Best

assets/js/app.js

@@ -121,26 +121,71 @@
     }
   });
 
-  // Close the modal once a bookmark write has come back and swapped, leaving
-  // the status line up long enough to be read.
   document.body.addEventListener('htmx:afterSwap', function (event) {
     markVerses(event.target);
-    if (event.detail.target && event.detail.target.id === 'bookmark') {
-      setTimeout(hideModal, 900);
-    }
+    var target = event.detail.target;
+    if (!target) return;
+    // Close the modal once a bookmark write has come back and swapped, leaving
+    // the status line up long enough to be read.
+    if (target.id === 'bookmark') return setTimeout(hideModal, 900);
+    if (target.id === 'content') land();
+  });
+
+  // A history restore does not go through the request pipeline -- htmx swaps
+  // the element straight in and fires this instead -- so the work afterSwap
+  // does has to be repeated here or a page reached by the back button arrives
+  // with dead verse numbers.
+  document.body.addEventListener('htmx:historyRestore', function () {
+    markVerses();
+    land();
   });
 
   // -- startup ------------------------------------------------------------
 
+  function hashTarget() {
+    if (!location.hash) return null;
+    return document.getElementById(decodeURIComponent(location.hash.slice(1)));
+  }
+
+  // Every scroll here is a correction, not a gesture: the page is meant to
+  // arrive already in position. So they all say instant.
+  //
+  // Saying nothing would not mean instant. The default is "auto", which means
+  // "whatever scroll-behavior computes to" -- and Bootstrap's Reboot sets
+  // :root { scroll-behavior: smooth }, so the default animates. Bootstrap
+  // wraps that in prefers-reduced-motion, which is the right call for the
+  // chapter nav's own anchors; these are not that.
+  function jumpTo(el) {
+    el.scrollIntoView({ block: 'start', behavior: 'instant' });
+  }
+
   // A worker-composed page is an ordinary document and the browser scrolls to
   // the anchor itself. One composed by boot.html is not: it replaced a
   // document the browser had already finished with, so the fragment identifier
   // has been spent. Repeating it costs nothing in the first case and is what
-  // makes a link to GEN.html#v1_1 land on the verse in the second.
+  // makes a link to GEN#v1_1 land on the verse in the second.
   function scrollToHash() {
-    if (!location.hash) return;
-    var el = document.getElementById(decodeURIComponent(location.hash.slice(1)));
-    if (el) el.scrollIntoView();
+    var el = hashTarget();
+    if (el) jumpTo(el);
+  }
+
+  // Where a swapped-in page should sit before it is ever seen.
+  //
+  // htmx does this itself -- scrolling to the anchor a boosted href named, or
+  // to the top of the target when it named none -- but from the settle
+  // callback, which is a setTimeout of defaultSettleDelay, 20ms. The browser
+  // paints the new content at the old scroll offset first, so the jump is
+  // visible every time. Here it runs in the same task as the swap, before any
+  // paint, so the page simply appears where it belongs. htmx's own scroll
+  // still follows and finds nothing left to do.
+  //
+  // htmx has already pushed the new URL by this point -- history is updated
+  // before the swap, not after -- so location.hash is the anchor that was
+  // asked for.
+  function land() {
+    var el = hashTarget();
+    if (el) jumpTo(el);
+    else window.scrollTo({ top: 0, behavior: 'instant' });
   }
 
   // api/bookmark has no origin server -- it is answered by the worker -- so