Fix

assets/sw.js

@@ -311,9 +311,19 @@ function verseLabels(chapters, number) {
 // no verse anchors to offer.
 //
 // anchor says which chapter to show the verses of, and which verse to mark
-// selected. Null starts at 1:1, which is where every book starts: this says
-// where you are going, not where you are, and the address bar is the only
-// record of the latter.
+// selected. Anything this cannot read -- nothing at all, an empty select, a
+// footnote id, a chapter past the end of the book -- is chapter 1, and chapter
+// 1 is filled in as if it had been picked. There is no state where a chapter
+// is only sort of chosen: a select showing an option is a select that chose
+// it, and the verses beside it have to be that chapter's.
+//
+// Every book that gets a picker has verses in its first chapter -- the two
+// that do not, the front matter and the glossary, are turned away above -- so
+// falling back to 1 always fills the verse list rather than emptying it.
+//
+// The verse is left unselected when the anchor names only a chapter. That is
+// not the same as unfilled: the options are chapter 1's, and the select shows
+// the first of them. It says where you are going, not where you are.
 function referenceFor(map, code, anchor) {
   const chapters = map && Object.prototype.hasOwnProperty.call(map, code)
     ? map[code] : null;
@@ -328,12 +338,15 @@ function referenceFor(map, code, anchor) {
 
   const at = parseAnchor(anchor) || { chapter: 1, verse: null };
   const number = at.chapter >= 1 && at.chapter <= chapters.length ? at.chapter : 1;
+  // Only when the anchor got as far as naming this chapter. A fallback to 1
+  // has not chosen a verse, it has just run out of anchor.
+  const verse = at.chapter === number ? at.verse : null;
 
   return {
     book: code,
     chapter: 'ch' + number,
     chapters: chapters.map((_, i) => ({ id: 'ch' + (i + 1), label: String(i + 1) })),
-    verse: at.verse,
+    verse: verse,
     verses: verseLabels(chapters, number)
       .map((label) => ({ id: 'v' + number + '_' + label, label: label }))
   };
@@ -415,19 +428,30 @@ router.get('/api/bookmark', () => bookmarkFragment(''));
 
 // The picker, and the two moves it makes.
 //
-//   no parameters   the whole picker, for whichever book is on screen. Asked
-//                   for by the picker itself, after a history restore -- which
-//                   swaps the history element straight in and processes no
-//                   out-of-band elements -- and when a worker first appears
-//                   under a page boot.html composed.
+//   no parameters   the whole picker, standing where the anchor in the address
+//                   bar puts it. Asked for by the picker itself: on load,
+//                   after a history restore -- which swaps the history element
+//                   straight in and processes no out-of-band elements -- and
+//                   when a worker first appears under a page boot.html
+//                   composed.
 //   chapter=ch3     the verses of that chapter, and land on the chapter.
 //   verse=v3_16     the same verses, that one selected, and land on the verse.
 //
-// The book is not in the URL, deliberately: it comes from HX-Current-URL,
-// which is the address the page is showing now rather than the address it was
-// showing when the picker was last rendered. The picker sits in the navbar and
-// outlives the page under it, so anything baked into its attributes is the one
-// thing here that can go stale.
+// Neither the book nor the anchor is in the URL, deliberately. Both come from
+// HX-Current-URL, which htmx sets from location.href on every request it
+// makes: the whole address, fragment included.
+//
+// For the book, because the picker sits in the navbar and outlives the page
+// under it -- an address baked into its attributes is the one thing here that
+// can go stale. For the anchor, because this is the only way a fragment
+// reaches this file at all. A browser opening /GEN#v3_16 asks for /GEN and
+// keeps the rest to itself, so the shell is composed without it and the picker
+// is rendered at 1:1 like any other. The page then asks this route for itself,
+// and that request is the one carrying the anchor.
+//
+// Which also puts the picker where it belongs after a back or forward, and
+// under a page boot.html composed once a worker turns up, for nothing extra:
+// those requests carry the address bar too.
 //
 // What the response headers are doing is the whole of what app.js used to do
 // on a change event, and htmx has a name for each part of it:
@@ -442,11 +466,33 @@ router.get('/api/bookmark', () => bookmarkFragment(''));
 //                history entry per option spun past.
 router.get('/api/reference', async (call) => {
   const params = call.url.searchParams;
-  const anchor = params.get('verse') || params.get('chapter');
   const page = call.currentUrl();
-  const reference = await referenceOf(bookOf(page), anchor);
+  // Which select the reader moved, if either did -- by whether the parameter
+  // is there, not by whether it says anything. A select posts an empty value
+  // when it has no options, and reading that as "no select moved" answers it
+  // with a whole picker: htmx swaps a <div> into a <select>, which renders as
+  // nothing, and the select is then empty for good -- every change after that
+  // posts the same empty value and gets the same answer.
+  //
+  // An empty value is still an answerable question. It names no chapter, so it
+  // gets chapter 1, which is what everything here does with an anchor it
+  // cannot read.
+  const moved = params.has('verse') ? params.get('verse')
+    : params.has('chapter') ? params.get('chapter')
+    : null;
 
-  if (!anchor) return view.render('reference.njk', { reference: reference });
+  // The address bar is the fallback, and only that: once a select has been
+  // used it is the one saying where to go, and HX-Replace-Url has not caught
+  // up yet.
+  const reference = await referenceOf(
+    bookOf(page), moved === null ? (page && page.hash.slice(1)) : moved);
+
+  // settled, because this picker is already standing where the anchor put it.
+  // The one that came with the page is not, and carries a load trigger to ask
+  // -- which this answer must not carry as well, or it would ask forever.
+  if (moved === null) {
+    return view.render('reference.njk', { reference: reference, settled: true });
+  }
   // The options were rendered from this map, so failing to parse them back
   // means the map moved under an open page: leave the picker alone rather
   // than swapping in options for a book that is no longer on screen.