jlibghostty/README.md

# jlibghostty

Java FFM bindings for Ghostty's `libghostty-vt`.

This targets Java 22+ and uses `java.lang.foreign`, not JNI. The public API is intentionally small while Ghostty's C API is still marked unstable upstream.

## Build

```sh
nix build
```

The default Nix package builds:

- `share/java/jlibghostty-0.1.0-SNAPSHOT.jar`
- `maven/dev/jlibghostty/jlibghostty/0.1.0-SNAPSHOT/...`

The jar contains the host platform `libghostty-vt` under `dev/jlibghostty/native/<platform>/`.

## Gradle Consumer

After `nix build`, another Gradle project can consume the generated Maven repository:

```kotlin
repositories {
    maven {
        url = uri("/home/anon/Dev/jlibghostty/result/maven")
    }
}

dependencies {
    implementation("dev.jlibghostty:jlibghostty:0.1.0-SNAPSHOT")
}

tasks.withType<JavaExec>().configureEach {
    jvmArgs("--enable-native-access=ALL-UNNAMED")
}
```

## GraalVM Native Image Consumer

`jlibghostty` ships GraalVM reachability metadata at:

```text
META-INF/native-image/dev.jlibghostty/jlibghostty/reachability-metadata.json
```

That metadata registers the FFM downcalls used by this library and includes the bundled native library resource. GraalVM 25 enables Native Image FFM support by default, but the build still needs native access:

```sh
native-image --enable-native-access=ALL-UNNAMED ...
```

If your app uses the module path, prefer:

```sh
native-image --enable-native-access=dev.jlibghostty ...
```

For a Nix-built downstream project, the usual shape is:

```nix
{
  inputs = {
    nixpkgs.url = "github:NixOS/nixpkgs/nixos-unstable";
    jlibghostty.url = "path:/home/anon/Dev/jlibghostty";
  };

  outputs = { nixpkgs, jlibghostty, ... }:
    let
      system = "x86_64-linux";
      pkgs = import nixpkgs { inherit system; };
      jlib = jlibghostty.packages.${system}.jlibghostty;
    in {
      packages.${system}.default = pkgs.stdenvNoCC.mkDerivation {
        pname = "my-native-app";
        version = "0.1.0";
        src = ./.;

        nativeBuildInputs = [
          pkgs.graalvmPackages.graalvm-ce
          pkgs.gradle
        ];

        buildPhase = ''
          export GRADLE_USER_HOME=$TMPDIR/gradle
          gradle --offline -PjlibghosttyMavenRepo=${jlib}/maven installDist
          native-image \
            --enable-native-access=ALL-UNNAMED \
            -cp build/install/my-app/lib/'*' \
            -o my-app \
            com.example.Main
        '';

        installPhase = ''
          mkdir -p "$out/bin"
          cp my-app "$out/bin/"
        '';
      };
    };
}
```

In that downstream Gradle build:

```kotlin
repositories {
    mavenCentral()
    maven {
        url = uri(providers.gradleProperty("jlibghosttyMavenRepo").get())
    }
}

dependencies {
    implementation("dev.jlibghostty:jlibghostty:0.1.0-SNAPSHOT")
}
```

If the app runs on the module path, use:

```sh
--enable-native-access=dev.jlibghostty
```

## External Native Library

The library normally loads the bundled native `libghostty-vt`. To override it:

```sh
java -Djlibghostty.library.path=/path/to/libghostty-vt.so ...
```

or set:

```sh
export JLIBGHOSTTY_LIBRARY=/path/to/libghostty-vt.so
```

## Example

```java
try (Terminal terminal = Ghostty.open(TerminalOptions.of(80, 24))) {
    terminal.write("hello\r\n");
    System.out.println(terminal.snapshot());
}
```

## Kitty Graphics

Kitty graphics storage can be enabled and inspected:

```java
try (Terminal terminal = Ghostty.open(TerminalOptions.of(80, 24))) {
    terminal.setKittyImageStorageLimit(64 * 1024 * 1024);
    terminal.setKittyImageMediumFile(true);
    terminal.setKittyImageMediumTemporaryFile(true);
    terminal.setKittyImageMediumSharedMemory(true);

    terminal.write(kittyGraphicsSequenceBytes);

    for (KittyPlacement placement : terminal.kittyGraphics().orElseThrow().placements()) {
        placement.image().ifPresent(image -> {
            // Hand image.data() and placement.renderInfo() to your renderer.
        });
    }
}
```

The Kitty handles returned by `libghostty-vt` are borrowed from the terminal and are invalidated by mutating terminal calls. The Java API returns snapshots for images and placements to make renderer handoff simpler.

PNG decode callbacks from `ghostty_sys_set(GHOSTTY_SYS_OPT_DECODE_PNG, ...)` are not exposed yet. Raw Kitty image formats can be inspected; PNG image ingestion will need a Java callback bridge or a small native helper that allocates decoded RGBA data through Ghostty's allocator.

## Development Shell

```sh
nix develop
```

The shell provides Java, Gradle, and `JLIBGHOSTTY_LIBRARY` pointing at the Nix-built `libghostty-vt`.