Implement support for sticky banners and utilize them

pep_sphinx_extensions/pep_processor/parsing/pep_banner_directive.py

@@ -23,7 +23,7 @@ class PEPBanner(rst.Directive):
     admonition_post_text = ""
 
     admonition_class = nodes.important
-    css_classes = ["pep-banner"]
+    css_classes = []
 
 
     def run(self) -> list[nodes.admonition]:
@@ -48,7 +48,7 @@ def run(self) -> list[nodes.admonition]:
 
         source_lines = [pre_text] + list(self.content or []) + [post_text]
         admonition_node = self.admonition_class(
-            "\n".join(source_lines), classes=self.css_classes)
+            "\n".join(source_lines), classes=["pep-banner"] + self.css_classes)
 
         admonition_node.append(pre_text_node)
         if self.content:
@@ -75,7 +75,7 @@ class CanonicalDocBanner(PEPBanner):
         "See :pep:`1` for how to propose changes."
     )
 
-    css_classes = [*PEPBanner.css_classes, "canonical-doc"]
+    css_classes = ["canonical-doc", "sticky-banner"]
 
 
 
@@ -97,5 +97,6 @@ class CanonicalPyPASpecBanner(PEPBanner):
         "<https://www.pypa.io/en/latest/specifications/#handling-fixes-and-other-minor-updates>`__ "
         "for how to propose changes."
     )
+    admonition_class = nodes.attention
 
-    css_classes = [*PEPBanner.css_classes, "canonical-pypa-spec"]
+    css_classes = ["canonical-pypa-spec", "sticky-banner"]

pep_sphinx_extensions/pep_theme/static/sticky_banner.js

@@ -0,0 +1,28 @@
+"use strict";
+
+// Inject a style element into the document head that adds scroll-margin-top to
+// all elements with an id attribute. This is used to offset the scroll position
+// when clicking on a link to an element with an id attribute. The offset is
+// equal to the height of the sticky banner.
+document.addEventListener("DOMContentLoaded", () => {
+  const stickyBanners = document.getElementsByClassName("sticky-banner");
+  if (!stickyBanners.length) {
+    return;
+  }
+
+  const stickyBanner = stickyBanners[0];
+  const node = document.createElement("style");
+  node.id = "sticky-banner-style";
+  document.head.appendChild(node);
+
+  function adjustBannerMargin() {
+    const text = document.createTextNode(
+      ":target { scroll-margin-top: " + stickyBanner.offsetHeight + "px; }"
+    );
+    node.replaceChildren(text);
+  }
+
+  adjustBannerMargin();
+  document.addEventListener("resize", adjustBannerMargin);
+  document.addEventListener("load", adjustBannerMargin);
+});

pep_sphinx_extensions/pep_theme/static/style.css

@@ -321,10 +321,10 @@ div.error {
 div.warning {
     background-color: var(--colour-warning);
 }
+div.attention,
 div.caution {
     background-color: var(--colour-caution);
 }
-div.attention,
 div.important {
     background-color: var(--colour-attention);
 }
@@ -405,3 +405,9 @@ dl.footnote > dd {
   white-space: nowrap !important;
   border: 0 !important;
 }
+
+/* Sticky banners */
+.sticky-banner {
+  top: 0;
+  position: sticky;
+}

pep_sphinx_extensions/pep_theme/templates/page.html

@@ -51,5 +51,6 @@ <h2>Contents</h2>
     </section>
     <script src="{{ pathto('_static/colour_scheme.js', resource=True) }}"></script>
     <script src="{{ pathto('_static/wrap_tables.js', resource=True) }}"></script>
+    <script src="{{ pathto('_static/sticky_banner.js', resource=True) }}"></script>
 </body>
 </html>