Let MathTex handle multiline strings

manim/mobject/text/tex_mobject.py

@@ -469,7 +469,11 @@ def _locate_first_match(
         first_match_length = 0
         first_match = None
         for substring in substrings_to_isolate:
-            match = re.match(f"(.*?)({re.escape(substring)})(.*)", unprocessed_string)
+            match = re.match(
+                f"(.*?)({re.escape(substring)})(.*)",
+                unprocessed_string,
+                flags=re.DOTALL,
+            )
             if match and len(match.group(1)) < first_match_start:
                 first_match = match
                 first_match_start = len(match.group(1))

tests/module/mobject/text/test_texmobject.py

@@ -136,6 +136,17 @@ def test_split_double_braces(tex_string, expected_segments):
     assert MathTex._split_double_braces(tex_string) == expected_segments
 
 
+def test_multiline_tex():
+    multiline_string = Tex(
+        """This is a very long string,
+        which will test how well the new implementation of Tex handles such long strings.""",
+        substrings_to_isolate=["This", "implementation"],
+    )
+    assert len(multiline_string.get_part_by_tex("This").submobjects) == 4
+    assert len(multiline_string.get_part_by_tex("implementation").submobjects) == 14
+    assert len(multiline_string.submobjects[0]) == 90
+
+
 def test_tex(config):
     Tex("The horse does not eat cucumber salad.")
     assert Path(config.media_dir, "Tex", "5384b41741a246bd.svg").exists()