1 files changed, 61 insertions, 0 deletions
diff --git a/sphinx/util/math.py b/sphinx/util/math.py
new file mode 100644
index 0000000..ef0eb39
--- /dev/null
+++ b/sphinx/util/math.py
@@ -0,0 +1,61 @@
+"""Utility functions for math."""
+
+from __future__ import annotations
+
+from typing import TYPE_CHECKING
+
+if TYPE_CHECKING:
+    from docutils import nodes
+
+    from sphinx.builders.html import HTML5Translator
+
+
+def get_node_equation_number(writer: HTML5Translator, node: nodes.math_block) -> str:
+    if writer.builder.config.math_numfig and writer.builder.config.numfig:
+        figtype = 'displaymath'
+        if writer.builder.name == 'singlehtml':
+            key = f"{writer.docnames[-1]}/{figtype}"  # type: ignore[has-type]
+        else:
+            key = figtype
+
+        id = node['ids'][0]
+        number = writer.builder.fignumbers.get(key, {}).get(id, ())
+        return '.'.join(map(str, number))
+    else:
+        return node['number']
+
+
+def wrap_displaymath(text: str, label: str | None, numbering: bool) -> str:
+    def is_equation(part: str) -> str:
+        return part.strip()
+
+    if label is None:
+        labeldef = ''
+    else:
+        labeldef = r'\label{%s}' % label
+        numbering = True
+
+    parts = list(filter(is_equation, text.split('\n\n')))
+    equations = []
+    if len(parts) == 0:
+        return ''
+    elif len(parts) == 1:
+        if numbering:
+            begin = r'\begin{equation}' + labeldef
+            end = r'\end{equation}'
+        else:
+            begin = r'\begin{equation*}' + labeldef
+            end = r'\end{equation*}'
+        equations.append('\\begin{split}%s\\end{split}\n' % parts[0])
+    else:
+        if numbering:
+            begin = r'\begin{align}%s\!\begin{aligned}' % labeldef
+            end = r'\end{aligned}\end{align}'
+        else:
+            begin = r'\begin{align*}%s\!\begin{aligned}' % labeldef
+            end = r'\end{aligned}\end{align*}'
+        for part in parts:
+            equations.append('%s\\\\\n' % part.strip())
+
+    concatenated_equations = ''.join(equations)
+    return f'{begin}\n{concatenated_equations}{end}'