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MLC111: Updater-bearing object is in neither the scene family nor an animation

qual reports MLC111 when frames are rendered (a play or wait) while an object with a registered updater is provably outside the scene family and not the target of an animation issued by that statement. Manim only invokes a mobject updater while the mobject is reachable from the scene or owned by an in-flight animation: an orphaned updater host is invisible and its callback never runs.

  • Default severity: info
  • Minimum confidence: medium (the builtin min-confidence default is high, so displaying this rule needs min-confidence = "medium" or lower)
  • Implementation phase: 2
  • Fix: inserting self.add(...) before the rendering statement is suggested as an unsafe fix

The rule fires only on definite facts: the registration must happen on every path, and the object must be provably absent from the scene family and provably not an animation target of the rendering statement. Maybe membership (e.g. self.add inside a branch) never violates. Registering an updater and adding the object (or playing an introducer on it) before any frame renders is fine.

Wrong

class Demo(Scene):
    def construct(self):
        dot = Dot()
        dot.add_updater(lambda m, dt: m.rotate(dt))
        self.wait(1)  # dot is not in the scene: nothing shows, updater never runs

class Demo(Scene):
    def construct(self):
        dot = Dot()
        dot.add_updater(lambda m, dt: m.rotate(dt))
        self.add(dot)
        self.wait(1)