Added TOC object entry support for the C++ domain (#11221)

When ``toc_object_entries_show_parents = 'domain'`` in the config,
the TOC entries omit the namespaces added by the ``cpp:namespace`` and ``cpp:namespace-push`` directives.

Co-authored-by: Adam Turner <9087854+AA-Turner@users.noreply.github.com>

CHANGES

@@ -32,6 +32,8 @@ Features added
 * #9662: Add the ``:no-typesetting:`` option to suppress textual output
   and only create a linkable anchor.
   Patch by Latosha Maltba.
+* #11221: C++: Support domain objects in the table of contents.
+  Patch by Rouslan Korneychuk.
 
 Bugs fixed
 ----------

sphinx/domains/cpp.py

@@ -613,6 +613,9 @@ def __init__(self, identifier: str) -> None:
         assert len(identifier) != 0
         self.identifier = identifier
 
+    def _stringify(self, transform: StringifyTransform) -> str:
+        return transform(self.identifier)
+
     def is_anon(self) -> bool:
         return self.identifier[0] == '@'
 
@@ -7432,10 +7435,38 @@ def before_content(self) -> None:
         self.oldParentKey: LookupKey = self.env.ref_context['cpp:parent_key']
         self.env.temp_data['cpp:parent_symbol'] = lastSymbol
         self.env.ref_context['cpp:parent_key'] = lastSymbol.get_lookup_key()
+        self.env.temp_data['cpp:domain_name'] = (
+            *self.env.temp_data.get('cpp:domain_name', ()),
+            lastSymbol.identOrOp._stringify(str),
+        )
 
     def after_content(self) -> None:
         self.env.temp_data['cpp:parent_symbol'] = self.oldParentSymbol
         self.env.ref_context['cpp:parent_key'] = self.oldParentKey
+        self.env.temp_data['cpp:domain_name'] = self.env.temp_data['cpp:domain_name'][:-1]
+
+    def _object_hierarchy_parts(self, sig_node: desc_signature) -> tuple[str, ...]:
+        return tuple(s.identOrOp._stringify(str) for s in
+                     self.env.temp_data['cpp:last_symbol'].get_full_nested_name().names)
+
+    def _toc_entry_name(self, sig_node: desc_signature) -> str:
+        if not sig_node.get('_toc_parts'):
+            return ''
+
+        config = self.env.app.config
+        objtype = sig_node.parent.get('objtype')
+        if config.add_function_parentheses and objtype in {'function', 'method'}:
+            parens = '()'
+        else:
+            parens = ''
+        *parents, name = sig_node['_toc_parts']
+        if config.toc_object_entries_show_parents == 'domain':
+            return '::'.join((*self.env.temp_data.get('cpp:domain_name', ()), name + parens))
+        if config.toc_object_entries_show_parents == 'hide':
+            return name + parens
+        if config.toc_object_entries_show_parents == 'all':
+            return '::'.join(parents + [name + parens])
+        return ''
 
 
 class CPPTypeObject(CPPObject):