The latest freetype release offers new subpixel hinting options: http://git.savannah.gnu.org/cgit/freetype/freetype2.git/commit/devel/ftoption.h?id=596157365aeff6bb842fe741f8cf322890a952fe When freetype 2.6.5 is compiled with "TT_CONFIG_OPTION_SUBPIXEL_HINTING 2" which according the the information in the freetype commit is the new default mode, then konsole is lagging and utilizing 100% CPU usage when switching tabs or redrawing the screen, e.g. when opening/closing a file in vi, showing a git diff --cached and so on. Why I'm reporting this here and not on the freetype bugtracker is because everything else seems to work fine, it's only konsole showing that extreme CPU usage and lag. Attaching a screenshot of ksysguard showing the intense CPU usage causing lags and delays when trying to work with konsole. Reproducible: Always
Created attachment 100068 [details] konsole_freetype.png
I guess this can be closed, after also upgrading fontconfig to 2.12.0, rebuilding the font cache with $ fc-cache -fr and doing another reboot I can no longer reproduce this issue for now.
Thanks for the update, closing.