Editor

Active contributors: Veykril, SomeoneToIgnore, ConradIrwin, mikayla-maki

Purpose

crates/editor is the editor view. At ~147k LOC it is the largest crate in the workspace. It renders a MultiBuffer with cursors, selections, decorations, completions, hover popovers, signature help, code actions, inline diagnostics, and the rest of the surface a code editor exposes. Most editor-facing features live here or in adjacent UI crates.

Directory layout

crates/editor/                         ~147k LOC
├── Cargo.toml
├── benches/                           # Hot-path benchmarks
└── src/
    ├── editor.rs                      # Module root
    ├── element.rs                     # The GPUI Element implementation that draws editors
    ├── display_map/                   # Buffer offsets ↔ display rows/columns
    ├── selection_history.rs           # Undo/redo for selections
    ├── inlay_hint_cache.rs            # LSP inlay hints
    ├── code_actions.rs                # Quick-fixes, refactors
    ├── lsp/                           # Editor-side LSP integration (completions, hover, …)
    ├── git/                           # Inline blame, hunk gutter
    └── ...                            # 100+ modules

crates/multi_buffer/                   # The "logical" buffer
crates/text/                           # CRDT text buffer (offsets, anchors, history)
crates/rope/                           # Underlying rope data structure
crates/buffer_diff/                    # Diff between two buffers (used for git, agent edits, …)

Key abstractions

Type	File	Description
Editor	crates/editor/src/editor.rs	The view entity
EditorElement	crates/editor/src/element.rs	The GPUI Element that paints an editor
MultiBuffer	crates/multi_buffer/src/multi_buffer.rs	A logical buffer composed of excerpts from multiple Buffers
Buffer	crates/language/src/buffer.rs	A single text file, with text + syntax + diagnostics
DisplayMap	crates/editor/src/display_map.rs	Wrapping, folds, inlay hints, blocks
Anchor	crates/text/src/anchor.rs, crates/multi_buffer/src/anchor.rs	Edit-resilient positions
Selection	crates/editor/src/editor.rs	A (start, end, head) range
Rope	crates/rope/src/rope.rs	Persistent rope of UTF-8 chunks
BufferDiff	crates/buffer_diff/src/buffer_diff.rs	Per-line diff state

How it works

graph TD
    P[Project] -->|provides Buffer| MB[MultiBuffer]
    MB -->|excerpts| E[Editor]
    E -->|render| EE[EditorElement]
    EE -->|paint| W[Window]
    LSP[LSP] -->|completions, diagnostics| E
    Tree[tree-sitter] -->|syntax highlighting| MB
    Git[GitStore] -->|hunk diffs| E
    Agent[Agent] -->|streamed edits| E
    User[User input] -->|key events| EE
    EE --> E

Display map

DisplayMap is the layer that translates between buffer space (UTF-8 byte offsets in the underlying Buffer) and display space (rows/columns of what the user actually sees). It accounts for:

• Soft wrap.
• Folds (collapsed regions).
• Inlay hints (LSP-provided ghost text).
• Block decorations (e.g. expanded diagnostic, agent message).
• Replacement folds (e.g. summarised function bodies).

Most rendering code works in display space; most semantic code works in buffer space.

Selections and cursors

A single Editor can have arbitrarily many selections (multi-cursor). Each is a Selection with start, end, and head (the active end, where the cursor sits). Mutations preserve selection invariants by mapping anchors through edits.

MultiBuffer

A MultiBuffer is one logical document made of excerpts pulled from many Buffers. It powers:

• Search results across files.
• Diagnostic panels.
• Project-wide code-actions.
• Git diff views.
• The agent's "files I edited" view (acp_thread::ThreadFileEdits).

Edits in a MultiBuffer route back into the underlying Buffers, so a save still writes to the original files.

Tree-sitter integration

Syntax trees live on the Buffer (in crates/language) and update incrementally as text changes. The editor reads the tree to drive highlighting, brackets, smart indent, and outline.

Integration points

• Below: multi_buffer, text, rope, buffer_diff, language, tree-sitter.
• Sibling: crates/git_ui (for hunk gutter), crates/diagnostics (for inline diagnostics), crates/code_actions (where applicable).
• Above: crates/workspace for tab/pane management.

Entry points for modification

• New decoration kind — crates/editor/src/display_map/.
• New cursor / selection action — extend the action set in crates/editor/src/editor.rs. Wire up to keymaps in assets/keymaps/.
• New LSP capability surfacing — crates/editor/src/lsp/.
• Tweak rendering hot paths — crates/editor/src/element.rs plus the benches.

Related pages

• Project — supplies buffers
• Language services — supplies syntax + per-language behaviour
• LSP — supplies semantic features
• Vim mode — modal layer over Editor