✨ Code Folding

[gaetgu]

Description

Code folding allows developers to collapse and expand sections of code (such as functions, classes, conditionals, and comments) to reduce visual clutter and focus on the parts they’re working on. This feature is particularly useful when navigating large files or deeply nested structures.

Proposed Behavior

• Enable folding for code blocks such as:
  • Functions and methods
  • Classes and structs
  • Loops and conditionals
  • Multi-line comments and regions
• Display a vertical folding ribbon in the gutter next to line numbers, where users can click to collapse or expand blocks.
• Collapsed blocks should show an inline indicator with an expand toggle.
• Optionally, include editor commands for fold all / unfold all.

Implementation Notes

• Can be powered by the existing Tree-sitter syntax trees to determine foldable ranges based on code structure.
• Should maintain fold state across file/tab switches and ideally across sessions.
• Folding ribbon interactions should be smooth and intuitive, with hover states and visual cues.
• Should add animation for folding and unfolding to make transitions feel natural and responsive.

Benefits

• Reduces visual noise and helps maintain focus while editing.
• Makes it easier to navigate and manage large files.
• Provides a cleaner overview of structural code layout.

Additional Context

The folding ribbon provides a familiar and discoverable UI for interacting with folded sections and complements keyboard or menu-based folding commands.

Screenshots

https://user-images.githubusercontent.com/47652746/164981601-56c531e4-9420-4d46-96d7-f9d8456e5821.mov

Additional Screenshots

Hover:

Clicked (folded code):

dark and light mode:

In Progress TODOs

• [x] Fold Ribbon
  • [x] Draw nested folds
  • [x] Draw adjacent folds with a horizontal line (instead of overlapping rounded edges)
  • [x] Draw folded ranges
• [x] Fold Model
  • [x] Generate folds from a provider for a document
  • [x] Update folds as a document is edited
• [ ] Fold Providers
  • [x] Line indent provider
  • [ ] TreeSitter provider
• [ ] Perform Folding
  • [x] Draw text attachment for fold range
  • [ ] Animate folded text

[gaetgu]

I have been messing around with CoreGraphics a little bit, and it looks like the ribbon is a gray (in light mode), transparent line with a width of 7 (not 6 or 8, which I find strange) and a round cap. They also have a very fine white stroke around the edge. My experiments are not that great and I can't quite get them to play nice with SwiftUI views, but I thought I would leave that basic information here in case it helps.

[nanashili]

I have been messing around with CoreGraphics a little bit, and it looks like the ribbon is a gray (in light mode), transparent line with a width of 7 (not 6 or 8, which I find strange) and a round cap. They also have a very fine white stroke around the edge. My experiments are not that great and I can't quite get them to play nice with SwiftUI views, but I thought I would leave that basic information here in case it helps.

Apple likes using odd numbers in everything

[austincondiff]

I never understood this. I typically like designing in multiples of 2 (2, 4, 8, 12, 16, 20, 24, 32, 40, 48, 56, 64, 72, 80, 96, 104, etc.) because they can always divide into two without falling on a subpixel. This is especially helpful when dealing with responsive layouts and 1x and 2x densities. I think Apple chooses to design in odd numbers so that it can always have a center pixel.

[austincondiff]

This may require #127 to be complete in order to begin working on this.