32cd2100d9dd11140705c848850e86c4f79191c4
max
  Tue Sep 1 07:02:04 2026 -0700
Reusable "view snapshot" sessions for durable, minimal Share-a-link links

"Share a link" could only share the whole cart: it saved a session holding
every track, setting and position, which bloated the central db and leaked
the sharer's unrelated tracks to whoever opened the link.  Anonymous share
sessions (under the reserved user "l") were also never reaped, so they
accumulated forever, and their 8-char names were generated client-side with
no uniqueness check, so two shares could collide and silently overwrite.

Adds a lightweight "snapshot session" facility (lib/snapshotSession.c): a
snapshot stores only the handful of cart variables a feature declares (a
registered snapshotType, e.g. "blat" -> {db, blatLastBigBed}), moves only
those variables' trash files into durable sessionData storage, and is saved
under a "__"-prefixed name.  The "__" marks it machine-made: hidden from the
My Sessions list by default and eligible for reaping.  For the anonymous "l"
owner the durable files fan out over two extra hash levels so one directory
never fills with millions of entries.

Every anonymous link now shares one server-side name generator
(snapshotNewName): a unique (db-checked), crypto-strong, "__"-prefixed token,
so tokens never collide.  The hgSession doSaveSessionJson endpoint gained
hgS_snapshotType (save a minimal snapshot rather than the whole cart) and
hgS_doAnonName (reserve a unique anonymous name without saving, so the
top-right dialog can preview the exact link before it is created).

Wired three callers to the facility:
- hgc htcBlatAlign "Share a link": a minimal "blat" snapshot instead of a
full-cart anonymous session.
- hgBlat results "Share a link": creates a "blat" snapshot on click and
reveals its ?u=&s= reopen link (rebuilt from the durable bigPsl by the
existing doShareReopen), replacing the trash-only reveal.
- top-right "Share a link": anonymous links use the reserved server name;
logged-in named shares are unchanged.

snapshotReaper (hg/utils) garbage-collects abandoned anonymous snapshots: it
deletes user "l" "__" rows whose lastUse is older than the TTL (hg.conf
snapshot.ttlDays, default ~4 years) and removes their durable files.  lastUse
is bumped on every open by the existing session load, so a link stays alive
as long as it is used.  Meant to run from the trash-cleaner cron.

Also folds in the recent Share-dialog work in these files: the auto share
name is a short "_" prefix instead of "share_", the dialog previews the link
and creates it only when the button is clicked (no orphan session just from
opening the dialog), an optional name field with an overwrite warning, and
the anonymous save path forces the reap-eligible "__" name.

refs #38197

diff --git src/hg/js/hgBlat.js src/hg/js/hgBlat.js
index ff1122b26a3..092cbb5bd71 100644
--- src/hg/js/hgBlat.js
+++ src/hg/js/hgBlat.js
@@ -1,931 +1,974 @@
 // hgBlat.js - client-side rendering of the hgBlat "Table" output mode.
 //
 // hgBlat.c emits an inline object  var hgBlatData = { config, hits }  and an empty
 // <div id="blatResults">.  This script builds the whole results UI from that data:
 //   - a card with a summary strip (query / length / assembly / hit count + actions)
 //   - a sortable, filterable DataTable whose cells are rendered here (identity bar,
 //     query-coverage bar, linked loci, action links, comma-formatted position)
 //   - a docked "selected hit" detail panel updated on row click
 // Header tooltips reuse the Genome Browser's own mechanism (title + convertTitleTagsToMouseovers).
 
 /* jshint esnext: true */
 /* global $, hgBlatData, convertTitleTagsToMouseovers, htmlEncode, commify, gbShowTimingDialog */
 
 var blatSelectedRank = null;   // rank of the row shown in the detail panel
 
 function blatFmt(n) {
     // 12345 -> "12,345"
     return Number(n).toLocaleString('en-US');
 }
 
 function blatIdColor(id) {
     // UCSC identity semantic colors
     if (id >= 98) { return '#1f7a34'; }
     if (id >= 95) { return '#4d7c0f'; }
     if (id >= 90) { return '#b45309'; }
     return '#b1301f';
 }
 
 // ---- cell renderers ------------------------------------------------------
 
 function blatPositionCell(hit) {
     // For alt/fix/random/chrUn sequences show an info icon linking to the FAQ ("What is chr_alt &
     // chr_fix?"), with the short explanation as its tooltip.  (Sits after the position link, not
     // nested inside it.)
     var note = hit.chromNote ?
         ` <a class="chrNote" target="_blank" href="../FAQ/FAQblat.html#blat1c" ` +
         `title="${htmlEncode(hit.chromNote)} Click to learn more in the BLAT FAQ.">&#9432;</a>` : '';
     // The position links to the Genome Browser at this match; the new-tab icon right after it opens
     // the same in a new tab (whitespace between them, no divider).
     // URLs are htmlEncode'd before going into href="": they can carry the user's query name, so an
     // unescaped double-quote would otherwise break out of the attribute (XSS).
     return `<a class="blatPos" title="Open the Genome Browser at this location" ` +
         `href="${htmlEncode(hit.browserUrl)}">${htmlEncode(hit.chrom)}:` +
         `${blatFmt(hit.tStart)}-${blatFmt(hit.tEnd)}</a>` +
         ` <a class="blatNewTab" target="_blank" href="${htmlEncode(hit.newTabUrl)}" ` +
         `title="Open match in a new tab" aria-label="Open match in a new tab"></a>${note}`;
 }
 
 function blatActionsCell(hit) {
     // The "Open" column now holds just the base-by-base alignment link (Browser moved to the Position
     // column).  detailsUrl is htcUserAli on a fresh search, htcBlatAlign on a shared-link reopen; guard
     // in case a future caller omits it.
     if (!hit.detailsUrl) { return ''; }
     // htmlEncode the URL: detailsUrl embeds the user's query name, so an unescaped quote could break
     // out of the href attribute (XSS).
     return `<a title="Show the base-by-base alignment of your sequence to the genome" ` +
         `href="${htmlEncode(hit.detailsUrl)}">Alignment</a>`;
 }
 
 function blatLocusCell(hit) {
     // Locus is plain text (not a link): the gene names are shown for context only.  The cell grows with
     // its content up to a max-width, then a very long locus (many overlapping genes) is clipped with a
     // CSS ellipsis; the full string is always available on mouseover (title).
     if (!hit.locusText) { return ''; }
     return `<div class="blatLocus" title="${htmlEncode(hit.locusText)}">${htmlEncode(hit.locusText)}</div>`;
 }
 
 function blatScoreCell(hit, maxScore) {
     // Score with a little bar chart after it, scaled to the highest score in this result set.
     var pct = maxScore > 0 ? (hit.score / maxScore * 100) : 0;
     return `<span class="blatScoreWrap"><span class="blatScoreVal">${blatFmt(hit.score)}</span>` +
         `<span class="blatScoreBar"><i style="width:${pct.toFixed(1)}%"></i></span></span>`;
 }
 
 function blatIdentityCell(hit) {
     // Just the percentage now (the bar chart moved to the Score column), kept in its semantic color.
     var c = blatIdColor(hit.identity);
     return `<span class="blatIdPct" style="color:${c}">${hit.identity.toFixed(1)}%</span>`;
 }
 
 function blatUnit() {
     // A protein query is measured in amino acids, everything else in bases.
     return hgBlatData.config.isProt ? 'aa' : 'bp';
 }
 
 function blatCoverageCell(hit) {
     var left = (hit.qStart - 1) / hit.qSize * 100;
     var width = (hit.qEnd - hit.qStart + 1) / hit.qSize * 100;
     var u = blatUnit();
     var tip = `Query matches the genome at ${blatFmt(hit.qStart)}-${blatFmt(hit.qEnd)}${u} out of ${blatFmt(hit.qSize)}${u}`;
     return `<span class="blatCov" title="${tip}"><i style="left:${left.toFixed(1)}%;` +
         `width:${width.toFixed(1)}%"></i></span>`;
 }
 
