Kotlin extensions for libGDX.

Introduction

KTX is a Kotlin game framework built on libGDX. It aims to make libGDX as Kotlin-friendly as possible without completely rewriting the API. It provides modular utilities and extensions for selected parts of libGDX with poor Kotlin support.

Examples of Kotlin language features used to improve usability, performance, and readability of libGDX include:

• Operator overloads for collections and mathematical operations.
• Extension methods improving original libGDX APIs without the use of inheritance.
• Inline methods with reduced runtime overhead for various listeners, builders, and loggers.
• Nullable types which improve typing information of selected interfaces and functions.
• Default parameters reducing boilerplate code.
• Type-safe builders for GUI, styling, and physics engine.
• Default interface methods for common interfaces, simplifying their implementations.
• Coroutines context providing concurrency utilities and non-blocking asset loading.
• Reified types that simplify usage of methods normally consuming Class parameters.

See the Choosing KTX article for pros and cons of this framework.

Modules

KTX was designed to be modular from day one - in fact, many of its libraries are just a single Kotlin file. You can include selected KTX modules based on the needs of your application.

Module	Description
ktx-actors	Scene2D GUI extensions for stages, actors, actions, and event listeners.
ktx-app	ApplicationListener implementations and general application utilities.
ktx-ashley	Ashley entity-component-system utilities.
ktx-assets	Resources management utilities.
ktx-assets-async	Non-blocking asset loading using coroutines.
ktx-async	Coroutines context based on libGDX threading model.
ktx-box2d	Box2D physics engine utilities.
ktx-collections	Extensions for libGDX custom collections.
ktx-freetype	FreeType fonts loading utilities.
ktx-freetype-async	Non-blocking FreeType fonts loading using coroutines.
ktx-graphics	Utilities related to rendering tools and graphics.
ktx-i18n	Internationalization API utilities.
ktx-inject	A dependency injection system with low overhead and no reflection usage.
ktx-json	Utilities for libGDX JSON serialization API.
ktx-log	Minimal runtime overhead cross-platform logging using inlined functions.
ktx-math	Operator functions for libGDX math API and general math utilities.
ktx-preferences	Improved API for accessing and saving preferences.
ktx-reflect	Utilities for libGDX reflection API.
ktx-scene2d	Type-safe Kotlin builders for Scene2D GUI.
ktx-script	Kotlin scripting engine for desktop applications.
ktx-style	Type-safe Kotlin builders for Scene2D widget styles extending Skin API.
ktx-tiled	Utilities for Tiled maps.
ktx-vis	Type-safe Kotlin builders for VisUI.
ktx-vis-style	Type-safe Kotlin builders for VisUI widget styles.

Installation

KTX modules are uploaded to Maven Central and are fully compatible with the Gradle build tool, which is used in libGDX projects by default.

All libraries follow the same naming schema:

api "io.github.libktx:$module:$ktxVersion"

Replace $module with the name of the selected KTX library (see the table above).

For example, including the app module with the ktx-app identifier would require the following changes in your build.gradle file:

// Groovy DSL:
ext {
  // Update this version to match the latest KTX release:
  ktxVersion = '1.11.0-rc2'
}

dependencies {
  api group: 'io.github.libktx', name: 'ktx-app', version: ktxVersion
}

// Kotlin DSL:

// Update this version to match the latest KTX release:
val ktxVersion = "1.11.0-rc2"

dependencies {
  api(group = "io.github.libktx", name = "ktx-app", version = ktxVersion)
}

You can find the latest KTX version on Maven Central:

KTX modules should generally be added to the dependencies of the shared core module of your libGDX application.

As a side note, defining ktxVersion as a property in ext is not necessary, as versions can be set directly in the dependencies section. However, extracting the dependencies versions is a good practice, especially if they can be reused throughout the build files. This will speed up updating of your project if you include multiple KTX modules.

Versioning

KTX versions match the libGDX versions that they were compiled against. $ktxVersion will usually match your libGDX version, but it might end with -rc suffix if it is a stable release, or -SNAPSHOT if you are using the development branch. Older KTX releases use the -b suffix to mark milestone releases.

You can browse through our official releases on Maven and on GitHub.

Unfortunately, libGDX does not follow the semantic versioning guidelines. Both minor and patch versions can introduce breaking changes. Please read the libGDX and KTX change logs before updating.

Although KTX still uses beta release tags, the official releases are stable enough for production use. All modules are thoroughly tested with unit tests.

Latest changes

The master branch is the default branch of the repository. It represents the latest stable release of KTX. It ensures that the documentation in the repository is in sync with the latest version.

The newest changes can be found on the develop branch instead.

You do not have to compile the sources manually to use the latest features. The preview snapshot releases are uploaded to the https://oss.sonatype.org/content/repositories/snapshots/ repository. To use them in your application, add the following Maven repository, and modify the prefix of ktxVersion to -SNAPSHOT:

// Groovy DSL:
repositories {
  // Include your other repositories here.
  maven { url 'https://oss.sonatype.org/content/repositories/snapshots/' }
}

ext {
  // Update this version to match the latest libGDX release:
  ktxVersion = '1.11.0-SNAPSHOT'
}

// Kotlin DSL:
repositories {
  // Include your other repositories here.
  maven("https://oss.sonatype.org/content/repositories/snapshots/")
}

// Update this version to match the latest libGDX release:
val ktxVersion = "1.11.0-SNAPSHOT"

The latest snapshot version name can be found on the develop branch.

Even the snapshots are rather stable, as the libraries are not pushed to Maven Central unless they pass their extensive test suites. However, the public APIs in snapshot releases might be changed prior to a stable release.

Documentation

Official guides

Each module contains a README.md file with a list of all its features and a guide with useful code snippets. Browse through the directories in the root folder to find out more about each library.

Source documentation

All functionalities are documented with Kotlin KDocs. You can access the source documentation by:

• Viewing the generated Dokka files hosted on the project website.
• Extracting the doc folders with Dokka files from the release archives.
• Reading the sources directly.

Links

KTX wiki lists some useful resources that can help you get started.

Most official guides and code examples in this repository assume that the reader is at least a bit familiar with the libGDX API. If you are just getting to know the framework, it might be helpful to go through the official libGDX wiki, and convert some Java examples to Kotlin.

Contribution

Suggestions, questions, typo fixes, documentation improvements and code contributions are always welcome.

Do not hesitate to start a discussion with questions about the framework. Feel free to advertise your KTX project, propose new features, discuss game jams, or even create a personal devlog.

If you would like to contribute, please read the contribution guideline, and browse through the active issues. The develop is the active development branch. When creating pull requests, make sure to choose develop as the target branch.

You can check the list of the contributors via GitHub insights and on the contributors list.

Licensing

This project is dedicated to public domain.

Working from sources

See this section of the contribution guideline to get started.