Hello Again Slick2D

11 October 2014 ~ blog java groovy

I am finally getting back around to working on my little game programming project and I realized that somewhere along the
way, my project stopped working. I am using the Slick2D library, which seems to have little
in the way of formal release or distribution so it didn't surprise me. I think I had something hacked together making it
work last time. I decided to try and put some more concrete and repeatable steps around basic setup, at least for how I use it - I'm no
game programmer.

I'm using Groovy as my development language and Gradle for building. In the interest of time and clarity, I am going to use a
dump-and-describe approach here; there are only two files, so it should not be a big deal.

The build.gradle file is as follows:

group = 'com.stehno.demo'
version = '0.1'

buildscript {
    repositories {

        maven {
            url 'http://dl.bintray.com/cjstehno/public/'

    dependencies {
        classpath 'com.stehno:gradle-natives:0.2'

apply plugin:'groovy'
apply plugin:'application'
apply plugin:'com.stehno.natives'

compileJava {
    sourceCompatibility = 1.8
    targetCompatibility = 1.8

mainClassName = 'helloslick.HelloSlick'

repositories {

dependencies {
    compile 'org.codehaus.groovy:groovy-all:2.3.6'

    compile 'org.slick2d:slick2d-core:1.0.1'

test {
    systemProperty 'java.library.path', file('build/natives/windows')

run {
    systemProperty 'java.library.path', file('build/natives/windows')

natives {
    jars = [
    platforms = 'windows'

task wrapper(type: Wrapper) {
    gradleVersion = '2.1'

The first point of note, is that I am using my Gradle Natives plugin, not as
a self-promotion, but since this is the reason I wrote it. This plugin takes care of extracting all the little native
libraries and putting them in your build so that they are easily accessible by your code. The configuration is found near
the bottom of the file, in the natives block - we want to extract the native libraries from the lwjgl and jinput libraries
for this project and in my case, I only care about the Windows versions (leave off platforms to get all platforms).

There was one interesting development during my time away from this project, a 3rd-party jar version of Slick2D has been pushed to maven central, which makes it a lot easier - I think I had to build it myself and fiddle with pushing it to my local maven repo or something. Now it's just another remote library (hopefully it works as expected - I have not played with it yet).

The last point of interest here is the use of the application plugin. This plugin provides an easy way to run your game
while specifying the java.library.path which is the painful part of running applications with native libraries. With the
application plugin and the run configuration in place, you can run the game from Gradle - admittedly not ideal, but this
is just development; I actually have a configuration set for the IzPack installer that I will write about later.

Now, we need some code to run, and the Slick2D wiki provides a simple Hello world sample that I have tweaked a bit for my
use - mostly just cosmetic changes:

package helloslick

import groovy.util.logging.Log
import org.newdawn.slick.*

import java.util.logging.Level

class HelloSlick extends BasicGame {

    HelloSlick(String gamename){

    public void init(GameContainer gc) throws SlickException {}

    public void update(GameContainer gc, int i) throws SlickException {}

    public void render(GameContainer gc, Graphics g) throws SlickException {
        g.drawString 'Hello Slick!', 50, 50

    public static void main(String[] args){
        try {
            AppGameContainer appgc = new AppGameContainer(new HelloSlick('Simple Slick Game'))
            appgc.setDisplayMode(640, 480, false)

        } catch (SlickException ex) {
            log.log(Level.SEVERE, null, ex)

This just opens a game window and writes "Hello Slick!" in it, but if you have that working, you should be ready for playtime
with Slick2D.

Once you have the project setup (build.gradle in the root, and HelloSlick.groovy in /src/main/groovy/helloslick), you
are ready to go. Run the following to run the project.

gradle unpackNatives run

And if all is well, you will see the game window and message.

Like I said, this is mostly just for getting my development environment up and running as a sanity check, but maybe it is useful to others.

Yes, the explicit unpackNatives calls are annoying, it's something I am working on.

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