Terminal.Gui/docfx/docs/drivers.md

Cross-Platform Driver Model

Overview

The driver model is the mechanism by which Terminal.Gui supports multiple platforms. Windows, Mac, Linux, and unit test environments are all supported through a modular, component-based architecture.

Terminal.Gui v2 uses a sophisticated driver architecture that separates concerns and enables platform-specific optimizations while maintaining a consistent API. The architecture is based on the Component Factory pattern and uses multi-threading to ensure responsive input handling.

Available Drivers

Terminal.Gui provides console driver implementations optimized for different platforms:

• DotNetDriver (dotnet) - A cross-platform driver that uses the .NET System.Console API. Works on all platforms (Windows, macOS, Linux). Best for maximum compatibility.
• WindowsDriver (windows) - A Windows-optimized driver that uses native Windows Console APIs for enhanced performance and platform-specific features.
• UnixDriver (unix) - A Unix/Linux/macOS-optimized driver that uses platform-specific APIs for better integration and performance.
• FakeDriver (fake) - A mock driver designed for unit testing. Simulates console behavior without requiring a real terminal.

Automatic Driver Selection

The appropriate driver is automatically selected based on the platform when you call Application.Init():

• Windows (Win32NT, Win32S, Win32Windows) → WindowsDriver
• Unix/Linux/macOS → UnixDriver

Explicit Driver Selection

You can explicitly specify a driver in three ways:

// Method 1: Set ForceDriver property before Init
Application.ForceDriver = "dotnet";
Application.Init();

// Method 2: Pass driver name to Init
Application.Init(driverName: "unix");

// Method 3: Pass a custom IConsoleDriver instance
var customDriver = new MyCustomDriver();
Application.Init(driver: customDriver);

Valid driver names: "dotnet", "windows", "unix", "fake"

Architecture

Component Factory Pattern

The v2 driver architecture uses the Component Factory pattern to create platform-specific components. Each driver has a corresponding factory:

• NetComponentFactory - Creates components for DotNetDriver
• WindowsComponentFactory - Creates components for WindowsDriver
• UnixComponentFactory - Creates components for UnixDriver
• FakeComponentFactory - Creates components for FakeDriver

Core Components

Each driver is composed of specialized components, each with a single responsibility:

IConsoleInput<T>

Reads raw console input events from the terminal. The generic type T represents the platform-specific input type:

• ConsoleKeyInfo for DotNetDriver and FakeDriver
• WindowsConsole.InputRecord for WindowsDriver
• char for UnixDriver

Runs on a dedicated input thread to avoid blocking the UI.

IConsoleOutput

Renders the output buffer to the terminal. Handles:

• Writing text and ANSI escape sequences
• Setting cursor position
• Managing cursor visibility
• Detecting terminal window size

IInputProcessor

Translates raw console input into Terminal.Gui events:

• Converts raw input to Key events (handles keyboard input)
• Parses ANSI escape sequences (mouse events, special keys)
• Generates MouseEventArgs for mouse input
• Handles platform-specific key mappings

IOutputBuffer

Manages the screen buffer and drawing operations:

• Maintains the Contents array (what should be displayed)
• Provides methods like AddRune(), AddStr(), Move(), FillRect()
• Handles clipping regions
• Tracks dirty regions for efficient rendering

IWindowSizeMonitor

Detects terminal size changes and raises SizeChanged events when the terminal is resized.

ConsoleDriverFacade<T>

A unified facade that implements IConsoleDriver and coordinates all the components. This is what gets assigned to Application.Driver.

Threading Model

The driver architecture employs a multi-threaded design for optimal responsiveness:

┌─────────────────────────────────────────────┐
│         ApplicationImpl.Init()              │
│  Creates MainLoopCoordinator<T> with        │
│  ComponentFactory<T>                        │
└────────────────┬────────────────────────────┘
                 │
                 ├──────────────────┬───────────────────┐
                 │                  │                   │
        ┌────────▼────────┐ ┌──────▼─────────┐ ┌──────▼──────────┐
        │  Input Thread   │ │  Main UI Thread│ │ ConsoleDriver   │
        │                 │ │                 │ │   Facade        │
        │ IConsoleInput   │ │ ApplicationMain│ │                 │
        │ reads console   │ │ Loop processes │ │ Coordinates all │
        │ input async     │ │ events, layout,│ │ components      │
        │ into queue      │ │ and rendering  │ │                 │
        └─────────────────┘ └────────────────┘ └─────────────────┘

• Input Thread: Started by MainLoopCoordinator, runs IConsoleInput.Run() which continuously reads console input and queues it into a thread-safe ConcurrentQueue<T>.

• Main UI Thread: Runs ApplicationMainLoop.Iteration() which:

  1. Processes input from the queue via IInputProcessor
  2. Executes timeout callbacks
  3. Checks for UI changes (layout/drawing)
  4. Renders updates via IConsoleOutput

This separation ensures that input is never lost and the UI remains responsive during intensive operations.

