a0a3411bca2fdd6d704ce2be7c9c8fca7682913a
braney
  Sat Sep 19 18:19:36 2026 -0700
bedItemRgbTester: pin the order of the itemRgb and color tests

bedItemRgb() decides whether a BED track draws its items in the colors its file
carries or in the one color its stanza names.  The rule has four steps, and the
order of the first three is the whole of #36212: an explicit "itemRgb off"
wins, then an explicit "itemRgb on" wins, and only then does the presence of a
"color" setting turn item colors off by default.  88d620e6c82 folded those
tests together, so a stanza saying both "itemRgb on" and "color" -- which means
items from the file and labels from color -- lost its item colors.

The pairs are what matter here.  Every single-setting case passed while the bug
was live, so a test that exercised one setting at a time would have proved
nothing.  A child that says "itemRgb on" under a parent that says "color" is
the same case reached through trackDbSettingClosestToHome.

Two runs, with and without hg.conf's alwaysItemRgb, since the last step of the
rule reads it and a mirror that turns it off must still honour a stanza that
asks for item colors explicitly.

The test lives in hg/lib/tests because hg/cgilib has no tests directory; its
link line adds jkhgapcgi.a.

Watched to fail and then pass: with the color test moved back in front of the
itemRgb test, three lines flip, and they are the three that pair the two
settings.  Recorded as sandbox-ab in utils/testRegistry.

refs #36212, refs #38391

diff --git src/hg/lib/tests/bedItemRgbTester.c src/hg/lib/tests/bedItemRgbTester.c
new file mode 100644
index 00000000000..7bebcb50abf
--- /dev/null
+++ src/hg/lib/tests/bedItemRgbTester.c
@@ -0,0 +1,106 @@
+/* bedItemRgbTester - check which stanza wins when a track says both "itemRgb" and "color".
+ *
+ * bedItemRgb() decides whether a BED track draws its items in the colors the file carries or
+ * in the one color the stanza names.  It lives in hg/cgilib/bedCart.c, and the test is here
+ * because hg/cgilib has no tests directory of its own; the link line below pulls in
+ * jkhgapcgi.a for it.
+ *
+ * The rule has four steps and the order of the first three is the whole of #36212.  An
+ * explicit "itemRgb off" wins, then an explicit "itemRgb on" wins, and only then does the
+ * presence of a "color" setting turn item colors off by default.  Commit 88d620e6c82 folded
+ * the first two tests together with the third, so a stanza saying both "itemRgb on" and
+ * "color" -- which means "items from the file, labels from color" -- lost its item colors.
+ *
+ * Nothing about that is visible to a test that only looks at one setting at a time, which is
+ * why the pairs below matter more than the singles: every single-setting case passed while
+ * the bug was live.
+ *
+ * The last step reads hg.conf's alwaysItemRgb, so the makefile runs this twice, once with
+ * that knob left alone and once with it off, and both answers are diffed.  A mirror that
+ * turns it off must still get item colors from a stanza that explicitly asks for them.
+ *
+ * refs #36212 */
+
+/* Copyright (C) 2026 The Regents of the University of California
+ * See kent/LICENSE or http://genome.ucsc.edu/license/ for licensing information. */
+
+#include "common.h"
+#include "hash.h"
+#include "hgConfig.h"
+#include "trackDb.h"
+#include "bedCart.h"
+
+static struct trackDb *tdbWith(char *settings)
+/* A track with the given settings, as they would be spelled in a trackDb stanza. */
+{
+struct trackDb *tdb;
+AllocVar(tdb);
+tdb->track = cloneString("testTrack");
+tdb->table = cloneString("testTrack");
+tdb->type = cloneString("bed 9 .");
+tdb->settings = cloneString(settings);
+tdb->settingsHash = trackDbSettingsFromString(tdb, tdb->settings);
+return tdb;
+}
+
+static void say(char *what, boolean got)
+{
+printf("  %-52s %s\n", what, got ? "item colors" : "one color");
+}
+
+static void singles()
+/* One setting at a time.  Every one of these passed while #36212 was live. */
+{
+printf("one setting\n");
+say("(nothing)", bedItemRgb(tdbWith("")));
+say("itemRgb on", bedItemRgb(tdbWith("itemRgb on\n")));
+say("itemRgb off", bedItemRgb(tdbWith("itemRgb off\n")));
+say("color 255,0,0", bedItemRgb(tdbWith("color 255,0,0\n")));
+}
+
+static void pairs()
+/* Both settings in one stanza, which is what #36212 is about. */
+{
+printf("\nboth settings\n");
+say("itemRgb on  + color 255,0,0",
+    bedItemRgb(tdbWith("itemRgb on\ncolor 255,0,0\n")));
+say("itemRgb off + color 255,0,0",
+    bedItemRgb(tdbWith("itemRgb off\ncolor 255,0,0\n")));
+say("color 255,0,0 + itemRgb on  (other order)",
+    bedItemRgb(tdbWith("color 255,0,0\nitemRgb on\n")));
+}
+
+static void inherited()
+/* trackDbSettingClosestToHome walks up to the parent, so a child can be ruled by a color it
+ * does not carry itself, and can overrule it with its own itemRgb. */
+{
+printf("\nfrom a parent\n");
+struct trackDb *parent = tdbWith("color 255,0,0\n");
+struct trackDb *child = tdbWith("");
+child->parent = parent;
+say("child of a stanza with color", bedItemRgb(child));
+
+struct trackDb *saysOn = tdbWith("itemRgb on\n");
+saysOn->parent = parent;
+say("child says itemRgb on, parent says color", bedItemRgb(saysOn));
+}
+
+static void noTrack()
+/* Callers reach this with no track at all, and the answer has to be the default rather than
+ * a crash. */
+{
+printf("\nno track\n");
+say("NULL", bedItemRgb(NULL));
+}
+
+int main(int argc, char *argv[])
+{
+printf("======== hg.conf alwaysItemRgb=%s\n",
+       cfgOptionDefault("alwaysItemRgb", "(not set, defaults on)"));
+singles();
+pairs();
+inherited();
+noTrack();
+printf("\n");
+return 0;
+}