Fixed expand animation for :class:.ManimBanner (#3298)

* fixed "a" appearing before shapes

* added animation test for ManimBanner

* added xelatex to linux pipeline

* xelatex -> xetex

Author: behackl

.github/workflows/ci.yml

@@ -68,7 +68,7 @@ jobs:
         uses: teatimeguest/setup-texlive-action@v2
         with:
           cache: true
-          packages: scheme-basic fontspec inputenc fontenc tipa mathrsfs calligra xcolor standalone preview doublestroke ms everysel setspace rsfs relsize ragged2e fundus-calligra microtype wasysym physics dvisvgm jknapltx wasy cm-super babel-english gnu-freefont mathastext cbfonts-fd
+          packages: scheme-basic fontspec inputenc fontenc tipa mathrsfs calligra xcolor standalone preview doublestroke ms everysel setspace rsfs relsize ragged2e fundus-calligra microtype wasysym physics dvisvgm jknapltx wasy cm-super babel-english gnu-freefont mathastext cbfonts-fd xetex
 
       - name: Start virtual display (Linux)
         if: runner.os == 'Linux'

manim/mobject/logo.py

@@ -209,7 +209,7 @@ def slide_and_uncover(mob, alpha):
             for letter in mob.anim:
                 if mob.square.get_center()[0] > letter.get_center()[0]:
                     letter.set_opacity(1)
-                    self.add(letter)
+                    self.add_to_back(letter)
 
             # Finish animation
             if alpha == 1:

tests/test_graphical_units/control_data/logo/banner.npz

@@ -0,0 +1,13 @@
+from __future__ import annotations
+
+from manim import ManimBanner
+from manim.utils.testing.frames_comparison import frames_comparison
+
+__module_test__ = "logo"
+
+
+@frames_comparison(last_frame=False)
+def test_banner(scene):
+    banner = ManimBanner()
+    scene.play(banner.create(), run_time=0.5)
+    scene.play(banner.expand(), run_time=0.5)