From 9745514c1833bee05ce0a2ee28cd92d62fd4a8dc Mon Sep 17 00:00:00 2001
From: John Denker <jsd@av8n.com>
Date: Thu, 11 Nov 2021 08:40:48 -0700
Subject: fix it so that the set of "allowed functions" shows up in even rows
 and almost-even columns

---
 edit_algebra_form.php | 22 ++++++++++++++++++----
 1 file changed, 18 insertions(+), 4 deletions(-)

diff --git a/edit_algebra_form.php b/edit_algebra_form.php
index e091418..3ab31ac 100644
--- a/edit_algebra_form.php
+++ b/edit_algebra_form.php
@@ -89,18 +89,32 @@ class qtype_algebra_edit_form extends question_edit_form {
 
         // Create an array which will store the function checkboxes.
         $funcgroup = array();
+// KLUDGE: illogical, but works better than the alternative:
+// <br> doesn't separate rows the way you want; try a full-width div instead:
+        $rowSep = '<div style="width:100%"></div>';
+
+// FIXME:
+// Trying to align columns using flexbox + spacers is an unsound design.
+// It fails in ways the server cannot anticipate, because of variable-width fonts.
+// Such things should be aligned using an html table or css grid,
+// or by wrapping each checkbox in a fixed-width wrapper:
+// https://stackoverflow.com/questions/257505/css-fixed-width-in-a-span
         // Create an array to add spacers between the boxes.
-        $spacers = array('<br>');
+        $spacers = array($rowSep);
+        $itemsPerRow = 6;
         // Add the initial all functions box to the list of check boxes.
         $funcgroup[] =& $mform->createElement('checkbox', 'all', '', get_string('allfunctions', 'qtype_algebra'));
         // Create a checkbox element for each function understood by the parser.
+// FIXME: why do the function names show up on the page in some weird order???
         for ($i = 0; $i < count(qtype_algebra_parser::$functions); $i++) {
             $func = qtype_algebra_parser::$functions[$i];
             $funcgroup[] =& $mform->createElement('checkbox', $func, '', $func);
-            if (($i % 6) == 5) {
-                $spacers[] = '<br>';
+            if (((1+$i) % $itemsPerRow) == 0) {
+                $spacers[] = $rowSep;
             } else {
-                $spacers[] = str_repeat('&nbsp;', 8 - strlen($func));
+// KLUDGE: far from perfect, but
+//   usable approximation for typical variable-width fonts:
+                $spacers[] = str_repeat('&nbsp;', 2.0*(8 - strlen($func)));
             }
         }
         // Create and add the group of function controls to the form.
-- 
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