use numfig for numbering equations by section rather than page

7 files changed, 44 insertions, 5 deletions

diff --git a/CHANGES b/CHANGES
index 957881a53..6e203777f 100644
--- a/CHANGES
+++ b/CHANGES
@@ -37,6 +37,7 @@ Features added
 * #4052: viewcode: Sort before highlighting module code
 * #1448: qthelp: Add new config value; :confval:`qthelp_namespace`
 * #4140: html themes: Make body tag inheritable
+* #3991, #4080: Add :confval:`math_numfig` for equation numbering by section
 
 
 Features removed
diff --git a/doc/ext/math.rst b/doc/ext/math.rst
index 54d77ed6c..fe7b85c83 100644
--- a/doc/ext/math.rst
+++ b/doc/ext/math.rst
@@ -44,6 +44,14 @@ or use Python raw strings (``r"raw"``).
 
    Example: ``'Eq.{number}'`` is rendered as ``Eq.10``
 
+.. confval:: math_numfig
+
+   If ``True``, displayed math equations are numbered across pages using numfig.
+   The :confval:`numfig` config value must be enabled and
+   :confval:`numfig_secnum_depth` is respected.  The ``:eq:`` role must be used
+   to refererence these equation numbers, not the ``:numref:`` role.
+   Default is ``False``.
+
 :mod:`.mathbase` defines these new markup elements:
 
 .. rst:role:: math
diff --git a/sphinx/ext/imgmath.py b/sphinx/ext/imgmath.py
index 8bf4fcad5..04d6b708a 100644
--- a/sphinx/ext/imgmath.py
+++ b/sphinx/ext/imgmath.py
@@ -30,6 +30,7 @@ from sphinx.util.png import read_png_depth, write_png_depth
 from sphinx.util.osutil import ensuredir, ENOENT, cd
 from sphinx.util.pycompat import sys_encoding
 from sphinx.ext.mathbase import setup_math as mathbase_setup, wrap_displaymath
+from sphinx.ext.mathbase import get_node_equation_number
 
 if False:
     # For type annotation
@@ -333,7 +334,8 @@ def html_visit_displaymath(self, node):
     self.body.append(self.starttag(node, 'div', CLASS='math'))
     self.body.append('<p>')
     if node['number']:
-        self.body.append('<span class="eqno">(%s)' % node['number'])
+        number = get_node_equation_number(self.builder.env, node)
+        self.body.append('<span class="eqno">(%s)' % number)
         self.add_permalink_ref(node, _('Permalink to this equation'))
         self.body.append('</span>')
     if fname is None:
diff --git a/sphinx/ext/jsmath.py b/sphinx/ext/jsmath.py
index dc57c13c6..978e3f3d6 100644
--- a/sphinx/ext/jsmath.py
+++ b/sphinx/ext/jsmath.py
@@ -16,6 +16,7 @@ import sphinx
 from sphinx.locale import _
 from sphinx.application import ExtensionError
 from sphinx.ext.mathbase import setup_math as mathbase_setup
+from sphinx.ext.mathbase import get_node_equation_number
 
 
 def html_visit_math(self, node):
@@ -35,7 +36,8 @@ def html_visit_displaymath(self, node):
         if i == 0:
             # necessary to e.g. set the id property correctly
             if node['number']:
-                self.body.append('<span class="eqno">(%s)' % node['number'])
+                number = get_node_equation_number(self.builder.env, node)
+                self.body.append('<span class="eqno">(%s)' % number)
                 self.add_permalink_ref(node, _('Permalink to this equation'))
                 self.body.append('</span>')
             self.body.append(self.starttag(node, 'div', CLASS='math'))
diff --git a/sphinx/ext/mathbase.py b/sphinx/ext/mathbase.py
index f83ca5da8..31b33fe2a 100644
--- a/sphinx/ext/mathbase.py
+++ b/sphinx/ext/mathbase.py
@@ -84,6 +84,13 @@ class MathDomain(Domain):
                 newnode['target'] = target
                 return newnode
             else:
+                if env.config.math_numfig and env.config.numfig:
+                    if docname in env.toc_fignumbers:
+                        id = 'equation-' + target
+                        number = env.toc_fignumbers[docname]['displaymath'].get(id, ())
+                        number = '.'.join(map(str, number))
+                    else:
+                        number = ''
                 try:
                     eqref_format = env.config.math_eqref_format or "({number})"
                     title = nodes.Text(eqref_format.format(number=number))
@@ -126,6 +133,20 @@ class MathDomain(Domain):
         return len(targets) + 1
 
