https://bugs.documentfoundation.org/show_bug.cgi?id=156125
Bug ID: 156125 Summary: Slow scrolling of documents with many Math formulas Product: LibreOffice Version: 7.5.3.2 release Hardware: All OS: Linux (All) Status: UNCONFIRMED Severity: normal Priority: medium Component: Writer Assignee: libreoffice-bugs@lists.freedesktop.org Reporter: jrheinlaen...@users.sourceforge.net Created attachment 188162 --> https://bugs.documentfoundation.org/attachment.cgi?id=188162&action=edit Writer file containing numerous Math objects with varying font sizes When editing a Writer document that has many Math formulas, scrolling can become irregular. After examining this with callgrind, I found the reason in vcl/unx/generic/fontmanager/fontconfig.cxx class CachedFontConfigFontOptions. Here the font options cache is coded to a size of 10. Apparently Math formulas can contain a lot of fonts in varying sizes. Thus the font cache is quickly filled. On scrolling, an enormous amount of calls to PrintFontManager::getFontOptions() is generated. Unless cached, these are handled by libfontconfig's FcFontSetMatch(). On typical Ubuntu systems, several thousand fonts can be installed (run fc-list). Thus libfontconfig uses a significant time to handle the calls. Scrolling performance can be greatly improved by increasing the font options cache size to e.g. 100. Since memory usage is probably not as critical as it used to be when the font options cache was first implemented, that should be a safe change. Find attached a sample file with a lot of Math formulas containing different font sizes. -- You are receiving this mail because: You are the assignee for the bug.