After upgrading fontconfig from 2.2.3-4 and restarting my graphical
environment, I saw all truetype fonts are compressed vertically (aspect
ratio was changed), at least on GTK apps (ROX-Filer, Firefox) and IceWM --
not checked others yet.  This is very annoying because it makes many
small-size labels hard to read or unreadable, when they were perfect with
the previous version.

I double checked that fontconfig is the culprit, by downgrading (only) it
to the previous version, restarting my environment, and seeing all was good
again.

I will try to attach two shots showing the problem with ROX-Filer.

That's really weird looking.  Can you tell me what font you're using?
Also, the output from 'fc-match' using that font would probably be
helpful in diagnosing the problem.

In ROX-Filer:  I didn't specified anything, this seems to be ROX' choice.
After looking at magnified shots, I guessed (not 100% sure) this must be
"Bitstream Vera Sans Mono 12".

    $ fc-match "Bitstream Vera Sans Mono 12"
    Vera.ttf: "Bitstream Vera Sans" "Roman"

I suspect you need it with --verbose, here it is ;)
    Pattern 25 of 32
	    autohint: FcFalse(s)
	    charset: set(s)
	    dpi: 75(f)(s)
	    family: "Bitstream Vera Sans"(s)
	    familylang: "en"(s)
	    file: "/usr/share/fonts/truetype/ttf-bitstream-vera/Vera.ttf"(s)
	    fontformat: "TrueType"(s)
	    fontversion: 131072(i)(s)
	    foundry: "bitstream"(s)
	    globaladvance: FcTrue(s)
	    hinting: FcTrue(s)
	    hintstyle: 3(i)(s)
	    index: 0(i)(s)
	    lang: aa|ast|ay|bi|br|ch|co|da|de|en|es|et|eu|fi|fj|fo|fr|fur|fy|gd|gl|gv|ho|ia|id|ie|io|is|it|lb|mg|nb|nds|nl|nn|no|oc|om|pt|rm|sma|smj|so|sq|sv|sw|tn|tr|ts|vo|vot|wa|xh|yap|zu(s)
	    outline: FcTrue(s)
	    pixelsize: 12.5(f)(s)
	    scalable: FcTrue(s)
	    scale: 1(f)(s)
	    size: 12(f)(s)
	    slant: 0(i)(s)
	    style: "Roman"(s)
	    stylelang: "en"(s)
	    verticallayout: FcFalse(s)
	    weight: 80(i)(s)
	    width: 100(f)(s)

In IceWM, this was more easy to find, though I had to look into theme
files, the fonts are specified as SomethingFontNameXft = "Sans:size=10" or
"Sans:size=10:bold".

fc-match --verbose gives:
    Pattern 25 of 32
	    autohint: FcFalse(s)
	    charset: set(s)
	    dpi: 75(f)(s)
	    family: "Bitstream Vera Sans"(s)
	    familylang: "en"(s)
	    file: "/usr/share/fonts/truetype/ttf-bitstream-vera/VeraBd.ttf"(s)
	    fontformat: "TrueType"(s)
	    fontversion: 131072(i)(s)
	    foundry: "bitstream"(s)
	    globaladvance: FcTrue(s)
	    hinting: FcTrue(s)
	    hintstyle: 3(i)(s)
	    index: 0(i)(s)
	    lang: aa|ast|ay|bi|br|ch|co|da|de|en|es|et|eu|fi|fj|fo|fr|fur|fy|gd|gl|gv|ho|ia|id|ie|io|is|it|lb|mg|nb|nds|nl|nn|no|oc|om|pt|rm|sma|smj|so|sq|sv|sw|tn|tr|ts|vo|vot|wa|xh|yap|zu(s)
	    outline: FcTrue(s)
	    pixelsize: 10.4167(f)(s)
	    scalable: FcTrue(s)
	    scale: 1(f)(s)
	    size: 10(f)(s)
	    slant: 0(i)(s)
	    style: "Bold"(s)
	    stylelang: "en"(s)
	    verticallayout: FcFalse(s)
	    weight: 200(i)(s)
	    width: 100(f)(s)

Don't hesitate to ask me more information if you need to.

I can't reproduce the bug because of the ancient versions of the
packages reported, but I suppose that after 9 years (almost), this bug
could be closed or archived.