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| Crate | Description |
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| helix-core | Core editing primitives, functional. |
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| helix-syntax | Tree-sitter grammars |
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| helix-lsp | Language server client |
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| helix-view | UI abstractions for use in backends, imperative shell. |
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| helix-term | Terminal UI |
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| helix-tui | TUI primitives, forked from tui-rs, inspired by Cursive |
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This document contains a high-level overview of Helix internals.
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> NOTE: Use `cargo doc --open` for API documentation as well as dependency
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> documentation.
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## Core
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The core contains basic building blocks used to construct the editor. It is
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heavily based on [CodeMirror 6](https://codemirror.net/6/docs/). The primitives
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are functional: most operations won't modify data in place but instead return
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a new copy.
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The main data structure used for representing buffers is a `Rope`. We re-export
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the excellent [ropey](https://github.com/cessen/ropey) library. Ropes are cheap
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to clone, and allow us to easily make snapshots of a text state.
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Multiple selections are a core editing primitive. Document selections are
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represented by a `Selection`. Each `Range` in the selection consists of a moving
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`head` and an immovable `anchor`. A single cursor in the editor is simply
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a selection with a single range, with the head and the anchor in the same
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position.
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Ropes are modified by constructing an OT-like `Transaction`. It's represents
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a single coherent change to the document and can be applied to the rope.
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A transaction can be inverted to produce an undo. Selections and marks can be
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mapped over a transaction to translate to a position in the new text state after
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applying the transaction.
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> NOTE: `Transaction::change`/`Transaction::change_by_selection` is the main
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> interface used to generate text edits.
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`Syntax` is the interface used to interact with tree-sitter ASTs for syntax
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highling and other features.
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## View
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The `view` layer was supposed to be a frontend-agnostic imperative library that
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would build on top of `core` to provide the common editor logic. Currently it's
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tied to the terminal UI.
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A `Document` ties together the `Rope`, `Selection`(s), `Syntax`, document
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`History`, language server (etc.) into a comprehensive representation of an open
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file.
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A `View` represents an open split in the UI. It holds the currently open
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document ID and other related state.
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> NOTE: Multiple views are able to display the same document, so the document
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> contains selections for each view. To retrieve, `document.selection()` takes
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> a `ViewId`.
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The `Editor` holds the global state: all the open documents, a tree
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representation of all the view splits, and a registry of language servers. To
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open or close files, interact with the editor.
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## LSP
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A language server protocol client.
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## Term
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The terminal frontend.
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The `main` function sets up a new `Application` that runs the event loop.
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`commands.rs` is probably the most interesting file. It contains all commands
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(actions tied to keybindings).
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`keymap.rs` links commands to key combinations.
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## TUI / Term
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TODO: document Component and rendering related stuff
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