System accent colour

The user picked a colour in their OS settings. Honour it. system-color exposes the system accent and the high-contrast flag as Compose-reactive state — no polling, no manual refresh.

TL;DR

• systemAccentColor(): Color? — null when the platform does not support it.
• isSystemInHighContrast(): Boolean — flips when the user toggles high contrast.
• Native bridges: NSColor KVO on macOS, registry watch on Windows, GSettings on Linux.

Install

dependencies {
    implementation("dev.nucleusframework:nucleus.system-color:<version>")
}

Quickstart

import dev.nucleusframework.systemcolor.*
import androidx.compose.material3.*

@Composable
fun App() {
    val accent = systemAccentColor()
    val highContrast = isSystemInHighContrast()

    val scheme = when {
        accent != null -> darkColorScheme(primary = accent)
        else -> darkColorScheme()
    }

    MaterialTheme(colorScheme = scheme) {
        // UI recomposes when accent or contrast changes.
    }
}

How it works

Each backend wires the OS's native change notification into a StateFlow<Color?>, which Compose reads. The composable returns null when the platform cannot supply a meaningful value — most notably on macOS when the user picks Multicolor in System Settings → Appearance, the documented signal for "use your own brand colour".

Reference

fun isSystemAccentColorSupported(): Boolean   // gate UI before composition
@Composable fun systemAccentColor(): Color?    // reactive
@Composable fun isSystemInHighContrast(): Boolean

Notes

• Pair with darkmode-detector to derive a complete OS-driven theme.
• Use isSystemAccentColorSupported() outside Compose (e.g. in a settings screen) to disable an "Use system accent" toggle on unsupported platforms.