Comment 27 for bug 1766938

Yeah it's just a missing/unsupported bit depth in old versions of mutter:

static int
standard_pict_format_for_depth (int depth)
{
  switch (depth)
    {
    case 1:
      return PictStandardA1;
    case 24:
      return PictStandardRGB24;
    case 32:
      return PictStandardARGB32;
    default:
      g_assert_not_reached ();
    }
}