That the picture of the FontChooserDiaglog on that page displays each font using the user preview text string and the font name ( as smaller text ) above it.
In my FontChooserDiaglog, this does not seem to be possible, and each font text is just the font name ( it does not use the preview text string ).
Is this something which was introduced in a later version of Gtk, or am I missing something ?
The preview text is underneath the font list. It is editable by the user. You can do dialog.set_preview_text('This is a test') before running dialog.run() to set the text you want to show there.
I meant in my screenshot the “The quick brown fox jumps over the laz…” text underneath the list of fonts. That is the preview text. It renders in the font the user clicks.