Flatten genindex to not group names.

Also better width in the tables.

docs/extensions/builder.py

@@ -0,0 +1,46 @@
+from sphinx.builders.html import StandaloneHTMLBuilder
+from sphinx.environment.adapters.indexentries import IndexEntries
+
+class DPYStandaloneHTMLBuilder(StandaloneHTMLBuilder):
+    # This is mostly copy pasted from Sphinx.
+    def write_genindex(self) -> None:
+        # the total count of lines for each index letter, used to distribute
+        # the entries into two columns
+        genindex = IndexEntries(self.env).create_index(self, group_entries=False)
+        indexcounts = []
+        for _k, entries in genindex:
+            indexcounts.append(sum(1 + len(subitems)
+                                   for _, (_, subitems, _) in entries))
+
+        genindexcontext = {
+            'genindexentries': genindex,
+            'genindexcounts': indexcounts,
+            'split_index': self.config.html_split_index,
+        }
+
+        if self.config.html_split_index:
+            self.handle_page('genindex', genindexcontext,
+                             'genindex-split.html')
+            self.handle_page('genindex-all', genindexcontext,
+                             'genindex.html')
+            for (key, entries), count in zip(genindex, indexcounts):
+                ctx = {'key': key, 'entries': entries, 'count': count,
+                       'genindexentries': genindex}
+                self.handle_page('genindex-' + key, ctx,
+                                 'genindex-single.html')
+        else:
+            self.handle_page('genindex', genindexcontext, 'genindex.html')
+
+def get_builder(app):
+    """This is necessary because RTD injects their own for some reason."""
+    try:
+        original = app.registry.builders['readthedocs']
+    except KeyError:
+        return DPYStandaloneHTMLBuilder
+    else:
+        injected_mro = tuple(base if base is not StandaloneHTMLBuilder else DPYStandaloneHTMLBuilder
+                             for base in original.mro()[1:])
+        return type(original.__name__, injected_mro, {'name': 'readthedocs'})
+
+def setup(app):
+    app.add_builder(get_builder(app), override=True)