Problems of table editing mode about Chinese characters

[theopathyreg]

When use table edit mode, there are some problems when input Chinese characters. because one Chinese character takes two letters space. Can't make the line fix together in edit window. I think that Japanese and some other characters should have the same problems. Really hope it can be fixed. Thank you.
example

|      |     |     |
|------|-----|-----|
|你好    |     |     |
|你们好   |     |     |
|中文不能对齐|     |     |

[mitya57]

I took a look at this today. Here are some notes:

This problem happens not only with East Asian languages, but also with emojis, zero-width characters and more.

How much width a character takes depends on a font. Some fonts try to fit all characters into a single width, some fonts are duospaced.

To get a character width in a font, one can use QFontMetrics class (we are already using it for some other purposes). Also, Python has an east_asian_width function in the standard library which returns a code from this classifier.

The problem with the current table editing mode code (written by @Griffon26) is that Qt gives us only the number of added or removed characters, not their values or widths:

retext/ReText/editor.py

Line 441 in 0987c28

tablemode.adjustTableToChanges(self.document(), pos, added - removed, markupClass)

So to fix this issue one would need to rewrite this code to align cells without relying on information about added/removed lengths.

Pull requests for this are welcome. I am not sure if I will ever have time to rewrite this :(