Improve search aria label generation performance

[KuromiAK]

When using search, if a matched line is really long (i.e. from a minified file), the UI freezes briefly because of a call to strings.lcut() which internally calls split(/\b/). This change removes the call with no change to behavior.

[roblourens]

#31551

I think that it's also due to the search tool producing large amounts of text and sending it all back from the search process. Also, it looks like we are still calling .preview for every match anyway? But the call you've replaced was definitely unnecessary so it looks like a good optimization. I'll try it out, thanks!

[KuromiAK]

I did not remove the other preview call because it would alter the existing behavior. That said, I managed to rewrite the lcut function to reduce its memory footprint and speed it up quite a bit. It is also strange that lcut can return a string longer than n.

function lcut2(text, n) {
	if (text.length < n) {
		return text;
	}

	let re = /\b/g;
	let i = re.lastIndex;
	while (re.test(text)) {
		if (text.length - re.lastIndex < n) {
			break;
		}
		i = re.lastIndex;
		re.lastIndex += 1;
	}
	return text.substring(i).replace(/^\s/, '');
}

[roblourens]

The aria label change is a huge speedup! Nice find. The lcut change looks good too. Do you want to add it to the PR? I can just copy it in but I want to give you credit.

[roblourens]

We should have some unit tests for that function before we rewrite it.

[KuromiAK]

I'll leave lcut to you.