[FFmpeg-trac] #9745(ffmpeg:new): [drawtext filter]fontconfig doesn't work well

[FFmpeg]

#9745: [drawtext filter]fontconfig doesn't work well
-------------------------------------+-------------------------------------
             Reporter:  Hellena      |                     Type:  defect
               Status:  new          |                 Priority:  important
            Component:  ffmpeg       |                  Version:  git-
             Keywords:               |  master
  drawtext,fontconfig,font-style     |               Blocked By:
             Blocking:               |  Reproduced by developer:  0
Analyzed by developer:  0            |
-------------------------------------+-------------------------------------
 Summary of the bug:
 I want to use some style for drawtext filter, such as
 bold/italis/underline/strikeline.
 In the document of ffmpeg filter, there's the example:

 {{{
 Use fontconfig to set the font. Note that the colons need to be escaped.
 drawtext='fontfile=Linux Libertine O-40\:style=Semibold:text=FFmpeg'
 }}}


 I try this code, but it only work when I use a few value, ex:style=bold.
 {{{
 ffmpeg -loglevel debug -i "mul/bg1.png" \
 -filter_complex "[0]drawtext=x=50:y=60:\
 fontfile='YuantiSC\\:style=underline\\:size=140\\:spacing=20':\
 text=FFmpeg" \
 -c:a aac -r 25 -s 720:1280 -c:v libx264 \
 -pix_fmt yuv420p \
 -y test_blod_cut5.mp4
 }}}

 The version I have checked in my computer is:
 ffmpeg 5.0.1，fonconfig 2.14.0

 Any problem in the code?
 And how can I accomplish the requirment of underline/strikeline and so on.
-- 
Ticket URL: <https://trac.ffmpeg.org/ticket/9745>
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