 // ---- summary strip + detail panel ---------------------------------------
 
 function blatSummaryStrip(cfg, queryCount) {
     var stat = (k, v) => `<div class="gbStat"><span class="k">${k}</span>` +
         `<span class="v">${v}</span></div>`;
     var div = '<span class="gbDiv"></span>';
     var assembly = stat('Assembly', htmlEncode(cfg.organism) + ' / ' + htmlEncode(cfg.db)) + div +
         stat('Matches', blatFmt(cfg.hitCount));
     var stats;
     if (cfg.multiQuery) {
         // With more than one query sequence a single query name/length would be wrong, so show the
         // number of distinct queries; each hit's own query is in the table's Query column.
         stats = stat('Queries', blatFmt(queryCount)) + div + assembly;
     } else {
         stats = stat('Query', htmlEncode(cfg.queryName)) + div +
             stat('Length', blatFmt(cfg.querySize) + ' ' + blatUnit()) + div + assembly;
     }
     var actions = '';
     // "View all in browser" is the primary action, so it comes first.
     if (cfg.viewAllUrl) {
         actions += `<a class="gbPill" title="Open the Genome Browser with all these BLAT hits shown together as one custom track" href="${htmlEncode(cfg.viewAllUrl)}">View all in browser</a>`;
     }
     // "Show Query Sequence" opens the query FASTA in a panel (with Download / Copy). Only on a fresh
     // search, where the uploaded sequence is available (cfg.querySeqs emitted by hgBlat.c).
     if (cfg.querySeqs && cfg.querySeqs.length) {
         actions += '<button type="button" class="gbPill" id="blatSeqBtn" ' +
             'title="Show the sequence you searched with, in FASTA format">Show Query Sequence</button>';
     }
-    // "Share a link" just reveals the page's stable URL (cfg.shareUrl, a trash-backed reopen link).
-    // cfg.canShare covers old session-based links (?u=&s=), where the current URL is already shareable.
-    if (cfg.shareUrl || cfg.canShare) {
+    // "Share a link" creates a durable, minimal snapshot session (db + results bigPsl only) and shows
+    // its ?u=&s= reopen link (see blatShareLink).  Only offered when a durable bigPsl backs the
+    // results (cfg.canShare = autoBigPsl); without it there is nothing for the shared link to reopen.
+    if (cfg.canShare) {
         // A small share-nodes icon precedes the label so users learn to associate it with sharing.
         var shareIcon = '<svg class="blatShareIcon" viewBox="0 0 24 24" width="13" height="13" ' +
             'fill="none" stroke="currentColor" stroke-width="2" stroke-linecap="round" ' +
             'stroke-linejoin="round" aria-hidden="true"><circle cx="18" cy="5" r="3"></circle>' +
             '<circle cx="6" cy="12" r="3"></circle><circle cx="18" cy="19" r="3"></circle>' +
             '<line x1="8.6" y1="10.5" x2="15.4" y2="6.5"></line>' +
             '<line x1="8.6" y1="13.5" x2="15.4" y2="17.5"></line></svg>';
         actions += '<button type="button" class="gbPill" id="blatShareBtn" ' +
-            'title="Show a link that reopens these results (works for a limited time)">' +
+            'title="Create a durable link that reopens these BLAT results">' +
             shareIcon + 'Share a link</button>';
     }
     // "Rename BLAT Track" opens a modal to rename the results custom track. This is a JS-native
     // button (renders immediately with the strip) that replaces the old C-emitted inline form, which
     // only appeared after the buildBigPsl AJAX finished and reflowed the page when clicked.
     if (cfg.canRename) {
         actions += '<button type="button" class="gbPill" id="blatRenameBtn" ' +
             'title="Rename this BLAT results custom track and its description">Rename BLAT Track</button>';
     }
     return `<div class="gbStrip">${stats}<span class="gbStripActions">${actions}</span></div>`;
 }
 
 var BLAT_TILE_TIPS = {
     'Score': 'BLAT score: matches minus mismatches and gap penalties. Higher is better.',
     'Identity': 'Percent identity of the aligned bases.',
     'Matches': 'Query bases that match the genome.',
     'Mismatch': 'Bases that differ between query and genome.',
     'Gaps': 'Number of gaps (insertions or deletions) in the alignment.',
     'Blocks': 'Number of ungapped aligned blocks.',
     'Strand': 'Genome strand the query matched (+ or -).',
     'Q span': 'Range of the query sequence that aligned (1-based).'
 };
 
 function blatTileSkeleton(label, id, color) {
     var style = color ? ` style="color:${color}"` : '';
     var tip = BLAT_TILE_TIPS[label] || '';
     return `<div class="blatTile"><div class="k" title="${htmlEncode(tip)}">${label}</div>` +
         `<div class="v" id="${id}"${style}></div></div>`;
 }
 
 function blatDetailSkeleton() {
     // Built once; blatRenderDetail() only updates values, so the tile-label tooltips
     // are wired a single time by convertTitleTagsToMouseovers.
     var tiles =
         blatTileSkeleton('Score', 'dvScore') +
         blatTileSkeleton('Identity', 'dvIdentity') +
         blatTileSkeleton('Matches', 'dvMatches') +
         blatTileSkeleton('Mismatch', 'dvMismatch') +
         blatTileSkeleton('Gaps', 'dvGaps') +
         blatTileSkeleton('Blocks', 'dvBlocks') +
         blatTileSkeleton('Strand', 'dvStrand') +
         blatTileSkeleton('Q span', 'dvQspan');
     document.getElementById('blatDetail').innerHTML =
         `<div class="dhead"><span class="lab">Selected hit</span>` +
         `<span class="loc" id="dvLoc"></span></div>` +
         `<div class="blatDetailCard"><div class="blatDetailCol">` +
         `<div class="blatTiles">${tiles}</div>` +
         `<div class="blatDetailActions">` +
         `<a class="gbPill" id="dvBrowser" title="Open this hit in the Genome Browser" href="#">Open in browser</a>` +
         `<a class="gbPill" id="dvNewTab" target="_blank" title="Open this hit in the Genome Browser in a new tab" href="#">Open in new tab</a></div></div>` +
         `<div id="dvAlignBox" class="blatAlignBox">` +
         `<div class="blatTile"><div class="k">Alignment</div></div>` +
         `<div id="dvAlign" class="blatAlignText"></div>` +
         `<a class="gbPill" id="dvViewAlign" ` +
         `title="See the base-by-base alignment of your query against this hit" href="#">` +
         `View alignment</a></div></div>`;
     if (typeof convertTitleTagsToMouseovers === 'function') { convertTitleTagsToMouseovers(); }
 }
 
