[Libreoffice-bugs] [Bug 131740] New: TrueType fonts with Chinese slow down LibreOffice

[bugzilla-daemon at bugs.documentfoundation.org]

https://bugs.documentfoundation.org/show_bug.cgi?id=131740

            Bug ID: 131740
           Summary: TrueType fonts with Chinese slow down LibreOffice
           Product: LibreOffice
           Version: 6.4.2.2 release
          Hardware: All
                OS: All
            Status: UNCONFIRMED
          Severity: normal
          Priority: medium
         Component: framework
          Assignee: libreoffice-bugs at lists.freedesktop.org
          Reporter: xqqy189 at hotmail.com

Description:
Hello. I found that LibreOffice is so slow and its CPU range is so high if use
TrueType fonts like source code pro built in LibreOffice or OpenSans typing
Chinese in kubuntu19.10 and Windows 10. I tried to turn OpenGL on and off, it
is not work. My reasons about why I thought TrueType fonts cause this problem
because "Nato Sans CJK HK" ，"SourceHanSansCN" and "Noto Serif CJK SC" will not
make this problem. These are OpenType fonts.

I attached 2 file that one of it may cause problem(OpenSans.odt) and which is
not(Noto Sans CJK HK.odt) But be aware that this problem not only happen in
writer but also calc.(I didn't try impress since it require a lot of word to
reproduce this problem)

I am using Libreoffice 6.4.2.2 

Steps to Reproduce:
1. Change fonts to a TrueType font, OpenSans on Ubuntu are the best for
reproduce this problem.
2. Typing a lot of Chinese character into the file, at least one page. Here is
some of Chinese character for you to copy: 测试用的中文字符，把这些字符输满至少一页



Actual Results:
Libreoffice process will take a lot of CPU range, and its UI would stuck.

Expected Results:
smoothly response as using OpenType fonts. 


Reproducible: Always


User Profile Reset: Yes



Additional Info:
I have asked on
https://ask.libreoffice.org/en/question/235485/truetype-fonts-slow-down-libreoffice/
and seems it is a bug.
Due to my mother langurage is not English, maybe what I am saying here is not
so clear enough and may have a lot of grammar problems.

seems only Chinese character cause this problem, English will not cause this
problem.

Tried turn OpenGl on and off. Both could reproduce this problem.

I can't found the "Add an Attachment" link. But I have a file that could
reproduce this problem. If in need, I'd like to send this file with E-mail

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