Code Layout

Runebender is one library, one editor, and one website.

What each repository is for

runebender-core	Every operation on a font, the document model, and the runebender command line. No window.
runebender-gpui	The editor. The window, the input, the drawing, and nothing that changes a font.
runebender-dot-org	This site: the documentation, and the browser build of the editor.

The library depends on norad and kurbo. The editor depends on the library and on GPUI. The site depends on neither, and copies the browser build in as a static asset.

If an operation changes a font, or reads one to answer a question, it lives in core.

The test is whether another front-end needs it. Where a click lands is the editor’s business. What that click does to the outline is core’s. An operation in core can be tested in milliseconds without a window. It can also run from the command line, from a script, or from an agent.

Continuous integration keeps the rule honest. Every push to either crate runs the same gate on Linux and macOS.

What CI checks

cargo fmt —check	Formatting is not a review topic.
cargo clippy —all-targets	With warnings denied. Both crates are clean today.
cargo doc —no-deps	With warnings denied, so a broken doc link fails the build.
cargo test	Core: 299 tests. Editor: 38, all of them about the shell itself.
Minimum Rust	Core also builds at the rust-version in its manifest.

Core forbids unsafe in its manifest. The editor denies it, and the two tests that set an environment variable allow it explicitly.

Modules are named for what they do to a font. The crate has no folders below src/ except path/, editing/, and model/. This is the map in src/lib.rs, expanded.

Outline editing

glyph_ops	Point moves, deletion with segment surgery, smooth constraints, pen primitives, shapes, decompose, remove overlap, metrics, kerning.
point_ops, segment_ops	Hit testing and insertion on points and segments.
knife, shape	Slicing, and the rectangle and ellipse primitives.
cleanup	Operations that keep the shape and fix its points: tidy, direction, rounding, extremes, handle fitting.
effects	Operations that make a new shape: offset, extrude, roughen, expand stroke, corner components, bolden.
convert	Quadratic to cubic and back.
embolden	Learn a per-point offset from reference pairs, and apply it.

Reading a font

measure	Stems, sidebearings, joining bands.
optical, spacing	Sampled ink density, and sidebearings checked against the family’s grid.
curve	Curvature: continuity, kinks, extrema.
category, search	Unicode categories, and the glyph search query language.

Lib keys and formats

lib_keys	Every com.runebender.* key: masks, annotations, saved filters, HOI intermediates. One reader and one writer per key.
metrics_keys, mark_color, color_font	The Glyphs and ufo2ft keys the editor shares with other tools.
svg, binary_import, glyphs_import, image_trace	Other formats in and out: SVG, compiled fonts, .glyphs, images.

Families, text, and the document

project	The open document: Master and Project. See the next section.
var_model, composites	Interpolation across a designspace, and components with anchors.
shaping, text	OpenType shaping, and the text-context editing model.
editing/, font_memory, sidebar	Selection, undo, viewport, in-memory fonts, and the glyph grid’s filter data.
theme, theme_oklch	The token file every editor resolves its colours from. See Themes.
bin/runebender	The command line over all of the above.

src/project.rs holds what the editor used to hold on its own.

A Master is one UFO with its bookkeeping and a paint-ready cache. The bookkeeping is which glyphs changed since the last save, and whether kerning did. The cache is a GlyphEntry per glyph, in the order the grid shows. An entry holds the outline as a kurbo path, its points, its anchors, and its ink box. A Project holds the masters, the axes and their locations, the variation model, the named instances, and the sparse brace sources.

Nothing in this layer knows how a glyph is drawn. Names are Arc<str>, not the toolkit’s string type. The front-end reads the cache and paints it, and every front-end gets the same cache.

The editor is one Workspace struct, split across files by concern.

src/

main.rs	The Workspace state, the actions, the menus, the render tree, and main().
commands.rs	One method per user-facing command. The menu item, the shortcut, and the context menu all land here.
canvas.rs	The glyph grid and the editing view: everything painted with paths.
panels.rs	The regions either side of the canvas.
input.rs	Pointer and keyboard on the canvas.
theme.rs	Theme accessors. Call these instead of naming a colour or a radius.
config.rs, journal.rs	The config file, and the operation log.
widgets/	The controls the editor owns: text input, slider, resizable split, and the in-window menu bar for platforms without a native one.
web_host.rs	What the browser build needs and the native build does not.
tests.rs	Tests of the shell itself. Anything checkable without a window belongs in core instead.

The editor imports what it needs from core by name, at the top of main.rs. That list is a fair summary of the seam between the two crates.

Tests live next to the code they test, in a tests module at the bottom of the file.

Core tests that need a real font load Virtua Grotesk from the runebender-web repository, so the crate stays small. src/test_fonts.rs is the one place that knows where. It reads RUNEBENDER_TEST_FONTS, or looks for ../runebender-web/assets/test-fonts beside the checkout, and fails with the expected path when neither exists.

CI checks that repository out beside core, sparse to the fonts.

What a change is expected to do

One file, one concern	A module is named for what it does to a font, and its header comment says so in a sentence.
norad in, norad out	Core functions take norad::Glyph or norad::Font and kurbo geometry, and return the same. No private model.
Report what changed	An operation that edits in place returns whether it changed anything, or how many things it changed.
Document every public item	Say what it does and what the caller is responsible for. A doc comment that names a type wraps it in backticks, because rustdoc treats an angle bracket as HTML.
Keys in one place	A UFO lib key has one constant, one reader, and one writer, in lib_keys or the module for its format.
Commit messages say why	The diff shows what changed. The message records what was wrong and what the change decided.
Builds anywhere	No path to a sibling checkout in a committed file. Local overrides live in a .cargo/config.toml above the repositories.

The rule holds. The shape inside the editor does not yet.

Known, and in order of cost

impl Workspace	About 5,300 lines in one block in main.rs. It is a document, an edit session, a view state, tool state, and a render, all with methods on one struct.
main()	About 1,300 lines. Window setup, key bindings, and file watching share one function.
text	The largest module in core, and the least documented. It began as a port of the web editor’s text buffer.
model/workspace	The old Xilem-era glyph types. They survive only as the intermediate form for hyperbezier conversion in path/.
Two versions of kurbo	The hyperbezier solver is on kurbo 0.9, the rest on 0.13, and path/hyper.rs converts between them.
Missing docs are not enforced	The missing_docs lint is off. Turning it on is the next lint change, after text is documented.
No wasm job in CI	The browser build needs a nightly toolchain and a rebuilt standard library, and is checked by hand.

Core will become a Cargo workspace of small crates, layered the way the Linebender crates are. Each crate is one concept, and depends only on the layer below.

The intended split

path	Contours and points, hyperbeziers, quadratic and cubic conversion. Kurbo only.
font	The document model and every lib key.
ufo	Reading and writing sources. The only crate that names norad.
ops	Every edit: point operations, knife, cleanup, effects, booleans.
analysis	Measurement, optical weight, spacing, curvature. Read only.
text	Shaping and the text buffer.
theme	The token file and its contrast tests.
cli	The runebender binary.

The two moves that made this possible are done: the font operations and the document layer left the editor. The crate boundaries now fall out of what is already separated. What is left is the names, and the order to do it in.