Search box in the deployed html page

Dockerfile

@@ -5,6 +5,7 @@ ARG VERSION
 ADD LICENSE /slidefactory/
 ADD fonts/ /slidefactory/fonts/
 ADD theme/ /slidefactory/theme/
+ADD filters/ /slidefactory/filters/
 ADD slidefactory.py /slidefactory/
 
 # Remove possible temporary files
@@ -90,6 +91,12 @@ RUN wget https://github.com/jgm/pandoc/releases/download/2.19.2/pandoc-2.19.2-1-
     dpkg -i tmp.deb && \
     rm -f tmp.deb
 
+# Pagefind (static search index builder, used by the `pages` sub-command)
+RUN wget https://github.com/Pagefind/pagefind/releases/download/v1.5.2/pagefind-v1.5.2-x86_64-unknown-linux-musl.tar.gz -O tmp.tar.gz && \
+    tar xzf tmp.tar.gz -C /usr/bin pagefind && \
+    chmod 755 /usr/bin/pagefind && \
+    rm -f tmp.tar.gz
+
 # Chromium
 RUN apt-get update -qy && \
     apt-get install -qy --no-install-recommends \

filters/duplicate_heading_ids.py

@@ -0,0 +1,33 @@
+#!/usr/bin/env python3
+# ------------------------------------------------------------------------- #
+# Function: Pandoc JSON filter that gives each slide heading its own `id`   #
+#           attribute, matching the identifier pandoc's reveal.js writer   #
+#           already puts on the wrapping <section>.                        #
+# ------------------------------------------------------------------------- #
+#
+# Pandoc's reveal.js writer moves a Header's identifier onto the wrapping
+# <section> and omits it from the <hN> tag itself. Pagefind's automatic
+# per-slide search anchors only recognize (non-empty) heading elements that
+# carry their own id, so without this every search hit would link to the
+# deck's first slide instead of the one that actually matched.
+#
+# Any other key-value attribute on a Header (unlike the identifier) is
+# passed straight through onto both the <section> and the <hN> tag, so
+# adding a plain "id" key-value pair here - separate from the special
+# identifier field - is enough to make pandoc's own writer put a real `id`
+# directly on the heading tag, with no HTML post-processing required.
+from pandocfilters import toJSONFilter, Header
+
+
+def duplicate_heading_id(key, value, format, meta):
+    if key != 'Header':
+        return None
+    level, attr, inlines = value
+    identifier, classes, keyvals = attr
+    if identifier and not any(k == 'id' for k, v in keyvals):
+        keyvals = keyvals + [['id', identifier]]
+        return Header(level, [identifier, classes, keyvals], inlines)
+
+
+if __name__ == '__main__':
+    toJSONFilter(duplicate_heading_id)