Korean text rendering

[Konstantin Kharlamov]

On Thu, 2025-05-15 at 12:46 +0300, Igor Mironchik wrote:
> Hi.
> 
> On 15.05.2025 10:48, Konstantin Kharlamov wrote:
> > On Thu, 2025-05-15 at 10:38 +0300, Igor Mironchik wrote:
> > > I guess too this is system specific. I'm on openSUSE Tumbleweed.
> > > Changing editor's font to Droid Sans doesn't help.
> > > 
> > > Ok. I see that this issue is system specific, so my question is
> > > answered. Maybe somebody can check this issue on Tumbleweed only?
> > One thought: is everything's alright with graphics drivers, could
> > it be
> > apps are rendered with software rendering?
> > 
> > If not, try creating a performance flamegraph of Kate with:
> > 
> > 	$ perf record --call-graph dwarf kate -b ./myfile.txt
> > 	$ perf script | stackcollapse-perf | flamegraph >
> > /tmp/out.svg
> > 
> > and see if perhaps something interesting comes up.
> 
> 
> With English
> 
> https://drive.google.com/file/d/1Qnf8Tv4TOcYGkMmCSjMFj_bjXgpBMuh3/view?usp=drive_link
> 
> With Korean
> 
> https://drive.google.com/file/d/1Kf_6ENPlz-Lpq1WLaI8SqufB49xALEIw/view?usp=drive_link
> 
> Korean takes time for loading font...

I see, to most of the time in problematic case seems to be taken by
harfbuzz and freetype.

Try regenerating fonts cache with `fc-cache -vf`, see if that makes any
difference. Also, what harfbuzz and freetype versions do you have,
maybe it's a bug in some older release? For me harfbuzz is 11.2.0 and
freetype is 2.13.3.

If nothing helps, maybe you might want to repeat flamegraphs with
debugging symbols for harfbuzz and freetype installed, to see where
exactly its processing is spent. But I'm not good at how fonts work, so
at that point it may be worth delegating the question to harfbuzz and
freetype devs.