I've read a bunch of google answers about this, but haven't figured out yet what to do. It is clear that something is wrong with the GTK theme, but what?
In the firefox window - both the page and the menu characters.
Thanks for your attention
The problem is: KDE has no support to "demi bold" (or semi bold) fonts, while GTK yes.
I was using a font that has a "demi bold" option, which was translated by KDE to bold.
This appears to be fixed since version 4.8, but not an option for Kubuntu users (mainly if you're using 12.04 LTS, as me).
First: on KDE Settings > Application Appearence > Fonts. Mark Anti-aliasing as "enabled", click on "Configure", UNcheck "Exclude range", check "Use subpixel", and select "Slight" for "Hinting".
Then do one of the following steps:
Workaround 1: go to KDE Settings, Font Management, and disable the "demi bold" and "light" variations from the font you're using.
Workaround 2: select a font with no "semi bold" and "light" variations, like Tahoma.
Try this, it fixed my gtik application so hopefully will also fixe your gtk applications.
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