fix(numbers): preserve rotation and size in DecimalNumber.set_value

manim/mobject/text/numbers.py

@@ -16,6 +16,7 @@
 from manim.mobject.types.vectorized_mobject import VMobject
 from manim.mobject.value_tracker import ValueTracker
 from manim.typing import Vector3DLike
+from manim.utils.space_ops import angle_between_vectors
 
 string_to_mob_map: dict[str, SingleStringMathTex] = {}
 
@@ -290,10 +291,22 @@ def set_value(self, number: float) -> Self:
         old_font_size = self.font_size
         move_to_point = self.get_edge_center(self.edge_to_fix)
         old_submobjects = self.submobjects
+        direction = self.get_right() - self.get_center()
+        rotation_angle = (
+            angle_between_vectors(RIGHT, direction)
+            if np.linalg.norm(direction) > 1e-8
+            else 0
+        )
+        if abs(rotation_angle) > 1e-8:
+            measure = self.copy()
+            measure.rotate(-rotation_angle, about_point=measure.get_center())
+            old_font_size = measure.font_size
 
         self._set_submobjects_from_number(number)
         self.font_size = old_font_size
         self.move_to(move_to_point, self.edge_to_fix)
+        if abs(rotation_angle) > 1e-8:
+            self.rotate(rotation_angle, about_point=self.get_center())
         for sm1, sm2 in zip(self.submobjects, old_submobjects, strict=False):
             sm1.match_style(sm2)
 

tests/module/mobject/text/test_numbers.py

@@ -1,6 +1,7 @@
 from __future__ import annotations
 
-from manim import RED, DecimalNumber, Integer
+from manim import DEGREES, RED, RIGHT, DecimalNumber, Integer
+from manim.utils.space_ops import angle_between_vectors
 
 
 def test_font_size():
@@ -38,6 +39,27 @@ def test_set_value_size():
     assert round(num.height, 12) == round(test_num.height, 12)
 
 
+def test_set_value_preserves_rotation():
+    """Test that set_value keeps rotation applied to the number."""
+    num = DecimalNumber(0, font_size=48)
+    num.rotate(45 * DEGREES)
+    direction = num.get_right() - num.get_center()
+    angle_before = angle_between_vectors(RIGHT, direction)
+
+    num.set_value(1)
+
+    direction = num.get_right() - num.get_center()
+    angle_after = angle_between_vectors(RIGHT, direction)
+    assert angle_before == angle_after
+
+
+def test_set_value_preserves_font_size_when_rotated():
+    num = DecimalNumber(0, font_size=48)
+    num.rotate(45 * DEGREES)
+    num.set_value(1)
+    assert num._font_size == 48
+
+
 def test_color_when_number_of_digits_changes():
     """Test that all digits of an Integer are colored correctly when
     the number of digits changes.