Rainbow & tree-sitter

Macros colors nested brackets by their nesting depth — rainbow delimiters — using the live tree-sitter parse tree rather than raw characters. Because it asks the grammar for bracket nodes, brackets inside strings and comments are skipped automatically. That makes it correct for non-Lisp languages (C, JS, Rust, …) as well as S-expression languages.

It's off by default. Once enabled, it paints when a file opens and repaints (debounced) as you type.

Configuration#

All settable from your init.scm (loaded after the built-in defaults):

;; Palette — any length; brackets cycle through it by depth.
(rainbow-set-colors '("#ff5555" "#50fa7b" "#bd93f9"))

;; Live-refresh debounce, in milliseconds.
(rainbow-set-delay 150)

;; Turn it on (it's off by default).
(rainbow-enable)

Interactively: M-x rainbow-delimiters toggles it, and rainbow-refresh repaints the current buffer.

The palette is registered as theme faces rainbow-1 … rainbow-N, so a theme can also define these colors.

Sharing the overlay layer#

Rainbow uses overlay faces, the same layer used by LSP semantic tokens, Org headings, and Magit diff accents. Two features painting that layer in one buffer will conflict — so if you enable semantic tokens for a language, disable rainbow for that buffer (or vice versa). Rainbow already skips .org buffers so it never fights Org fontification.

The tree-sitter bridge#

Rainbow is built on a general bridge that exposes the parse tree to Scheme:

• tree-sitter-query — run a query against the buffer's parse tree (async, with a callback).
• tree-sitter-node-at — get the syntax node at a position.

These let you write your own structural features — structural motion, context-aware indentation, custom highlighting — on the same incremental parse tree the editor maintains. rainbow.scm in the source is a compact, readable example to start from. For adding highlighting to a new file type, bundling a grammar, and building a major mode, see Languages & modes; for the primitives, Scripting with Steel.