 function blatSet(id, prop, val) {
     var e = document.getElementById(id);
     if (!e) { return; }
     if (prop === 'text') { e.textContent = val; }
     else if (prop === 'href') { e.setAttribute('href', val); }
     else if (prop === 'color') { e.style.color = val; }
 }
 
 function blatRenderDetail(hit) {
     if (!hit || !document.getElementById('blatDetail')) { return; }
     if (!document.getElementById('dvScore')) { blatDetailSkeleton(); }
     var idc = blatIdColor(hit.identity);
     // Location line is plain text, so set it via textContent (blatSet 'text') - no HTML, nothing to
     // escape.  q and locus stay raw here for that reason.
     var locus = hit.locusText ? hit.locusText + ' · ' : '';
     var q = hgBlatData.config.multiQuery ? hit.qName + ' · ' : '';
     blatSet('dvLoc', 'text',
         `#${hit.rank} · ${q}${locus}${hit.chrom}:${blatFmt(hit.tStart)}-${blatFmt(hit.tEnd)}`);
     blatSet('dvScore', 'text', blatFmt(hit.score));
     blatSet('dvIdentity', 'text', hit.identity.toFixed(1) + '%');
     blatSet('dvIdentity', 'color', idc);
     blatSet('dvMatches', 'text', blatFmt(hit.matches));
     blatSet('dvMismatch', 'text', blatFmt(hit.misMatch));
     blatSet('dvGaps', 'text', blatFmt(hit.gaps));
     blatSet('dvBlocks', 'text', blatFmt(hit.blocks));
     blatSet('dvStrand', 'text', hit.strand);
     blatSet('dvQspan', 'text', blatFmt(hit.qStart) + '–' + blatFmt(hit.qEnd));
     blatSet('dvBrowser', 'href', hit.browserUrl);
     blatSet('dvNewTab', 'href', hit.newTabUrl);
     // Show the Alignment box whenever a base-by-base alignment page is available (htcUserAli on a
     // fresh search, htcBlatAlign on a shared-link reopen); hide it only if detailsUrl is missing.
     var alignBox = document.getElementById('dvAlignBox');
     if (alignBox) { alignBox.style.display = hit.detailsUrl ? '' : 'none'; }
     if (hit.detailsUrl) {
         blatSet('dvViewAlign', 'href', hit.detailsUrl);
         blatSet('dvAlign', 'text',
             'See the base-by-base alignment of your query against ' + hit.chrom +
             ': matches, mismatches and gaps across the whole span.');
     }
 }
 
 function blatSelect(dt, rank) {
     blatSelectedRank = rank;
     $('#blatTable tbody tr').each(function() {
         var d = dt.row(this).data();
         $(this).toggleClass('blatSel', !!d && d.rank === rank);
     });
     var hit = hgBlatData.hits.find(h => h.rank === rank);
     blatRenderDetail(hit);
 }
 
 // ---- header tooltips (reuse the browser's title -> mouseover system) -----
 
 var BLAT_HEADER_TIPS = {
     '#': 'Rank by the chosen sort order',
     'Query': 'The query sequence this hit came from',
     'Open in Genome Browser': 'Genomic location of the match (1-based). Click the position to ' +
         'open the Genome Browser there, or the icon to open it in a new tab.',
     'Show': 'Show the base-by-base alignment of your sequence to the genome',
     'Locus': 'Nearest gene(s), and whether the hit falls in an exon, intron, or intergenic region',
     'Score': 'BLAT score: matches minus mismatches and gap penalties. Higher is better.',
     'Identity': 'Percent identity of the aligned bases',
     'Strand': 'Genome strand the query matched (+ or -)',
     'Query coverage': 'Which part of the query aligned (blue) across its full length',
     'Span': 'Length of the match on the genome (bp). Larger than the query length means ' +
         'the alignment crosses introns or deletions.'
 };
 
 function blatApplyTooltips() {
     $('#blatTable thead th').each(function() {
         var tip = BLAT_HEADER_TIPS[$(this).text().trim()];
         if (tip) { $(this).attr('title', tip); }
     });
     if (typeof convertTitleTagsToMouseovers === 'function') {
         convertTitleTagsToMouseovers();
     }
 }
 
 // ---- share a link --------------------------------------------------------
 
-function blatShareLink() {
-    // No session, no AJAX: the results page already has a stable, shareable URL (hgBlat.c emits it as
-    // cfg.shareUrl and blatBuild() pins it into the address bar with history.replaceState), so this
-    // just shows/copies window.location.  The link reopens straight from the trash .pslx/.fa, so it
-    // works until those trash files are cleaned - hence the retention note.
-    var box = document.getElementById('gbShareBox');
-    if (!box) { return; }
-    if (box.style.display === 'flex') { box.style.display = 'none'; return; }   // toggle off
-    var url = window.location.href;
+// The snapshot link we created for this page view, cached so re-opening the box doesn't make another.
+var blatShareCachedUrl = null;
+
+// Render the share box.  url set -> show the link + Copy; url null -> "Creating link…"; msg (url null)
+// -> show an error.
+function blatShowShareBox(box, url, msg) {
     box.style.display = 'flex';
+    if (msg) {
+        box.innerHTML = '<span class="gbShareMsg gbShareFull" style="color:#a00">' +
+            htmlEncode(msg) + '</span>';
+        return;
+    }
+    if (!url) {
+        box.innerHTML = '<span class="gbShareMsg gbShareFull">Creating link…</span>';
+        return;
+    }
     box.innerHTML =
-        '<span class="gbShareMsg gbShareFull">Shareable link — anyone with it can reopen ' +
-        'these results. The results are stored temporarily, so the link works for at least 48 hours ' +
-        'after they were last viewed.</span>' +
+        '<span class="gbShareMsg gbShareFull">Shareable link — anyone with it can reopen these ' +
+        'BLAT results. It stores only the results (not your other tracks or settings) and stays ' +
+        'active as long as it is used.</span>' +
         '<input id="gbShareInput" class="gbShareInput" type="text" readonly>' +
         '<button type="button" class="gbPill" id="blatShareCopy" title="Copy the link to the clipboard">Copy</button>';
     var inp = document.getElementById('gbShareInput');
     inp.value = url;
     inp.focus();
     inp.select();
     $('#blatShareCopy').on('click', function() {
         inp.select();
         if (navigator.clipboard) { navigator.clipboard.writeText(url); }
         else { document.execCommand('copy'); }
         this.textContent = 'Copied';
     });
 }
 
