Manage maya callback after reload

Author: csaez

mscreen.py

@@ -30,6 +30,7 @@
 logger.addHandler(logging.NullHandler())
 
 try:
+    import maya
     import maya.cmds as mc
     import maya.OpenMayaUI as omui
     import maya.OpenMayaRender as omr
@@ -457,28 +458,33 @@ def __init__(self):
         # `mscreen` works by registering ONE callback in a Maya 3dview, said
         # callback calls to `__draw` where all the registered primitives are
         # proccessed.
+        self.callback = omui.MUiMessage.add3dViewPostRenderMsgCallback(
+            self.getCurrentModelPanel(), lambda *args: self.__draw())
         self.primitives = list()
-        # `_callback` holds Maya's callback ID.
-        self._callback = None
+        self.refresh()
 
-    def __registerCallback(self):
-        if self._callback is not None:
+    # Maya's callback is stored as a singleton in the maya module so it can be
+    # managed after reloading this module avoiding memory leaks.
+    @property
+    def callback(self):
+        if hasattr(maya, "mscreen_callback"):
+            return maya.mscreen_callback
+
+    @callback.setter
+    def callback(self, value):
+        del self.callback
+        maya.mscreen_callback = value
+
+    @callback.deleter
+    def callback(self):
+        if not self.callback:
             return
-        self._callback = omui.MUiMessage.add3dViewPostRenderMsgCallback(
-            self.getCurrentModelPanel(), lambda *args: self.__draw())
-
-    def __unregisterCallback(self):
-        if self._callback is not None and len(self.primitives) == 0:
-            try:
-                omui.MUiMessage.removeCallback(self._callback)
-            except Exception as err:
-                logger.debug(err)
-            self._callback = None
+        omui.MUiMessage.removeCallback(self.callback)
+        del maya.mscreen_callback
 
     def __draw(self):
         for each in self.primitives:
             each.draw(self.view, self.renderer)
-        self.__unregisterCallback()
 
     def refresh(self):
         """
@@ -494,7 +500,6 @@ def clear(self):
 
     def registerPrimitive(self, primitive):
         self.primitives.append(primitive)
-        self.__registerCallback()
 
     def unregisterPrimitive(self, primitive):
         if primitive in self.primitives:

tests/test_bezier.py

@@ -1,10 +1,6 @@
 import random
 import mscreen
-
-mscreen.clear()
-mscreen.refresh()
-
-reload(mscreen)
+reload(mscreen)  # debugging purposes
 
 
 NUM_CVS = 6

tests/test_deform.py

@@ -2,8 +2,7 @@
 import maya.api.OpenMaya as om2
 
 import mscreen
-mscreen.clear()
-reload(mscreen)
+reload(mscreen)  # debugging purposes
 
 
 def deformById(curve, mobjects):

tests/test_linearInterpolate.py

@@ -1,10 +1,7 @@
 import random
 import mscreen
+reload(mscreen)  # debugging purposes
 
-mscreen.clear()
-mscreen.refresh()
-
-reload(mscreen)
 
 POS_A = (random.randint(-10, 0), random.randint(0, 10), random.randint(-5, 5))
 POS_B = (random.randint(0, 10), random.randint(0, 10), random.randint(-5, 5))

tests/test_lines.py

@@ -1,9 +1,5 @@
 import mscreen
-
-mscreen.clear()
-mscreen.refresh()
-
-reload(mscreen)
+reload(mscreen)  # debugging purposes
 
 
 POINTS = ((2.0, 0.0, 2.0), (2.0, 0.0, -2.0), (-2.0, 0.0, -2.0),

tests/test_parent.py

@@ -1,8 +1,7 @@
 import maya.cmds as cmds
-import mscreen
 
-mscreen.clear()
-reload(mscreen)
+import mscreen
+reload(mscreen)  # debugging purposes
 
 
 # create a curve

tests/test_points.py

@@ -1,10 +1,7 @@
 import random
 import mscreen
+reload(mscreen)  # debugging purposes
 
-mscreen.clear()
-mscreen.refresh()
-
-reload(mscreen)
 
 NUM_POINTS = 50
 COLORS = (

tests/test_readme.py

@@ -1,8 +1,6 @@
 import random
 import mscreen
-
-mscreen.clear()
-reload(mscreen)
+reload(mscreen)  # debugging purposes
 
 # let's draw a square
 POINTS = ((2.0, 0.0, 2.0), (2.0, 0.0, -2.0), (-2.0, 0.0, -2.0),

tests/test_transforms.py

@@ -1,10 +1,7 @@
 import random
 import mscreen
+reload(mscreen)  # debugging purposes
 
-mscreen.clear()
-mscreen.refresh()
-
-reload(mscreen)
 
 # Lets draw a few matrices...
 for _ in range(10):