GtkCustomSorter compare callback receives undefined args (untyped gconstpointer not marshalled)

[romgrk]

Summary

Gtk.CustomSorter's compare callback receives undefined for both items it is supposed to compare, so the sorter can never order anything. Any GtkSortListModel driven by a CustomSorter silently keeps the model's original order.

The root cause appears to be that GtkCustomSortFunc is declared as

int (*GtkCustomSortFunc) (gconstpointer a, gconstpointer b, gpointer user_data);

i.e. the two items are untyped gconstpointers. With no GI type information for a/b, node-gtk passes undefined into the JS callback instead of wrapping the underlying GObjects.

Reproduction

const gi = require('node-gtk');
const Gtk = gi.require('Gtk', '4.0');
Gtk.init();

const list = Gtk.StringList.new(['banana', 'apple', 'cherry']);
let firstArgs = null;
const sorter = Gtk.CustomSorter.new((a, b) => {
  if (!firstArgs) firstArgs = [a, b];
  const av = a && a.getString ? a.getString() : a;
  const bv = b && b.getString ? b.getString() : b;
  return av < bv ? -1 : av > bv ? 1 : 0;
});
const sorted = Gtk.SortListModel.new(list, sorter);

console.log('callback first args:', firstArgs);
const out = [];
for (let i = 0; i < sorted.getNItems(); i++) out.push(sorted.getItem(i).getString());
console.log('result order:', out.join(', '));

Actual

callback first args: [ undefined, undefined ]
result order: banana, apple, cherry

Expected

a and b should be the GtkStringObject items being compared, and the result should be apple, banana, cherry.

Impact

CustomSorter is the only GtkSorter that takes a plain compare function; the expression-based sorters (StringSorter/NumericSorter) require a GtkExpression, and ClosureExpression.new wants a real GObject.Closure rather than a JS function. So there is currently no working way to do a custom sort (e.g. "directories first, then by name" for a file tree) from JS. The practical workaround is to sort in JS and feed a Gio.ListStore.

The same limitation presumably affects any callback whose arguments are untyped gpointer/gconstpointer (e.g. GCompareDataFunc, GtkMapListModel map funcs returning into untyped slots, etc.).

Environment

• node-gtk 2.0.0
• node v22.22.3
• GTK 4.22.4, GLib 2.88.1