Contributing to Terminal.Gui

📘 This document is the single source of truth for all contributors (humans and AI agents) to Terminal.Gui.

Welcome! This guide provides everything you need to know to contribute effectively to Terminal.Gui, including project structure, build instructions, coding conventions, testing requirements, and CI/CD workflows.

Project Overview
Key Architecture Concepts
Coding Conventions
Building and Testing
Testing Requirements
API Documentation Requirements
Pull Request Guidelines
CI/CD Workflows
Repository Structure
Branching Model
What NOT to Do

Project Overview

Terminal.Gui is a cross-platform UI toolkit for creating console-based graphical user interfaces in .NET. It's a large codebase (~1,050 C# files) providing a comprehensive framework for building interactive console applications with support for keyboard and mouse input, customizable views, and a robust event system.

Key characteristics:

Language: C# (net8.0)
Platform: Cross-platform (Windows, macOS, Linux)
Architecture: Console UI toolkit with driver-based architecture
Version: v2 (Beta), v1 (maintenance mode)
Branching: GitFlow model (develop is default/active development)

Key Architecture Concepts

⚠️ CRITICAL - AI Agents MUST understand these concepts before starting work.

Application Lifecycle - How Application.Init, Application.Run, and Application.Shutdown work - Application Deep Dive
Cancellable Workflow Patern - CWP Deep Dive
View Hierarchy - Understanding View, Runnable, Window, and view containment - View Deep Dive
Layout System - Pos, Dim, and automatic layout - Layout System
Event System - How keyboard, mouse, and application events flow - Events Deep Dive
Driver Architecture - How console drivers abstract platform differences - Drivers
Drawing Model - How rendering works with Attributes, Colors, and Glyphs - Drawing Deep Dive

Building and Testing

Required Tools

.NET SDK: 8.0.0 (see global.json)
Runtime: .NET 8.x (latest GA)
Optional: ReSharper/Rider for code formatting (honor .editorconfig and Terminal.sln.DotSettings)

Build Commands (In Order)

ALWAYS run these commands from the repository root:

Restore packages (required first, ~15-20 seconds):
```
dotnet restore
```
Build solution (Debug, ~50 seconds):
```
dotnet build --configuration Debug --no-restore
```
- Expect ~326 warnings (nullable reference warnings, unused variables, etc.) - these are normal
- 0 errors expected

Build Release (for packaging):

dotnet build --configuration Release --no-restore

Test Commands

Two test projects exist:

Non-parallel tests (depend on static state, ~10 min timeout):
```
dotnet test --project Tests/UnitTests --no-build --verbosity normal
```
- Uses Application.Init and static state
- Cannot run in parallel
- Includes --diagnostic flag for logging
Parallel tests (can run concurrently, ~10 min timeout):
```
dotnet test --project Tests/UnitTestsParallelizable --no-build --verbosity normal
```
- No dependencies on static state
- Preferred for new tests

Integration tests:

dotnet test --project Tests/IntegrationTests --no-build --verbosity normal

Common Build Issues

Issue: NativeAot/SelfContained Build

Solution: Restore these projects explicitly:

dotnet restore ./Examples/NativeAot/NativeAot.csproj -f
dotnet restore ./Examples/SelfContained/SelfContained.csproj -f

Coding Conventions

⚠️ CRITICAL - These rules MUST be followed in ALL new or modified code

Code Style Tenets

Six-Year-Old Reading Level - Readability over terseness
Consistency, Consistency, Consistency - Follow existing patterns ruthlessly
Don't be Weird - Follow Microsoft/.NET conventions
Set and Forget - Rely on automated tooling
Documentation is the Spec - API docs are source of truth

Code Formatting

⚠️ CRITICAL - These rules MUST be followed in ALL new or modified code:

AI or AI Agent Written or Modified Code MUST Follow these instructions

Read and study .editorconfig and Terminal.sln.DotSettings to determine code style and formatting.
Format code with:
1. ReSharper/Rider (Ctrl-E-C)
2. JetBrains CleanupCode CLI tool (free)
3. Visual Studio (Ctrl-K-D) as fallback
Only format files you modify
Follow .editorconfig settings

ALWAYS use explicit types - Never use var except for built-in simple types (int, string, bool, double, float, decimal, char, byte)

// ✅ CORRECT - Explicit types
View view = new () { Width = 10 };
MouseEventArgs args = new () { Position = new Point(5, 5) };
List<View?> views = new ();
var count = 0;  // OK - int is a built-in type
var name = "test";  // OK - string is a built-in type

// ❌ WRONG - Using var for non-built-in types
var view = new View { Width = 10 };
var args = new MouseEventArgs { Position = new Point(5, 5) };
var views = new List<View?>();

ALWAYS use target-typed new () - Use new () instead of new TypeName() when the type is already declared

// ✅ CORRECT - Target-typed new
View view = new () { Width = 10 };
MouseEventArgs args = new ();

// ❌ WRONG - Redundant type name
View view = new View() { Width = 10 };
MouseEventArgs args = new MouseEventArgs();

ALWAYS use collection initializers if possible:

// ✅ CORRECT - Collection initializer
List<View> views = [
    new Button("OK"),
    new Button("Cancel")
];

// ❌ WRONG - Adding items separately
List<View> views = new ();
views.Add(new Button("OK"));
views.Add(new Button("Cancel"));

⚠️ CRITICAL - These conventions apply to ALL code - production code, test code, examples, documentation, and samples.

