Some additional information and corrections:
I have downloaded the latest sources for FreeSerif (normal and bold) and
FreeSans and done some more testing.
I have realized that another difference between my two Linux systems is
that the Qt 5.3 system had FreeSerif FreeSans already installed
A small detail: I discovered that the 'standard' FreeSans.ttf coming with my
distro has a different structure than FreeSerif: if open with FontForge, it
lacks kerning data for Latin (as 'our' FreeSans does); possibly they are in
the old-style 'kern' table rather than in the GPOS table / 'kern'
I start by limiting my observations to Linux, where I can analyse things more
thoroughly. My system: Linux Mint 17 64bit, with self compiled sources with
Qt Creator 3.1.2 and Qt lib 5.2.1. MuseScore built-in .ttf fonts are used as
they come in the current master.
I had the additional problem that
Thanks for the investigation! That's good information about the reason for
the lack of kerning in FreeSans. Also good advice about the string to test
with. You are of course correct that VA is an easy case to test. But
FWIW, I found that this pair will *not* kern for me if I build