Initialization Flow

When you call Application.Init():

1. ApplicationImpl.Init() is invoked
2. Creates a MainLoopCoordinator<T> with the appropriate ComponentFactory<T>
3. MainLoopCoordinator.StartAsync() begins:
   • Starts the input thread which creates IConsoleInput<T>
   • Initializes the main UI loop which creates IConsoleOutput
   • Creates ConsoleDriverFacade<T> and assigns to Application.Driver
   • Waits for both threads to be ready
4. Returns control to the application

Shutdown Flow

When Application.Shutdown() is called:

1. Cancellation token is triggered
2. Input thread exits its read loop
3. IConsoleOutput is disposed
4. Main thread waits for input thread to complete
5. All resources are cleaned up

Component Interfaces

IConsoleDriver

The main driver interface that the framework uses internally. Provides:

• Screen Management: Screen, Cols, Rows, Contents
• Drawing Operations: AddRune(), AddStr(), Move(), FillRect()
• Cursor Management: SetCursorVisibility(), UpdateCursor()
• Attribute Management: CurrentAttribute, SetAttribute(), MakeColor()
• Clipping: Clip property
• Events: KeyDown, KeyUp, MouseEvent, SizeChanged
• Platform Features: SupportsTrueColor, Force16Colors, Clipboard

Note: The driver is internal to Terminal.Gui. View classes should not access Driver directly. Instead:

• Use @Terminal.Gui.App.Application.Screen to get screen dimensions
• Use @Terminal.Gui.ViewBase.View.Move for positioning (with viewport-relative coordinates)
• Use @Terminal.Gui.ViewBase.View.AddRune and @Terminal.Gui.ViewBase.View.AddStr for drawing
• ViewBase infrastructure classes (in Terminal.Gui/ViewBase/) can access Driver when needed for framework implementation

IConsoleDriverFacade

Extended interface for v2 drivers that exposes the internal components:

• IInputProcessor InputProcessor
• IOutputBuffer OutputBuffer
• IWindowSizeMonitor WindowSizeMonitor

This interface allows advanced scenarios and testing.

Platform-Specific Details

DotNetDriver (NetComponentFactory)

• Uses System.Console for all I/O operations
• Input: Reads ConsoleKeyInfo via Console.ReadKey()
• Output: Uses Console.Write() and ANSI escape sequences
• Works on all platforms but may have limited features
• Best for maximum compatibility and simple applications

WindowsDriver (WindowsComponentFactory)

• Uses Windows Console API via P/Invoke
• Input: Reads InputRecord structs via ReadConsoleInput
• Output: Uses Windows Console API for optimal performance
• Supports Windows-specific features and better performance
• Automatically selected on Windows platforms

Visual Studio Debug Console Support

When running in Visual Studio's debug console (VSDebugConsole.exe), WindowsDriver detects the VSAPPIDNAME environment variable and automatically adjusts its behavior:

• Disables the alternative screen buffer (which is not supported in VS debug console)
• Preserves the original console colors on startup
• Restores the original colors and clears the screen on shutdown

This ensures Terminal.Gui applications can be debugged directly in Visual Studio without rendering issues.

UnixDriver (UnixComponentFactory)

• Uses Unix/Linux terminal APIs
• Input: Reads raw char data from terminal
• Output: Uses ANSI escape sequences
• Supports Unix-specific features
• Automatically selected on Unix/Linux/macOS platforms

FakeDriver (FakeComponentFactory)

• Simulates console behavior for unit testing
• Uses FakeConsole for all operations
• Allows injection of predefined input
• Captures output for verification
• Always used when Application._forceFakeConsole is true

Example: Checking Driver Capabilities

Application.Init();

// The driver is internal - access through Application properties
// Check screen dimensions
var screenWidth = Application.Screen.Width;
var screenHeight = Application.Screen.Height;

// Check if 24-bit color is supported
bool supportsTrueColor = Application.Driver?.SupportsTrueColor ?? false;

// Access advanced components (for framework/infrastructure code only)
if (Application.Driver is IConsoleDriverFacade facade)
{
    // Access individual components for advanced scenarios
    IInputProcessor inputProcessor = facade.InputProcessor;
    IOutputBuffer outputBuffer = facade.OutputBuffer;
    IWindowSizeMonitor sizeMonitor = facade.WindowSizeMonitor;
    
    // Use components for advanced scenarios
    sizeMonitor.SizeChanging += (s, e) => 
    {
        Console.WriteLine($"Terminal resized to {e.Size}");
    };
}

Important: View subclasses should not access Application.Driver. Use the View APIs instead:

• View.Move(col, row) for positioning
• View.AddRune() and View.AddStr() for drawing
• Application.Screen for screen dimensions

Custom Drivers

To create a custom driver, implement IComponentFactory<T>:

public class MyComponentFactory : ComponentFactory<MyInputType>
{
    public override IConsoleInput<MyInputType> CreateInput()
    {
        return new MyConsoleInput();
    }
    
    public override IConsoleOutput CreateOutput()
    {
        return new MyConsoleOutput();
    }
    
    public override IInputProcessor CreateInputProcessor(
        ConcurrentQueue<MyInputType> inputBuffer)
    {
        return new MyInputProcessor(inputBuffer);
    }
}

Then use it:

ApplicationImpl.ChangeComponentFactory(new MyComponentFactory());
Application.Init();

Legacy Drivers

Terminal.Gui v1 drivers that implement IConsoleDriver but not IConsoleDriverFacade are still supported through a legacy compatibility layer. However, they do not benefit from the v2 architecture improvements (multi-threading, component separation, etc.).

See Also

• @Terminal.Gui.Drivers - API Reference
• @Terminal.Gui.App.Application - Application class
• @Terminal.Gui.App.ApplicationImpl - Application implementation
• @Terminal.Gui.App.MainLoopCoordinator`1 - Main loop coordination