+function blatShareLink() {
+    // Create (or reveal) a durable share link.  It is backed by a lightweight "snapshot" session that
+    // stores only db + the results bigPsl - not the whole cart - under a server-generated unique name
+    // (see lib/snapshotSession.c).  hgBlat's ?u=&s= reopen (doShareReopen) rebuilds the results table
+    // from that bigPsl.  The token generation, uniqueness and reaping are shared with hgc and the
+    // top-right "Share a link".
+    var box = document.getElementById('gbShareBox');
+    if (!box) { return; }
+    if (box.style.display === 'flex') { box.style.display = 'none'; return; }   // toggle off
+
+    // Already viewing a shared session link: the current URL is itself the shareable link.
+    if (/[?&]s=/.test(window.location.search)) { blatShowShareBox(box, window.location.href); return; }
+    // Already created one this page view: reuse it rather than creating another session.
+    if (blatShareCachedUrl) { blatShowShareBox(box, blatShareCachedUrl); return; }
+
+    var cfg = hgBlatData.config;
+    blatShowShareBox(box, null);   // "Creating link…"
+    var body = 'hgsid=' + encodeURIComponent(cfg.hgsid || '') +
+        '&hgS_doSaveSessionJson=1&hgS_shareAnon=1&hgS_snapshotType=blat';
+    fetch('../cgi-bin/hgSession', {method: 'POST', credentials: 'same-origin',
+            headers: {'Content-Type': 'application/x-www-form-urlencoded'}, body: body})
+        .then(function(r) { return r.json(); })
+        .then(function(data) {
+            if (!data || !data.name) {
+                blatShowShareBox(box, null, (data && data.error) || 'Could not create the link.');
+                return;
+            }
+            blatShareCachedUrl = window.location.origin + '/cgi-bin/hgBlat?u=l&s=' +
+                encodeURIComponent(data.name);
+            blatShowShareBox(box, blatShareCachedUrl);
+        })
+        .catch(function() {
+            blatShowShareBox(box, null, 'Could not reach the server. Please try again.');
+        });
+}
+
 // ---- Rename BLAT track (modal) -------------------------------------------
 // The results custom track is built (and renamed) by hgBlat.c's inline code, which exposes a small
 // window.blatRenameCt(name, description) helper (it POSTs to hgc's buildBigPsl and rebuilds the
 // track).  We reuse that helper (no new endpoint), just swapping its old inline toggle-form UI for a
 // proper modal dialog.  The current name/description come from cfg (hgBlat.c), not a global, so this
 // does not depend on any generic page-global.
 
 function blatRenameModalHtml(cfg) {
     // hgSession link is relative (same /cgi-bin/), carrying db + hgsid so the session page opens in
     // this assembly and cart.
     var sessionUrl = `hgSession?db=${encodeURIComponent(cfg.db)}&hgsid=${encodeURIComponent(cfg.hgsid)}`;
     return '<div id="gbModalBg" class="gbModalBg" style="display:none">' +
         '<div class="gbModal" role="dialog" aria-modal="true" aria-labelledby="gbModalTitle">' +
         '<div class="gbModalTitle" id="gbModalTitle">Rename BLAT Track</div>' +
         '<div class="gbModalText">Every BLAT result is stored in its own track in the Genome ' +
         'Browser. You can rename the track here. Results will disappear after 2–3 days, unless ' +
         `they are saved into a <a href="${sessionUrl}">Session link</a>.</div>` +
         '<label class="gbModalLabel" for="blatRenameName">Track name</label>' +
         '<input id="blatRenameName" class="gbModalInput" type="text" maxlength="80">' +
         '<label class="gbModalLabel" for="blatRenameDesc">Description</label>' +
         '<input id="blatRenameDesc" class="gbModalInput" type="text" maxlength="120">' +
         '<div class="gbModalBtns">' +
         '<button type="button" class="gbPill" id="blatRenameCancel">Cancel</button>' +
         '<button type="button" class="gbPill primary" id="blatRenameOk">OK</button>' +
         '</div></div></div>';
 }
 
 function blatCloseRename() {
     var bg = document.getElementById('gbModalBg');
     if (bg) { bg.style.display = 'none'; }
 }
 
 function blatOpenRename() {
     var bg = document.getElementById('gbModalBg');
     if (!bg) { return; }
     // Pre-fill with the track's current name/description (emitted by hgBlat.c in cfg).
     var cfg = hgBlatData.config;
     document.getElementById('blatRenameName').value = cfg.trackName || '';
     document.getElementById('blatRenameDesc').value = cfg.trackDescription || '';
     bg.style.display = 'flex';
     document.getElementById('blatRenameName').focus();
     document.getElementById('blatRenameName').select();
 }
 
 function blatWireRename() {
     $('#blatRenameBtn').on('click', blatOpenRename);
     $('#blatRenameCancel').on('click', blatCloseRename);
     // Click on the dark backdrop (but not the dialog itself) closes.
     $('#gbModalBg').on('click', function(ev) {
         if (ev.target === this) { blatCloseRename(); }
     });
     $(document).on('keydown.blatRename', function(ev) {
         var bg = document.getElementById('gbModalBg');
         if (bg && bg.style.display !== 'none' && ev.key === 'Escape') { blatCloseRename(); }
     });
     $('#blatRenameOk').on('click', function() {
         var name = document.getElementById('blatRenameName').value.trim();
         var desc = document.getElementById('blatRenameDesc').value.trim();
         if (!name) { document.getElementById('blatRenameName').focus(); return; }
         // Reuse hgBlat.c's window.blatRenameCt(name, description): rebuilds the custom track under the
         // new name via the existing hgc buildBigPsl call.  Keep cfg in sync so a re-open of the modal
         // shows the new values.
         if (typeof window.blatRenameCt === 'function') {
             hgBlatData.config.trackName = name;
             hgBlatData.config.trackDescription = desc;
             window.blatRenameCt(name, desc);
         }
         blatCloseRename();
     });
 }
 
 // ---- FASTA viewer (generic) ----------------------------------------------
 
 function blatToFasta(seqs) {
     // seqs: [{name, seq}, ...] -> FASTA text, sequence wrapped at 60 chars per line.
     return seqs.map(function(s) {
         var body = String(s.seq || '').toUpperCase().replace(/(.{60})/g, '$1\n').replace(/\n$/, '');
         return '>' + s.name + '\n' + body;
     }).join('\n');
 }
 
 function blatShowFasta(box, seqs, fileName) {
     // Render seqs as FASTA inside `box`, with Copy-to-clipboard and Download buttons. Generic — takes
     // any [{name, seq}] list so it can be reused for other sequences later.
     var fasta = blatToFasta(seqs);
     box.style.display = 'flex';
     box.innerHTML =
         '<div class="blatSeqBar">' +
         '<span class="gbShareMsg">Query sequence (FASTA):</span>' +
         '<button type="button" class="gbPill" id="blatSeqCopy" title="Copy the FASTA to the clipboard">Copy to Clipboard</button>' +
         '<button type="button" class="gbPill" id="blatSeqDownload" title="Download the FASTA as a .fa file">Download</button>' +
         '<button type="button" class="gbPill" id="blatSeqClose" title="Hide the query sequence">Close</button>' +
         '</div><textarea id="blatSeqText" class="blatSeqText" readonly></textarea>';
     var ta = document.getElementById('blatSeqText');
     ta.value = fasta;
     document.getElementById('blatSeqCopy').addEventListener('click', function() {
         ta.select();
         if (navigator.clipboard) { navigator.clipboard.writeText(fasta); }
         else { document.execCommand('copy'); }
         this.textContent = 'Copied';
     });
     document.getElementById('blatSeqDownload').addEventListener('click', function() {
         var a = document.createElement('a');
         a.href = URL.createObjectURL(new Blob([fasta], { type: 'text/plain' }));
         a.download = fileName || 'query.fa';
         document.body.appendChild(a);
         a.click();
         document.body.removeChild(a);
         setTimeout(function() { URL.revokeObjectURL(a.href); }, 0);
     });
     document.getElementById('blatSeqClose').addEventListener('click', function() {
         box.style.display = 'none';
     });
 }
 
 function blatShowQuerySeq() {
     var box = document.getElementById('blatSeqBox');
     if (box.style.display === 'flex') { box.style.display = 'none'; return; }   // toggle off
     blatShowFasta(box, hgBlatData.config.querySeqs, 'blatQuery.fa');
 }
 
