5dc1d6e658ab009f27314e192340275a6bb70237
max
  Tue Jun 2 16:20:48 2026 -0700
Add colorFields trackDb setting for bigBed/bigGenePred color scheme switching

Adds a new trackDb statement `colorFields` that renders a "Color by:" dropdown
in the track controls page, letting users switch among multiple pre-computed
color schemes stored as extra bigBed fields containing R,G,B strings.

The `default="label"` key renames the standard itemRgb option in the dropdown.
Other entries name extra bigBed fields whose R,G,B values override itemRgb when
selected. When a non-default scheme is active, a "(Coloring by: label)" suffix
appears in the track long label.

Changes:
- hui.c/hui.h: new colorFieldsCfgUi() rendered inside bedScoreCfgUi() for bigBed
- bigBedTrack.c: colorFieldIdx lookup + per-item filterColor override + longLabel suffix
- tagTypes.tab: register colorFields for bigBed and bigGenePred
- trackDbLibrary.shtml, trackDbDoc.html, trackDbHub.v3.html, changes.html: documentation

refs #26253

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

diff --git src/hg/htdocs/goldenPath/help/trackDb/changes.html src/hg/htdocs/goldenPath/help/trackDb/changes.html
index e52678170c8..1f319f4fb00 100755
--- src/hg/htdocs/goldenPath/help/trackDb/changes.html
+++ src/hg/htdocs/goldenPath/help/trackDb/changes.html
@@ -33,30 +33,42 @@
 
 <DIV class="trackDbDoc_intro">
 <H1>Track Database Definition</H1>
 
 <p>This document summarizes the changes to the <a href="trackDbHub.html">UCSC Genome Browser Hub TrackDb specification</a>.<p>
 
 <TABLE class="settingsTable" id="Common_Settings">
 <tbody>
 <tr valign="TOP">
 <th width="100">Date</th>
 <th width="15%">Track Types</th>
 <th width="15%">Link to Doc</th>
 <th>Change</th>
 </tr>
 
+<tr>
+    <td>2026-06-02</td>
+    <td>bigBed, bigGenePred</td>
+    <td><a href="trackDbHub.html#colorFields">colorFields</a></td>
+    <td>New <code>colorFields</code> setting adds a <b>Color by:</b> dropdown to the
+    track controls page, letting users switch among multiple pre-computed color schemes
+    stored as extra bigBed fields containing <code>R,G,B</code> strings.
+    The special name <code>default="label"</code> renames the standard itemRgb option.
+    When a non-default scheme is selected, a <em>(Coloring by: label)</em> suffix
+    appears in the track long label.</td>
+</tr>
+
 <tr>
     <td>2026-05-08</td>
     <td>bed, bigBed</td>
     <td><a href="trackDbHub.html#filterPriority">filterPriority</a> / <a href="trackDbHub.html#highlightPriority">highlightPriority</a></td>
     <td>New <code>filterPriority.&lt;fieldName&gt;</code> setting controls the
     display order of filter controls on the track configuration page. A
     companion <code>highlightPriority.&lt;fieldName&gt;</code> setting orders
     highlight controls.</td>
 </tr>
 <tr>
     <td>2026-04-22</td>
     <td>faceted composite tracks</td>
     <td><a href="trackDbHub.html#subtrackUrls">subtrackUrls</a></td>
     <td>An update for the subtrackUrls option for faceted composites, which
     enables links out to other resources in the faceted table.</td>