Not all fontconfig settings are used by Qt5. It reacts on changing some of the fontconfig settings, but not all of them are respected. It happens with qt 5.3.0_beta. I'm absolutely not sure, but it seems to me that 5.2.1 was rendering fonts correctly Reproducible: Always Steps to Reproduce: 1. lauch any Qt5 GUI application and compare font rendering with the rest of the system Actual Results: They differ Expected Results: Fonts are rendered in the same way dev-qt/qtgui-5.3.0_beta was built with the following: USE="doc evdev gif glib harfbuzz jpeg opengl png udev xcb -accessibility -debug -eglfs -gles2 -ibus -kms -test" media-libs/harfbuzz-0.9.26-r1 was built with the following: USE="cairo glib graphite icu introspection truetype -static-libs -test" ABI_X86="32 64 -x32" media-libs/freetype-2.5.3-r1 was built with the following: USE="X adobe-cff bzip2 infinality png -auto-hinter -bindist -debug -doc -fontforge -harfbuzz -static-libs -utils" ABI_X86="32 64 -x32" media-libs/fontconfig-2.11.1 was built with the following: USE="-doc -static-libs" ABI_X86="32 64 -x32"
Created attachment 376068 [details] illustration cmake-gui (qt5 version) window on top of Kile window
Are you suggesting that this is a downstream bug?
(In reply to Davide Pesavento from comment #2) > Are you suggesting that this is a downstream bug? ping?
Excuse me for the delay. No, this is not a Gentoo issue, but certainly is upstream bug.
Then I suggest you report it upstream, there's not much we can do about it, sorry.
There are many such reports in upstream JIRA