Introduction

Termina is a reactive terminal UI (TUI) framework for .NET that brings modern application development patterns to console applications.

What is Termina?

Termina provides:

• Reactive MVVM Architecture - ViewModels with source-generated observable properties that automatically update the UI
• Declarative Layout System - Build UIs by composing layout nodes in a tree structure
• ASP.NET Core-Style Routing - Navigate between pages using familiar route templates
• Direct ANSI Rendering - Custom terminal rendering engine with surgical region-based updates

Key Concepts

Pages and ViewModels

Termina uses the MVVM (Model-View-ViewModel) pattern:

• Pages define the UI layout and bind to ViewModel properties
• ViewModels contain the application logic and state
• When ViewModel properties change, the UI automatically updates

Reactive Properties

The [Reactive] attribute generates observable properties via source generators:

public partial class MyViewModel : ReactiveViewModel
{
    [Reactive] private string _message = "Hello";

    // Source generator creates:
    // - public string Message { get; set; }
    // - public IObservable<string> MessageChanged
}

Layout Nodes

UIs are built by composing layout nodes:

protected override ILayoutNode BuildLayout()
{
    return Layouts.Vertical()
        .WithChild(new TextNode("Header").Bold())
        .WithChild(new PanelNode().WithContent(new TextNode("Content")))
        .WithChild(new TextNode("Footer"));
}

Routing

Navigate between pages using route templates:

// Register routes
termina.RegisterRoute<HomePage, HomeViewModel>("/");
termina.RegisterRoute<TaskPage, TaskViewModel>("/tasks/{id:int}");

// Navigate
Navigate("/tasks/42");

When to Use Termina

Termina is ideal for:

• Interactive CLI tools that need rich user interfaces
• Dashboard applications with multiple updating regions
• Chat interfaces with streaming text
• Data entry forms in terminal environments
• Development tools that run in the terminal

Comparison with Alternatives

Feature	Termina	Spectre.Console	Terminal.Gui
Architecture	Reactive MVVM	Procedural	Imperative widgets
UI Updates	Observable-driven	Manual	Event-based
Layout	Declarative tree	Render calls	Widget hierarchy
Routing	Built-in	None	None
AOT Support	Full	Full	Limited

Next Steps

• Getting Started - Build your first Termina app
• Installation - Package installation options
• Render Loop Threading - Marshal async and timer callbacks onto the Termina loop
• Upgrading to 0.11.0 - Native selection, copy, paste, and input mode guidance
• Counter Tutorial - Step-by-step tutorial