 // ---- build ---------------------------------------------------------------
 
 function blatBuild() {
     var cfg = hgBlatData.config;
     var hits = hgBlatData.hits;
     // When loaded with &measureTiming=1 the C side attaches hgBlatData.timing; time the client
     // render too so the dialog shows the full server+client picture.
     var tBuildStart = (hgBlatData.timing && window.performance) ? performance.now() : 0;
 
     // Pin a stable, shareable URL into the address bar (no server redirect) so refresh, bookmark and
     // "Share a link" all use the trash-backed reopen link instead of the transient POST/search URL.
     if (cfg.shareUrl) {
         try { history.replaceState(null, '', cfg.shareUrl); } catch (e) { /* older browsers: ignore */ }
     }
 
     var back = cfg.backUrl ?
         `<a class="gbPill" title="Return to the Genome Browser at your previous location (${htmlEncode(cfg.backPos)})" ` +
         `href="${htmlEncode(cfg.backUrl)}">Back to Genome Browser</a>` : '';
     // The page actions live in the gold main-header bar (framework #sectTtl), next to the title -
     // so there is no separate toolbar (.blatHead is gone).  Injected into #sectTtl below.
     var headActions =
         `${back}<a class="gbPill primary" title="Start a new BLAT search" href="${htmlEncode(cfg.newSearchUrl)}">New BLAT search</a>`;
 
     // Top banner: note this is the new page, link back to the classic page (fresh searches only,
     // where the trash files still exist), and invite feedback.  The old page also clears the
     // blatNewPage preference so later searches use the classic page until the user opts back in.
     var origPage = cfg.canOldPage ?
         ` You can go back to <a title="Show these results on the classic BLAT results page" ` +
         `href="hgBlat?blatNewPage=0&blatReopen=1&hgsid=${encodeURIComponent(cfg.hgsid)}">the original page</a> anytime.` : '';
     var bannerHtml =
         `<div class="gbBanner">We are testing a new BLAT output page.${origPage} ` +
         `If you have feedback on this new page, do not hesitate to let us know via ` +
         `<a href="mailto:genome@soe.ucsc.edu">genome@soe.ucsc.edu</a>.</div>`;
 
     var queryCount = new Set(hits.map(h => h.qName)).size;
 
     var th = [];
     th.push('<th class="num">#</th>');
     if (cfg.multiQuery) { th.push('<th>Query</th>'); }
     th.push('<th>Open in Genome Browser</th>');
     th.push('<th>Show</th>');
     th.push('<th>Query coverage</th>');
     if (cfg.hasLocus) { th.push('<th>Locus</th>'); }
     th.push('<th class="num">Score</th>');
     th.push('<th class="num">Identity</th>');
     th.push('<th>Strand</th>');
     th.push('<th class="num">Span</th>');
 
     // detail dock sits above the table: with long hit lists a bottom dock scrolls out of view
     document.getElementById('blatResults').innerHTML =
         bannerHtml +
         `<div class="gbCard">${blatSummaryStrip(cfg, queryCount)}` +
         `<div id="gbShareBox" class="gbShareBox" style="display:none"></div>` +
         `<div id="blatSeqBox" class="gbShareBox" style="display:none"></div>` +
         `<div id="blatDetail" class="blatDetail"></div>` +
         `<table id="blatTable" class="display"><thead><tr>${th.join('')}</tr></thead></table></div>` +
         (cfg.canRename ? blatRenameModalHtml(cfg) : '');
 
     // Put the page actions in the gold main-header bar, to the right of the title (framework #sectTtl).
     var sectTtl = document.getElementById('sectTtl');
     if (sectTtl) {
         var acts = document.createElement('span');
         acts.className = 'blatHeadActions';
         acts.innerHTML = headActions;
         sectTtl.appendChild(acts);
     }
 
     $('#blatShareBtn').on('click', blatShareLink);
     $('#blatSeqBtn').on('click', blatShowQuerySeq);
     blatWireRename();
 
     var columns = [];
     columns.push({ data: 'rank', className: 'num rankCol' });
     if (cfg.multiQuery) { columns.push({ data: 'qName', className: 'queryCol' }); }
     columns.push({ data: null, orderable: false, className: 'blatPos',
         render: (d, type, row) => (type === 'display' ? blatPositionCell(row) : row.chrom + ':' + row.tStart) });
     columns.push({ data: null, orderable: false, className: 'actionsCol',
         render: (d, type, row) => (type === 'display' ? blatActionsCell(row) : '') });
     columns.push({ data: null, className: 'covCol', orderable: false,
         render: (d, type, row) => (type === 'display' ? blatCoverageCell(row) :
             (row.qEnd - row.qStart + 1)) });
     if (cfg.hasLocus) {
         columns.push({ data: 'locusText',
             render: (d, type, row) => (type === 'display' ? blatLocusCell(row) : (d || '')) });
     }
     // Score carries a bar scaled to the highest score in this result set (raw score kept for sorting).
     var maxScore = hits.reduce((m, h) => Math.max(m, h.score || 0), 0);
     columns.push({ data: 'score', className: 'num scoreCol',
         render: (d, type, row) => (type === 'display' ? blatScoreCell(row, maxScore) : d) });
     columns.push({ data: 'identity', className: 'num identCol',
         render: (d, type, row) => (type === 'display' ? blatIdentityCell(row) : d) });
     columns.push({ data: 'strand', className: 'strandCol' });
     columns.push({ data: 'span', className: 'num',
         render: (d, type, row) => (type === 'display' ? blatFmt(d) : d) });
 
     var dt = $('#blatTable').DataTable({
         data: hits,
         columns: columns,
         paging: false,
         info: false,
         order: [],
         language: { search: '', searchPlaceholder: 'Filter hits by locus, chrom, position…' }
     });
 
     $('#blatTable tbody').on('click', 'tr', function(ev) {
         if ($(ev.target).closest('a').length) { return; }   // let links work normally
         var d = dt.row(this).data();
         if (d) { blatSelect(dt, d.rank); }
     });
 
     // Keep the selected-row highlight after sort/filter.  Header tooltips are wired once below (the
     // <thead> persists across draws); we deliberately do NOT re-run convertTitleTagsToMouseovers on
     // every draw, as it re-scans the whole document and adds global listeners on each call.
     dt.on('draw', function() {
         if (blatSelectedRank !== null) { blatSelect(dt, blatSelectedRank); }
     });
 
     // No hit is pre-selected: several hits are often tied on score/identity, so picking one for the
     // user is misleading.  The detail panel shows a prompt until a row is clicked.
     document.getElementById('blatDetail').innerHTML =
         `<div class="blatSelectHint">Click a hit below to see its alignment details. ` +
         `If you are missing matches that you think should be there, ` +
         `<a target="_blank" href="../FAQ/FAQblat.html#blat1b">read our BLAT FAQ</a> or ` +
         `<a href="mailto:genome@soe.ucsc.edu">contact us</a>.</div>`;
 
