feat(viewport): horizontal scroll

[tty2]

implement #235

[meowgorithm]

Thanks for the PR! One immediate things is jumping out here:

len() counts bytes and not runes, which are not always the same. Similarly, some runes occupy two cells. For example:

// 3 bytes, 3 cells
Hi!

// 7 bytes, 5 cells:
世界!

So, in short, keep in mind that horizontal scrolling will need to handle double-width runes. Here’s a more in-depth example that breaks it down further:

https://go.dev/play/p/7lPoU2SMjn5

[tty2]

Thanks for the PR! One immediate things is jumping out here:

len() counts bytes and not runes, which are not always the same. Similarly, some runes occupy two cells. For example:

// 3 bytes, 3 cells
Hi!

// 7 bytes, 5 cells:
世界!

So, in short, keep in mind that horizontal scrolling will need to handle double-width runes. Here’s a more in-depth example that breaks it down further:

https://go.dev/play/p/7lPoU2SMjn5

It's a good point. I guess I have to use lipgloss.Width here.

[tty2]

Waiting for this PR merge and tagging.
Will continue after that.

[tty2]

Don't merge it yet, please.
I'm gonna write some simple tests later this evening.

[tty2]

Done!
@meowgorithm could you check it, please?
I can suppose that last test case (list: with y offset: horizontal scroll) can be too complicated. But I'm not sure it it's better to change it.
WDYT?

[meowgorithm]

Thanks, @tty2. Before we get to this, do you mind adding some tests with double-width runes? That is going to be the number one thing we'll want to verify. In particular, cases where there's a mix of single and double width runes.

[tty2]

These tests I've written inside go-runewidth library. For TruncateLeft function I use here.
But ok I'll write them here as well. I'll do it tomorrow.

[tty2]

@meowgorithm
Done! Check the last test case.

[tty2]

Hi, @meowgorithm
Should I change anything?

[meowgorithm]

Hey, @tty2! Thanks for all your work on this so far. It's going to be a little bit of time until we can give this a proper review, but I promise we'll get to it.

[bobziuchkovski]

We'd absolutely love this functionality as well!

However, I tested this branch and found a potential issue: the rune trimming also trims color codes. The below are a series of screens showing horizontal scroll of a terraform plan that includes colored text:

[kalensk]

It would be great to have this feature as well.