Introducing lin.el for Emacs

Buffer-local remapping of the hl-line face

2021-11-01

I published a new package which I intend to submit to GNU ELPA sometime before the 10th of November (together with mct.el—see my Emacs packages).

LIN Is Noticeable (aka LIN, lin, lin.el, etc.) remaps hl-line face buffer-locally to a style that is optimal for major modes where line selection is the primary mode of interaction.

Quote from the manual on the rationale for this package:

The idea is that hl-line cannot work equally well for contexts with competing priorities: (i) line selection, or (ii) simple line highlight. In the former case, the current line needs to be made prominent because it carries a specific meaning of some significance in the given context. Whereas in the latter case, the primary mode of interaction does not revolve around the line highlight itself: it may be because the focus is on editing text or reading through the buffer’s contents, so the current line highlight is more of a gentle reminder of the point’s location on the vertical axis.

LIN provides the end-user with the flexibility of optimising for the specifics of each type of interaction. The user must set up the major modes where that is to take effect.

By means of illustration, the default style of the hl-line face in my Modus themes (built into Emacs 28 or higher) is a subtle gray background. While there is the modus-themes-hl-line option to make it more intense, add an accented background, and the like, the fact remains that you still cannot apply a case-by-case approach for different types of line highlighting.

Whereas with LIN, we can keep one style for regular text editing and use lin-mode in contexts where hl-line-mode is meant to be all about line selection, such as in Elfeed and Notmuch buffers.

Here is a sample with the modus-operandi theme, with the top buffer showing the regular hl-line face and the bottom buffer displaying a Notmuch listing with lin-mode enabled (click to enlarge):

LIN’s source code is available on Gitlab: https://gitlab.com/protesilaos/lin. There also exists a Github mirror: https://github.com/protesilaos/lin.