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
Created attachment 159187 [details] One file would cause this problem, one wouldn't "OpenSans.odt" would cause this problem and "Noto Sans CJK HK.odt" would not
As I've said in bug 130949 (comment #2 and #8 there), this is a wildly reported problem, but never properly diagnosed, because it depends a lot on the user's font configuration. Your problem most likely doesn't stem from the "OpenSans" font you specified - since I doubt it covers any Chinese glyphs - but instead from whatever the fallback font on your KUbuntu system. Unfortunately, I don't know any easy way to identify this fallback font in LO. The workaround is to specify a font that's known good for displaying Chinese characters, like "Noto Sans CJK HK" in your second file. You can always specify separate fonts for Latin and Chinese text if you prefer OpenSans for its Latin and digital glyphs. FWIW, on my Windows 10 system with LO 6.4.3, I can open both attached files without any slowdown. I have neither "OpenSans" or "Noto Sans CJK HK" fonts installed (I have "Source Han Sans SC" instead).
Thanks. I know change a font could solve this problem. Whatever, "Source Han Sans SC" would not cause this problem on my computer either...... I admire it is really hard to found which fallback font Libreoffice is using. But after I compare the two document under KUbuntu, I have a more wild guess: It is not the specific font cause this problem but the fallback mechanism cause that. Since I checked that seems my system fallback is Noto Sans CJK and both document looks like same in my system. Just a guess. This problem seems so complex for me to dig it out.
You could take a performance profile of the slow down. Install debug packages for LibreOffice: https://wiki.ubuntu.com/Debug%20Symbol%20Packages Install perf and FlameGraph and do the trace: https://wiki.documentfoundation.org/Development/How_to_debug#Performance_debugging_.28perf.29 So you run LibreOffice, then in a terminal you say perf record -F 200 --call-graph dwarf,62000 --pid=`pidof soffice.bin` Then you open the slow file. You exit perf by Ctrl-C in the terminal. Then you can create the SVG flamegraph.
Thanks for reporting this issue. Could you please try to reproduce it with the latest version of LibreOffice from https://www.libreoffice.org/download/libreoffice-fresh/ ? I have set the bug's status to 'NEEDINFO'. Please change it back to 'UNCONFIRMED' if the bug is still present in the latest version.
Thanks for replying. Since it is a long long ago problem and I can't reproduce this problem anymore with the latest libreoffice, I have set the status to "resolved worksforme'.