feat: game of Pong with JBang, Java and LWJGL

[wfouche]

$ jbang run Pong.java

[maxandersen]

not sure that kind of deps resolution does what you hope for...only one of org.lwjgl:* artifacts will get included...first one wins.

I think that explains why I get :

jbang examples/game/Pong.java 
[jbang] Resolving dependencies...
[jbang]    org.lwjgl:lwjgl:3.3.3
[jbang]    org.lwjgl:lwjgl-glfw:3.3.3
[jbang]    org.lwjgl:lwjgl-opengl:3.3.3
[jbang] Dependencies resolved
[jbang] Building jar for Pong.java...
[LWJGL] Platform/architecture mismatch detected for module: org.lwjgl
        JVM platform:           macOS aarch64 21.0.7
                OpenJDK 64-Bit Server VM v21.0.7+6-LTS by Eclipse Adoptium
        Platforms available on classpath:
                windows/x64
                linux/x64
                macos/x64
[LWJGL] Failed to load a library. Possible solutions:
        a) Add the directory that contains the shared library to -Djava.library.path or -Dorg.lwjgl.librarypath.
        b) Add the JAR that contains the shared library to the classpath.
[LWJGL] Enable debug mode with -Dorg.lwjgl.util.Debug=true for better diagnostics.
[LWJGL] Enable the SharedLibraryLoader debug mode with -Dorg.lwjgl.util.DebugLoader=true for better diagnostics.
Exception in thread "main" java.lang.UnsatisfiedLinkError: Failed to locate library: liblwjgl.dylib
        at org.lwjgl.system.Library.loadSystem(Library.java:174)
        at org.lwjgl.system.Library.loadSystem(Library.java:64)
        at org.lwjgl.system.Library.<clinit>(Library.java:52)
        at org.lwjgl.system.MemoryUtil.<clinit>(MemoryUtil.java:100)
        at org.lwjgl.system.Pointer$Default.<clinit>(Pointer.java:67)
        at org.lwjgl.system.Callback.<clinit>(Callback.java:40)
        at Pong.init(Pong.java:79)
        at Pong.run(Pong.java:64)
        at Pong.main(Pong.java:280)

[wfouche]

You're running on macOS aarch64 which is not currently supported by the Pong.java program.

Platforms available via the classpath as reported by the runtime are:

• windows/x64
• linux/x64
• macos/x64

I'll check if a native library for aarch64 is available.

[maxandersen]

love it - did you make the game or copied from somewhere? should make ref if from somewhere else.

we'll need to figure out how to do the deps in a portable way.

[wfouche]

This game was developed from scratch using Google Gemini AI.

I tested the game on Linux and Windows, had to a make a small timing change so that Linux was properly supported.

[wfouche]

we'll need to figure out how to do the deps in a portable way.

It should work now on macOS (arm64) as well.

[maxandersen]

i gets further but errors with:

jbang examples/game/Pong.java 
[jbang] Resolving dependencies...
[jbang]    org.lwjgl:lwjgl:3.3.6
[jbang]    org.lwjgl:lwjgl-glfw:3.3.6
[jbang]    org.lwjgl:lwjgl-opengl:3.3.6
[jbang] Dependencies resolved
[jbang] Building jar for Pong.java...
Exception in thread "main" java.lang.IllegalStateException: GLFW may only be used on the main thread and that thread must be the first thread in the process. Please run the JVM with -XstartOnFirstThread. This check may be disabled with Configuration.GLFW_CHECK_THREAD0.
	at org.lwjgl.glfw.EventLoop.check(EventLoop.java:33)
	at org.lwjgl.glfw.GLFW.glfwInit(GLFW.java:1108)
	at Pong.init(Pong.java:100)
	at Pong.run(Pong.java:82)
	at Pong.main(Pong.java:298) 

i can make it work using this:

jbang -R=-XstartOnFirstThread examples/game/Pong.java

not sure if adding //RUNTIME_OPTIONS -XstartOnFirstThread` to it will have bad impact on windows/linux?

[maxandersen]

btw. i'm surprised the fix worked ...trying to grok if bug or feature :)

[maxandersen]

remarkably fatjar of that is "only 3.7mb...

[wfouche]

I've disabled the main thread check using runtime option -Dorg.lwjgl.glfw.checkThread0=false.

@maxandersen , please check if this resolves the macOS issue. -XstartOnFirstThread does not work on Windows, so cannot be used.

[maxandersen]

I no longer get an error but now it just hangs/doing nothing.

jbang -R=-XstartOnFirstThread examples/game/Pong.java still works

what error are you getting on windows?

[wfouche]

There currently is no way to get this to work without explicitly specifying the -XstartOnFirstThread option when running the program on macOS. I think we need a way of specifying OS specific runtime options that will only be used if a particular OS is detected. For example

//RUNTIME_OPTIONS  -Xmx2g
//RUNTIME_OPTIONS:MACOS -XstartOnFirstThread

will set the heap size to 2GB for all platforms and only on MacOS also add option -XstartOnFirstThread

One could extend this to also allow specifying an optional ARCH_TYPE as well, but it I'm not quite sure if that's really needed.

• //RUNTIME_OPTIONS:MACOS:ARM64

Comments?

[maxandersen]

See jbangdev/jbang#2186

Similar issue for //DEPS we might want to consider {key=value} being applicable to directives ... At least to things like runtime options.

[wfouche]

Moved the JBang directives to file Config.java.

//usr/bin/env jbang "$0" "$@" ; exit $?

// Game developed using Google Gemini AI (2.5 Pro)

//SOURCES Config.java

import org.lwjgl.glfw.*;
import org.lwjgl.opengl.*;
import org.lwjgl.system.*;

...

[maxandersen]

Why? You plan to share that Config.java between multiple games in this repo or how?

[wfouche]

Why? You plan to share that Config.java between multiple games in this repo or how?

It was an experiment. Reverted the change again.