     // Timing report (only when loaded with &measureTiming=1): a pill in the summary strip that opens
     // the shared dialog with the server phases plus the client render time.
     if (hgBlatData.timing) {
         var clientRows = [{ label: 'build page (JS)',
                             ms: Math.round(performance.now() - tBuildStart) }];
         var pill = document.createElement('button');
         pill.type = 'button';
         pill.className = 'gbPill';
         pill.id = 'blatTimingBtn';
         pill.innerHTML = '&#9201; Timing';
         pill.title = 'Show where this page spent its time (server and browser)';
         pill.addEventListener('click', function() {
             gbShowTimingDialog(hgBlatData.timing, clientRows);
         });
         var strip = document.querySelector('#blatResults .gbStripActions') ||
                     document.querySelector('#blatResults .gbStrip');
         if (strip) { strip.appendChild(pill); }
         // measureTiming=1 on the URL is an explicit request to see the numbers, so open the dialog
         // right away; the pill stays for reopening it after Close.
         gbShowTimingDialog(hgBlatData.timing, clientRows);
     }
 
     blatApplyTooltips();
 }
 
 // ==== search form (the input page) ========================================
 // hgBlat.c emits  var hgBlatFormData = {...}  together with a real <form name="mainForm"> that
 // contains an empty <div id="blatFormBox"> and the C-generated genome search bar.  We build the
 // controls as real form fields *inside that form*, so the browser serializes them natively -
 // including the file input - and Submit / I'm feeling lucky / Clear stay plain submit buttons
 // handled by the existing C code.  There is no shadow form and no copying of values on submit.
 // Styling comes from hgBlat.css (loaded by webIncludeResourceFile in hgBlat.c), shared with the results page.
 
 // The Genome Browser's standard info icon, copied from printInfoIconSvg() in hg/lib/hui.c so the
 // form's icons are pixel-identical to the C-rendered ones elsewhere in the browser.
 var BLAT_INFO_SVG =
     "<svg style='height:1.1em; vertical-align:top' viewBox='0 0 24 24' fill='none' " +
     "xmlns='http://www.w3.org/2000/svg'>" +
     "<circle cx='12' cy='12' r='10' stroke='#1C274C' stroke-width='1.5'/>" +
     "<path d='M12 17V11' stroke='#1C274C' stroke-width='1.5' stroke-linecap='round'/>" +
     "<circle cx='1' cy='1' r='1' transform='matrix(1 0 0 -1 11 9)' fill='#1C274C'/></svg>";
 
 // The assembly-search syntax help.  setupGenomeSelector hides the info icon that
 // printGenomeSearchBar (hg/lib/web.c) normally puts next to the box, so the new form loses that
 // explanation of +word/-word/word*/"phrase"; we re-attach it to an icon after the label instead.
 // Kept word-for-word in sync with searchHelpText in web.c so both pickers explain the box the same
 // way.  This is HTML (a bullet list), rendered as such by the mouseover, so it is NOT htmlEncode'd -
 // like the C printInfoIcon, it relies on the string containing no double quotes to sit in a title=.
 var BLAT_GENOME_SEARCH_HELP =
     "All genome searches are case-insensitive.  Single-word searches default to prefix " +
     "matching if an exact match is not found. " +
     "<ul id='searchTipList' class='noBullets'>" +
     "<li> Force inclusion: Use a + sign before <b>+word</b> to ensure it appears in result.</li>" +
     "<li> Exclude words: Use a - sign before <b>-word</b> to exclude it from the search result.</li>" +
     "<li> Wildcard search: Add an * (asterisk) at end of <b>word*</b> to search for all terms starting with that prefix.</li>" +
     "<li> Phrase search: Enclose 'words in quotes' to search for the exact phrase.</li>" +
     "</ul>";
 
 // Cross-session memory of the "Keep results" checkbox.  A plain '1'/'0' string under one key;
 // wrapped in try/catch because localStorage throws in private-mode / disabled-storage browsers, in
 // which case we simply fall back to the cart-supplied default and skip persistence.
 var BLAT_KEEP_RESULTS_KEY = 'blatKeepResults';
 
 function blatGetKeepResultsPref() {
     // Returns true/false for a stored preference, or null if the user has never set one here.
     try {
         var v = localStorage.getItem(BLAT_KEEP_RESULTS_KEY);
         return v === null ? null : (v === '1');
     } catch (e) { return null; }
 }
 
 function blatSetKeepResultsPref(on) {
     try { localStorage.setItem(BLAT_KEEP_RESULTS_KEY, on ? '1' : '0'); } catch (e) { /* ignore */ }
 }
 
 function blatOpts(list, cur) {
     return list.map(function(v) {
         return `<option value="${htmlEncode(v)}"${v === cur ? ' selected' : ''}>${htmlEncode(v)}</option>`;
     }).join('');
 }
 
 function blatFormCount() {
     // Live character count under the textarea.  Only these two nodes are touched on input - the
     // textarea itself is never re-rendered, so the caret stays where the user put it.
     var ta = document.getElementById('blatUserSeq');
     var out = document.getElementById('blatCountText');
     if (!ta || !out) { return; }
     var n = ta.value.replace(/[^A-Za-z*]/g, '').length;
     out.textContent = blatFmt(n) + ' of 25,000 characters';
     $('#blatLimitLink').toggleClass('over', n > 25000);
 }
 
 function blatFormTab(showUpload) {
     $('#blatTabPaste').toggleClass('on', !showUpload);
     $('#blatTabUpload').toggleClass('on', showUpload);
     $('#blatPanePaste').toggle(!showUpload);
     $('#blatPaneUpload').toggle(showUpload);
 }
 
 function blatFormLimitsModal() {
     var row = (k, v) => `<div class="blatLimitRow"><span>${k}</span><strong>${v}</strong></div>`;
     return '<div id="blatLimitsBg" class="gbModalBg" style="display:none">' +
         '<div class="gbModal" role="dialog" aria-modal="true" aria-labelledby="blatLimitsTitle">' +
         '<div class="gbModalTitle" id="blatLimitsTitle">Input limits</div>' +
         row('DNA per sequence', '25,000 bases') +
         row('Protein / translated', '10,000 letters') +
         row('Sequences per run', '25') +
         row('Total per submission', '50,000 bases') +
         '<div class="gbModalText gbModalNote">Queries above these limits are rejected ' +
         'before alignment. For larger jobs, run BLAT from the ' +
         '<a target="_blank" href="https://hgdownload.soe.ucsc.edu/downloads.html#utilities_downloads">' +
         'command line</a> on your own server.</div>' +
         '<div class="gbModalBtns"><button type="button" class="gbPill" id="blatLimitsClose">Close</button></div>' +
         '</div></div>';
 }
 
 function blatFormSetDb(db) {
     // Called by hgBlat.c's setupGenomeSearchBar onSelect.  Picking a genome does not reload the
     // page, so everything on it that depends on db is updated here instead: the hidden field that
     // the search is submitted with, and the sidebar links that carry a db= parameter.  The current
     // assembly label is updated by setupGenomeSearchBar itself.
     document.mainForm.db.value = db;
     $('#blatFormBox a[data-urltpl]').each(function() {
         this.href = this.getAttribute('data-urltpl').replace('$DB$', encodeURIComponent(db));
     });
 }
 
