How to make Ghostscript embed a Type 1 font to the PDF in one part, without splitting

I was facing a problem with Ghostscript 8.54 -sDEVICE=pdfwrite. When embedding a Type 1 font to the PDF, Ghostscript splitted the font to two font objects (and the corresponding FontDescriptor and CFF stream objects as well), instead of generating only one font object. This blog post explains how I solved the problem.

Please note that the problem didn't happen with a newer Ghostscript (such as GPL Ghostscript 8.61 (2007-11-21), it always generated a single PDF font object.

In a few hours I was able to reduce the source font to two glyphs, Ghostscript still splitting it to two 1-glyph fonts. Then I had the idea to change the /Encoding array, putting the two glyph names next to each other. It solved the problem, Ghostscript didn't split the font anymore. In fact, it turned out that one of the glyphs was missing from the /Encoding, and once I added it (anywhere), the problem was solved.

See the source PostScript file on http://www.math.bme.hu/~pts/twob.ps.txt . It contains the 2-glyph font, demonstrates the problem and shows the solution as well (when compiled with -dfill_encoding=true).