Open the Configure Panel dialog box. Select the Appearance option. The following (.xsession-errors) messages appear immediately.

libpng warning: Ignoring gAMA chunk with gamma=0
libpng warning: Ignoring attempt to set negative chromaticity value
libpng warning: Ignoring attempt to set cHRM RGB triangle with zero area

Repeatable with an existing 3.5.10 or new Trinity profile. The messages probably are generated by libpng, but only happens when opening Appearances.

I thought the problem was related to using button backgrounds, but selecting "Default" causes the messages too.

I checked and see the error messages in 3.5.10 too. Thus, some legacy code is causing these messages in Trinity.

Based on the context of the messages I suspect something in the Trinity/KDE code is not accessing the libpng libraries correctly.

Darrell