Prefer early return - Use guard clauses to reduce nesting:

// ✅ CORRECT - Early return
if (view is null)
{
    return;
}

DoWork (view);

// ❌ WRONG - Unnecessary nesting
if (view is not null)
{
    DoWork (view);
}

One type per file - Each public or internal type gets its own file, named to match the type (e.g., Button.cs for class Button). Private nested types belong in their containing type's file.

Unicode and Grapheme Handling

Think in graphemes, not runes. A grapheme cluster is what the user perceives as a single character, but it may consist of multiple Rune values (e.g., base character + combining marks, or ZWJ emoji sequences).

Always use string.GetColumns() to measure display width — never EnumerateRunes().Sum(r => r.GetColumns()) (inflates multi-rune clusters) or string.Length (counts chars, not terminal cells)
Iterate by grapheme using GraphemeHelper.GetGraphemes() when rendering text — never iterate by Rune and call AddRune for each (breaks combining marks and ZWJ sequences)
Render with AddStr passing complete grapheme strings — AddRune with individual runes from a cluster will not compose correctly

// ✅ CORRECT — grapheme-aware width measurement
int width = text.GetColumns ();

// ❌ WRONG — inflates width for ZWJ emoji (e.g., 👨‍👩‍👦‍👦 → 8 instead of 2)
int width = text.EnumerateRunes ().Sum (r => r.GetColumns ());

// ✅ CORRECT — grapheme-aware rendering
foreach (string grapheme in GraphemeHelper.GetGraphemes (text))
{
    AddStr (grapheme);
}

// ❌ WRONG — breaks combining marks (é rendered as e + ́ separately)
foreach (Rune rune in text.EnumerateRunes ())
{
    AddRune (rune);
}

Exception: Rune-level iteration is appropriate when inspecting individual Unicode scalar values (e.g., counting zero-width runes for vertical text layout), not for rendering or measurement.

Testing Requirements

Code Coverage

Never decrease code coverage - PRs must maintain or increase coverage
Target: 70%+ coverage for new code
Coverage collection:
Temporarily disabled in CI during xUnit v3 / MTP migration
Will be re-enabled once an MTP-compatible coverage solution is integrated

Test Patterns

AI Created Tests MUST follow these patterns exactly.
Add comment indicating the test was AI generated - e.g., // CoPilot - ChatGPT v4
Make tests granular - Each test should cover smallest area possible
Follow existing test patterns in respective test projects
Avoid adding new tests to the UnitTests Project - Make them parallelizable and add them to UnitTests.Parallelizable
Avoid static dependencies - DO NOT use the legacy/static Application API or ConfigurationManager in tests unless the tests explicitly test related functionality.
Don't use [AutoInitShutdown] or [SetupFakeApplication] - Legacy pattern, being phased out

Test Configuration

xunit.runner.json - xUnit configuration
coverlet.runsettings - Coverage settings (currently unused, pending MTP integration)

API Documentation Requirements

All public APIs MUST have XML documentation:

Clear, concise <summary> tags
Use <see cref=""/> for cross-references
Add <remarks> for context
Include <example> for non-obvious usage
Complex topics → docfx/docs/*.md files
Proper English and grammar - Clear, concise, complete. Use imperative mood.

Pull Request Guidelines

PR Requirements

ALWAYS include instructions for pulling down locally at end of Description
Title: "Fixes #issue. Terse description". If multiple issues, list all, separated by commas (e.g. "Fixes #123, #456. Terse description")

Description:

Include "- Fixes #issue" for each issue near the top
Suggest user setup a remote named copilot pointing to your fork

Example:

# To pull down this PR locally:
git remote add copilot <your-fork-url>
git fetch copilot <branch-name>
git checkout copilot/<branch-name>

Tests: Add tests for new functionality (see Testing Requirements)
Coverage: Maintain or increase code coverage
Scenarios: Update UICatalog scenarios when adding features
Warnings: CRITICAL - PRs must not introduce any new warnings
- Any file modified in a PR that currently generates warnings MUST be fixed to remove those warnings
- Exception: Warnings caused by [Obsolete] attributes can remain
- Action: Before submitting a PR, verify your changes don't add new warnings and fix any warnings in files you modify

