IDE-style window docking for Compose Multiplatform: splits, tab groups, drag-to-dock with docking handles, floating windows, maximize, and layout persistence.

A port of the concepts and algorithms of ModernDocking (Java Swing, MIT) to an idiomatic Compose API.

Status: early development. Published, but expect breaking API changes between 0.x releases.

Floating OS windows and cross-window drag are desktop (JVM) features. Everything else — splits, tabs, in-window drag-to-dock, tab reordering, maximize, persistence — is common code and works on every target.

Depend on a renderer; it exposes the core as an api dependency, so you do not need to declare compose-docking-core yourself.

repositories {
    // Compose itself resolves from Google's repository, so mavenCentral() alone
    // is not enough - the transitive androidx artifacts will not be found.
    google()
    mavenCentral()
}

dependencies {
    implementation("com.seanproctor:compose-docking-material3:0.2.0")
    // ...or, for the IntelliJ look on desktop:
    // implementation("com.seanproctor:compose-docking-jewel:0.2.0")
}

In a multiplatform build these go in commonMain, except compose-docking-jewel, which is JVM only and belongs in jvmMain (or desktopMain).

fun main() = application {
    val state = rememberDockState(
        initialLayout = {
            dockLayout {
                mainWindow {
                    dock("project")
                    dock("editor", target = "project", region = DockRegion.East, proportion = 0.75f)
                    dock("terminal", target = "editor", region = DockRegion.South, proportion = 0.3f)
                    dock("problems", target = "terminal", region = DockRegion.Center)
                    display("terminal")
                }
            }
        },
    ) {
        dockable("project", title = { "Project" }, options = DockableOptions(closable = false)) {
            ProjectTree()
        }
        dockable("editor", title = { "Editor" }) { EditorPane() }
        dockable("terminal", title = { "Terminal" }) { TerminalPane() }
        dockable("problems", title = { "Problems" }) { ProblemsPane() }
        dockable("todo", title = { "TODO" }) { TodoPane() }
    }

    // Restore on launch + debounced auto-save on every layout change.
    rememberAutoPersist(state, FileLayoutStorage(File(configDir, "layout.json")))

    Window(onCloseRequest = ::exitApplication, title = "My App") {
        MaterialTheme {
            Material3Docking {
                registerDockingWindow(state)   // desktop: cross-window drag + focus handling
                DockArea(state, modifier = Modifier.fillMaxSize())
            }
        }
    }
    // One OS window per floating entry, plus the drag preview window.
    MaterialTheme {
        Material3Docking { FloatingDockWindows(state) }
    }
}

On web/mobile, drop the two desktop calls and just use DockArea inside Material3Docking.

IntUiTheme(isDark = true) {
    JewelDocking {
        registerDockingWindow(state)
        DockArea(state, Modifier.fillMaxSize())
    }
}

The Jewel adapter only reads from JewelTheme, so it works under both the standalone IntUiTheme and the IDE SwingBridgeTheme. Jewel 0.39+ ships Java 25 bytecode — run on a JDK 25+ (JetBrains Runtime recommended).

• DockState — the single source of truth. Holds an immutable layout value (windows → tree of splits / tab groups / dockables), the dockable registry, and every operation: dock, undock, close (with veto), maximize, moveToNewWindow, show, … Observe with snapshotFlow { state.layout } or the state.events flow.
• Dockables are declared once with reactive title/icon lambdas, per-dockable DockableOptions (closable, floatable, docking style, anchor, …), optional saveState/restoreState for persisted per-panel state, and the content composable. Content keeps all internal state when re-docked within a window; hoist what must survive a move between windows into rememberSaveable.
• Drag-to-dock replicates ModernDocking: docking handles (window edges + hovered panel), a translucent drop preview, 35% edge-region sensitivity, bidirectional docking-style filtering, tab-strip insertion, tearing off into floating windows, and Esc-cancel with full layout restore.
• Anchors give layouts named regions that survive close-all: a placeholder stays in the tree when the last anchored dockable leaves, and reopening docks back into it. Set DockingSettings(collapsedAnchorThickness = 24.dp) to draw an empty one as a strip instead of a full-size pane, so the area gives its space back while it is empty and still takes a drop, and add emptyAnchorVisibility = EmptyAnchorVisibility.WhileDragging to hide the strip entirely until a drag starts - an empty area then costs nothing at all until there is something to drop into it.
• Persistence is JSON (kotlinx.serialization) with a version field and migration hooks; unknown dockables in a saved layout are kept as placeholders and fill in when registered (or are created on demand via a DockableResolver). Named layout snapshots live on state.layouts.
• Renderer SPI — DockingRenderer is a slot interface; core builds all models and gesture modifiers, adapters only draw. Implement it to match any design system, and provide it via LocalDockingRenderer + LocalDockingTheme.

./gradlew :demo:demo-material3:run                       # Material 3, desktop
./gradlew :demo:demo-material3:wasmJsBrowserDevelopmentRun   # Material 3, browser
./gradlew :demo:demo-jewel:run                           # IntelliJ look (needs JDK 25 toolchain)

The docking model — drop-target precedence, region sensitivity, anchors, and layout persistence semantics — is ported from ModernDocking by Andrew Auclair (MIT).

MIT