Yaru — GTK / LibAdwaita

GNOME applications don't have title bars — they have header bars. Buttons sit where the user told GSettings to put them. Yaru is Ubuntu's GNOME theme; the Nucleus Yaru toolkit gives you a DecoratedWindow that respects this.

TL;DR

• Header-bar layout that reads org.gnome.desktop.wm.preferences.button-layout.
• LibAdwaita accent colours, light / dark variants.
• Renders the right close / minimise / maximise icons from decorated-window-core.
• Built on Tao for native Wayland support.

Install

dependencies {
    implementation("dev.nucleusframework:nucleus.nucleus-application:<version>")
    implementation("dev.nucleusframework:nucleus.decorated-window-tao:<version>")
    // implementation("dev.nucleusframework:nucleus.decorated-window-yaru:<version>") [FACT-CHECK: artifact id]
}

[FACT-CHECK: artifact id] — the Yaru toolkit pack is announced for Nucleus 2.0. In the meantime, build the look with the Linux icons and button-layout helpers in decorated-window-core.

Quickstart

import androidx.compose.foundation.layout.*
import androidx.compose.runtime.*
import androidx.compose.ui.Modifier
import androidx.compose.ui.graphics.Color
import androidx.compose.ui.unit.*
import dev.nucleusframework.application.*
import dev.nucleusframework.window.core.*

fun main() = nucleusApplication(backend = NucleusBackend.Tao) {
    val dark = isSystemInDarkMode()
    val layout = rememberLinuxButtonLayout()           // reads user GSettings
    val titleBarStyle = TitleBarStyle(
        colors = TitleBarColors(
            background = if (dark) Color(0xFF2D2D2D) else Color(0xFFF5F5F4),
            inactiveBackground = if (dark) Color(0xFF222222) else Color(0xFFEDEDEC),
            content = if (dark) Color.White else Color(0xFF1A1A1A),
            border = Color.Transparent,
        ),
        metrics = TitleBarMetrics(height = 46.dp),
        icons = linuxTitleBarIcons(),
    )

    NucleusDecoratedWindowTheme(isDark = dark, titleBarStyle = titleBarStyle) {
        DecoratedWindow(onCloseRequest = ::exitApplication, title = "Yaru") {
            TitleBar { _ ->
                // Place your header-bar widgets here. Nucleus places the
                // close/min/max buttons according to `layout`.
            }
            Box(Modifier.fillMaxSize()) { /* content */ }
        }
    }
}

How it works

rememberLinuxButtonLayout() reads the user's preferred caption-button layout from GSettings (button-layout defaults to appmenu:close on GNOME, close,minimize,maximize: on Ubuntu). The Yaru style places the buttons accordingly and leaves the rest of the header bar — title, breadcrumb, search — to your Composable.

linuxTitleBarIcons() returns the right symbolic icons for the active theme. The bundled set follows the GNOME symbolic palette so it composes with system accent colours.

On Wayland, the Tao backend negotiates client-side decorations via xdg-decoration. On X11, Nucleus draws the header bar itself. Both end up looking identical.

Reference

• rememberLinuxButtonLayout(): LinuxButtonLayout — current GSettings caption-button layout.
• LinuxTitleBarButton.{Close, Minimize, Maximize} — caption button identifiers.
• linuxTitleBarIcons(...): LinuxTitleBarIconSet — symbolic icons.
• GnomeControlButtonsIcons — extension vals for .Maximize / .Close / .Minimize painters.