 function blatFormSidebar(cfg) {
     // Same links the classic page offered.  hgBlat.c supplies them as templates holding $DB$ (see
     // blatFormSetDb); the template is kept in data-urltpl so the link can be retargeted later.
     var tools = '';
     var tplLink = (tpl, label) => {
         var href = tpl.replace('$DB$', encodeURIComponent(hgBlatFormData.db));
         return `<a data-urltpl="${htmlEncode(tpl)}" href="${htmlEncode(href)}">${label}</a>`;
     };
     if (cfg.pcrUrlTpl) {
         tools += `<div>${tplLink(cfg.pcrUrlTpl, 'In-Silico PCR')} — better than BLAT for ` +
             'locating PCR primers.</div>';
     }
     if (cfg.oligoMatchUrlTpl) {
         tools += `<div>${tplLink(cfg.oligoMatchUrlTpl, 'Short Sequence Match')} — for ` +
             'sequences under 20 bp, within the region shown in the Genome Browser.</div>';
     }
     tools += '<div><a target="_blank" href="https://hgdownload.soe.ucsc.edu/downloads.html#utilities_downloads">' +
         'findMotifs</a> — command-line search across a whole genome.</div>';
     return '<div>' +
         (tools ? `<div class="gbCard"><h3>Similar tools</h3>${tools}</div>` : '') +
         '<div class="gbCard"><h3>Help</h3>' +
         '<div><a href="../FAQ/FAQblat.html">BLAT FAQ</a></div>' +
         '<div><a href="../goldenPath/help/hgTracksHelp.html#BLATAlign">BLAT documentation</a></div>' +
         // No "Search all genomes FAQ" here: that link now lives in the "Search many genomes"
         // tooltip, next to the checkbox it actually explains.
         '<div><a href="../FAQ/FAQblat.html#blat14">Programmatic / batch BLAT</a></div>' +
         '</div>' +
         '<div class="gbCard"><h3>About BLAT</h3>' +
         '<div>DNA BLAT quickly finds sequences of 95% and greater similarity that are at least 25 bases ' +
         'long; it finds perfect matches down to 20 bases, and may miss shorter or more divergent ' +
         'alignments. Protein BLAT finds sequences of 80% and greater similarity at least 20 amino acids ' +
         'long.</div>' +
         '<div>Kent WJ. <a target="_blank" href="https://genome.cshlp.org/content/12/4/656.abstract">' +
         'BLAT — the BLAST-like alignment tool</a>. Genome Res. 2002 Apr;12(4):656-64.</div>' +
         '</div></div>';
 }
 
 function blatFormBuild() {
     var cfg = hgBlatFormData;
 
     var banner = '';
     if (cfg.classicUrl) {
         banner = '<div class="gbBanner">We are testing a new BLAT search page. You can go back to ' +
             `<a href="${htmlEncode(cfg.classicUrl)}">the original page</a> anytime. If you have feedback ` +
             'on this new page, do not hesitate to let us know via ' +
             '<a href="mailto:genome@soe.ucsc.edu">genome@soe.ucsc.edu</a>.</div>';
     }
 
     // Checkbox plus the browser's standard info icon.  Same SVG and same title +
     // convertTitleTagsToMouseovers mechanism as printInfoIcon()/printInfoIconSvg() in hg/lib/hui.c,
     // so these read identically to the info icons on every other Genome Browser page.
     var check = (name, on, label, tip) =>
         `<span class="blatCheck"><label><input type="checkbox" name="${name}" ` +
         `id="blat_${name}"${on ? ' checked' : ''}>${label}</label>` +
         `<span class="blatInfo" title="${htmlEncode(tip)}">${BLAT_INFO_SVG}</span></span>`;
 
     // "Keep results" starting state.  The cart (cfg.keepResults) only remembers the choice within a
     // session; localStorage carries it across sessions so a user who wants their BLAT results to
     // accumulate does not have to re-tick the box on every visit.  localStorage wins when set (it is
     // the more durable record of the user's own preference); the cart is the fallback for a browser
     // that has never stored one.  Only consulted where the box is actually shown (blatOldTracks=
     // delete); elsewhere the choice has no effect, so there is nothing worth persisting.
     var keepResultsInit = cfg.keepResults;
     if (cfg.showKeepResults) {
         var storedKeep = blatGetKeepResultsPref();
         if (storedKeep !== null) { keepResultsInit = storedKeep; }
     }
 
     document.getElementById('blatFormBox').innerHTML =
         banner +
         '<div class="blatFormGrid"><div>' +
 
         '<div class="gbSection">Search &ndash; type keywords to find the target assembly</div>' +
         '<div class="blatRow">' +
             '<div class="blatField blatGenomeSlot"><span>Genome or assembly ' +
                 `<span class="blatInfo" title="${BLAT_GENOME_SEARCH_HELP}">${BLAT_INFO_SVG}</span>` +
                 '</span>' +
                 '<div id="blatGenomeSlot"></div></div>' +
             `<label class="blatField"><span>Query type</span><select name="type">${blatOpts(cfg.types, cfg.type)}</select></label>` +
             // Sort and output are submitted but not offered: sorting by anything other than score
             // is rarely useful, and this page always wants the hyperlink (results table) output.
             // Kept as hidden fields so the request hgBlat receives is unchanged.
             `<input type="hidden" name="sort" value="${htmlEncode(cfg.sort)}">` +
             `<input type="hidden" name="output" value="${htmlEncode(cfg.output)}">` +
         '</div>' +
 
         '<div class="blatChecks">' +
             // The mouseover popup keeps itself open while the pointer is inside it (see the
             // mouseoverContainer mouseenter handler in utils.js), and renders its text as HTML, so
             // a link in the tip is genuinely clickable.  htmlEncode keeps the title attribute
             // well-formed; the browser decodes it back to markup before it is injected.
             // Only offered where hg.conf blatOldTracks=delete, i.e. where there is something to opt
             // out of.  Unlike the three below (which keep the classic form's plain-checkbox
             // behaviour), this one is submitted through an explicit hidden field: a checkbox sends
             // nothing when unticked, so cartUsualBoolean would never see it go back to false and
             // "Keep results" could not be switched off again once used.
             (cfg.showKeepResults ?
                 '<span class="blatCheck">' +
                 `<input type="hidden" name="blatKeepResults" id="blatKeepResultsVal" value="${keepResultsInit ? 1 : 0}">` +
                 `<label><input type="checkbox" id="blat_keepResults"${keepResultsInit ? ' checked' : ''}>` +
                 'Keep results</label>' +
                 `<span class="blatInfo" title="${htmlEncode(
                     'A new BLAT search always overrides your previous BLAT results: each search ' +
                     'replaces the result track of the one before it in the Genome Browser. Check ' +
                     'this box to keep earlier results instead, so every search adds its own track ' +
                     'and results accumulate. Your choice is remembered for next time.')}">` +
                 `${BLAT_INFO_SVG}</span></span>` : '') +
             check('autoRearr', cfg.autoRearr, 'Show rearrangements',
                 'Shows duplications of the query sequence using multiple lines with connecting lines ' +
                 'between fragments, and displays inversions better (the "snakes" display). Can also ' +
                 'be switched on or off from the BLAT track configuration page.') +
             check('allResults', cfg.allResults, 'No min. score',
                 'Turns off minimum-match filtering so every alignment is returned. A human DNA search ' +
                 'normally requires 20 matching bases, based on the genome size, to filter out ' +
                 'lower-quality results; useful for short queries and the tiny genomes of ' +
                 'microorganisms.') +
             check('allGenomes', cfg.allGenomes, 'Search many genomes',
                 'Runs the same query against every default assembly and attached hub that has a ' +
                 'dedicated BLAT server. Dynamic BLAT servers are skipped and listed as such in the ' +
                 "output. See our <a target='_blank' href='../FAQ/FAQblat.html#blat9'>BLAT All FAQ</a> " +
                 'for more information.') +
         '</div>' +
 