 
+def get_node_equation_number(env, node):
+    if env.config.math_numfig and env.config.numfig:
+        docname = node['docname']
+        if docname in env.toc_fignumbers:
+            id = node['ids'][0]
+            number = env.toc_fignumbers[docname]['displaymath'].get(id, ())
+            number = '.'.join(map(str, number))
+        else:
+            number = ''
+    else:
+        number = node['number']
+    return number
+
+
 def wrap_displaymath(math, label, numbering):
     # type: (unicode, unicode, bool) -> unicode
     def is_equation(part):
@@ -341,6 +362,7 @@ def setup_math(app, htmlinlinevisitors, htmldisplayvisitors):
     # type: (Sphinx, Tuple[Callable, Any], Tuple[Callable, Any]) -> None
     app.add_config_value('math_number_all', False, 'env')
     app.add_config_value('math_eqref_format', None, 'env', string_classes)
+    app.add_config_value('math_numfig', False, 'env')
     app.add_domain(MathDomain)
     app.add_node(math, override=True,
                  latex=(latex_visit_math, None),
@@ -348,7 +370,7 @@ def setup_math(app, htmlinlinevisitors, htmldisplayvisitors):
                  man=(man_visit_math, None),
                  texinfo=(texinfo_visit_math, None),
                  html=htmlinlinevisitors)
-    app.add_node(displaymath,
+    app.add_enumerable_node(displaymath, 'displaymath',
                  latex=(latex_visit_displaymath, None),
                  text=(text_visit_displaymath, None),
                  man=(man_visit_displaymath, man_depart_displaymath),
diff --git a/sphinx/ext/mathjax.py b/sphinx/ext/mathjax.py
index f25f91e74..aff5c103b 100644
--- a/sphinx/ext/mathjax.py
+++ b/sphinx/ext/mathjax.py
@@ -17,6 +17,7 @@ import sphinx
 from sphinx.locale import _
 from sphinx.errors import ExtensionError
 from sphinx.ext.mathbase import setup_math as mathbase_setup
+from sphinx.ext.mathbase import get_node_equation_number
 
 
 def html_visit_math(self, node):
@@ -36,7 +37,8 @@ def html_visit_displaymath(self, node):
 
     # necessary to e.g. set the id property correctly
     if node['number']:
-        self.body.append('<span class="eqno">(%s)' % node['number'])
+        number = get_node_equation_number(self.builder.env, node)
+        self.body.append('<span class="eqno">(%s)' % number)
         self.add_permalink_ref(node, _('Permalink to this equation'))
         self.body.append('</span>')
     self.body.append(self.builder.config.mathjax_display[0])
diff --git a/sphinx/ext/pngmath.py b/sphinx/ext/pngmath.py
index 85010b799..968139f15 100644
--- a/sphinx/ext/pngmath.py
+++ b/sphinx/ext/pngmath.py
@@ -30,6 +30,7 @@ from sphinx.util.png import read_png_depth, write_png_depth
 from sphinx.util.osutil import ensuredir, ENOENT, cd
 from sphinx.util.pycompat import sys_encoding
 from sphinx.ext.mathbase import setup_math as mathbase_setup, wrap_displaymath
+from sphinx.ext.mathbase import get_node_equation_number
 
 if False:
     # For type annotation
@@ -242,7 +243,8 @@ def html_visit_displaymath(self, node):
     self.body.append(self.starttag(node, 'div', CLASS='math'))
     self.body.append('<p>')
     if node['number']:
-        self.body.append('<span class="eqno">(%s)</span>' % node['number'])
+        number = get_node_equation_number(self.builder.env, node)
+        self.body.append('<span class="eqno">(%s)</span>' % number)
     if fname is None:
         # something failed -- use text-only as a bad substitute
         self.body.append('<span class="math">%s</span></p>\n</div>' %