eglot-inactive-regions

Emacs Eglot extension to visually style inactive preprocessor branches.

Highlights inactive code in a LSP aware way, taking into account compile time includes and defines for current project.

Features

• Visual indication of inactive code: dimmed colors, shaded background or custom face can be used to quickly identify disabled code sections.
• Automatic integration with eglot when the eglot-inactive-regions-mode global minor mode is enabled.

Shading styles

• darken-foreground dims inactive code foreground colors
• shade-background shades inactive code background (similar to eclipse style)
• shadow-face applies the shadow face (or any face you like) to inactive code sections

Supported servers

• clangd (since clangd-17) with inactiveRegions extension
• ccls with skippedRanges extension. Still experimenting with this. Poorly documented, seems to emit notifications only on file save, feedback welcome!

Screenshots

darken-foreground style, gruvbox dark theme, 30% opacity

Inactive regions are provided by the language server so they will honor your include paths and compile time defines. Here I'm looking at my emacs-29 branch configured to build on MacOS and you can see Windows code is correctly disabled.

shade-background style, modus operandi theme, 10% shading

Requirements

• emacs 29.1+
• clangd with inactiveRegions support (clangd-17+)
• ccls with skippedRanges support

Installation

It's in NonGNU ELPA so you can just install it with Emacs built-in package manager from M-x list-packages or just add it to your configuration with use-package as described below.

Usage

(use-package eglot-inactive-regions
  :custom
  (eglot-inactive-regions-style 'darken-foreground)
  (eglot-inactive-regions-opacity 0.4)
  :config
  (eglot-inactive-regions-mode 1))

Customization

M-x customize-group inactive-regions can be used to select the preferred shading style, customize text opacity and background shading or customize the base faces.

Caveats

As far as I know Emacs doesn't have a way to set foreground text opacity. Best would be a face attribute so that you can set it in an overlay covering each inactive region and be done with it. Unfortunately there is no attribute for this yet.

Hence darken-foreground style is a probably fragile and inefficient hack around fontification: for each inactive region it looks for symbols with different faces and applies to each of them a different overlay with a dimmed foreground color.

It seems to work with cc and c-ts modes and I've been using it daily for more than a year now, but could totally break other modes or features I'm not aware of.

If you know a better way please do let me know.