Taffy4J

Java 11 bindings for Taffy 0.13.0, with Flexbox, Grid, Block, float layout, parsing, measurement callbacks, and native binaries for Linux, Windows, and macOS on x86-64 and ARM64.

Quick start

Add Taffy4J from Maven Central:

repositories {
    mavenCentral()
}

dependencies {
    implementation("com.antepod:taffy4j:0.13.0-2")
}

The artifact includes native libraries for every supported platform; no separate native dependency or java.library.path configuration is required.

import com.antepod.taffy.geometry.Size;
import com.antepod.taffy.style.AvailableSpace;
import com.antepod.taffy.style.Display;
import com.antepod.taffy.style.Style;
import com.antepod.taffy.tree.Layout;
import com.antepod.taffy.tree.NodeId;
import com.antepod.taffy.tree.TaffyTree;

try (TaffyTree<Void> tree = new TaffyTree<>()) {
    NodeId child = tree.newLeaf(Style.builder().size(120.0f, 40.0f).build());
    NodeId root = tree.newWithChildren(
            Style.builder().display(Display.FLEX).size(640.0f, 480.0f).build(),
            child);

    tree.computeLayout(root, new Size<>(
            AvailableSpace.definite(640.0f),
            AvailableSpace.definite(480.0f)));

    Layout layout = tree.layout(child);
    System.out.println(layout.location.x + ", " + layout.location.y);
}

The tree owns native memory, so use try-with-resources. A tree is not thread-safe; synchronize externally if multiple threads share it.

See Getting started, installation, the platform matrix, and layout-change tracking.

Retained-mode layout invalidation

Taffy4J can return exact observable layout changes from one native compute and one packed JNI result:

LayoutChanges changes = tree.computeLayoutWithChanges(root, availableSpace);
for (LayoutChange change : changes) {
    if (change.geometryChanged()) {
        // update retained UI geometry
    }
}

An optional listener provides the same batch one record at a time after native compute has returned. Existing compute methods keep their original non-tracking native path when no listener is installed.

Taffy4J requires Java 11 or newer. Published classes target Java 11 bytecode.

Native access on JDK 24+

Taffy4J loads its bundled JNI library with System.load. JDK 24 and newer warn when native access is not explicitly enabled; a future JDK will deny it by default. Applications using Taffy4J from the class path should start with:

java --enable-native-access=ALL-UNNAMED ...

For Gradle's application plugin:

application {
    applicationDefaultJvmArgs = listOf("--enable-native-access=ALL-UNNAMED")
}