feat: Use custom character to draw editor rulers

[dylangiles]

This pull request adds functionality requested in #5190.

The user may specify a character that is used when rendering rulers, instead of colouring a line in the editor. The default behaviour is retained - if the user does not specify the ruler character config, the original behaviour is used. This functionality will be useful for users that want to, for example, use a box-drawing character to draw the ruler.

Please feel free to make suggestions and comments on my pull request, as it is my first time contributing to Helix. Additionally, I would like to thank the Helix project for making an awesome piece of software that has helped with my daily tasks.

Example config:

[editor]
ruler = [70]
ruler-char = '│'

Screenshot:

[pascalkuthe]

hmm I am not sure about this one. This will draw over any rendered text (so if you write to the ruler the text there is hidden). A similar issues already occurs with rulers hiding cursors.

IMO the right solution is to use the new infrastructure in #6417 and render the rulers before the text and the ruler highlights after the text highlights but before the selection highlights

[the-mikedavis]

I'm also unsure of this but for a different reason. This will introduce some issues with the theming for rulers, sort of opposite of the problem we have now in #5721. Themes should define rulers with background colors rather than foreground colors. If you configure a ruler-char with this change though you want the ruler's foreground to be themed rather than the background though. So themes will either look wrong if you have ruler-char set or if you don't.

[the-mikedavis]

This is unnecessary because the struct is tagged with #[serde(rename_all = "kebab-case")]

[the-mikedavis]

This should be reset

[the-mikedavis]

No need to reformat the tables, let's leave them as-is. Reformatting them inflates the diff and may introduce conflicts with other PRs that touch these docs

[codingjerk]

Can I continue working on this PR? I want to use character rulers myself a lot.

@the-mikedavis, what are the problems right now?

1. Styling issues

• Reformatted table @ book/src/configuration.md
• Unnecessary removal of newline @ helix-core/src/syntax.rs
• Unnecessary rename annotation @ helix-view/src/editor.rs

2. Problem with themes: background vs foreground color
3. Drawing ruler under the text

Anything else?

[codingjerk]

I played with code a bit and I have some points here, except styling related, since they are trivial:

1. For themes, I think it will be better to introduce another theme in addition to ui.virtual.ruler, like ui.virtual.ruler.char or ui.virtual.ruler-char when editor.ruler-char is set.
2. To draw ruler under text I simply move render_rulers call before render_document. This change will be required if we will use DecorationManager for rulers in future anyway. Cause render_document takes ownership on it.

For now it looks great on my setup, I would like to send PR.

I'm not completely happy with rendering code and introducing two separate theme keys tho. So I would appreciate any help.

[codingjerk]

I created a PR #11798 and I suggest moving further work there