Syntax Highlighting

Full-file syntax highlighting for source code files in Ferrite's raw editor mode.

Overview

Ferrite now supports syntax highlighting for source code files (Rust, Python, JavaScript, etc.) in the raw editor mode. This feature uses the existing syntect library that was previously only used for code blocks in markdown preview.

Supported Languages

The following file extensions are supported:

Category	Extensions
Systems	.rs (Rust), .c, .cpp, .h, .hpp, .go, .swift
Web	.js, .ts, .tsx, .jsx, .html, .css, .scss, .sass, .less
Scripting	.py, .rb, .php, .lua, .pl, .sh, .bash, .ps1
JVM	.java, .kt, .scala, .clj
Data	.json, .yaml, .yml, .toml, .xml
Functional	.hs, .ex, .exs, .erl
Other	.sql, .vim, .diff, .ini, .cmake, .dockerfile, .makefile

Usage

Enabling/Disabling

1. Open Settings (Ctrl+,)
2. Navigate to the Editor section
3. Toggle Syntax Highlighting checkbox

The setting is enabled by default.

How It Works

• When you open a source code file, Ferrite detects the language from the file extension
• If syntax highlighting is enabled and the language is recognized, the editor applies colored text formatting
• Syntax colors automatically adapt to light/dark theme (using base16-ocean.dark for dark mode and InspiredGitHub for light mode)
• Markdown files are handled separately by the rendered/WYSIWYG editor, so syntax highlighting only affects other file types in raw mode

Implementation Details

Files Modified

File	Changes
src/config/settings.rs	Added syntax_highlighting_enabled: bool setting
src/ui/settings.rs	Added checkbox in Editor section
src/markdown/syntax.rs	Added language_from_path() and can_highlight_file() helpers
src/editor/widget.rs	Modified layouter to use syntax highlighting
src/app.rs	Passed syntax highlighting config to EditorWidget

Key Components

1. Language Detection: language_from_path() in syntax.rs maps file extensions to syntect language identifiers

2. Highlighter Integration: The EditorWidget layouter creates a colored LayoutJob using highlight_code() when a language is detected

3. Theme Selection: Dark mode uses base16-ocean.dark, light mode uses InspiredGitHub

Performance Considerations

• Caching: Highlighted output is cached in egui's memory and only regenerated when content changes (detected via content hash). This makes static viewing essentially zero-cost.
• The syntect SyntaxSet and ThemeSet are loaded once globally and reused
• Cache is keyed by (editor_id, content_hash, language, dark_mode) for correctness

Testing

1. Open a .rs, .py, .js, or .json file
2. Verify syntax colors appear (keywords, strings, comments should have distinct colors)
3. Toggle setting off in Settings → Editor → Syntax Highlighting
4. Colors should disappear (plain text)
5. Switch between light/dark theme - colors should adapt

Known Limitations

• Bold/italic font styles from syntect are not applied (egui TextFormat limitation)
• No per-file-type theme customization (uses global dark/light themes)
• Initial highlighting of very large files (>10,000 lines) may take a moment on first open