Repository Structure

Root Directory Files

Terminal.sln - Main solution file
Terminal.sln.DotSettings - ReSharper code style settings
.editorconfig - Code formatting rules (111KB, extensive)
global.json - .NET SDK version pinning
Directory.Build.props - Common MSBuild properties
Directory.Packages.props - Central package version management
GitVersion.yml - Version numbering configuration
CONTRIBUTING.md - This file - contribution guidelines (source of truth)
AGENTS.md - Pointer to this file for AI agents
README.md - Project documentation

Main Directories

/Terminal.Gui/ - Core library (496 C# files):

App/ - Application lifecycle (Application.cs static class, SessionToken, MainLoop)
Configuration/ - ConfigurationManager for settings
Drivers/ - Console driver implementations (dotnet, Windows, Unix, ansi)
Drawing/ - Rendering system (attributes, colors, glyphs)
Input/ - Keyboard and mouse input handling
ViewBase/ - Core View class hierarchy and layout
Views/ - Specific View subclasses (Window, Dialog, Button, ListView, etc.)
Text/ - Text manipulation and formatting
FileServices/ - File operations and services

/Tests/:

UnitTests/ - Non-parallel tests (use Application.Init, static state)
UnitTestsParallelizable/ - Parallel tests (no static dependencies) - Preferred
IntegrationTests/ - Integration tests
StressTests/ - Long-running stress tests (scheduled daily)
coverlet.runsettings - Code coverage configuration

/Examples/:

UICatalog/ - Comprehensive demo app for manual testing
Example/ - Basic example
NativeAot/, SelfContained/ - Deployment examples
ReactiveExample/, CommunityToolkitExample/ - Integration examples

/docfx/ - Documentation source:

docs/ - Conceptual documentation (deep dives)
api/ - Generated API docs (gitignored)
docfx.json - DocFX configuration

/Scripts/ - PowerShell build utilities (requires PowerShell 7.4+)

/.github/workflows/ - CI/CD pipelines (see CI/CD Workflows)

Branching Model

GitFlow Model

develop - Default branch, active development
main - Stable releases, matches NuGet
v1_develop, v1_release - Legacy v1 (maintenance only)

Release Process

Automated Release Workflow

Releases are now automated using GitHub Actions to prevent manual errors. To create a release:

Navigate to Actions tab in the GitHub repository
Select "Create Release" workflow from the left sidebar
Click "Run workflow" button
Configure release parameters:
- Branch: Ensure main is selected
- Release type: Choose from prealpha, alpha, beta, rc, or stable
- Version override: (Optional) Specify exact version (e.g., 2.0.0), otherwise GitVersion calculates it automatically
Click "Run workflow" to start the automated release process

The workflow will:

Create an annotated git tag (e.g., v2.0.0-prealpha or v2.0.0)
Create a release commit on main
Push the tag and commit to the repository
Create a GitHub Release
Automatically trigger the publish workflow to push the package to NuGet.org

What NOT to Do

❌ Don't add new linters/formatters (use existing)
❌ Don't modify unrelated code
❌ Don't remove/edit unrelated tests
❌ Don't break existing functionality
❌ Don't add tests to UnitTests if they can be parallelizable
❌ Don't use Application.Init in new tests
❌ Don't decrease code coverage
❌ Don't use var for anything but built-in simple types (use explicit types)
❌ Don't use redundant type names with new (ALWAYS PREFER target-typed new ())
❌ Don't introduce new warnings (fix warnings in files you modify; exception: [Obsolete] warnings)
❌ Don't use EnumerateRunes().Sum(GetColumns) for display width — use string.GetColumns()
❌ Don't use AddRune in a rune loop to render text — iterate by grapheme with GraphemeHelper.GetGraphemes() and use AddStr

Thank you for contributing to Terminal.Gui! 🎉

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Contributing to Terminal.Gui

Table of Contents

Project Overview

Key Architecture Concepts

Building and Testing

Required Tools

Build Commands (In Order)

Test Commands

Common Build Issues

Issue: NativeAot/SelfContained Build

Coding Conventions

Code Style Tenets

Code Formatting

Unicode and Grapheme Handling

Testing Requirements

Code Coverage

Test Patterns

Test Configuration

API Documentation Requirements

Pull Request Guidelines

PR Requirements

Repository Structure

Root Directory Files

Main Directories

Branching Model

GitFlow Model

Release Process

Automated Release Workflow

What NOT to Do

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CONTRIBUTING.md

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CONTRIBUTING.md

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Contributing to Terminal.Gui

Table of Contents

Project Overview

Key Architecture Concepts

Building and Testing

Required Tools

Build Commands (In Order)

Test Commands

Common Build Issues

Issue: NativeAot/SelfContained Build

Coding Conventions

Code Style Tenets

Code Formatting

Unicode and Grapheme Handling

Testing Requirements

Code Coverage

Test Patterns

Test Configuration

API Documentation Requirements

Pull Request Guidelines

PR Requirements

Repository Structure

Root Directory Files

Main Directories

Branching Model

GitFlow Model

Release Process

Automated Release Workflow

What NOT to Do