A high-performance terminal emulator for .NET, built with Avalonia UI and optimized for speed and memory efficiency.

Last updated: 2026-06-17

Dotty is a modern terminal emulator composed of:

• Dotty.App — Avalonia-based GUI application with hardware-accelerated rendering
• Dotty.Terminal — High-performance terminal core with zero-allocation parsing
• Dotty.NativePty — POSIX-native PTY helper for proper pseudo-terminal support
• Dotty.Abstractions — Clean interfaces for extensibility

• Hardware-accelerated rendering via SkiaSharp (ligatures, underline styles, rounded corners)
• Optimized ANSI/VT parser with minimal allocations
• Native PTY support on Linux/Unix systems
• Efficient buffer management with scrollback support
• Ligature support via HarfBuzz font shaping
• Undercurl, dotted, and dashed underline rendering
• Rounded rectangle clip regions for modern terminal aesthetics
• Runtime C# configuration hot-reload via CSharpConfigWatcher
• PromptMark (OSC 1337) shell integration for prompt tracking

• .NET 10 SDK (or .NET 9)
• Linux/Unix system (for native PTY support)
• make, gcc/clang

# Build native PTY helper
cd src/Dotty.NativePty && make

# Build solution
cd ../..
dotnet build Dotty.sln -c Release

dotnet run --project src/Dotty.App

dotnet test tests/Dotty.App.Tests

Dotty features a dual configuration system: compile-time C# source generation for zero-overhead defaults, plus runtime C# hot-reload for live configuration changes without restarting.

Dotty automatically creates a configuration project on first run:

• Linux/macOS: ~/.config/dotty/Dotty.UserConfig/
• Windows: %APPDATA%/dotty/Dotty.UserConfig/

The generated project includes:

• Config.cs with sensible defaults (DarkPlus theme, JetBrains Mono 15pt)
• .csproj with NuGet reference to Dotty.Abstractions for full IntelliSense
• Helpful comments explaining all available options

To customize:

# 1. Open the config folder in your IDE
code ~/.config/dotty/Dotty.UserConfig/

# 2. Edit Config.cs (see example below)

# 3. Rebuild dotty to apply changes
dotnet build

Quick Example:

using Dotty.Abstractions.Config;
using Dotty.Abstractions.Themes;

namespace Dotty.UserConfig;

public partial class MyDottyConfig : IDottyConfig
{
    // Font: JetBrains Mono at 14pt
    public string? FontFamily => "JetBrains Mono, Fira Code, monospace";
    public double? FontSize => 14.0;
    
    // Theme: Dracula
    public IColorScheme? Colors => BuiltInThemes.Dracula;
    
    // Cursor: Blinking beam
    public ICursorSettings? Cursor => new CursorSettings
    {
        Shape = CursorShape.Beam,
        Blink = true
    };
}

Dotty watches your Config.cs file and automatically rebuilds + hot-reloads configuration without restarting the application:

# Edit config — changes apply live
code ~/.config/dotty/Dotty.UserConfig/Config.cs

The CSharpConfigWatcher monitors your config file for changes, triggers a background build via the .NET SDK, and pushes the new configuration to the running application through a web socket channel. No restart needed.

• Configuration Guide — Complete user guide with examples and troubleshooting
• Architecture — How the source generator works
• Advanced Topics — Custom themes, transparency, and more

dotty --generate-config  # ⚠️ Overwrites existing config

src/
  Dotty.App/         — Avalonia UI application
  Dotty.Terminal/    — Terminal engine (parsers, buffers, adapters)
  Dotty.NativePty/   — C-based POSIX PTY helper
  Dotty.Abstractions/ — Shared interfaces
tests/               — Unit tests
docs/                — Architecture and implementation docs

• Architecture Overview
• Rendering System
• Parser Implementation
• Native PTY
• Testing
• GUI Harness Benchmarking
• Performance Analysis

MIT License - See License for details.

• Repository: https://github.com/dominic-codespoti/dotty
• Issues: https://github.com/dominic-codespoti/dotty/issues