zgui-editor

An embeddable, high-performance code editor component for Zgui applications — from a small syntax-highlighted field inside another app up to the foundation of a full editor or IDE.

use zgui::prelude::*;
use zgui_editor::{Editor, EditorProps};

view! {
    Editor(class = "my-editor", text = source, language = "rust")
}

What it does

• Very large files. One retained element paints only the visible lines; the scroll model is the editor's own f64 fractional line, so a ten-million-line buffer scrolls to pixel precision and a keystroke costs a keystroke. The buffer is a rope (ropey); snapshots for background work are O(1).
• Tree-sitter highlighting, incrementally. A worker thread owns the parser and the tree; edits cross as tree.edit deltas, queries run only over the viewport (± overscan), and stale results are dropped by revision. Grammars are pluggable through LanguageRegistry; common ones are bundled behind cargo features (lang-rust, lang-toml, lang-markdown).
• App-definable key handling. An on_key filter hears every key before the editor does. The bundled vim example (examples/vim) implements modal editing — counts, operators, registers, / search — entirely outside the component, over the public Command vocabulary and the synchronous EditorHandle::query API.
• Editing model. Multi-cursor-capable selections, grapheme-aware movement, vim-style undo coalescing, word motions, plain-text search.
• One buffer, several windows. A Document handed to two Editors is two views of one file: an edit in either is the edit, either can undo it, and each keeps its own carets, scroll position and theme. A change reports the replacements that made it, in the order they applied — which is what a language server's incremental synchronisation is.
• Marks an application draws. Named layers of bands, squiggles and gutter marks, each naming a custom property of its own, so diagnostics, search hits and git hunks replace one at a time. point_for_byte turns a byte into a place on the window, which is what a hover card, an inline diagnostic or a leap label is positioned by.
• Mouse. Click/drag selection with pointer capture and edge autoscroll, double-click word and triple-click line selection, middle-click primary-selection paste on Linux, scrollbar dragging.
• Smooth scrolling. Wheel input glides (critically-damped), trackpads track exactly, scrolloff-style caret margins are configurable.
• Line numbers. Absolute, relative (vim-style), or none.
• Completion popovers. The caret's window rectangle is a signal (handle.caret_rect()), edits and selection moves are events, and the key filter lets an open popover steal its keys — see examples/completion.rs.

Theming is CSS

The element's color is the text and its background is the background; everything else is a custom property, inheriting through the cascade like any other:

.my-editor {
    font-family: 'JetBrains Mono', monospace;
    font-size: 14px;
    tab-size: 4;
    --editor-selection: rgba(137, 180, 250, 0.3);
    --editor-cursor: #f5e0dc;
    --editor-current-line: rgba(88, 91, 112, 0.35);
    --editor-gutter-fg: #6c7086;
    --syntax-keyword: #cba6f7;
    --syntax-function: #89b4fa;
    --syntax-string: #a6e3a1;
    --syntax-comment: #6c7086;
}

Syntax colours map from tree-sitter capture names with dots as hyphens (function.method → --syntax-function-method), falling back along the dots and then to the foreground.

Driving it

Everything is a Command, applied through the EditorHandle delivered by on_ready (and via local context). The handle also answers synchronous reads — query(|snapshot| ...) exposes the rope, the selections, motion ranges, and search — and publishes signals (cursor_position(), scroll_state(), caret_rect(), revision()) for status lines and custom chrome.

Examples

cargo run --example basic --features lang-rust [-- path/to/file]
cargo run --example vim --features lang-rust [-- path/to/file]
cargo run --example completion --features lang-rust

Known limitations

• IME: input methods do not compose over the editor yet. The platform only starts compositions over the runtime's intrinsic editable elements; see src/ime.rs for the limitation and the upstream path. Dead-key composition works.
• No soft wrap: long lines scroll horizontally. The line cache and scroll model keep the seam open for it.
• Injections (markdown embedding rust) are parsed single-layer for now.

Development

The framework is pre-1.0; .cargo/config.toml patches the git dependencies to a local checkout. Tests run headlessly:

cargo test --all-features            # unit + component + pipeline tests
cargo test --example vim --features lang-rust   # the vim layer, end to end