[EXPERIMENTAL] Fix ManimBanner animations by modifying Mobject.become(), Mobject.get_center(), and ManimBanner.expand() (#4556)

* Fix ManimBanner animations by modifying Mobject.become(), Mobject.get_center(), and ManimBanner.expand()

* Add ManimBanner animations to test_new_rendering.py

example_scenes/test_new_rendering.py

@@ -37,6 +37,14 @@ class Test(Scene):
         )
         self.play(FadeOut(VGroup(hexagon, circle, star)))
 
+    @group
+    def manim_banner(self) -> None:
+        banner = ManimBanner().scale(0.5)
+        self.play(banner.create())
+        self.play(banner.expand())
+        self.wait(1)
+        self.play(Unwrite(banner))
+
     @group
     def never_run(self) -> None:
         self.play(Write(Text("This should never be run")))

manim/mobject/logo.py

@@ -327,11 +327,13 @@ class ManimBanner(VGroup):
                 slide_and_uncover,
                 run_time=run_time * 2 / 3,
                 rate_func=ease_in_out_cubic,
+                introducer=True,
             ),
             UpdateFromAlphaFunc(
                 self,
                 slide_back,
                 run_time=run_time * 1 / 3,
                 rate_func=smooth,
+                introducer=True,
             ),
         )

manim/mobject/opengl/opengl_mobject.py

@@ -2471,7 +2471,7 @@ class OpenGLMobject:
 
     def get_center(self) -> np.ndarray:
         """Get center coordinates."""
-        return self.get_bounding_box()[1]
+        return self.get_bounding_box()[1].copy()
 
     def get_center_of_mass(self):
         return self.get_all_points().mean(0)
@@ -2850,7 +2850,12 @@ class OpenGLMobject:
                     circ.become(square)
                     self.wait(0.5)
         """
-        # Manim CE Weird stretching thing which also modifies the original mobject
+        # TODO: ideally, only copy the Mobject when it has to be modified
+        # (if stretch, match_height, match_width, match_depth, or match_center are True).
+        # Currently, it's necessary to always copy it because the final code ported
+        # from 3b1b/manim seems to modify the mobject, which is an issue especially when
+        # applying Mobject.restore() which makes a Mobject become its saved state.
+        mobject = mobject.copy()
         if stretch:
             mobject.stretch_to_fit_height(self.height)
             mobject.stretch_to_fit_width(self.width)