Polymode: Multiple Major Modes and How to Use SQL and Python in one Buffer - Mastering Emacs

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2023-02-04 19:00:17

How do you mix and match programming languages in the same buffer? That is a question that Emacs users have struggled with in ever-greater numbers as programming languages meld together in spaghetti-like ways: Templating Languages and Code; Documentation and Code; Code and more Code. Most of us have to deal with a soup of Jinja and YAML; Javascript and HTML; and so on – and that presents a number of unique challenges to text editors.

The answer – one of several, as is Emacs’s wont – is Polymode. Polymode seamlessly blends two or more major modes together in the same buffer. Now to understand why that is interesting, a quick history lesson…

Back in the day, the idea of buffers having ephemeral “modes” that you can activate and deactivate at will was a bit of a revelation, and one that drove the design of many other editors — even if they never really adopted the same flexibility as Emacs.

You have one major mode, and it would drive the bulk of your interactions with that buffer: it would font lock (syntax highlight), bind keys to helper commands, manage the indentation, and other mode-specific tasks. All of it supported by generous helpings of gnarly regexp, for font locking, and dastardly arcane elisp for the indentation (anyone who doubts me is encouraged to peruse the C mode’s indentation engine, weighing in at half a meg of elisp.)