What do you say when someone asks you: "where's your cursor?" Probably something like "line 18", or if you're feeling go

Zed Decoded: Text Coordinate Systems

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2024-07-07 12:00:04

What do you say when someone asks you: "where's your cursor?" Probably something like "line 18", or if you're feeling good that day and it's a single digit you might add the column too: "line 18, column 5." Lines and columns — simple, easy.

Text editors, Zed included, also use lines and columns to describe positions, but — to my surprise when I first explored Zed's codebase — there's quite a few other coordinate systems in Zed. There are offsets, offsets in UTF-16, display points, and anchors.

To finally understand these different text coordinate systems and when which one is is used, I talked to Nathan and Antonio, two of Zed's co-founders, and asked them to walk me through it all, from Point to DisplayPoint to Anchor.

This post comes with a 1hr companion video, in which Thorsten, Nathan, and Antonio start by writing some tests around Points and Offsets and then venture into DisplayPoint and Anchor land.