A VS Code extension for the FastLED WASM compiler that allows you to compile and run FastLED sketches directly in your browser.

Target-specific VSIX packages contain a verified native clangd server for Windows x64/ARM64, Linux x64/ARM64, and macOS x64/ARM64. The universal VSIX is intentionally offline-only: it contains no server and reports a structured universal-package result to the extension API. No package downloads clangd, searches PATH, or modifies dynamic-library environment variables at runtime.

To reproduce a package locally (Node 22 and uv required):

cd vscode-plugin
npm ci
python scripts/package_extension.py --target win32-x64 --out dist
python scripts/package_extension.py --target universal --out dist

Use FastLED: Show Bundled clangd Diagnostics to see the resolved target, version and path, or a non-sensitive structured failure reason. Delete resources/clangd (or run python scripts/ingest_clangd.py --clean --output resources/clangd) if an interrupted local package needs to be reset. The artifact lock is intentionally pinned to clang-tool-chain-bins 0.4.6; updating clangd requires changing that reviewed lock rather than resolving a latest version.

FastLED configures one C/C++ language engine for the whole VS Code window. The extension pack installs both the LLVM clangd and Microsoft C/C++ extensions, but it deliberately never leaves both language services active for the same sketch:

• auto (default) uses the native clangd bundled in a platform VSIX when the clangd VS Code extension is available; otherwise it uses Microsoft C/C++.
• clangd, cpptools, and off are explicit choices in the fastled.intelliSenseEngine setting.
• FastLED: Refresh IntelliSense Configuration regenerates the compile_commands.json, .clangd, .vscode/settings.json, and .vscode/c_cpp_properties.json files for every FastLED sketch folder.

The generated settings associate .ino files with C++, while FastLED keeps a preprocessed live snapshot and prototype prelude current for unsaved Arduino tabs. After opening a Blink sketch, use Go to Definition on CRGB, FastLED, or FastLED.addLeds; the result should open the materialized FastLED headers. Use View: Output → FastLED WASM to inspect engine selection and setup failures.

• One-click compilation: Compile and run FastLED sketches with a single command
• Multiple build modes: Quick, Debug, and Release compilation modes
• Project initialization: Initialize new FastLED projects with example sketches
• Server management: Start and stop the FastLED compiler server
• Syntax highlighting: Full syntax highlighting for Arduino (.ino) files with FastLED-specific keywords
• Code snippets: Common FastLED patterns and boilerplate code
• Browser integration: Automatically open compiled results in your browser
• File watching: Automatic recompilation on file changes (when supported)

• FastLED WASM compiler must be installed and available in your PATH
• Docker (recommended for local compilation) or internet connection for web compiler

1. Open VS Code
2. Go to Extensions (Ctrl+Shift+X)
3. Search for "FastLED WASM"
4. Click Install

1. Clone this repository
2. Navigate to the vscode-plugin directory
3. Run npm install
4. Run npm run compile
5. Press F5 to open a new Extension Development Host window

Access all commands via the Command Palette (Ctrl+Shift+P) or through the context menu:

• FastLED: Compile & Run - Compile the current sketch and open in browser
• FastLED: Compile & Run (Quick Mode) - Fast compilation with minimal optimizations
• FastLED: Compile & Run (Web Compiler) - Use the online web compiler
• FastLED: Just Compile (No Browser) - Compile without opening browser

• FastLED: Initialize New Project - Create a new FastLED project with example code
• FastLED: Open FastLED Output in Browser - Open the last compiled output

• FastLED: Start Compiler Server - Start a local FastLED compiler server
• FastLED: Stop Compiler Server - Stop the running server

• FastLED: Update Compiler - Update the FastLED compiler to the latest version
• FastLED: Purge Docker Containers - Clean up FastLED Docker containers and images

Configure the extension through VS Code Settings (File > Preferences > Settings, search for "FastLED"):

• Default Compile Mode: Choose between quick, debug, or release mode (default: quick)
• Auto Open Browser: Automatically open browser after compilation (default: true)
• Use Web Compiler: Use web compiler by default instead of local Docker (default: false)
• Web Compiler URL: URL for the web compiler (default: https://fastled.onrender.com)
• Watch Files: Enable file watching for automatic recompilation (default: true)

1. Open a folder containing FastLED sketches (.ino files)
2. The extension will automatically detect FastLED projects
3. Use FastLED: Compile & Run to compile and view your sketch

1. Open an empty folder in VS Code
2. Run FastLED: Initialize New Project
3. Select an example from the list
4. The project will be initialized with the selected example

1. Open a FastLED sketch (.ino file)
2. Right-click in the editor and select FastLED: Compile & Run
3. Or use the Command Palette (Ctrl+Shift+P) and search for FastLED commands
4. The compiled output will open in your default browser

The extension provides comprehensive syntax highlighting for:

• Standard Arduino functions (setup, loop, pinMode, digitalWrite, etc.)
• FastLED types (CRGB, CHSV, CRGBPalette16, etc.)
• FastLED functions (addLeds, show, setBrightness, fill_solid, etc.)
• FastLED constants (WS2812B, APA102, color names, etc.)

Type these prefixes and press Tab to expand:

• fastled-setup - Basic FastLED setup with common configuration
• fastled-clock - FastLED setup with clock pin for APA102/DotStar LEDs
• fill-solid - Fill all LEDs with solid color
• fill-rainbow - Fill LEDs with rainbow colors
• every-n-ms - Execute code every N milliseconds
• fade-black - Fade all LEDs toward black
• beatsin8 - 8-bit sine wave that cycles with a given BPM
• random-color - Generate a random RGB color
• hsv-color - Create HSV color
• palette-color - Get color from palette
• fire-effect - Simple fire effect
• sparkle-effect - Sparkle effect with fade
• wave-effect - Simple wave effect

Make sure the FastLED WASM compiler is installed and available in your PATH:

npm install -g fastled
# or
pip install fastled

If you're having issues with local compilation:

1. Make sure Docker is installed and running
2. Try using the web compiler with FastLED: Compile & Run (Web Compiler)
3. Use FastLED: Update Compiler to get the latest version

1. Check the Output panel (View > Output, select "FastLED WASM")
2. Ensure your sketch directory contains a valid .ino file
3. Try FastLED: Update Compiler if you're using an older version

This extension is part of the FastLED WASM project.

To contribute:

1. Fork the repository
2. Make your changes in the vscode-plugin directory
3. Test your changes
4. Submit a pull request

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

• FastLED WASM Compiler
• FastLED Library
• Online Demo