feat(viewport): gutter column, soft wrap, search highlight

[caarlos0]

This adds a ColumnSign API (name is the worst part of this so far), which allows you to define a left column in the viewport, which isn't taken into account when horizontal scrolling.

You can use to show line numbers, for example:

vp.ColumnSignFn = func(i, total int) string {
	if i >= total {
		return lineNumberStyle.ToLipgloss().Render("   ~ │ ")
	}
	return lineNumberStyle.ToLipgloss().Render(fmt.Sprintf("%4d │ ", i+1))
}

which would render something like:

CleanShot.2025-01-07.at.16.36.30.mp4

As you can notice in the video and code, it also fills to the height if the viewport if the number of lines is lower than the available height, similar to what neovim and other editors do.

It also adds the ability to highlight ranges, e.g. from regex matches. This should work regardless of ansi sequences and/or grapheme clusters.

Finally, it adds options to soft wrap lines and to fill the height with empty lines.

Things to take into account here:

• we should probably move the soft wrap features into here as well
• the API for sure needs more changes, e.g. some way to inform it is a soft wrapped line and not a real line
• no tests so far as I'm just experimenting
• it depends on feat(viewport): horizontal scroll #240

[caarlos0]

showing off soft wrap and search as well (on gum):

CleanShot.2025-01-08.at.12.00.51.mp4

[bashbunni]

we should def remember to remove this before merging 😄

[caarlos0]

looks like this right now (using it in gum):

CleanShot.2025-01-08.at.22.56.32.mp4

[bashbunni]

highlightLines*

[bashbunni]

*SetHighlights

[bashbunni]

TODO: create a runnable example with the API changes @bashbunni

[bashbunni]

Highlight*