Selection with search and unicode

Combining, surrogate or fullwidth chars in the line and/or the search string lead to weird selection offset problems. Steps to repro:

• insert into demo: echo -en 'combining: ééé\nfullwidth: ￥￥￥\nsurrogate: 𓂀𓂀𓂀\n'
• search for ‘ééé’, ‘￥￥￥’ and ‘𓂀𓂀𓂀’

The selection is kinda off for all 3 types, it gets even worse if the line contains any of these before their occurence. It seems the renderer and the selection manager do not agree on the chars widths and lengths.

Since I had a similar problem with the linkifier, it might be fixable the same way (#1678).

[Tyriar]

@JasinYip there’s some discussion about the fix in https://github.com/xtermjs/xterm.js/pull/3236, been a while since I looked and don’t have time atm though.

[jerch]

@jerch I’m having a bit of a difficult time determining how and where cell offsetting should be (or is) implemented. Within BufferLine.ts?

Ah yepp thats abit hidden in the codebase, the code regarding this is in Buffer.ts and BufferLine.ts, both contain several methods that demostrate how to walk cells, easiest startpoint might be this: https://github.com/xtermjs/xterm.js/blob/e8153d929d6bb4f7012d3f20aa8c74abc335715d/src/common/buffer/Buffer.ts#L480

Not sure if you can directly use this method, you have to take care where your string index origin is (whether col 0 of wrapped or unwrapped lines).