         '<div class="gbSection">Query sequence</div>' +
         '<div class="blatTabs">' +
             '<button type="button" class="blatTab on" id="blatTabPaste">Paste sequence</button>' +
             '<button type="button" class="blatTab" id="blatTabUpload">Upload file</button>' +
         '</div>' +
 
         '<div id="blatPanePaste">' +
             '<div class="blatPaneHint"><span>Separate multiple sequences with a &gt;name line. ' +
             'Up to 25 sequences.</span>' +
             `<a href="#" id="blatExample">${htmlEncode(cfg.exampleLabel)}</a></div>` +
             '<textarea class="blatSeq" name="userSeq" id="blatUserSeq" spellcheck="false" ' +
             'aria-label="Paste in a query sequence"></textarea>' +
             '<div class="blatCount"><span id="blatCountText"></span>' +
             '<a href="#" id="blatLimitLink">Show input limits</a></div>' +
         '</div>' +
 
         '<div id="blatPaneUpload" style="display:none">' +
             '<div class="blatDrop" id="blatDrop">' +
                 '<div class="blatDropTitle">Drop a sequence file here</div>' +
                 '<div class="blatDropSub">Plain text or FASTA, up to 50,000 bases total</div>' +
                 '<input type="file" name="seqFile" id="blatSeqFile">' +
                 '<div class="blatFileName" id="blatFileName"></div>' +
             '</div>' +
         '</div>' +
 
         '<div class="blatActions">' +
             '<input type="submit" class="gbPill primary" name="Submit" value="Submit" ' +
             `title="${htmlEncode('Align the sequence and show all matches')}">` +
             '<input type="submit" class="gbPill" name="Lucky" value="I&#39;m feeling lucky" ' +
             `title="${htmlEncode('Skip the list of matches and open the best-scoring one straight ' +
                 'away in the Genome Browser. Ignored when "Search many genomes" is ticked.')}">` +
             '<input type="submit" class="gbPill" name="Clear" value="Clear" ' +
             `title="${htmlEncode('Empty the query sequence box')}">` +
         '</div>' +
 
         '</div>' + blatFormSidebar(cfg) + '</div>' +
         blatFormLimitsModal();
 
     // Move the C-generated genome search bar (real autocomplete over every assembly, already wired
     // by setupGenomeSearchBar) into its slot, rather than reimplementing it with a hardcoded list.
     var holder = document.getElementById('blatGenomeHolder');
     if (holder) { document.getElementById('blatGenomeSlot').appendChild(holder); }
 
 
     // Show the current assembly in the search bar itself instead of in a separate "Current genome:"
     // line - the bar is wide enough for the whole description.  setupGenomeSearchBar writes the new
     // one in on each pick, and focusing the bar selects all of it, so it reads as a filled-in search
     // box rather than as a value the user has to clear by hand.
     var genomeInput = document.getElementById('genomeSearch');
     if (genomeInput && cfg.dbLabel) { genomeInput.value = cfg.dbLabel; }
 
     // Restore the sequence from the cart without going through innerHTML (avoids re-escaping).
     document.getElementById('blatUserSeq').value = cfg.userSeq || '';
     blatFormCount();
 
     $('#blatUserSeq').on('input', blatFormCount);
     // Mirror the "Keep results" checkbox into its hidden field so an unticked box submits an
     // explicit 0 rather than nothing at all, and remember the choice in localStorage so it comes
     // back pre-set on the user's next visit (see keepResultsInit above).
     $('#blat_keepResults').on('change', function() {
         document.getElementById('blatKeepResultsVal').value = this.checked ? '1' : '0';
         blatSetKeepResultsPref(this.checked);
     });
     $('#blatTabPaste').on('click', function() { blatFormTab(false); });
     $('#blatTabUpload').on('click', function() { blatFormTab(true); });
     // The example sequence is a real ~14 kb query, fetched on demand so it is not carried in every
     // page load.  The link doubles as its own status indicator while the request is in flight.
     $('#blatExample').on('click', function(ev) {
         ev.preventDefault();
         var link = this;
         var label = cfg.exampleLabel;
         link.textContent = 'Loading example…';
         fetch(cfg.exampleUrl)
             .then(function(resp) {
                 if (!resp.ok) { throw new Error('HTTP ' + resp.status); }
                 return resp.text();
             })
             .then(function(fa) {
                 var ta = document.getElementById('blatUserSeq');
                 ta.value = fa.trim();
                 blatFormCount();
                 ta.focus();
                 ta.setSelectionRange(0, 0);
                 ta.scrollTop = 0;
                 link.textContent = label;
                 blatFormTab(false);   // in case the user was on the upload tab
             })
             .catch(function(err) {
                 link.textContent = 'Could not load example';
                 // Leave the message up briefly, then let the user try again.
                 setTimeout(function() { link.textContent = label; }, 4000);
                 console.error('hgBlat: example fetch failed:', err);
             });
     });
     $('#blatLimitLink').on('click', function(ev) {
         ev.preventDefault();
         $('#blatLimitsBg').css('display', 'flex');
     });
     $('#blatLimitsClose').on('click', function() { $('#blatLimitsBg').hide(); });
     $('#blatLimitsBg').on('click', function(ev) { if (ev.target === this) { $(this).hide(); } });
     $(document).on('keydown.blatLimits', function(ev) {
         if (ev.key === 'Escape') { $('#blatLimitsBg').hide(); }
     });
 
     var fileInput = document.getElementById('blatSeqFile');
     var drop = document.getElementById('blatDrop');
     $(fileInput).on('change', function() {
         document.getElementById('blatFileName').textContent =
             this.files && this.files.length ? this.files[0].name : '';
     });
     ['dragenter', 'dragover'].forEach(function(e) {
         drop.addEventListener(e, function(ev) { ev.preventDefault(); drop.classList.add('hot'); });
     });
     ['dragleave', 'drop'].forEach(function(e) {
         drop.addEventListener(e, function(ev) { ev.preventDefault(); drop.classList.remove('hot'); });
     });
     drop.addEventListener('drop', function(ev) {
         if (ev.dataTransfer.files.length) {
             fileInput.files = ev.dataTransfer.files;
             $(fileInput).trigger('change');
         }
     });
 
     if (typeof convertTitleTagsToMouseovers === 'function') { convertTitleTagsToMouseovers(); }
 }
 
 $(document).ready(function() {
     if (typeof hgBlatData !== 'undefined' && document.getElementById('blatResults')) {
         blatBuild();
     }
     if (typeof hgBlatFormData !== 'undefined' && document.getElementById('blatFormBox')) {
         blatFormBuild();
     }
 });