attach(self):
+        if not self._attached:
+            FreeCADGui.Selection.addObserver(self)
+            self._attached = True
+            self.onChanged()
+
+    def detach(self):
+        if self._attached:
+            FreeCADGui.Selection.removeObserver(self)
+            self._attached = False
+            self.clearSelection('')
+
+
 class AsmCmdType(ProxyType):
     def register(cls):
         super(AsmCmdType,cls).register()
@@ -36,12 +71,20 @@ class AsmCmdBase(with_metaclass(AsmCmdType,object)):
 
     @classmethod
     def IsActive(cls):
-        if FreeCAD.ActiveDocument and cls._active:
+        if cls._active and cls._id>=0 and FreeCAD.ActiveDocument:
             return True
 
+    @classmethod
+    def checkActive(cls):
+        pass
+
+    @classmethod
+    def deactive(cls):
+        pass
+
 class AsmCmdNew(AsmCmdBase):
     _id = 0
-    _menuText = 'Create a new assembly'
+    _menuText = 'Create assembly'
     _iconName = 'Assembly_New_Assembly.svg'
 
     def Activated(self):
@@ -49,17 +92,16 @@ class AsmCmdNew(AsmCmdBase):
 
 class AsmCmdSolve(AsmCmdBase):
     _id = 1
-    _menuText = 'Solve the constraints of assembly(s)'
+    _menuText = 'Solve constraints'
     _iconName = 'AssemblyWorkbench.svg'
 
     def Activated(self):
         import asm3.solver as solver
         solver.solve()
 
-
 class AsmCmdMove(AsmCmdBase):
     _id = 2
-    _menuText = 'Move assembly'
+    _menuText = 'Move part'
     _iconName = 'Assembly_Move.svg'
 
     def Activated(self):