Repeated same letters are rendered differently after upgrading 1.16.0 -> 1.18.2

[fstmail-cairo at bio.ifi.lmu.de]

Hi,

when upgrading from openSUSE Leap 15.5 to 15.6 (or SLE 15 SP5 -> SP6)
libcaro2 has changed from 1.16.0 to 1.18.0 (but I also tested the
latest 1.18.2).

The new cairo lib causes a change in font rendering such that the
same letter is not always rendered the same way. I'm testing with
e.g. libreoffice 24.8.1.2 on openSUSE 15.6 and just exchange the
libcairo2 1.16.0 and 1.18.2 libraries and restart libreoffice.
The effect is reproducable whenever changing the libcairo libraries.

With 1.16.0 every identical letter is rendered the same way (old1.png),
but with 1.18.2 it changes every one or two letters (new1.png), depending
on the font size.

This causes a very noisy font face and makes texts harder to read
at certain font sizes. It's especially annoying when letters could be
rendered without anti-aliasing but get blurred due to this changing
rendering, like in old3.png vs. new3.png.

I haven't found anything about this issue, just some bug reports about
the Tahoma font (which I don't have).

Is this a bug or is it intended that the same letter can be rendered
in different ways?

Is there any setting about font hinting/subpixel etc. that could
restore the old behaviour as in 1.16.0?

Many thanks!
cu,
Frank



-- 
Dipl.-Inform. Frank Steiner   Web:  http://www.bio.ifi.lmu.de/~steiner/
Lehrstuhl f. Bioinformatik    Mail: http://www.bio.ifi.lmu.de/~steiner/m/
LMU, Amalienstr. 17           Phone: +49 89 2180-4049
80333 Muenchen, Germany       Fax:   +49 89 2180-99-4049
* Rekursion kann man erst verstehen, wenn man Rekursion verstanden hat. *
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