ASS LSP Server

A Language Server Protocol (LSP) implementation for Advanced SubStation Alpha (ASS/SSA) subtitle format.

Overview

This LSP server provides rich language support for ASS/SSA subtitle files, including syntax highlighting, code completion, hover information, and validation. It's designed to work with any LSP-compatible editor like VS Code, Neovim, Emacs, and others.

Features

• Syntax Validation: Real-time validation of ASS/SSA syntax and structure
• Code Completion: Intelligent autocompletion for:
  • Section headers ([Script Info], [V4+ Styles], [Events], etc.)
  • Override tags (\pos, \move, \c, \t, etc.)
  • Script info properties
  • Style and event format fields
• Hover Information: Detailed documentation for override tags and sections
• Advanced Analysis:
  • Style inheritance validation
  • Timing overlap detection
  • Performance suggestions
• Error Reporting: Clear diagnostics with line numbers and descriptions

Installation

From Source

git clone https://github.com/wiedymi/ass-lsp
cd ass-lsp
cargo build --release

The compiled binary will be available at target/release/ass-lsp.

From Crates.io

cargo install ass-lsp

Usage

VS Code

1. Install the ASS LSP extension from the marketplace
2. The extension will automatically use the LSP server

Neovim

Add this to your Neovim configuration:

local lspconfig = require('lspconfig')

lspconfig.ass_lsp = {
  default_config = {
    cmd = { 'ass-lsp' },
    filetypes = { 'ass', 'ssa' },
    root_dir = function(fname)
      return lspconfig.util.find_git_ancestor(fname) or vim.loop.os_homedir()
    end,
    settings = {},
  },
}

-- Setup the LSP
require('lspconfig').ass_lsp.setup{}

Emacs

Add this to your Emacs configuration:

(use-package lsp-mode
  :config
  (add-to-list 'lsp-language-id-configuration '(ass-mode . "ass"))
  (lsp-register-client
   (make-lsp-client
    :new-connection (lsp-stdio-connection "ass-lsp")
    :major-modes '(ass-mode)
    :server-id 'ass-lsp)))

Generic LSP Client

For any LSP-compatible editor, configure it to:

• Run the command: ass-lsp
• Associate with file extensions: .ass, .ssa
• Use stdio for communication

File Format Support

This LSP server supports:

• Advanced SubStation Alpha (ASS) format
• SubStation Alpha (SSA) format
• All standard sections: Script Info, Styles, Events, Fonts, Graphics
• Override tags and animations
• Style inheritance and references

Development

Prerequisites

• Rust 1.70+
• Cargo

Building

cargo build

Testing

cargo test

Running in Development

cargo run

Configuration

The LSP server currently runs with default settings. Future versions may support configuration files for customizing behavior.

Contributing

Contributions are welcome! Please feel free to submit issues and pull requests.

License

This project is licensed under the MIT License - see the LICENSE file for details.

Supported Override Tags

The LSP provides completion and documentation for all standard ASS override tags:

• Position & Movement: \pos, \move, \org, \clip
• Fonts & Text: \fn, \fs, \fsp, \fscx, \fscy
• Colors: \c, \1c, \2c, \3c, \4c, \alpha, \1a, \2a, \3a, \4a
• Animation: \t, \fade, \fad
• Rotation: \frx, \fry, \frz
• Borders & Shadows: \bord, \shad, \be, \blur
• Layout: \an, \a, \q, \r
• Effects: \k, \kf, \ko, \kt

Troubleshooting

LSP Server Not Starting

1. Ensure the ass-lsp binary is in your PATH
2. Check that your editor is configured to run the LSP for .ass and .ssa files
3. Look at your editor's LSP logs for error messages

No Completions Showing

1. Make sure your file has the correct extension (.ass or .ssa)
2. Try triggering completion manually (usually Ctrl+Space)
3. Check that the LSP server is running and connected

Performance Issues

For large subtitle files, you may experience slower response times. The LSP includes performance monitoring and will provide suggestions for optimization.