Visually fonts changes when user input mixed English and Chinese characters
The pango project supports rendering of multilingual text.
For language specific characters, it will rendering the text with the font for that language.
But there are some common characters defined by Unicode standards, pango will use the same language of neighborhood characters for common characters.
Currently there are two issues with font handling of mixed English and Chinese characters.
- number and punctuation characters changes
number and punctuation are defined as common characters, if common characters near English characters, it will use English fonts; if common characters near Chinese characters, it will use Chinese fonts.
But when typing, the common characters may use different fonts depending on nearby characters.
- character height changes for English and Chinese
Currently in Fedora 29, the height of default English and Chinese fonts are different. Beside the problem with common characters, this issue introduce another problem.
The Chinese fonts are taller than the English fonts. After inputting some English characters, as the height of English fonts are shorter than Chinese fonts; Then input some Chinese characters, the entire line of characters will move down a bit.
Both the issues will cause visually changes, which is not acceptable by users.